Ari, Csilla; Kálmán, Mihály
This article presents the first study on the glial architecture of a representative species of Holocephali, Callorhinchus milii (ghost shark). Holocephali are a small subclass of Chondrichthyes, with only a few extant genera, and those are considered to have a brain organization more similar to squalomorph sharks than to galeomorph sharks, skates, and rays. Three different astroglial markers--glial fibrillary acidic protein, S-100 protein, and glutamine synthetase (GS)--were investigated by immunohistochemical methods, applying both diaminobenzidine (DAB) and fluorescent techniques. They revealed similar glial structures, although most of them were detected by immunohistochemical reaction against GS and visualized by DAB. The predominant elements were radial ependymoglia spanning the area between the ventricular and meningeal surfaces, as in squalomorph sharks. Other similar features were the light appearance of myelinated neural tracts devoid of immunoreactivity, and the glial architecture of the reticular formation of the brain stem, cerebellum, and tectum, the latter with recognizable layers. The immunoreactivity of the vascular walls was similar; however, it is believed that different cell types form the blood-brain barrier in chimeras and in elasmobranchs. Some glial structures, however, resembled those of skates, rays, and galeomorph sharks. In C. milii astrocyte-like elements were observed in the telencephalon, using GS and S-100, although typical astrocyte-rich regions were not found. In some areas, especially the telencephalon, not only endfeet but also cell bodies were observed to be attached to the meningeal surface, with processes extending into the brain substance.
Johanson, Zerina; Boisvert, Catherine; Maksimenko, Anton; Currie, Peter; Trinajstic, Kate
The synarcual is a structure incorporating multiple elements of two or more anterior vertebrae of the axial skeleton, forming immediately posterior to the cranium. It has been convergently acquired in the fossil group ‘Placodermi’, in Chondrichthyes (Holocephali, Batoidea), within the teleost group Syngnathiformes, and to varying degrees in a range of mammalian taxa. In addition, cervical vertebral fusion presents as an abnormal pathology in a variety of human disorders. Vertebrae develop from axially arranged somites, so that fusion could result from a failure of somite segmentation early in development, or from later heterotopic development of intervertebral bone or cartilage. Examination of early developmental stages indicates that in the Batoidea and the ‘Placodermi’, individual vertebrae developed normally and only later become incorporated into the synarcual, implying regular somite segmentation and vertebral development. Here we show that in the holocephalan Callorhinchus milii, uniform and regular vertebral segmentation also occurs, with anterior individual vertebra developing separately with subsequent fusion into a synarcual. Vertebral elements forming directly behind the synarcual continue to be incorporated into the synarcual through growth. This appears to be a common pattern through the Vertebrata. Research into human disorders, presenting as cervical fusion at birth, focuses on gene misexpression studies in humans and other mammals such as the mouse. However, in chondrichthyans, vertebral fusion represents the normal morphology, moreover, taxa such Leucoraja (Batoidea) and Callorhinchus (Holocephali) are increasingly used as laboratory animals, and the Callorhinchus genome has been sequenced and is available for study. Our observations on synarcual development in three major groups of early jawed vertebrates indicate that fusion involves heterotopic cartilage and perichondral bone/mineralised cartilage developing outside the regular skeleton
Johanson, Zerina; Boisvert, Catherine; Maksimenko, Anton; Currie, Peter; Trinajstic, Kate
The synarcual is a structure incorporating multiple elements of two or more anterior vertebrae of the axial skeleton, forming immediately posterior to the cranium. It has been convergently acquired in the fossil group 'Placodermi', in Chondrichthyes (Holocephali, Batoidea), within the teleost group Syngnathiformes, and to varying degrees in a range of mammalian taxa. In addition, cervical vertebral fusion presents as an abnormal pathology in a variety of human disorders. Vertebrae develop from axially arranged somites, so that fusion could result from a failure of somite segmentation early in development, or from later heterotopic development of intervertebral bone or cartilage. Examination of early developmental stages indicates that in the Batoidea and the 'Placodermi', individual vertebrae developed normally and only later become incorporated into the synarcual, implying regular somite segmentation and vertebral development. Here we show that in the holocephalan Callorhinchus milii, uniform and regular vertebral segmentation also occurs, with anterior individual vertebra developing separately with subsequent fusion into a synarcual. Vertebral elements forming directly behind the synarcual continue to be incorporated into the synarcual through growth. This appears to be a common pattern through the Vertebrata. Research into human disorders, presenting as cervical fusion at birth, focuses on gene misexpression studies in humans and other mammals such as the mouse. However, in chondrichthyans, vertebral fusion represents the normal morphology, moreover, taxa such Leucoraja (Batoidea) and Callorhinchus (Holocephali) are increasingly used as laboratory animals, and the Callorhinchus genome has been sequenced and is available for study. Our observations on synarcual development in three major groups of early jawed vertebrates indicate that fusion involves heterotopic cartilage and perichondral bone/mineralised cartilage developing outside the regular skeleton. We
Ferrando, Sara; Gallus, Lorenzo; Gambardella, Chiara; Croce, Daniel; Damiano, Giulia; Mazzarino, Chiara; Vacchi, Marino
Chimaeroid fishes are the only extant Holocephali, a subclass of Chondrichthyes. We describe for the first time a well evidenced structure localized in the palate of the chimaeroid Chimaera monstrosa, here named a palatal organ (PO). Attention has been paid to the holocephalan head morphology, but there has been no mention of this particular organ in the literature. The PO is a soft-tissue mass located within a slight hollow in between the two vomerine toothplates, and it protrudes into the oral cavity, resembling the mammalian incisive papilla. It is characterized by dense connective tissue with abundant collagen and elastic fibers and no muscular tissue. The robust innervation but low density of taste buds suggest a role in gustation for the PO, but primary utility in general mechanical sensitivity likely implicated in food sorting. The presence of numerous multicellular serous glands in the anterior/dorsal part of the PO is quite surprising because, in gnathostome fish, the presence of multicellular glands within the mouth has been reported in only the rare case of teeth-associated venom glands. Hypothesized roles for these glands could include food lubrication, digestion and defense against pathogens. In the literature, the presence of a PO has been demonstrated in many published images of chimaeroid fishes, but has gone unnoticed. This trait could represent a peculiar characteristic of all or a subset of holocephalans.
Luchetti, E A; Iglésias, S P; Sellos, D Y
A new species of chimaeroid, Chimaera opalescens n. sp., was described from 31 type specimens caught in the north-eastern Atlantic Ocean at 950-1400 m depth. This species differed from all its congeners by the combination of the following characters: body uniformly pale brown to bronze, iridescent on fresh specimens; unpaired fins brown to purple, uniformly coloured or with pale or whitish edges; iris black; claspers tripartite and divided for a third of their length, not extending beyond the pelvic fins in adults; dorsal spine equal to or shorter than first dorsal fin; ventral caudal lobe equal to or deeper than dorsal caudal lobe. Comparison of DNA sequences of the CO1 gene with those of related species supported C. opalescens n. sp. as a distinct species. Specimens of C. opalescens n. sp. were previously misidentified as Chimaera monstrosa, a species sharing a similar geographical distribution. Chimaera opalescens n. sp. lives in deeper water and is a larger-bodied species than C. monstrosa. The two species were newly exploited by deep-sea fisheries and confused under a single landing name.
Hoganson, J.W.; Erickson, J.M.
A new species of chimaeroid, Ischyodus rayhaasi sp. nov., is described based primarily upon the number and configuration of tritors on palatine and mandibular tooth plates. This new species is named in honour of Mr Raymond Haas. Fossils of I. rayhaasi have been recovered from the Upper Maastrichtian Fox Hills Formation and the Breien Member and an unnamed member of the Hell Creek Formation at sites in south-central North Dakota and north-central South Dakota, USA. Ischyodus rayhaasi inhabited shallow marine waters in the central part of the Western Interior Seaway during the latest Cretaceous. Apparently it was also present in similar habitats at that time in the Volga region of Russia. Ischyodus rayhaasi is the youngest Cretaceous species Ischyodus known to exist before the Cretaceous/Tertiary extinction, and the species apparently did not survive that event. It was replaced by Ischyodus dolloi, which is found in the Paleocene Cannonball Formation of the Williston Basin region of North Dakota and is widely distributed elsewhere. ?? The Palaeontological Association.
Dessimoz, Christophe; Zoller, Stefan; Manousaki, Tereza; Qiu, Huan; Meyer, Axel; Kuraku, Shigehiro
Recent development of deep sequencing technologies has facilitated de novo genome sequencing projects, now conducted even by individual laboratories. However, this will yield more and more genome sequences that are not well assembled, and will hinder thorough annotation when no closely related reference genome is available. One of the challenging issues is the identification of protein-coding sequences split into multiple unassembled genomic segments, which can confound orthology assignment and various laboratory experiments requiring the identification of individual genes. In this study, using the genome of a cartilaginous fish, Callorhinchus milii, as test case, we performed gene prediction using a model specifically trained for this genome. We implemented an algorithm, designated ESPRIT, to identify possible linkages between multiple protein-coding portions derived from a single genomic locus split into multiple unassembled genomic segments. We developed a validation framework based on an artificially fragmented human genome, improvements between early and recent mouse genome assemblies, comparison with experimentally validated sequences from GenBank, and phylogenetic analyses. Our strategy provided insights into practical solutions for efficient annotation of only partially sequenced (low-coverage) genomes. To our knowledge, our study is the first formulation of a method to link unassembled genomic segments based on proteomes of relatively distantly related species as references.
Durán, Ana C; López-Unzu, Miguel A; Rodríguez, Cristina; Fernández, Borja; Lorenzale, Miguel; Linares, Andrea; Salmerón, Francisca; Sans-Coma, Valentín
the mixed ventricular myocardium is primitive for chondrichthyans. The reduction or even lack of compacta in holocephali has to be regarded as a derived anatomical trait. Our findings also fit in with the view that the mixed myocardium was the primitive condition in gnathostomes, and that the absence of compact ventricular myocardium in different actinopterygian groups is the result of a repeated loss of such type of cardiac muscle during fish evolution.
Rocco, Lucia; Liguori, Innocenza; Costagliola, Domenico; Morescalchi, Maria A; Tinti, Fausto; Stingo, Vincenzo
Although considerable progress has been made in elucidating the relationships within the Chondrichthyes, there is no agreement as it concerns the systematics of Batoidea, the most derived superorder among cartilaginous fishes, and many different interpretations exist. Our investigation provides the first assessment of relationships among the described batoid species using sequences from both mtDNA and nuclear genes as well as karyological morphology. Our work consists primarily in reconstructing the phylogenetic relationships of Batoidea by examining the mtDNA (16S) and nuclear gene (18S) sequences from 11 batoid species. The three analytical methods (NJ, MP and Bayesian analysis) grouped Rajiformes, Myliobatiformes and Rhinobatiformes. In these trees the two torpedoes diverge from the other batoid fishes. We also compare the molecular data with the available karyological evidence, which consist of the diploid number and the karyotype morphology of eight species belonging to the four orders examined. The results show that the karyological structure in the different species is generally consistent with the various phylogenetical trees, and that Torpediniformes confirm their unique genome organization.
Andreev, Plamen; Coates, Michael I; Karatajūtė-Talimaa, Valentina; Shelton, Richard M; Cooper, Paul R; Wang, Nian-Zhong; Sansom, Ivan J
The Mongolepidida is an Order of putative early chondrichthyan fish, originally erected to unite taxa from the Lower Silurian of Mongolia. The present study reassesses mongolepid systematics through the examination of the developmental, histological and morphological characteristics of scale-based specimens from the Upper Ordovician Harding Sandstone (Colorado, USA) and the Upper Llandovery-Lower Wenlock Yimugantawu (Tarim Basin, China), Xiushan (Guizhou Province, China) and Chargat (north-western Mongolia) Formations. The inclusion of the Mongolepidida within the Class Chondrichthyes is supported on the basis of a suite of scale attributes (areal odontode deposition, linear odontocomplex structure and lack of enamel, cancellous bone and hard-tissue resorption) shared with traditionally recognized chondrichthyans (euchondrichthyans, e.g., ctenacanthiforms). The mongolepid dermal skeleton exhibits a rare type of atubular dentine (lamellin) that is regarded as one of the diagnostic features of the Order within crown gnathostomes. The previously erected Mongolepididae and Shiqianolepidae families are revised, differentiated by scale-base histology and expanded to include the genera Rongolepisand Xinjiangichthys, respectively. A newly described mongolepid species (Solinalepis levis gen. et sp. nov.) from the Ordovician of North America is treated as family incertae sedis, as it possesses a type of basal bone tissue (acellular and vascular) that has yet to be documented in other mongolepids. This study extends the stratigraphic and palaeogeographic range of Mongolepidida and adds further evidence for an early diversification of the Chondrichthyes in the Ordovician Period, 50 million years prior to the first recorded appearance of euchondrichthyan teeth in the Lower Devonian.
Coates, Michael I.; Karatajūtė-Talimaa, Valentina; Shelton, Richard M.; Cooper, Paul R.
The Mongolepidida is an Order of putative early chondrichthyan fish, originally erected to unite taxa from the Lower Silurian of Mongolia. The present study reassesses mongolepid systematics through the examination of the developmental, histological and morphological characteristics of scale-based specimens from the Upper Ordovician Harding Sandstone (Colorado, USA) and the Upper Llandovery–Lower Wenlock Yimugantawu (Tarim Basin, China), Xiushan (Guizhou Province, China) and Chargat (north-western Mongolia) Formations. The inclusion of the Mongolepidida within the Class Chondrichthyes is supported on the basis of a suite of scale attributes (areal odontode deposition, linear odontocomplex structure and lack of enamel, cancellous bone and hard-tissue resorption) shared with traditionally recognized chondrichthyans (euchondrichthyans, e.g., ctenacanthiforms). The mongolepid dermal skeleton exhibits a rare type of atubular dentine (lamellin) that is regarded as one of the diagnostic features of the Order within crown gnathostomes. The previously erected Mongolepididae and Shiqianolepidae families are revised, differentiated by scale-base histology and expanded to include the genera Rongolepisand Xinjiangichthys, respectively. A newly described mongolepid species (Solinalepis levis gen. et sp. nov.) from the Ordovician of North America is treated as family incertae sedis, as it possesses a type of basal bone tissue (acellular and vascular) that has yet to be documented in other mongolepids. This study extends the stratigraphic and palaeogeographic range of Mongolepidida and adds further evidence for an early diversification of the Chondrichthyes in the Ordovician Period, 50 million years prior to the first recorded appearance of euchondrichthyan teeth in the Lower Devonian. PMID:27350896
Andrade, Isabel; Pequeño, Germán
We compared the geographic distribution of groups of chondrychthid fishes of two physically proximal, although geographically different, regions that include the Juan Fernández seamounts and the central Chilean continental slope, both sampled at mesopelagic and mesobenthonic depths. The ridge is in the Nazca Plate, while the slope region in on the South American Plate, and is closer to the South American continent. We found six species of Chondrichthyes for the seamounts (four orders, four families). The slope sampling produced ten species of Chondrichthyes, of which Torpedo tremens De Buen 1959, was the only species in common with the Juan Fernandez area. There are clear differences between the Chondrichthyes of the two regions. These fisheries require adequate administrative modes.
Tavares Schäfer, Bárbara; Malavasi, Carlos Eduardo; Favaron, Phelipe Oliveira; Ambrósio, Carlos Eduardo; Miglino, Maria Angelica; Ferreira De Amorim, Alberto; Grassi Rici, Rose Eli
We have conducted a morphological study of the ampullae of Lorenzini on two shark species from Squatina Genus. In both species, S. guggenheim and S. occulta, the ampullae were observed like small pores scattered in the head region similar to other species of the Chondrichthyes Class. However, differently of the other species a greatest density of ampullae of Lorenzini was observed along of the body surface. After fixation using 10% formaldehyde, the ampullae were removed and processed for light and scanning electron microscopy. Macroscopically, the two shark species differed by the presence of dorsal spines that appeared from the head to the first dorsal fin in S. guggenheim and were absent in S. occulta. Microscopically, there were no differences between the ampullae of Lorenzini channels in these two species. The wall of the ampulla was formed by a simple squamous epithelium. Bands of connective tissue, hyaline cartilage and collagen fibers were found between the ampulla and the skeletal striated muscle layer. Nerve branches responsible for conducting signal pulses to the central nervous system were visible between the muscle and connective tissue layers. Using scanning electron microscopy and histological analysis, we found that the channels were twisted and positioned parallel to the skin. The inside of the channels contained a large amount of a gelatinous secretion composed by polysaccharides. Therefore, we conclude that the morphological combination of extended distribution of the ampullae of Lorenzini and the body shape may represent an adaptation of these species to their way of life.
Summers, A P
The stingray family Myliobatidae contains five durophagous (hard prey specialist) genera and two planktivorous genera. A suite of morphological features makes it possible for the hard prey specialists to crush mollusks and crustaceans in their cartilaginous jaws. These include: 1) flat, pavement-like tooth plates set in an elastic dental ligament; 2) multiple layers of calcified cartilage on the surface of the jaws; 3) calcified struts running through the jaws; and 4) a lever system that amplifies the force of the jaw adductors. Examination of a range of taxa reveals that the presence of multiple layers of calcified cartilage, previously described from just a few species, is a plesiomorphy of Chondrichthyes. Calcified struts within the jaw, called "trabecular cartilage," are found only in the myliobatid genera, including the planktivorous Manta birostris. In the durophagous taxa, the struts are concentrated under the area where prey is crushed, thereby preventing local buckling of the jaws. Trabecular cartilage develops early in ontogeny, and does not appear to develop as a direct result of the stresses associated with feeding on hard prey. A "nutcracker" model of jaw function is proposed. In this model, the restricted gape, fused mandibular and palatoquadrate symphyses, and asynchronous contraction of the jaw adductors function to amplify the closing force by 2-4 times.
Takahashi, K; Kobayashi, K
This paper deals with the results of the investigation of the facial nerves of chondrichthyes in order to consider the phylogenetic origin of the Chorda tympani in human. Six species of elasmobranchs (Chlamydoselachus anguineus, Cephaloscyllium umbratile, Squalus acanthias, Dasyatis akajei, Raja kwangtungensis and Mobura diabolus) were dissected under a stereoscopic microscope for this purpose, and the following results were obtained. Ramus palatinus and R. pre-spiracularis were observed as pre-trematic branches, while R. mandibularis externus, R. mandibularis internus and R. hyoideus originating from R. hyomandibularis were observed as post-trematicus of the facial proper in chondrichtyes. The rami intermedii indicated by Tanaka and Nakao (1979) were observed only in Dasyatis akajei. The R. hyomandibularis of Squalus acanthias had cutaneous branches, and the same branches were described in Chimaera by Takahashi and Kobayashi (1988). R. pre-spiracularis and R. mandibularis internus supply the floor of mouth in Squalus acanthias. As for the other chondrichthyes, R. mandibularis internus was only the one that could be found at the floor of mouth cavity under a stereoscopic microscope. From the observations described above and from previous studies, it may be concluded that the problem of whether the Chorda tympani is homologous with whether the pre- or post-trematicus of branchial nerves seems to depend on the animal species.
Reinecke, M; Betzler, D; Forssmann, W G; Thorndyke, M; Askensten, U; Falkmer, S
As representatives of the vertebrate class of chondrichthyes the plagostomian species Squalus acanthias, Scyliorhinus canicula and Raja clavata as well as the holocephalan species Chimaera monstrosa were investigated for the presence of cardiac hormones of the atrial natriuretic polypeptide/cardiodilatin- (ANP/CDD-) family. ANP/CDD-immunoreactive cells were detected in the atria and the ventricles of all species studied. While these cells failed to react with antisera raised against the N-terminus of CDD-126 (= gamma-ANP) they reacted with all antisera directed against sequences of the C-terminus of CDD-126 (CDD 99-126) which is identical to alpha-ANP. The ANP/CDD-immunoreactive cells were found in high numbers in all regions of the atria and in moderate density also in the ventricles. In correspondence, in the electron microscope, myoendocrine cells which were characterized by dense-cored secretory granules were identified in the atrial and ventricular myocardium. With the use of the protein A-gold technique, ANP/CDD-immunoreactivity was determined within the secretory granules. Furthermore, in the bioassay, prepurified extracts of the atria and the ventricles of Scyliorhinus and Chimaera exerted dose-dependent relaxations of the pre-contracted mammalian (rabbit) aorta. In both cases the atrial extracts proved to be more potent than the ventricular extracts. The present findings indicate that myoendocrine cells occur in the atria and ventricles of chondrichthyes and that these cells contain homologous cardiac hormones of the ANP/CDD-family in their secretory granules. The results are compared with those obtained earlier for the other vertebrate classes and their phylogenetic and functional significance is discussed.
The marine leech Stibarobdella loricata (Harding, 1924) (Hirudinea, Piscicolidae), parasitic on the angel shark Squatina spp. and sandtiger shark Carcharias taurus Rafinesque, 1810 (Chondrichthyes: Squatinidae, Carchariidae) in Southern Brazilian waters.
Soto, J M R
The presence of the marine leech, Stibarobdella loricata (Harding, 1924) (Hirudinea, Piscicolidae), is reported on the southern coast of Brazil, based on seven lots with 47 specimens, between 71 and 182 mm in total length, collected on the dorsal region of angel sharks, Squatina argentina (Marini, 1930); S. guggenheim Marini, 1936; S. punctata Marini, 1936 (Chondrichthyes, Squatinidae); and on the head of a sandtiger shark, Carcharias taurus Rafinesque, 1810 (Chondrichthyes, Carchariidae). This is the first record of S. loricata in the western Atlantic and of its parasitic association with S. argentina, S. guggenheim, S. punctata, and C. taurus.
Neoselachians and Chimaeriformes (Chondrichthyes) from the latest Cretaceous-Paleogene of Sierra Baguales, southernmost Chile. Chronostratigraphic, paleobiogeographic and paleoenvironmental implications
Otero, Rodrigo A.; Oyarzún, José Luis; Soto-Acuña, Sergio; Yury-Yáñez, Roberto E.; Gutierrez, Nestor M.; Le Roux, Jacobus P.; Torres, Teresa; Hervé, Francisco
This paper discusses a well-represented fossil record of cartilaginous fishes (Chondrichthyes) from southern South America. The recovered samples allow the recognition of three assemblages with chronostratigraphic and paleogeographic value: i) typical Maastrichtian sharks and rays with affinities to eastern Pacific fauna, including the taxa Ischyrhiza chilensis, Serratolamna serrata, Centrophoroides sp. associated to Carcharias sp., and Dasyatidae indet.; ii) a scarce reworked assemblage of Paleocene-Early Eocene age including the taxa Otodus obliquus and Megascyliorhinus cooperi; iii) a rich assemblage with reworked taxa of Early to Middle Eocene age, together with autochthonous deposited Middle to Late Eocene taxa with close affinities to paleoichthyofaunas recovered from the North Atlantic, represented by Carcharias 'hopei', Odontaspis winkleri, Carcharoides catticus, Macrorhizodus praecursor, Carcharocles auriculatus, Striatolamia sp., Striatolamia macrota, Hexanchus agassizi, Notorhynchus sp., Myliobatis sp., Abdounia sp., Pristiophorus sp., Squatina sp., cf. Rhizoprionodon sp., Ischyodus sp., and one new species, Jaekelotodus bagualensis sp. nov. The studied samples include for the first time taxa with well established chronostratigraphic resolutions as well as taphonomic information that help clarifying the age of the fossil-bearing units. In addition, they provide relevant information about the evolution of the Magallanes (=Austral) Basin from the Upper Cretaceous to the Paleogene, suggesting a probable connection with the Quiriquina Basin of south-central Chile during the latest Cretaceous. Finally, the studied assemblages indicate a latitudinal pattern of distribution that provides valuable data on the environmental evolution and temperature of southern South America during the Paleogene.
Testing morphologically based phylogenetic theories within the cartilaginous fishes with molecular data, with special reference to the catshark family (Chondrichthyes; Scyliorhinidae) and the interrelationships within them.
Human, Brett A; Owen, E Patricia; Compagno, Leonard J V; Harley, Eric H
A molecular phylogenetic investigation was conducted to examine phylogenetic relationships between various members of the catsharks (Chondrichthyes; Carcharhiniformes; Scyliorhinidae), and is the largest chondrichthyan data set yet analysed, consisting of nearly 130,000 nucleotides. Three mitochondrial DNA genes were used to construct the phylogenies, cytochrome b, NADH-2, and NADH-4, with 41 sequences from 18 taxa being novel. These sequences were either used separately or combined into a single data set, and phylogenies were constructed using various methods, however, only the Bayesian inference tree derived from the cytochrome b data set was resolved sufficiently for phylogenetic inferences to be made. Interestingly, the family Scyliorhinidae was not supported by the results and was found to be paraphyletic. The Scyliorhininae and Pentanchinae were supported, whereas the Pentanchini clade was present, but not well supported. The Halaelurini hypothesis was supported with Holohalaelurus identified as the basal genus of that clade, and Haploblepharus edwardsii identified as the basal taxon for that genus. Elsewhere within the Chondrichthyes, the Carcharhiniformes and the Lamniformes were found to be monophyletic, and the Heterodontiformes was placed within the Squalimorphs. The placement of the skates and rays in these analyses support the Batoidea as being sister to the Elasmobranchii.
Díaz-Andrade, M C; Galíndez, E; Estecondo, S
Chondrichthyes have become an important economic resource in recent years. In spite of this importance, there is little knowledge about their reproductive biology, especially of species from the south-western Atlantic. In this work, we study the morphology and histology of the ovary of Sympterygia acuta. The results show that oogonia were present only in the immature females (stage I of maturity scale), whereas specimens in stages II and III of maturity displayed oocytes in all developmental steps. The most important histological features that vary throughout oocyte development are the presence or absence of yolk, the number of types and layers of follicular cells and the degree of development of the thecae. Follicular cells are, at least, of two different types. Finally, a new point of view for the determination of maturity stages in the field based on the size of follicles is discussed.
Rocha, S; Casal, G; Al-Quraishy, S; Azevedo, C
Microscopic and molecular procedures are used to describe a new myxosporean species, Chloromyxum clavatum n. sp., infecting the cartilaginous fish Raja clavata Linnaeus, 1758 (Chondrichthyes: Rajidae), collected from the northwest Atlantic coast of Portugal. Young plasmodia and mature spores were found floating free in the gall bladder of R. clavata . Spores were spherical to subspherical with a pointed anterior end, measuring14.4 ± 0.5 μm (n = 25) in length, 11.9 ± 0.5 μm (n = 25) in width, and 9.4 ± 0.5 μm (n = 15) in thickness. The spore's wall was composed of 2 equally sized valves, each displaying 6-8 elevated surface ridges and a bundle of several tapering caudal filaments attached to the basal portion. Spores contained 4 pyriform equally sized polar capsules (5.5 ± 0.4 μm × 2.9 ± 0.5 μm) (n = 25), each possessing an obliquely arranged isofilar polar filament coiled in 7-8 coils. Morphological data, host specificity, tissue tropism, and molecular analysis of the SSU rDNA gene identify this parasite as a new species of Chloromyxum. Neighbor-joining and maximum likelihood further reveal the parasite clustering with other species of Chloromyxum infecting the gall bladder of marine cartilaginous fish to form a clade positioned at the base of the freshwater clade, therefore constituting an exception to the major division of the class Myxosporea into the freshwater and marine clades, while supporting the existence of a correlation between tissue tropism and myxosporean phylogeny.
Kriwet, Jürgen; Engelbrecht, Andrea; Mörs, Thomas; Reguero, Marcelo; Pfaff, Cathrin
The Eocene La Meseta Formation on Seymour Island, Antarctic Peninsula, is known for its remarkable wealth of fossil remains of chondrichthyans and teleosts. Chondrichthyans seemingly were dominant elements in the Antarctic Paleogene fish fauna, but decreased in abundance from middle to late Eocene, during which time remains of bony fishes increase. This decline of chondrichthyans at the end of the Eocene generally is related to sudden cooling of seawater, reduction in shelf area, and increasing shelf depth due to the onset of the Antarctic thermal isolation. The last chondrichthyan records known so far include a chimeroid tooth plate from TELM 6 (Lutetian) and a single pristiophorid rostral spine from TELM 7 (Priabonian). Here, we present new chondrichthyan records of Squalus, Squatina, Pristiophorus, Striatolamia, Palaeohypotodus, Carcharocles, and Ischyodus from the upper parts of TELM 7 (Priabonian), including the first record of Carcharocles sokolovi from Antarctica. This assemblage suggests that chondrichthyans persisted much longer in Antarctic waters despite rather cool sea surface temperatures of approximately 5°C. The final disappearance of chondrichthyans at the Eocene–Oligocene boundary concurs with abrupt ice sheet formation in Antarctica. Diversity patterns of chondrichthyans throughout the La Meseta Formation appear to be related to climatic conditions rather than plate tectonics. PMID:28298806
Sharks and skates (Chondrichthyes: Elasmobranchii) have a glial blood-brain barrier, while all other vertebrates examined so far have an endothelial barrier. For comparative reasons it is desirable to examine the blood-brain barrier in species from the other subclass of cartilaginous fish, the holocephalans. The ultrastructure of cerebral capillaries in the chimaera (Chondrichthyes: Holocephali) is described in the present study. The endothelial cells are remarkably thick. Fenestrae and transendothelial channels were not observed. The endothelial cells are joined by elaborate tight junctions. The perivascular glial processes are separated by wide spaces (15-60 nm) without obliterating junctional complexes. These findings indicate that the chimaera has an endothelial blood-brain barrier.
Kröger, Ronald H H; Gustafsson, Ola S E; Tuminaite, Inga
We have investigated the apparatus suspending the crystalline lens in the eyes of basal vertebrates. Data are presented for Holocephali (Chondrichthyes) and the actinopterygians Polypteriformes, Polyodontidae (Acipenseriformes), Lepisosteiformes, Amiiformes, and one teleost species, the banded archerfish (Toxotes jaculatrix). We also studied the optical properties of the lens in Polypteriformes, Lepisosteiformes, and the archerfish. Together with previously published results, our findings show that there are three basic types of lens suspension in vertebrates. These are i) a rotationally symmetric suspension (Petromyzontida, lampreys; Ceratodontiformes, lungfishes; Tetrapoda), ii) a suspension with a dorso-ventral axis of symmetry and a ventral papilla (all Chondrichthyes and Acipenseriformes), and iii) an asymmetric suspension with a ventral muscle and a varying number of ligaments (all Actinopterygii except for Acipenseriformes). Large eyes with presumably high spatial resolution have evolved in all groups. Multifocal lenses creating well-focused color images are also present in all groups studied. Stable and exact positioning of the lens, in many cases in combination with accommodative changes in lens position or shape, is achieved by all three types of lens suspension. It is somewhat surprising that lens suspensions are strikingly similar in Chondrichthyes and Acipenseriformes (Actinopterygii), while the suspension apparatus in Polypteriformes, usually being regarded as an actinopterygian group more basal than Acipenseriformes, are considerably more teleostean-like. This study completes a series of investigations on lens suspensions in nontetrapod vertebrates, covering all major groups except for the rare and highly derived coelacanths.
Yang, Baojuan; Zhang, Jie; Yamaguchi, Atsuko; Zhang, Baowei
Dasyatis bennettii is a bottom-dweller that inhabits in the coastal waters of the Indian and Pacific Oceans as well as the freshwaters of Southern China. In this study, we determined the complete mitochondrial genome of this species of stingrays. The results showed that the total length of the mitogenome was 17,668 bp as a circular DNA and contained 13 protein-coding genes, 22 transfer RNA genes, 2 ribosomal RNA genes, and 1 control region. The base composition of the complete mitochondrial DNA was 31.1% A, 28.7% T, 26.7% C, and 13.5% G. All the genes in D. bennettii were distributed on the H-strand, except for the ND6 subunit gene and eight tRNA genes which were encoded on the L-strand.
The dentitions of lamniform sharks are said to exhibit a unique heterodonty called the "lamnoid tooth pattern." The presence of an inflated hollow "dental bulla" on each jaw cartilage allows the recognition of homologous teeth across most modern macrophagous lamniforms based on topographic correspondence through the "similarity test." In most macrophagous lamniforms, three tooth rows are supported by the upper dental bulla: two rows of large anterior teeth followed by a row of small intermediate teeth. The lower tooth row occluding between the two rows of upper anterior teeth is the first lower anterior tooth row. Like the first and second lower anterior tooth rows, the third lower tooth row is supported by the dental bulla and may be called the first lower intermediate tooth row. The lower intermediate tooth row occludes between the first and second upper lateral tooth rows situated distal to the upper dental bulla, and the rest of the upper and lower tooth rows, all called lateral tooth rows, occlude alternately. Tooth symmetry cannot be used to identify their dental homology. The presence of dental bullae can be regarded as a synapomorphy of Lamniformes and this character is more definable than the "lamnoid tooth pattern." The formation of the tooth pattern appears to be related to the evolution of dental bullae. This study constitutes the first demonstration of supraspecific tooth-to-tooth dental homologies in nonmammalian vertebrates.
Jerve, Anna; Johanson, Zerina; Ahlberg, Per; Boisvert, Catherine
Fin spines are commonly known from fossil gnathostomes (jawed vertebrates) and are usually associated with paired and unpaired fins. They are less common among extant gnathostomes, being restricted to the median fins of certain chondrichthyans (cartilaginous fish), including chimaerids (elephant sharks) and neoselachians (sharks, skates, and rays). Fin spine growth is of great interest and relevance but few studies have considered their evolution and development. We investigated the development of the fin spine of the chimaerid Callorhinchus milii using stained histological sections from a series of larval, hatchling, and adult individuals. The lamellar trunk dentine of the Callorhinchus spine first condenses within the mesenchyme, rather than at the contact surface between mesenchyme and epithelium, in a manner more comparable to dermal bone formation than to normal odontode development. Trabecular dentine forms a small component of the spine under the keel; it is covered externally with a thin layer of lamellar trunk dentine, which is difficult to distinguish in sectioned adult spines. We suggest that the distinctive characteristics of the trunk dentine may reflect an origin through co-option of developmental processes involved in dermal bone formation. Comparison with extant Squalus and a range of fossil chondrichthyans shows that Callorhinchus is more representative than Squalus of generalized chondrichthyan fin-spine architecture, highlighting its value as a developmental model organism.
Bustamante, Carlos; Vargas-Caro, Carolina; Bennett, Michael B
The abundance and species richness of the cartilaginous fish community of the continental shelf and slope off central Chile is described, based on fishery-independent trawl tows made in 2006 and 2007. A total of 194,705 specimens comprising 20 species (9 sharks, 10 skates, 1 chimaera) were caught at depths of 100-500 m along a 1,000 km transect between 29.5°S and 39°S. Sample site locations were grouped to represent eight geographical zones within this latitudinal range. Species richness fluctuated from 1 to 6 species per zone. There was no significant latitudinal trend for sharks, but skates showed an increased species richness with latitude. Standardised catch per unit effort (CPUE) increased with increasing depth for sharks, but not for skates, but the observed trend for increasing CPUE with latitude was not significant for either sharks or skates. A change in community composition occurred along the depth gradient with the skates, Psammobatis rudis, Zearaja chilensis and Dipturus trachyderma dominating communities between 100 and 300 m, but small-sized, deep-water dogfishes, such as Centroscyllium spp. dominated the catch between 300 and 500 m. Cluster and ordination analysis identified one widespread assemblage, grouping 58% of sites, and three shallow-water assemblages. Assemblages with low diversity (coldspots) coincided with highly productive fishing grounds for demersal crustaceans and bony fishes. The community distribution suggested that the differences between assemblages may be due to compensatory changes in mesopredator species abundance, as a consequence of continuous and unselective species removal. Distribution patterns and the quantitative assessment of sharks, skates and chimaeras presented here complement extant biogeographic knowledge and further the understanding of deep-water ecosystem dynamics in relation to fishing activity in the south-east Pacific Ocean.
Vargas-Caro, Carolina; Bennett, Michael B.
The abundance and species richness of the cartilaginous fish community of the continental shelf and slope off central Chile is described, based on fishery-independent trawl tows made in 2006 and 2007. A total of 194,705 specimens comprising 20 species (9 sharks, 10 skates, 1 chimaera) were caught at depths of 100–500 m along a 1,000 km transect between 29.5°S and 39°S. Sample site locations were grouped to represent eight geographical zones within this latitudinal range. Species richness fluctuated from 1 to 6 species per zone. There was no significant latitudinal trend for sharks, but skates showed an increased species richness with latitude. Standardised catch per unit effort (CPUE) increased with increasing depth for sharks, but not for skates, but the observed trend for increasing CPUE with latitude was not significant for either sharks or skates. A change in community composition occurred along the depth gradient with the skates, Psammobatis rudis, Zearaja chilensis and Dipturus trachyderma dominating communities between 100 and 300 m, but small-sized, deep-water dogfishes, such as Centroscyllium spp. dominated the catch between 300 and 500 m. Cluster and ordination analysis identified one widespread assemblage, grouping 58% of sites, and three shallow-water assemblages. Assemblages with low diversity (coldspots) coincided with highly productive fishing grounds for demersal crustaceans and bony fishes. The community distribution suggested that the differences between assemblages may be due to compensatory changes in mesopredator species abundance, as a consequence of continuous and unselective species removal. Distribution patterns and the quantitative assessment of sharks, skates and chimaeras presented here complement extant biogeographic knowledge and further the understanding of deep-water ecosystem dynamics in relation to fishing activity in the south-east Pacific Ocean. PMID:24918036
Chai, Aihong; Yamaguchi, Atsuko; Furumitsu, Keisuke; Zhang, Jie
Squatina japonica belonging to the monogenetic family Squatinidae is endemic to the Northwest Pacific. The complete mitochondrial genome sequence of S. japonica is 16,689 bp long and comprises 13 protein-coding genes, 22 tRNA genes, 2 rRNA genes, and 1 control region. The base composition of the genome is 31.10% A, 31.04% T, 24.42% C, and 13.43% G. The geographic clade and phylogenetic relationship of S. japonica are ambiguous. Therefore, studying the complete mitochondrial genome of S. japonica is highly important to understand the aforementioned aspect and to analyze the conservation genetics in the genus Squatina.
Gallo, V; Cavalcanti, M J; da Silva, R F L; da Silva, H M A; Pagnoncelli, D
The distributional patterns of the seven species of Rhizoprionodon were analysed using the panbiogeographical method of track analysis. The individual tracks of Rhizoprionodon suggest that the genus is mainly an Indian-Atlantic Ocean group. Five generalized tracks were found: (1) Caribbean, defined by R. porosus and R. terraenovae; (2) eastern coast of South America, defined by R. porosus and R. lalandei; (3) Indian Ocean, defined by R. acutus and R. oligolinx; (4) north-western Australia, defined by R. acutus, R. oligolinx and R. taylori; (5) north-north-eastern Australia, defined by R. acutus and R. taylori. Only R. longurio was not included in any generalized track, and its distribution is restricted to the eastern Pacific Ocean. Two biogeographical nodes were found at the intersection of the generalized tracks 1 and 2 (Caribbean Sea) and generalized tracks 4 and 5 (north Australia). The generalized tracks overlap with those found in several unrelated marine taxa. Overall, the generalized tracks are associated with warm currents. The biogeographical nodes found (Caribbean and Australian) are coincident with the global distribution of mangroves.
Last, Peter R; White, William T
Two new stingrays, Dasyatis longicauda sp. nov. and Himanturajavaensis sp. nov., are described from material collected in the eastern Indonesian Archipelago. These species, which are both relatively small stingrays (both probably smaller than 40 cm DW), have been confused with closest relatives in the region. Dasyatis longicauda sp. nov., known from West Papua, differs from its congener, the Australian endemic D. fluviorum, in having a slightly lower vertebral count, lower pectoral-radial count, a longer tail, larger and less numerous thorns along the mid-disc and tail, as well as a different CO1 Barcode. Himantura javaensis sp. nov., known only from southern Java (near Cilacap), belongs to a complex of small whiprays which also includes another Indonesian species, H. walga. Apart from major differences in squamation and a different CO1 Barcode, Himantura javaensis is more brownish in coloration, has more vertebrae, a longer tail, smaller eye and orbit, more posteriorly positioned sting, shorter adult claspers, shorter pelvic fin, and differs in various measurements around the head.
Fontenelle, João Pedro; de Carvalho, Marcelo R
The gross brain morphology, brain proportions, and position of cranial nerves in all four genera (Potamotrygon, Plesiotrygon, Paratrygon, and Heliotrygon) and 11 of the species of the Neotropical stingray family Potamotrygonidae were studied to provide new characters that may have a bearing on internal potamotrygonid systematics. The brain was also studied in four other stingray (Myliobatiformes) genera (Hexatrygon, Taeniura, Dasyatis, and Gymnura) to provide a more inclusive phylogenetic context for the interpretation of features of the brain in potamotrygonids. Our results indicate, based on neuroanatomical characters, that the genera Paratrygon and Heliotrygon are sister groups, as are the genera Potamotrygon and Plesiotrygon, agreeing with previous morphological and molecular phylogenetic studies. Both groups of genera share distinct conditions of the olfactory tracts, telencephalon and its central nuclei, hypophysis and infundibulum, morphology and orientation of the metencephalic corpus cerebelli, orientation of the glossopharyngeal nerve, and overall encephalic proportions. The corpus cerebelli of Paratrygon and Heliotrygon is interpreted as being more similar to the general batoid condition and, given their phylogenetic position highly nested within stingrays, is considered secondarily derived, not plesiomorphically retained. Our observations of the corpus cerebelli of stingrays, including Hexatrygon, corroborate that the general stingray pattern previously advanced by Northcutt is derived among batoids. The morphology of the brain is shown to be a useful source of phylogenetically informative characters at lower hierarchical levels, such as between genera and species, and thus, has significant potential in phylogenetic studies of elasmobranchs.
Liang, Liang; Reinick, Christina; Angleson, Joseph K; Dores, Robert M
There is general agreement that the presence of five melanocortin receptor genes in tetrapods is the result of two genome duplications that occurred prior to the emergence of the gnathostomes, and at least one local gene duplication that occurred early in the radiation of the ancestral gnathostomes. Hence, it is assumed that representatives from the extant classes of gnathostomes (i.e., Chondrichthyes, Actinopterygii, Sarcopterygii) should also have five paralogous melanocortin genes. Current studies on cartilaginous fishes indicate that while there is evidence for five paralogous melanocortin receptor genes in this class, to date all five paralogs have not been detected in the genome of a single species. This mini-review will discuss the ligand selectivity properties of the melanocortin-3 receptor of the elephant shark (subclass Holocephali) and the ligand selectivity properties of the melanocortin-3 receptor, melanocortin-4 receptor, and the melanocortin-5 receptor of the dogfish (subclass Elasmobranchii). The potential relationship of these melanocortin receptors to the hypothalamus/pituitary/interrenal axis will be discussed.
Angulo, Arturo; López, Myrna I; Bussing, William A; Murase, Atsunobu
A new species of Chimaera Linnaeus 1758 is described from three specimens collected from off the Pacific coasts of Costa Rica and Peru. Chimaera orientalis n. sp., the first species of the genus described from the eastern Pacific Ocean, is distinguished from its other congeners by a combination of coloration and morphology. Additionally, new records of occurrence for another four species of chimaeroid fishes (Harriotta raleighana (Goode & Bean 1895), Rhinochimaera africana Compagno, Stehmann & Ebert 1990, Hydrolagus colliei Lay & Bennett 1839, and H. macrophthalmus de Buen 1959) previously unknown for the continental shelf of the Pacific coast of Costa Rica and Central America are reported. A key to the eastern Pacific species of the order Chimaeriformes is also presented.
Awruch, C A
The class Chondrichthyes, that includes Elasmobranchii and Holocephali, is a diverse group of fish occupying a key position at the base of vertebrate evolution. Their evolutionary success is greatly attributed to their wide range of reproductive strategies controlled by different endocrine mechanics. As in other vertebrates, hormonal control of reproduction in chondrichthyans is mediated by the neuropeptide gonadotropin-releasing hormone (GnRH) that regulates the brain control of gonadal activity via a hypothalamus-pituitary-gonadal (HPG) axis. Chondrichthyans lack of a direct vascular supply from the hypothalamus to the zone of the pituitary where the gonadotropic activity resides, thus transport between these two zones likely occurs via the general circulation. In the brain of elasmobranchs, two groups of GnRH, GnRH-I and GnRH-II were identified, and the presence of two immunoreactive gonadotropins similar to the luteinising (LH) and follicle stimulating (FSH) hormones was identified in the pituitary. In holocephalans, only GnRH-II has been confirmed, and while gonadotropin activity has been found in the buccal pituitary lobe, the presence of gonadotropin receptors in the gonads remains unknowns. The diversity of reproductive strategies display by chondrichthyans makes it difficult to generalize the control of gametogenesis and steroidogenesis; however, some general patterns emerge. In both sexes, androgens and estrogens are the main steroids during gonadal growth; while progestins have maturational activity. Androgens also form the precursors for estrogen steroid production. Estrogens stimulate the hepatic synthesis of yolk and stimulate the development of different part of the reproductive tract in females. The role of other gonadal steroids may play in chondrichthyan reproduction remains largely unknown. Future work should concentrate in filling the gaps into the current knowledge of the HPG axis regulation, and the use of reproductive endocrinology as a non
Hester, Jennifer; Atwater, Kimberly; Bernard, Andrea; Francis, Malcolm; Shivji, Mahmood S
The basking shark (Cetorhinus maximus) is the world's second largest fish and the subject of strong conservation concern. Minimal genetic assessment exists for this globally distributed but regionally endangered species. We describe the complete mitochondrial genome sequence of C. maximus, obtained via polymerase chain reaction-based Sanger sequencing. The total length of the mitogenome is 16,670 bp and consists of 2 rRNAs, 22 tRNAs and 13 protein-coding genes. The base composition has an A + T bias (63.6%), as is often seen in other sharks. Gene order is equivalent to that found in most vertebrates.
Soares, Karla D A; Gadig, Otto F B; Gomes, Ulisses L
A new species of catshark (Carcharhiniformes, Scyliorhinidae), Scyliorhinus ugoi sp. nov., is described from off Northeastern and Southeastern Brazil. The new species is closest to the Scyliorhinus haeckelii/besnardi group and S. hesperius but differs in background coloration, head width, sexual maturity, and in cranial and body proportions.
Chang, Chia-Hao; Shao, Kwang-Tsao; Lin, Yeong-Shin; Ho, Hsuan-Ching; Liao, Yun-Chih
The complete mitochondrial genome of the big-eye thresher shark was sequenced using a polymerase chain reaction (PCR)-based method. The total length of mitochondrial DNA is 16,719 bp and includes 13 protein-coding genes, 2 ribosomal RNA, 22 transfer RNA genes, 1 replication origin region and 1 control region. The mitochondrial gene arrangement of the big-eye thresher shark is the same as the one observed in the most vertebrates. Base composition of the genome is A (31.8%), T (28.9%), C (25.8%) and G (13.5%).
Lisney, Thomas J; Yopak, Kara E; Camilieri-Asch, Victoria; Collin, Shaun P
Fishes exhibit lifelong neurogenesis and continual brain growth. One consequence of this continual growth is that the nervous system has the potential to respond with enhanced plasticity to changes in ecological conditions that occur during ontogeny. The life histories of many teleost fishes are composed of a series of distinct stages that are characterized by shifts in diet, habitat, and behavior. In many cases, these shifts correlate with changes in overall brain growth and brain organization, possibly reflecting the relative importance of different senses and locomotor performance imposed by the new ecological niches they encounter throughout life. Chondrichthyan (cartilaginous) fishes also undergo ontogenetic shifts in habitat, movement patterns, diet, and behavior, but very little is known about any corresponding shifts in the size and organization of their brains. Here, we investigated postparturition ontogenetic changes in brain-body size scaling, the allometric scaling of seven major brain areas (olfactory bulbs, telencephalon, diencephalon, optic tectum, tegmentum, cerebellum, and medulla oblongata) relative to the rest of the brain, and cerebellar foliation in a chondrichthyan, i.e., the bluespotted stingray Neotrygon kuhlii. We also investigated the unusual morphological asymmetry of the cerebellum in this and other batoids. As in teleosts, the brain continues to grow throughout life, with a period of rapid initial growth relative to body size, before slowing considerably at the onset of sexual maturity. The olfactory bulbs and the cerebellum scale with positive allometry relative to the rest of the brain, whereas the other five brain areas scale with varying degrees of negative allometry. None of the major brain areas showed the stage-specific differences in rates of growth often found in teleosts. Cerebellar foliation also increases at a faster rate than overall brain growth. We speculate that changes in the olfactory bulbs and cerebellum could reflect increased olfactory and locomotor capabilities, which may be associated with ontogenetic shifts in diet, habitat use, and activity patterns, as well as shifts in behavior that occur with the onset of sexual maturity. The frequency distributions of the three cerebellar morphologies exhibited in this species best fit a 2:1:1 (right-sided:left-sided:intermediate) distribution, mirroring previous findings for another stingray species.
Welten, Monique; Smith, Moya Meredith; Underwood, Charlie; Johanson, Zerina
A well-known characteristic of chondrichthyans (e.g. sharks, rays) is their covering of external skin denticles (placoid scales), but less well understood is the wide morphological diversity that these skin denticles can show. Some of the more unusual of these are the tooth-like structures associated with the elongate cartilaginous rostrum ‘saw’ in three chondrichthyan groups: Pristiophoridae (sawsharks; Selachii), Pristidae (sawfish; Batoidea) and the fossil Sclerorhynchoidea (Batoidea). Comparative topographic and developmental studies of the ‘saw-teeth’ were undertaken in adults and embryos of these groups, by means of three-dimensional-rendered volumes from X-ray computed tomography. This provided data on development and relative arrangement in embryos, with regenerative replacement in adults. Saw-teeth are morphologically similar on the rostra of the Pristiophoridae and the Sclerorhynchoidea, with the same replacement modes, despite the lack of a close phylogenetic relationship. In both, tooth-like structures develop under the skin of the embryos, aligned with the rostrum surface, before rotating into lateral position and then attaching through a pedicel to the rostrum cartilage. As well, saw-teeth are replaced and added to as space becomes available. By contrast, saw-teeth in Pristidae insert into sockets in the rostrum cartilage, growing continuously and are not replaced. Despite superficial similarity to oral tooth developmental organization, saw-tooth spatial initiation arrangement is associated with rostrum growth. Replacement is space-dependent and more comparable to that of dermal skin denticles. We suggest these saw-teeth represent modified dermal denticles and lack the ‘many-for-one’ replacement characteristic of elasmobranch oral dentitions. PMID:26473044
Welten, Monique; Smith, Moya Meredith; Underwood, Charlie; Johanson, Zerina
A well-known characteristic of chondrichthyans (e.g. sharks, rays) is their covering of external skin denticles (placoid scales), but less well understood is the wide morphological diversity that these skin denticles can show. Some of the more unusual of these are the tooth-like structures associated with the elongate cartilaginous rostrum 'saw' in three chondrichthyan groups: Pristiophoridae (sawsharks; Selachii), Pristidae (sawfish; Batoidea) and the fossil Sclerorhynchoidea (Batoidea). Comparative topographic and developmental studies of the 'saw-teeth' were undertaken in adults and embryos of these groups, by means of three-dimensional-rendered volumes from X-ray computed tomography. This provided data on development and relative arrangement in embryos, with regenerative replacement in adults. Saw-teeth are morphologically similar on the rostra of the Pristiophoridae and the Sclerorhynchoidea, with the same replacement modes, despite the lack of a close phylogenetic relationship. In both, tooth-like structures develop under the skin of the embryos, aligned with the rostrum surface, before rotating into lateral position and then attaching through a pedicel to the rostrum cartilage. As well, saw-teeth are replaced and added to as space becomes available. By contrast, saw-teeth in Pristidae insert into sockets in the rostrum cartilage, growing continuously and are not replaced. Despite superficial similarity to oral tooth developmental organization, saw-tooth spatial initiation arrangement is associated with rostrum growth. Replacement is space-dependent and more comparable to that of dermal skin denticles. We suggest these saw-teeth represent modified dermal denticles and lack the 'many-for-one' replacement characteristic of elasmobranch oral dentitions.
Carrillo-Briceño, Jorge D.; Aguilera, Orangel A.; Rodriguez, Félix
The study of the chondrichthyan fauna from the Angostura, Onzole, Canoa and Jama formations, in the Neogene of Bordón and Manabí basins, Ecuador, reveals the presence of 30 taxa, including the deep water shark †Chlamydoselachus landinii sp. nov. The assemblages are dominated by tropical shallow and deep water chondrichthyans, suggesting paleoenvironments associated with a short platform shelf bordering a deep margin. These assemblages are the most diverse shark and ray association known from the Tropical Central Eastern Pacific Ocean in the South American coastal basin, and provide new information on the paleoecology and paleodiversity of Neogene chondrichthyans.
The total lengths (L(T)) of 193 males (209-556 mm) and 130 females (275-515 mm) of Amblyraja doellojuradoi, a commercial by-catch species on the Argentinean continental shelf, which are increasingly retained, were analysed. No sexual dimorphism was observed in the L(T) at which 50% of individuals were sexually mature; males matured at 448 mm and females at 411 mm, c. 80 and 82% of maximum L(T). The hepato-somatic index was similar among sexes, but significantly different between maturity stages, being lower in mature than immature specimens. Males had no seasonal difference in the hepato-somatic index and females had the lowest index in autumn. The gonado-somatic index was lower in males than in females and significantly higher in mature than immature specimens of both sexes. Males had the highest index in autumn and females had no seasonal difference. Collectively, these results would indicate that A. doellojuradoi breeds in autumn.
Ebert, David A; White, William T; Ho, Hsuan-Ching
Hexanchus nakamurai Teng, 1962 is one of two valid nominal species in the genus Hexanchus; the other being H. griseus. The taxonomic history of H. nakamurai is somewhat convoluted due to questions about the validity of whether it constituted a publication or an unpublished dissertation. The issue appeared to have been resolved once it was determined that the Teng's original description met the criteria under the International Commission on Zoological Nomenclature code (Article 8a) of a publication. However, recent molecular studies have indicated that the western North Atlantic H. nakamurai (= ? H. vitulus) may be distinct from western Indian Ocean H. nakamurai. Compounding the issue is the loss of the holotype of H. nakamurai from Taiwan. A neotype is herein designated and the species redescribed based on the neotype and eight additional Taiwanese specimens.
Vaz, Diego F B; De Carvalho, Marcelo R
The morphology and taxonomy of species of Squatina from the southwestern Atlantic Ocean are revised. Species previously considered valid, Squatina argentina (Marini, 1930), Squatina guggenheim Marini, 1936 and Squatina occulta Vooren and da Silva, 1991, are investigated and described in detail, including a morphometric and meristic study of specimens from their recorded range. The taxonomic status of the doubtful nominal species Squatina punctata Marini, 1936 was also evaluated. This species was previously considered a junior synonym of S. argentina, a junior synonym of S. guggenheim, or a senior synonym of S. occulta. Although there is much morphological similarity between Squatina species, significant differences in dermal denticle patterns, dorsal coloration, tooth formula, and size at maturity are reported, enabling the recognition of S. argentina, S. guggenheim and S. occulta as valid species, and relegating S. punctata to the synonymy of S. guggenheim. Differences in skeletal morphology between valid species are described and considered supportive of the taxonomic hypothesis, corroborating a previous study of neurocrania. Additionally, an unidentified specimen is reported, as Squatina sp., from the continental shelf of Bahia state, Brazil, recognized by having more vertebral centra and a conspicuous dermal denticle morphology on interspiracular region, features not present in other South America angelshark species. A report on the only known syntype of Squatina dumeril Le Sueur, 1818 is presented, describing features that are still preserved and designating it as lectotype. Lateral-line sensory canals, skeleton, and cranial and hypobranchial muscles for the three valid species of Squatina from the southwestern Atlantic, as well as the brain and cranial nerves of S. guggenheim, are described and illustrated.
Menoret, Adriana; Ivanov, Verónica A
Two new species of Rhinebothrium (Cestoda, Rhinebothriidea) from potamotrygonid stingrays in the Neotropical region are herein described, which raises the total number of Rhinebothrium species known from Neotropical freshwaters to five. Rhinebothrium corbatai sp. n., and Rhinebothrium mistyae sp. n. were both collected from Potamotrygon motoro (Müller et Henle), captured in four tributaries of the Paraná River in Santa Fé Province, Argentina. The new species can be distinguished from their congeners, and from each other, by a combination of various features, including worm size (length and number of proglottids), number of loculi per bothridium, microthrix pattern, size of the cirrus sac, and the extent of the vas deferens. The discovery of these new species from P. motoro supports the pattern of high host specificity in this cestode genus, and reinforces the notion that some of the previous records of the enigmatic R. paratrygoni may correspond to new species of Rhinebothrium yet to be described.
Aschliman, Neil C; Nishida, Mutsumi; Miya, Masaki; Inoue, Jun G; Rosana, Kerri M; Naylor, Gavin J P
Skates, rays and allies (Batoidea) comprise more than half of the species diversity and much of the morphological disparity among chondrichthyan fishes, the sister group to all other jawed vertebrates. While batoids are morphologically well characterized and have an excellent fossil record, there is currently no consensus on the interrelationships of family-level taxa. Here we construct a resolved, robust and time-calibrated batoid phylogeny using mitochondrial genomes, nuclear genes, and fossils, sampling densely across taxa. Data partitioning schemes, biases in the sequence data, and the relative informativeness of each fossil are explored. The molecular phylogeny is largely congruent with morphology crownward in the tree, but the branching orders of major batoid groups are mostly novel. Body plan convergence appears to be widespread in batoids. A depressed, rounded pectoral disk supported to the snout tip by fin radials, common to skates and stingrays, is indicated to have been derived independently by each group, while the long, spiny rostrum of sawfishes similarly appears to be convergent with that of sawsharks, which are not batoids. The major extant batoid lineages are inferred to have arisen relatively rapidly from the Late Triassic into the Jurassic, with long stems followed by subsequent radiations in each group around the Cretaceous/Tertiary boundary. The fossil record indicates that batoids were affected with disproportionate severity by the end-Cretaceous extinction event.
Chang, Chia-Hao; Shao, Kwang-Tsao; Lin, Yeong-Shin; Tsai, An-Yi; Su, Pin-Xuan; Ho, Hsuan-Ching
The complete mitochondrial genome of the shortfin mako (Isurus oxyrinchus) was determined by using a PCR-based method. The total length of mitochondrial DNA is 16,701 bp and includes 13 protein-coding genes, 2 ribosomal RNA, 22 transfer RNA genes, 1 replication origin region, and 1 control region. The mitochondrial gene arrangement of the tiger tail seahorse is also matching the one observed in the most vertebrate creatures. Base composition of the genome is A (28.8%), T (28.0%), C (28.0%), and G (15.2%) with an A + T rich hallmark as that of other vertebrate mitochondrial genomes.
Franklin, Oliver; Palmer, Colin; Dyke, Gareth
The diverse cartilaginous fish lineage, Batoidea (rays, skates, and allies), sister taxon to sharks, comprises a huge range of morphological diversity which to date remains unquantified and unexplained in terms of evolution or locomotor style. A recent molecular phylogeny has enabled us to confidently assess broadscale aspects of morphology across Batoidea. Geometric morphometrics quantifies the major aspects of shape variation, focusing on the enlarged pectoral fins which characterize batoids, to explore relationships between ancestry, locomotion and habitat. A database of 253 specimens, encompassing 60 of the 72 batoid genera, reveals that the majority of morphological variation across Batoidea is attributable to fin aspect-ratio and the chordwise location of fin apexes. Both aspect-ratio and apex location exhibit significant phylogenetic signal. Standardized independent linear contrast analysis reveals that fin aspect-ratio can predict locomotor style. This study provides the first evidence that low aspect-ratio fins are correlated with undulatory-style locomotion in batoids, whereas high aspect-ratio fins are correlated with oscillatory locomotion. We also show that it is phylogeny that determines locomotor style. In addition, body- and caudal fin-locomotors are shown to exhibit low aspect-ratio fins, whereas a pelagic lifestyle correlates with high aspect-ratio fins. These results emphasize the importance of phylogeny in determining batoid pectoral fin shape, however, interactions with other constraints, most notably locomotor style, are also highlighted as significant.
Porter, Marianne E; Beltrán, Jennie L; Koob, Thomas J; Summers, Adam P
Elasmobranchs, particularly sharks, function at speed and size extremes, exerting large forces on their cartilaginous skeletons while swimming. This casts doubt on the generalization that cartilaginous skeletons are mechanically inferior to bony skeletons, a proposition that has never been experimentally verified. We tested mineralized vertebral centra from seven species of elasmobranch fishes: six sharks and one axially undulating electric ray. Species were chosen to represent a variety of morphologies, inferred swimming speeds and ecological niches. We found vertebral cartilage to be as stiff and strong as mammalian trabecular bone. Inferred swimming speed was a good, but not infallible, predictor of stiffness and strength. Collagen content was also a good predictor of material stiffness and strength, although proteoglycan was not. The mineral fraction in vertebral cartilage was similar to that in mammalian trabecular bone and was a significant predictor of material properties.
Chang, Chia-Hao; Jabado, Rima W; Lin, Yeong-Shin; Shao, Kwang-Tsao
The complete mitochondrial genome of the sand tiger shark consists of 16,773 bp and including 13 protein-coding genes, 2 ribosomal RNA, 22 transfer RNA genes, 1 replication origin region and 1 control region. The mitochondrial gene arrangement of the sand tiger shark is the same as the one observed in most vertebrates. Base composition of the genome is A (31.8%), T (28.7%), C (26.3%) and G (13.2%).
Chang, Chia-Hao; Shao, Kwang-Tsao; Lin, Yeong-Shin; Fang, Yi-Chiao; Ho, Hsuan-Ching
The complete mitochondrial genome of the great white shark having 16,744 bp and including 13 protein-coding genes, 2 ribosomal RNA, 22 transfer RNA genes, 1 replication origin region and 1 control region. The mitochondrial gene arrangement of the great white shark is the same as the one observed in the most vertebrates. Base composition of the genome is A (30.6%), T (28.7%), C (26.9%) and G (13.9%).
Bustamante, C; Vargas-Caro, C; Oddone, M C; Concha, F; Flores, H; Lamilla, J; Bennett, M B
Between 2000 and 2002, three artisanal landing sites were sampled in southern Chile, with data on population structure and reproductive development collected from 5477 yellownose skates Zearaja chilensis. Total length (L(T) ) ranged from 33 to 158 cm for females and 34 to 155 cm for males. No sexual dimorphism was evident in disc size (length or width) or in L(T)-mass relationships. The smallest mature female was 95 cm L(T) and the size at which 50% were mature (L(T50) ) was 109 cm. Males matured between 80 and 90 cm L(T) with a L(T50) of 88 cm. Although the largest Z. chilensis captured by the artisanal fishery was 155 cm L(T) , 89% of landings comprised relatively small, immature fish. This situation may compromise the stock integrity if intrinsic vulnerability and probable long-life span of Z. chilensis are considered. Consequences for the survival of the species and possible signs of a fishery collapse must be reviewed by management authorities by consideration of both artisanal and industrial landings in Chile.
Nakaya, Kazuhiro; Kawauchi, Junro
Sharks of the genus Apristurus from Taiwanese waters are reviewed for the first time, and incorrect scientific names and wrong taxonomic information given in the literature are corrected. After extensive examination of specimens deposited in various museums, universities and fisheries institutions in Taiwan, Japan and China, the following five species are recognized from Taiwanese waters: Apristurus herklotsi (Fowler, 1934), A. longicephalus Nakaya, 1975, A. gibbosus Meng, Chu & Li, 1985, A. macrostomus Chu, Meng & Li, 1985, and A. platyrhynchus (Tanaka, 1909). Apristurus herklotsi, A. longicephalus, A. gibbosus and A. macrostomus are reported from Taiwanese waters for the first time, and the presence of A. platyrhynchus is formally recognized based on a single voucher specimen. Each species is fully described, and a key to the species of Apristurus in Taiwanese waters is provided. Morphological and biological information of each species is also provided.
Soares, Mateus C; de Carvalho, Marcelo R
The superorder Galeomorph comprises the orders Heterodontiformes, Orectolobiformes, Lamniformes, and Carcharhiniformes. Recent morphological and molecular support that it is a monophyletic taxon. The phyletic relationship within the Galeomorphi are also well resolved. However, only few morphological characters of the mandibular and hyoid muscles have been employed, and a detailed description of these muscles and their variations may contribute new interpretations of homology and to the discussion of different hypothesis of intrarelationships. This paper provides a detailed description of mandibular and hyoid arch muscles in galeomorph sharks, within a comparative elasmobranch framework, with the objective to discuss putative homologies that may elucidate our understanding of galeomorph evolution. Twenty-eight galeomorph species were dissected, described, illustrated and compared with other elasmobranchs and with data from the literature. The Galeomorphi are supported as monophyletic by presenting the m. levator labii superioris attached directly to the neurocranium, different from the attachment through a tendon in basal squalomorphs. Heterodontiformes and Orectolobiformes share particular variations in the position and insertion of the m. levator labii superioris and the presence of a well-defined m. levator hyomandibulae. Lamniformes and Carcharhiniformes show similar patterns in the position and attachment of the m. levator labii superioris, subdivision of the m. adductor mandibulae, and the presence of an almost indivisible m. levator hyomandibulae and m. constrictor hyoideus dorsalis, similar to the condition, albeit independently, in basal squalomorphs. No specific mandibular or hyoid arch muscle character was found to support the clade composed of Orectolobiformes, Lamniformes, and Carcharhiniformes, as advocated by recent phylogenetic analyses.
Silva, João Paulo C B Da; Carvalho, Marcelo R De
The Neotropical freshwater stingray Potamotrygom orbignyi (Castelnau, 1855), and other similar "reticulated" species occurring in northern South American basins, were submitted to a thorough taxonomic analysis based on an extensive external and internal morphological study. The identity of P. orbignyi and the taxonomic status of the related nominal species Potamotrygon dumerilii (Castelnau, 1855), Potamotrygon reticulata (Günther, 1880), and Potamotrygon humerosa Garman, 1913, are defined. Taxonomic and morphological analyses revealed that P. reticulata and P. dumerilii fall within the range of variation found in P. orbignyi and were consequently treated as junior synonyms, corroborating previous works. The extensive variation in coloration observed in P. orbignyi could not be divided into consistent morphotypes; P. orbignyi is therefore a widespread species in the upper, mid and lower Amazonas basin, the Orinoco drainage, and in rivers of Suriname and the Guianas. Additionally, P. humerosa and Potamotrygon marinae Deynat, 2007 were found to present characters that support their validity, and are redescribed based on newly collected material. Potamotrygon humerosa occurs predominantly in the mid and lower Amazonas River and in lower reaches of many of its affluents, whereas P. marinae is known only from French Guiana and Suriname. Characters that proved valuable as diagnostic indicators, either in combination or as derived features, are primarily from coloration, dermal denticles and spines (morphology, development and distribution), meristic features (e.g. numbers of tooth rows, vertebrae and mesopterygial radials), morphometric proportions (e.g. snout length, tail width at base and length), and size at sexual maturity.
Chang, Chia-Hao; Shao, Kwang-Tsao; Lin, Yeong-Shin; Chiang, Wei-Chuan; Jang-Liaw, Nian-Hong
Here we describe the complete mitochondrial genome sequence of the megamouth shark, Megachasma pelagios, which is an extremely rare species of deepwater shark. The circle genome (16,694 bp) consists of 13 protein coding, 22 tRNA, 2 rRNA genes and 1 control region. It has the typical vertebrate mitochondrial gene arrangement.
González-Isáis, Mónica; Domínguez, Héctor Marcos Montes
The anatomy of species belonging to the superfamily Myliobatoidea was examined with the aim of better determining their phylogenetic relationships. A wide variation among genera was observed in skeletal anatomy, despite the fact that they all share a common morphological pattern. However, variation among species of the same genus was low, excepting Mobula. Dorsal musculature showed a substantial consistency, except for the epiaxialis muscle, which was larger in rhinopterids and mobulids. Variation in the ventral muscles was low among species of the same genus, but considerable among different genera. Mobulids have a reduction in ventral muscles, while rhinopterids and myliobatoids show an increase in muscular mass. A consensus tree shows a basal split into two groups. The first includes the family Gymnuridae with the genera Gymnura and Aetoplatea; this group is supported by seven synapomorphies, including: 27(1) ceratobranchialis fused proximally, 36(1) anterior lateral processes present in the synarcual, 52(0) quadratomandibularis internal muscle present. The second group is composed of the family Myliobatidae (Myliobatis, Aetomylaeus, Aetobatus, Rhinoptera, Mobula, and Manta), this group is supported by 11 synapomorphies, including: 5(1) first postorbital process fused with the second, 21(1) fused mandibular symphysis, 24(1) first hypobranchial cartilage absent, 48(2) epiaxialis muscle inserted in the cranial orbital region, 73(1) pectoral fins joined behind the orbital region. This study concluded that myliobatoids (Myliobatis, Aetomylaeus, and Aetobatus) integrate a monophyletic group which, unlike other phylogenies previously obtained, is the sister group of rhinopterids (Rhinoptera). Mobulids (Mobula and Manta) are the sister group of myliobatoids-rhinopterids.
Ebert, David A; Ho, Hsuan-Ching; White, William T; De Carvalho, Marcelo R
All 13 orders of chondrichthyan fishes occur in Taiwanese waters, representing 52 chondrichthyan families (31 shark, 19 batoid, 2 chimaeroid) and 98 genera (64 shark, 31 batoid, 3 chimaeroid). A total of 119 shark, 58 batoid, and 4 chimaera species may occur in the waters surrounding Taiwan, pending taxonomic resolution of some groups. Of the 34 nominally described species from Taiwan, 17 are currently considered valid. The majority of named species occurred during two peak periods in Taiwanese chondrichthyan research; the first between 1959-63, when 13 nominal species were described, of which 7 remain valid today, and a second peak period between 2003-13 when 9 nominal species were described, of which 6 remain valid. The overall species diversity of Taiwan's chondrichthyan fauna is comparable to that of other adjacent marine zoogeographic hotspots, e.g. Japan (126 shark, 75 batoid, 11 chimaeroid species) and the Philippines (81 shark, 46 batoid, 2 chimaeroid species). The Carcharhiniformes, Squaliformes, Myliobatiformes, and Rajiformes are the most dominant orders in terms of abundance and species-richness within this region. Each of these groups may increase in relative diversity with improved taxonomic resolution resulting from the incorporation of molecular tools and renewed morphological studies. Improved identification of Taiwan's chondrichthyan fauna will aid in developing better conservation and management practices.
Last, Peter R; Ho, Hsuan-Ching; Chen, Rou-Rong
A new species of wedgefish, Rhynchobatus immaculatus sp. nov., is described from a small collection of specimens obtained from fish markets in northern Taiwan. It is probably a medium-sized species (probably attaining ca. 1.5 m TL) because the largest known specimen, an immature male (ca. I m TL), has prolongated dorsal and caudal fins typical of adult wedgefishes. Rhynchobatus immaculatus is unique within the family in having a very high vertebral count (within the range of 165-170 total free centra) and in lacking a dark pectoral marking. Other Rhynchobatus species occurring in Taiwanese seas appear to attain a larger adult size, possess a dark pectoral marking at least in young, and have lower vertebral counts (fewer than 161 total fee centra). Rhynchobatus yentinesis, which was described from a specimen taken nearby at Wenzhou, China, has not yet been attributed to a currently recognised species. However, based on the illustration of the holotype, which reveals a broad-snouted species with a dark pectoral spot, it is closest to either R. palpebratus or R. springeri.
Timokhina, I. G.; Rodina, O. A.
The thorough investigation of four Frasnian-Famennian (Upper Devonian) boundary sections along the right side of the Tom River northwest of Kemerovo yielded new data on the composition of their foraminiferal and ichthyofaunal assemblages. These data were used for development of the zonal foraminiferal scale for Upper Devonian deposits of the northwestern Kuznetsk coal basin and the first zonal scale for their subdivision on the basis of Elasmobranchii remains and for correlation of the examined sections between each other and with Upper Devonian sequences in other regions. The analysis of foraminiferal and ichthyofaunal assemblages, which are the most widespread in upper Frasnian sections of the northwestern Kuznetsk coal basin, made it possible to specify the regional stratigraphic model.
Ebert, David A; Haas, Diane L; De Carvalho, Marcelo R
A new species of torpedo ray, Tetronarce cowleyi, sp. nov., is described from specimens collected from the southeastern Atlantic Ocean. The new species is placed in the genus Tetronarce based on a uniform dorsal coloration and absence of papillae around the spiracles. The new species is distinguished from its closest congeners, the North Atlantic Tetronarce nobiliana Bonnaparte, 1835, and southwestern Atlantic Tetronarce puelcha Lahille, 1926, by a combination of morphological characteristics including a shorter spiracular length, a proportionally greater head length as measured between snout margin and fifth gill openings, a proportionally greater preoral snout length, a uniform shiny black or dark gray dorsal surface, lacking any prominent markings, and a creamy white ventral color with dark edges in juveniles but fading with growth. Teteronarce cowleyi, sp. nov., is further distinguished from T. nobiliana by its more circular anterior disc shape (vs. relatively straight in T. nobiliana), fewer tooth rows (32/28 vs. 38-53/38-52 in T. nobiliana), greater mouth width (1.5-1.7 times as great as interorbital width vs. 0.5-0.6 times interorbital width in T. nobiliana), smaller distance between second dorsal and caudal fins (3.5-4.9% vs. 6.6-6.8% in T. nobiliana), and a clasper length extending nearly to lower caudal fin origin (claspers in T. nobiliana that extend only two-thirds distance between second dorsal and caudal fins). Teteronarce cowleyi, sp. nov., is known from Walvis Bay, Namibia to Algoa Bay, Eastern Cape, South Africa, at depths of 110 to 457 m.
Laxson, Carrie J; Condon, Nicole E; Drazen, Jeffrey C; Yancey, Paul H
In marine osmoconformers, cells use organic osmolytes to maintain osmotic balance with seawater. High levels of urea are utilized in chondrichthyans (sharks, rays, skates, and chimaeras) for this purpose. Because of urea's perturbing nature, cells also accumulate counteracting methylamines, such as trimethylamine N-oxide (TMAO), at about a 2∶1 urea∶methylamine ratio, the most thermodynamically favorable mixture for protein stabilization, in shallow species. However, previous work on deep-sea teleosts (15 species) and chondrichthyans (three species) found an increase in muscle TMAO content and a decrease in urea content in chondrichthyans with depth. We hypothesized that TMAO counteracts protein destabilization resulting from hydrostatic pressure, as is demonstrated in vitro. Chondrichthyans are almost absent below 3,000 m, and we hypothesized that a limitation in urea excretion and/or TMAO retention might play a role. To test this, we measured the content of major organic osmolytes in white muscle of 13 chondrichthyan species caught with along-contour trawls at depths of 50-3,000 m; the deepest species caught was from 2,165 m. Urea and TMAO contents changed significantly with depth, with urea∶TMAO declining from 2.96 in the shallowest (50-90 m) groups to 0.67 in the deepest (1,911-2,165 m) groups. Urea content was 291-371 mmol/kg in the shallowest group and 170-189 mmol/kg in the deepest group, declining linearly with depth and showing no plateau. TMAO content was 85-168 mmol/kg in the shallowest group and 250-289 mmol/kg in the deepest groups. With data from a previous study for a skate at 2,850 m included, a second-order polynomial fit suggested a plateau at the greatest depths. When data for skates (Rajidae) were analyzed separately, a sigmoidal fit was suggested. Thus, the deepest chondrichthyans may be unable to accumulate sufficient TMAO to counteract pressure; however, deeper-living specimens are needed to fully test this hypothesis.
Guinot, Guillaume; Cappetta, Henri
Modern neoselachian sharks may be separated from more basal relatives by the presence of tooth enameloid comprising three layers. Although enameloid microstructure studies were mostly used in the aim of differentiating supposed basal neoselachians from hybodonts, differences in the enameloid organization among neoselachians have been recognized suggesting the potential for use of enameloid microstructure as a phylogenetic tool within the neoselachian sharks. The enameloid microstructure of five taxa of neoselachian sharks belonging to two orders, the Hexanchiformes and Synechodontiformes, has been studied. The Hexanchiformes are a monophyletic order with extant representatives, whereas the extinct Synechodontiformes have been considered as monophyletic, paraphyletic, or polyphyletic by different authors. This study has revealed numerous new enameloid microstructures such as amalgamated crystallites in the internal units [parallel-bundled enameloid (PBE) and tangled-bundled enameloid], cavities at the shiny-layered enameloid (SLE)/PBE boundary, radial furrows in the PBE, as well as different original organizations at the base of the crown and in the PBE at the level of the cutting edges. Pachyhexanchus pockrandti (Hexanchiforme) and Welcommia bodeuri have the most of the features in common and they share more characters with those of Paraorthacodus sp. and Sphenodus sp. than with Synechodus sp.
Nakaya, Kazuhiro; Inoue, Shinsuke; Ho, Hsuan-Ching
Sharks of the genus Cephaloscyllium from Taiwan were reviewed. After extensive survey of the specimens deposited in useums, universities and fisheries institutions in Taiwan and Japan, the following four species were recognized as valid n Taiwanese waters: C. umbratile Jordan & Fowler, 1903, C. fasciatum Chan, 1966, C. sarawakensis Yano, Ahmad & Gambang, 2005, and C. formosanum Teng, 1962. Cephaloscyllium formosanum is resurrected herein. Four species (C. circulopullum Yano, Ahmad & Gambang, 2005, C. parvum Inoue & Nakaya, 2006, C. pardelotum Schaaf-da Silva & Ebert, 2008, C. maculatum Schaaf-da Silva & Ebert, 2008) are concluded to be junior synonyms. The four valid species here recognized are fully described, and a key to Taiwanese species is provided. The original description of C. formosanum was translated into English from Japanese and is included as an Appendix.
Flammang, Brooke E; Ebert, David A; Cailliet, Gregor M
The genus Apristurus has been divided formerly into three species subgroups based on morphological and molecular phylogenies. Previous studies have agreed on the separation into distinct species groups, the largest two of which have been described as the brunneus and spongiceps groups. An examination of the egg cases produced by these oviparous catsharks corroborates the distinction in species groups: egg cases of the brunneus group have long fibrous and curly tendrils at either end, whereas egg cases of the spongiceps group lack tendrils. The egg cases of A. kampae, A. manis, A. spongiceps and Apristurus sp. D are described for the first time, and the egg cases of A. brunneus and A. riveri are re-described to include comparable morphological characteristics. The ecological implications of egg case morphology on oviposition and ventilation are also discussed.
Chang, Chia-Hao; Jang-Liaw, Nian-Hong; Lin, Yeong-Shin; Carlisle, Aaron; Hsu, Hua Hsun; Liao, Yun-Chih; Shao, Kwang-Tsao
The complete mitochondrial genome of the salmon shark consists of 16,699 bp and includes 13 protein-coding genes, 2 ribosomal RNA genes, 22 transfer RNA genes, 1 replication origin region and 1 control region. The mitochondrial gene arrangement of the salmon shark is the same as that of most vertebrates. Base composition of the genome is A (29.6%), T (28.6%), C (27.1%), and G (14.8%).
Li, Chenhong; Matthes-Rosana, Kerri A; Garcia, Michael; Naylor, Gavin J P
Erroneous estimates of ingroup relationships can be caused by attributes in the outgroup chosen to root the tree. Phylogenetic analyses of DNA sequences frequently yield incorrect estimates of ingroup relationships when the outgroup used to "root" the tree is highly divergent from the ingroup. This is especially the case when the outgroup has a different base composition than the ingroup. Unfortunately, in many instances, alternative less divergent outgroups are not available. In such cases, investigators must either target genes with attributes that minimize the problem (slowly evolving genes with stationary base compositions--which are often not ideal for estimating relationships among the more closely related ingroup taxa) or use inference models that are explicitly tailored to deal with an attenuated historical signal with a superimposed non-stationary base composition. In this paper we explore the problem both empirically and through simulation. For the empirical component we looked at the phylogenetic relationships among elasmobranch fishes (sharks and rays), a group whose closest living outgroup, the holocephalan Ghost fishes, are separated from the elasmobranchs by more than 100 million years of evolution. We compiled a data set for analysis comprising 10 single-copy nuclear protein-coding genes (12,096 bp) for representatives of the major lineages within elasmobranchs and holocephalans. For the simulation, we used an evolutionary model on a fixed tree topology to generate DNA sequence data sets which varied both in their distance to the outgroup, and in their base compositional difference between ingroup and outgroup. Results from both the empirical data set and the simulation, support the idea that deviation from base compositional stationarity, in conjunction with distance from the root can act in concert to compromise accuracy of estimated relationships within the ingroup. We tested several approaches to mitigate such problems. We found, that excluding genes with overall faster rates and heterogeneous base compositions, while the least sophisticated of the methods evaluated, seemed to be the most effective.
Chang, Chia-Hao; Chiang, Wei-Chuan; Lin, Yeong-Shin; Jang-Liaw, Nian-Hong; Shao, Kwang-Tsao
Here we describe the complete mitochondrial genome sequence of the longfin mako, Isurus paucus, which is a pelagic shark found in temperate and tropical waters. The circle genome (16,704 bp) consists of 13 protein coding, 22 tRNA, 2 rRNA genes and 1 control region. It has the typical vertebrate mitochondrial gene arrangement.
Duncan, Wallice Paxiúba; da Costa, Oscar Tadeu Ferreira; Sakuragui, Marise Margareth; Fernandes, Marisa Narciso
The gill morphologies of six species of potamotrygonid freshwater stingrays from the Amazon basin were investigated using light and electron microscopy. Some unique features were found in the potamotrygonid gill: (1) fingerlike protuberances on the gill filament, (2) an Alcian blue/periodic acid-Schiff-positive histochemical reaction for several cell layers in the gill epithelium (except the basal ones), (3) pavement cells with numerous subapical mucous vesicles, (4) very large mucous cells, and (5) follicular Na(+)/K(+)-ATPase-rich (NKA-rich) mitochondria-rich cells (MRCs) in Potamotrygon sp. (known as the cururu ray). The fingerlike protuberances may constitute an additional resistance to water flow, helping to drive water through the lamellae. The secretion of a mucous substance by the pavement cells and mucous cells may help to protect the gills against mechanical injury and pathogens and aid in osmoregulation in the dilute water of the Amazon basin. All MRCs possess enfolded basolateral membranes and have poorly developed or absent tubular systems. NKA-rich MRCs are located high in the basolateral membrane. The cururu ray, which is endemic to the Rio Negro, has follicular NKA-rich MRCs (8-12 cells in cross section) that share the same apical pit in the filament; this may be considered to be an autapomorphy. The combination of these branchial characteristics may have favored tolerance to the freshwater environment during the evolution and diversification of potamotrygonids throughout the Amazon basin.
Castro-Aguirre, José Luis; Espinosa Pérez, Héctor; Huidobro Campos, Leticia
Two undescribed species of the genus Squatina, caught by bottom-trawl during the OGMEX VIII, IX and PROBEMEX II oceanographic cruises were compared with S. dumeril Lesueur, 1818, the only well known species from the northern Gulf of Mexico. The collections were made off Tamaulipas, Veracruz and Tabasco. The descriptions of the new species refer to morphology, coloration pattern and dorsal fin shape and size. An English description of each species is included. Some specimens erroneously assigned to S. dumeril are deposited in Mexican collections. With these two new species, besides S. californica Ayres, 1859 and S. dumeril, the number of documented species of this genus in Mexico ascends to four, and a total of five are known from the western Atlantic. A key is provided for their identification.
Kim, Il-Chan; Jung, Sang-Oun; Lee, Young-Mi; Lee, Chang Joo; Park, Joong-Ki; Lee, Jae-Seong
We isolated mitochondrial DNA from the rayfish Raja porosa by long-polymerase chain reaction (Long-PCR) with conserved primers, and sequenced it by primer walking method using flanking sequences as sequencing primers. R. porosa mitochondrial DNA consists of 16,972 bp and its structural organization is conserved in comparison with other fishes and mammals. Based on the mitochondrial cytochrome b (cyt b) sequence, the phylogenetic position of R. porosa among cartilaginous fishes was inferred using different phylogenetic methods (ML-based quartet puzzling, Neighbor-joining (NJ) and Bayesian approaches). In this paper, we report the characteristics of the R. porosa mitochondrial genome including structural organization, base composition of rRNAs, tRNAs and protein-encoding genes and characteristics of mitochondrial tRNAs. These findings are applicable to comparative mitogenomics of R. porosa with other related taxa.
Campbell, R A; Andrade, M
Echinobothrium raschii n. sp. from the spiral intestine of Rhinoraja longi in the Bering Sea, off the Aleutian Islands of Alaska is described. On the basis of the armature of the rostellum and cephalic peduncle the new species most closely resembles Echinobothrium acanthinophyllum, Echinobothrium acanthocolle, Echinobothrium coronatum and Echinobothrium helmymohamedi. Echinobothrium raschii n. sp. can be differentiated from all but E. coronatum by the possession of a continuous row of 27-36 lateral hooklets per side on the scolex and 21-26 spines per row on the cephalic peduncle. In E. acanthinophyllum there are fewer spines per row on the cephalic peduncle (13) and only 2 groups of 4 lateral hooklets per side instead of a continuous row of lateral hooklets; E. acanthocolle bears only 5 spines per row on the cephalic peduncle and has no lateral hooklets; E. helmymohamedi has 10-12 spines per row on the cephalic peduncle and bears no lateral hooklets. Echinobothrium raschii n. sp. can be distinguished from E. coronatum by number of spines per row on the cephalic peduncle (average 24 vs. 32) and testes number (17-23 vs. 9-11). The combined characters of 2 groups of 23-25 large apical hooks, a continuous alternating row of 27-36 hooklets on each side of the scolex between the groups of large apical hooks, 21-26 spines per row on the cephalic peduncle, and 17-23 testes per segment differentiates E. raschii from all other species of Echinobothrium. The prevalence of infection was 50% and mean intensity of infection was 8.7 worms per host. The current status of the genus Echinobothrium is discussed and a tabulation of the species presented.
Iwahori, N; Kawawaki, T; Baba, J
The neuronal organization of the spinal cord in red stingray was studied using the rapid Golgi method. The gray matter of the spinal cord was divided into seven laminae: RS-I, RS-II, RS-III, RS-IV, RS-V, RS-VI and RS-VII. RS-I is cell dense lamina which occupies the major part of the dorsal horn and corresponds to laminae I and II of the spinal cord of mammals, birds and reptiles. The neurons of the lamina I are interspersed with those of lamina II, without forming a discrete lamina. RS-II is located at the base of the dorsal horn and is considered to correspond to the nucleus proprius. RS-III and IV form the intermediate zone and are highly reticulated. A few neurons of various shapes and sizes are distributed among the numerous fibers. The nuclei such as the intermediolateral, intermediomedial or Clarke's nucleus cannot be identified in the intermediate zone. RS-V and VI constitute the ventral horn. RS-V occupies the major part of the ventral horn and contains motoneurons which are distributed diffusely, without forming any distinct cell groups. RS-VI is located in the ventromedial part of the ventral horn, contains commissural neurons and correspond to lamina VIII. RS-VII is a small area surrounding the central canal and corresponds to lamina X. Thus, while the major features of the spinal cord of the red stingray can be correlated with those of the spinal cord of mammals, birds and reptiles, the neuronal organization of the spinal cord of the red stingray remains in an undifferentiated state.
Zamparo, D; Brooks, D R; Barriga, R
A new species of tetraphyllidean eucestode inhabiting Urobatis tumbesensis from inshore waters of southeastern Ecuador shares 3 synapomorphies with Rhinebothroides spp.: apical bothridial suckers poorly differentiated from the marginal loculi, internal seminal vesicles, and insertion of the vas deferens dorsally closer to the poral than the aporal end of the cirrus sac. The new species differs from Rhinebothroides spp. by lacking medial bothridial septa and loculi and having symmetrical ovarian arms, and possesses an apparent autapomorphic trait by having the vas deferens tapering to a narrow tube before entering the cirrus sac, extending posteriorly to the posterior end of the cirrus sac where it expands into an external seminal vesicle running ventral to the cirrus sac anteriorly to anterior to the vagina. In Rhinebothroides spp., the vas deferens is expanded into an external seminal vesicle near the insertion into the cirrus sac As the sister group of Rhinebothroides, we propose a new genus to accommodate the new species. Phylogenetic evaluation of phyllobothriids recently assigned to Anthocephalum shows that they represent a paraphyletic assemblage of species of varying degrees of relatedness to Rhinebothroides spp. and the new species. Uncovering the relationships of the new species and the various species assigned to Anthocephalum permitted reevaluation of character transformations used in previous phylogenetic analysis of Rhinebothroides. Transformation series for 3 characters, previously based on functional outgroup comparisons, changed and a new character, length of cirrus sac, was added. The new phylogenetic analysis differs from the previous hypothesis only in placing R. scorzai as the sister species of R. circularisi + R. venezuelae + R. moralarai rather than of R. freitasi + R. glandularis + R. mclennanae. The occurrence of the sister species of Rhinebothroides in a Pacific Ocean stingray adds additional support to the hypothesis of Pacific origins of South American freshwater stingrays.
Miyake, T; Vaglia, J L; Taylor, L H; Hall, B K
Patterning, cellular differentiation, and developmental sequences of dermal denticles (denticles) are described for the skate Leucoraja erinacea. Development of denticles proceeds caudo-rostrally in the tail and trunk. Once three rows of denticles form in the tail and trunk, denticles begin to appear in the region of the pelvic girdle, medio-caudal to the eyes and on the pectoral fins. Although timing of cellular differentiation of denticles differs among different locations of the body, cellular development of a denticle is identical in all locations. Thickening of the epidermis as a denticle lamina marks initiation of development. A single lamina for each denticle forms, and a small group of mesenchymal cells aggregates underneath it. The lamina then invaginates caudo-rostrally to form the inner- and outer-denticle epithelia (IDE and ODE, respectively). Before nuclei of IDE cells are polarized, enameloid matrix appears between the basement membrane of the IDE and the apical surface of the pre-odontoblasts. Pre-dentin is then laid down along with collagenous materials. Von Kossa stain visualizes initial mineralization of dentin, but not enameloid. During the growth of a denticle, dense fibrous connective tissue of the dermis forms the deep dermal tissue over the dorsal musculature. Attachment fibers and tendons anchor denticles and dorsal musculature, respectively, on deep dermal tissue. Basal tissue of the denticles develops as the denticle crown grows. If the basal tissue is bone of attachment, then the cells along the basal tissue would be osteoblasts. However, these cells could not be distinguished from odontoblasts using immunolocalization of type I pro-collagen (Col I), alkaline phosphatase (APase), and neural cell adhesion molecule (N-CAM). Well-developed dentin, (not pre-dentin), the enameloid matrix (probably when it begins to mineralize), and deep dermal tissue are Verhoeff stain-positive, suggesting that these tissues contain elastin and/or elastin-like molecules. Our study demonstrates that the cellular development of denticles resembles tooth development in elasmobranchs, but that dermal denticles differ from teeth in forming from a single denticle lamina. Whether the basal tissue of denticles is bone of attachment remains undetermined. Confirmation and function of Verhoeff-positive proteins in enameloid, dentin, and deep dermal tissue remain to be determined. We discuss these issues along with an analysis of recent findings of enamel and enameloid matrices.
Marguee, F; Brooks, D R; Barriga, R
Six species of Acanthobothrium, 4 described as new, are reported in stingrays from southern Ecuador. Acanthobothrium atahualpai n. sp. in Gymnura afuerae most closely resembles Acanthobothrium fogeli and Acanthobothrium parviuncinatum by having bothridial hooks with recurved prongs and short handles. It differs from A. fogeli by having bothridial hooks 163-195 microns vs. 78-114 microns long and averaging 25 vs. 32 testes per pruglottis: it differs from A. parviuncinatum by having bothridial hooks 163-195 microns vs. 87 microns long and averaging 25 vs. 13 testes per proglottis. Acanthobothrium minusculus n. sp. in Urolophus tumbesensis most resembles Acanthobothrium campbelli and Acanthobothrium vargasi by being no more than 3 mm long and having 6-30 testes per proglottis. It can be distinguished from them by having bothridial hooks averaging 86 microns vs. 108-111 microns and 130-133 microns long, and 6-10 vs. 15-23 and 22-29 testes per proglottis, respectively. Acanthobothrium monksi n. sp. in Aetobatus narinari resembles Acanthobothrium tasajerasi from Himantura schmardae by having a prominent genital atrium and a large globose cirrus sac; it differs by averaging 21 vs. 35 testes per proglottis and having bothridial hooks averaging 150 microns vs. 165 microns long. Acanthobothrium obuncus n. sp. in Dasyatis longus resembles a group of species characterized by wider than long to square immature and mature proglottides, bothridia at least partially fused to the scolex at their posterior ends, and asymmetrical ovarian arms with aporal arms extending anteriorly to the vaginal level. It resembles Acanthobothrium americanum by averaging 73 vs. 72 testes per proglottis, but differs by having bothridial hooks averaging 120-131 microns vs. 151 microns long; it resembles Acanthobothrium chilensis by having bothridial hooks averaging 120-131 microns vs. 130 microns long, but differs by averaging 73 vs. 90 testes per proglottis. Acanthobothrium campbelli in Urotrygon chilensis and Acanthobothrium costarricense in Dasyatis longus, previously known in those hosts from the Pacific coast of Costa Rica, are reported from Ecuador for the first time.
Vélez-Zuazo, Ximena; Agnarsson, Ingi
Sharks are a diverse and ecologically important group, including some of the ocean's largest predatory animals. Sharks are also commercially important, with many species suffering overexploitation and facing extinction. However, despite a long evolutionary history, commercial, and conservation importance, phylogenetic relationships within the sharks are poorly understood. To date, most studies have either focused on smaller clades within sharks, or sampled taxa sparsely across the group. A more detailed species-level phylogeny will offer further insights into shark taxonomy, provide a tool for comparative analyses, as well as facilitating phylogenetic estimates of conservation priorities. We used four mitochondrial and one nuclear gene to investigate the phylogenetic relationships of 229 species (all eight Orders and 31 families) of sharks, more than quadrupling the number of taxon sampled in any prior study. The resulting Bayesian phylogenetic hypothesis agrees with prior studies on the major relationships of the sharks phylogeny; however, on those relationships that have proven more controversial, it differs in several aspects from the most recent molecular studies. The phylogeny supports the division of sharks into two major groups, the Galeomorphii and Squalimorphii, rejecting the hypnosqualean hypothesis that places batoids within sharks. Within the squalimorphs the orders Hexanchiformes, Squatiniformes, Squaliformes, and Pristiophoriformes are broadly monophyletic, with minor exceptions apparently due to missing data. Similarly, within Galeomorphs, the orders Heterodontiformes, Lamniformes, Carcharhiniformes, and Orectolobiformes are broadly monophyletic, with a couple of species 'misplaced'. In contrast, many of the currently recognized shark families are not monophyletic according to our results. Our phylogeny offers some of the first clarification of the relationships among families of the order Squaliformes, a group that has thus far received relatively little phylogenetic attention. Our results suggest that the genus Echinorhinus is not a squaliform, but rather related to the saw sharks, a hypothesis that might be supported by both groups sharing 'spiny' snouts. In sum, our results offer the most detailed species-level phylogeny of sharks to date and a tool for comparative analyses.
Huang, Wei; Hongjamrassilp, Watcharapong; Jung, Jae-Young; Hastings, Philip A; Lubarda, Vlado A; McKittrick, Joanna
Animal propulsion systems are believed to show high energy and mechanical efficiency in assisting movement compared to artificial designs. As an example, batoid fishes have very light cartilaginous skeletons that facilitate their elegant swimming via enlarged wing-like pectoral fins. The aim of this work is to illustrate the hierarchical structure of the pectoral fin of a representative batoid, the Longnose Skate (Raja rhina), and explain the mechanical implications of its structural design. At the macro level, the pectoral fins are comprised of radially oriented fin rays, formed by staggered mineralized skeletal elements stacked end-to-end. At the micro level, the midsection of each radial element is composed of three mineralized components, which consist of discrete segments (tesserae) that are mineralized cartilage and embedded in unmineralized cartilage. The radial elements are wrapped with aligned, unmineralized collagen fibers. This is the first report of the detailed structure of the ray elements, including the observation of a 3-chain mineralized tesserae. Structural analyses demonstrate that this configuration enhances stiffness in multiple directions. A two-dimensional numerical model based on the morphological analysis demonstrated that the tessera structure helps distributing shear, tensile and compressive stress more ideally, which can better support both lift and thrust forces when swimming without losing flexibility.
Underwood, Charlie J.; Johanson, Zerina; Welten, Monique; Metscher, Brian; Rasch, Liam J.; Fraser, Gareth J.; Smith, Moya Meredith
Shark and ray (elasmobranch) dentitions are well known for their multiple generations of teeth, with isolated teeth being common in the fossil record. However, how the diverse dentitions characteristic of elasmobranchs form is still poorly understood. Data on the development and maintenance of the dental patterning in this major vertebrate group will allow comparisons to other morphologically diverse taxa, including the bony fishes, in order to identify shared pattern characters for the vertebrate dentition as a whole. Data is especially lacking from the Batoidea (skates and rays), hence our objective is to compile data on embryonic and adult batoid tooth development contributing to ordering of the dentition, from cleared and stained specimens and micro-CT scans, with 3D rendered models. We selected species (adult and embryonic) spanning phylogenetically significant batoid clades, such that our observations may raise questions about relationships within the batoids, particularly with respect to current molecular-based analyses. We include developmental data from embryos of recent model organisms Leucoraja erinacea and Raja clavata to evaluate the earliest establishment of the dentition. Characters of the batoid dentition investigated include alternate addition of teeth as offset successional tooth rows (versus single separate files), presence of a symphyseal initiator region (symphyseal tooth present, or absent, but with two parasymphyseal teeth) and a restriction to tooth addition along each jaw reducing the number of tooth families, relative to addition of successor teeth within each family. Our ultimate aim is to understand the shared characters of the batoids, and whether or not these dental characters are shared more broadly within elasmobranchs, by comparing these to dentitions in shark outgroups. These developmental morphological analyses will provide a solid basis to better understand dental evolution in these important vertebrate groups as well as the general plesiomorphic vertebrate dental condition. PMID:25874547
Gillis, J Andrew; Dahn, Randall D; Shubin, Neil H
Chondrichthyan fishes possess visceral skeletons that differ considerably, morphologically, from those of their sister taxon, the osteichthyans. Here, we use histological techniques and whole-mount skeletal preparations to visualize and describe the sequence of visceral skeletal condensation and chondrogenesis in a chondrichthyan, the little skate (Leucoraja erinacea). We demonstrate that visceral skeletal condensation begins rostrally, with the mandibular arch, and progresses caudally with the hyoid arch and posterior branchial arches condensing soon after. We provide a detailed account of the condensation and chondrogenesis of all major components of the L. erinacea visceral skeleton and discuss these data in the context of what is known from classical descriptions of chondrichthyan visceral skeletal development. Significant differences exist between the hypobranchial and basibranchial skeleton of L. erinacea and other chondrichthyan species, and the possible evolutionary and developmental significance of this is considered. We discuss the homology of the chondrichthyan hyoid arch and, based on patterns of mesenchymal condensation, we propose a model of condensation splitting and diversification that may account for the morphological diversification of gnathostome branchial arch derivatives. Finally, we suggest that the unique presence of certain visceral skeletal elements in chondrichthyans make oviparous chondrichthyans an ideal system for addressing questions of endoskeletal axial patterning during development.
Underwood, Charlie J; Johanson, Zerina; Welten, Monique; Metscher, Brian; Rasch, Liam J; Fraser, Gareth J; Smith, Moya Meredith
Shark and ray (elasmobranch) dentitions are well known for their multiple generations of teeth, with isolated teeth being common in the fossil record. However, how the diverse dentitions characteristic of elasmobranchs form is still poorly understood. Data on the development and maintenance of the dental patterning in this major vertebrate group will allow comparisons to other morphologically diverse taxa, including the bony fishes, in order to identify shared pattern characters for the vertebrate dentition as a whole. Data is especially lacking from the Batoidea (skates and rays), hence our objective is to compile data on embryonic and adult batoid tooth development contributing to ordering of the dentition, from cleared and stained specimens and micro-CT scans, with 3D rendered models. We selected species (adult and embryonic) spanning phylogenetically significant batoid clades, such that our observations may raise questions about relationships within the batoids, particularly with respect to current molecular-based analyses. We include developmental data from embryos of recent model organisms Leucoraja erinacea and Raja clavata to evaluate the earliest establishment of the dentition. Characters of the batoid dentition investigated include alternate addition of teeth as offset successional tooth rows (versus single separate files), presence of a symphyseal initiator region (symphyseal tooth present, or absent, but with two parasymphyseal teeth) and a restriction to tooth addition along each jaw reducing the number of tooth families, relative to addition of successor teeth within each family. Our ultimate aim is to understand the shared characters of the batoids, and whether or not these dental characters are shared more broadly within elasmobranchs, by comparing these to dentitions in shark outgroups. These developmental morphological analyses will provide a solid basis to better understand dental evolution in these important vertebrate groups as well as the general plesiomorphic vertebrate dental condition.
Carvalho, Marcelo R De; White, William T
A new species of numbfish, Narcine baliensis, sp. nov., is described from the tropical eastern Indian Ocean from Indonesia. It is superficially similar to N. brevilabiata and N. atzi in aspects of its color pattern, but is distinguished from both congeners in details of its color pattern, in tooth band morphology, and in proportions of its dorsal fins, among other features. Narcine baliensis, sp. nov., is unique in having a dorsal color pattern composed of large, circular, ovoid or elongate dark brown spots or blotches on dorsal disc along with more numerous small (about eye-sized or slightly greater) brownish, subcircular spots, with large blotches and small spots surrounded by a very slender creamy-white pattern, as well as in having broadly circular upper and lower tooth bands of about the same width and shape. The genus Narcine is now composed of 20 valid species, but uncertainty remains concerning the identification and morphological variation of some of its species in the tropical Indo-West Pacific region.
Collin, Shaun P
As apex predators, chondrichthyans, or cartilaginous fishes, hold an important position within a range of aquatic ecosystems and influence the balance between species' abundance and biodiversity. Having been in existence for over 400 million years and representing the earliest stages of the evolution of jawed vertebrates, this group also covers a diverse range of eco-morphotypes, occupying both marine and freshwater habitats. The class Chondrichthyes is divided into two subclasses: the Elasmobranchii (sharks, skates, and rays) and the Holocephali (elephant sharks and chimaeras). However, many of their life history traits, such as low fecundity, the production of small numbers of highly precocious young, slow growth rates, and late maturity, make them highly susceptible to human exploitation. To mitigate the negative effects of human impacts, it is important that we understand the sensory strategies that elasmobranchs use for navigating within their environment, forming reproductive aggregations, feeding, and even communicating. One approach to investigate the sensory bases of their behavior is to examine the peripheral sense organs mediating vision, olfaction, gustation, lateral line, electroreception, and audition in a large range of species in order to identify specific adaptations, the range of sensitivity thresholds, and the compromise between sensory spatial resolution and sensitivity. In addition, we can quantitatively assess the convergence of sensory input to the central nervous system and the relative importance of different sensory modalities. Using a comparative approach and often a combination of anatomical, electrophysiological, and molecular techniques, significant variation has been identified in the spatial and chromatic sampling of the photoreceptors in the eye, the surface area and the number of olfactory lamellae within the nasal cavity, the level of gustatory sampling within the oral cavity, the type and innervation of neuromasts of the lateral
Kawauchi, Junro; Weigmann, Simon; Nakaya, Kazuhiro
A new deep-water catshark of the genus Apristurus Garman, 1913 is described based on nine specimens from the Gulf of Aden in the northwestern Indian Ocean. Apristurus breviventralis sp. nov. belongs to the 'brunneus group' of the genus and is characterized by having pectoral-fin tips reaching beyond the midpoint between the paired fin bases, a much shorter pectoral-pelvic space than the anal-fin base, a low and long-based anal fin, and a first dorsal fin located behind pelvic-fin insertion. The new species most closely resembles the western Atlantic species Apristurus canutus, but is distinguishable in having greater nostril length than internarial width and longer claspers in adult males. Apristurus breviventralis sp. nov. represents the sixth species of Apristurus from the western Indian Ocean and the 38th species globally.
Katsu, Yoshinao; Kohno, Satomi; Narita, Haruka; Urushitani, Hiroshi; Yamane, Koudai; Hara, Akihiko; Clauss, Tonya M; Walsh, Michael T; Miyagawa, Shinichi; Guillette, Louis J; Iguchi, Taisen
Sex-steroid hormones are essential for normal reproductive activity in both sexes in all vertebrates. Estrogens are required for ovarian differentiation during a critical developmental stage and promote the growth and differentiation of the female reproductive system following puberty. Recent studies have shown that environmental estrogens influence the developing reproductive system as well as gametogenesis, especially in males. To understand the molecular mechanisms of estrogen actions and to evaluate estrogen receptor-ligand interactions in Elasmobranchii, we cloned a single estrogen receptor (ESR) from two shark species, the cloudy catshark (Scyliorhinus torazame) and whale shark (Rhincodon typus) and used an ERE-luciferase reporter assay system to characterize the interaction of these receptors with steroidal and other environmental estrogens. In the transient transfection ERE-luciferase reporter assay system, both shark ESR proteins displayed estrogen-dependent activation of transcription, and shark ESRs were more sensitive to 17beta-estradiol compared with other natural and synthetic estrogens. Further, the environmental chemicals, bisphenol A, nonylphenol, octylphenol and DDT could activate both shark ESRs. The assay system provides a tool for future studies examining the receptor-ligand interactions and estrogen disrupting mechanisms in Elasmobranchii.
Viana, Sarah T De F; Carvalho, Marcelo R De; Gomes, Ulisses L
Squalus is a genus of reportedly cosmopolitan shark species that have a high taxonomic complexity due to difficulties in their morphological differentiation; many of its species need revision. Currently, there are 26 valid species of Squalus, which have been divided into three species-groups according to overall morphological similarity, the S. acanthias, S. megalops, and S. mitsukurii groups. Loss of type specimens, propagation of erroneous identifications in the literature, and difficulties in obtaining representative series for comparison are secondary challenges that have impeded a global taxonomic revision of the genus. This problem applies clearly to species from the Southwestern Atlantic Ocean, including species that occur off Brazil. Following a current global tendency, a regional taxonomic revision of Squalus was conducted in order to investigate which species are valid in the Southwestern Atlantic Ocean and provide diagnostic morphological characters that can be efficiently used for identifying species. Comparative detailed analysis of external (e.g. morphometrics, dentition, and color pattern) and skeletal morphology (primarily meristic data, neurocrania and claspers) of specimens of Squalus from the region revealed four new species that are herein described (S. albicaudus sp. nov., S. bahiensis sp. nov., S. lobularis sp. nov., and S. quasimodo sp. nov.), as well as S. acanthias, which is redescribed from the region based on new material. Comparisons are offered based on examinations of congeneric species; this work is part of a global systematic revision of Squalus.
This article describes the anatomy of the dorsal and ventral cephalic musculature of Gymnura marmorata, G. micrura, Aetobatus narinari, Myliobatis californica, M. longirostris, Rhinoptera steindachneri, Mobula munkiana, and M. thurstoni. It was observed that muscles of the dorsal cephalic region showed little variation among species, with the exception of the dorsal longitudinal bundles and the cucullaris muscle. The ventral cephalic musculature showed wider differences, mainly in the depressor hyomandibulae, coracomandibularis, and mandibular adductor muscles. M. munkiana and M. thurstoni revealed a significant muscle reduction, while M. californica, M. longirostris, A. narinari, and R. steindachneri showed a significant development of the ventral cephalic musculature. The species in this comparative study were clearly grouped based on their feeding habits. Data gathered on the muscle arrangements correspond to other taxonomy studies conducted on these groups. However, the results of this study agree only partially with those from previously described phylogenetic models. Therefore, further phylogenetic research is recommended.
Egan, Aaron; Fox, Jennifer; Greenfield, Adam; Mariani, Stefano
Skates are widely consumed across the globe, but many large species are subject to considerable concern regarding their conservation and management. Within Europe such issues have recently driven policy changes so that, for the first time, reports of skate landings now have to be made under species-specific names. Total allowable catches have also been established for many groups, which have been set to zero for a number of the most vulnerable species (e.g., Dipturus batis, Raja undulata and Rostoraja alba). Whilst accurate species identification has become an important issue for landings, the sale of skates is still usually made under a blanket term of “skate” or “ray”. The matter of identifying species of skate is further complicated by their morphologically conservative nature and the fact that they are commercially valued for their wings. Thus, before sale their bodies are usually discarded (i.e., “winged”) and often skinned, making morphological identification impossible. For the first time, DNA barcoding (of the mitochondrial COI gene) was applied to samples of skate wings from retail outlets across the British Isles, providing insight into which species are sold for consumption. A total of 98 wing samples were analysed, revealing that six species were sold; blonde ray (Raja brachyura), spotted ray (Raja montagui), thornback ray (Raja clavata), cuckoo ray (Leucoraja naevus) small-eyed ray (Raja microocellata) and shagreen ray (Leucoraja fullonica). Statistical testing demonstrated that there were significant differences in the species sold in the distinct retail groups which suggests complex drivers behind the patterns of sale in skates. The results also indicate that endangered species are not commonly being passed on to consumers. In addition, the practice of selling skate wings under ambiguous labels is highlighted as it makes it extremely difficult for consumers to exercise a right to avoid species of conservation concern. Interestingly, a single retailer chain labelled their wings as originating from three smaller-growing species (generally to be considered of lower conservation concern); of the six samples analysed from this company a third were mislabelled and originated from the thornback ray (a larger species that is currently undergoing population declines). PMID:24024082
Shen, Kang-Ning; Chang, Chih-Wei; Tsai, Shiou-Yi; Wu, Shan-Chun; Lin, Zi-Han; Chan, Yen-Fan; Chen, Ching-Hung; Hsiao, Chung-Der; Borsa, Philippe
The Leopard whipray (Himantura leoparda) and Blue-spotted stingray (Neotrygon kuhlii) are distributed in the Indian and West Pacific Ocean and considered as complex species based on morphological and molecular evidences. In this study, we used the next-generation sequencing method to decode two complete mitogenomes of H. leoparda and N. kuhlii. The assembled mitogenome, consisting lengths of 17,690 bp for H. leoparda and 17,974 bp for N. kuhlii, shows 78% identity to each other. Both mitogenomes follow the typical vertebrate arrangement, including 13 protein-coding genes, 22 transfer RNAs, 2 ribosomal RNAs genes and a non-coding control region of D-loop. D-loop with the lengths 1931 bp (H. leoparda) and 2243 bp (N. kuhlii) is located between tRNA-Pro and tRNA-Phe. The overall GC content is 40.3% for H. leoparda and 39.8% for N. kuhlii. The complete mitogenome of H. leoparda and N. kuhlii provides essential and important DNA molecular data for further phylogenetic and evolutionary analyses for stingray species complex.
Lameiras, Juliana Luiza Varjão; da Costa, Oscar Tadeu Ferreira; Moroni, Fábio Tonissi; Araújo, José de Ribamar; Caranhas, Sandra Maria Evangelista; Marques, Carlos Melquiades Almeida; Dos-Santos, Maria Cristina; Duncan, Wallice Luiz Paxiúba
Injuries caused by freshwater stingrays are characterized by intense pain and pathological changes at the lesion site, including oedema, erythema and, in most cases, necrosis. In this study, the systemic myotoxic activity induced by mucus extracts from the dorsal region and stinger of the stingrays Plesiotrygon iwamae and Potamotrygon motoro was described, analysed and quantified. Twenty-four hours after injection of 400 μg of the extracts into the gastrocnemius muscle of mice, the following effects were observed: coagulative necrosis of the muscle tissue, muscle fibre regeneration and the presence of inflammatory infiltrates, including neutrophils, macrophages, and a reduced number of eosinophils and lymphocytes. These changes were also observed, although to a lesser extent, in the gastrocnemius muscles of the contralateral limbs, demonstrating that the extracts from the two species could induce systemic rhabdomyolysis. Based on morphometric analysis, it was observed that the stinger extract of P. motoro was more potent in inducing local and systemic myotoxic activity, followed by the dorsal extract from P. motoro and stinger and dorsal extracts from P. iwamae, which induced similar effects.
González-Solís, David; Ali, Atheer H
The nematode Paraleptus chiloscyllii Yin et Zhang, 1983 (Physalopteridae) is redescribed on the basis of new material collected from the stomach of the Arabian carpetshark Chiloscyllium arabicum Gubanov (Hemiscylliidae) from marine waters off Iraq. Originally, P. chiloscyllii was found in C. plagiosum (Anonymous [Bennett]) from Fujian, China, but its description was rather poor and some important morphological features, such as deirids, shape and number of structures surrounding mouth, ventral unpaired papilla on the anterior cloacal lip, among others, were overlooked. It differs from its congeners in the shape of spicules and body length, although is very similar to the type species, P. scyllii Wu, 1927, only differing in the inequality of spicules. The generic diagnosis of Paraleptus was amended. Paraleptus minnanensis (Damin et Heqing, 2001) is considered a junior synonym of P. chiloscyllii and some morphological details of the posterior end of a male of P. australis Johnston et Mawson, 1943 are provided. The present finding of P. chiloscyllii in C. arabicum from off Iraq represents new host and geographical records.
Menoret, Adriana; Ivanov, Verónica A
Rhinebothrium paranaensis n. sp. (Tetraphyllidea: Cestoda) is described from the freshwater stingray Potamotrygon falkneri collected in the Colastiné River, a tributary to the Lower Parana River in Argentina. The specimens were studied in detail using light and scanning electron microscopy and histology. Rhinebothrium paranaensis can be distinguished from all valid species in the genus using the following combination of characters: worm length, number of proglottids, diamond-shaped bothridia lacking constriction, number of loculi on the distal surface of bothridium, and the lack of vaginal sphincter and external seminal vesicle.
Almeida, M P; Lins, P M O; Charvet-Almeida, P; Barthem, R B
The stomach contents of 137 examples of Potamotrygon motoro caught in 3 locations (Muaná, Afuá and Lake Arari) on Marajó Island were analysed. The values of the Index of Relative Importance (IRI) and its respective percentage (%IRI) were calculated. The level of repletion 1 (1/4 full) was the most representative for both sexes, as well as for immature and mature specimens. Most of the food items found were well-digested. The food items identification indicated the presence of 15 orders, including insects, mollusks, crustaceans, annelids and fish. Differences in diet were observed among the locations studied when comparing %IRI, crustaceans being the most preferred in Afuá, fish in Lake Arari and mollusks in Muaná.
Rocco, L; Costagliola, D; Fiorillo, M; Tinti, F; Stingo, V
We used silver nitrate staining, CMA3 and FISH to study the chromosomal localization of both the major ribosomal genes and the nucleolar organizer regions as well as that of the minor ribosomal genes (5S rDNA) in two species of Batoidea, Taeniura lymma (Dasyatidae) and Raja montagui (Rajidae). In both species, all the metaphases examined showed the presence of multiple NOR-bearing sites, while the gene for 5S rRNA proved to be localized on two chromosome pairs. Furthermore, one of the two 5S rDNA sites in T. lymma was shown to be co-localized with the major ribosomal cluster. The presence of multiple nucleolar organizer regions in the two species might be interpreted as being the result of intraspecific polymorphisms, or as a phenomenon of the amplified transposition of mobile elements of the genome. We also determined the nucleotide sequence of the 5S rRNA gene, consisting of 564 bp in R. montagui and 612 bp in T. lymma. We also found TATA-like and (TGC)n trinucleotides, (CA)n dinucleotides and (GTGA)n tetranucleotides, which probably influence gene regulation.
Duncan, Wallice P; Silva, Naara F; Fernandes, Marisa N
Detailed measurements of gill area and constituent variables (total filament number, total filament length and mean filament length), and immunolocalization of the α-subunit of Na⁺/K⁺-ATPase and Na⁺/K⁺-ATPase activity were performed on both hemibranchs of all five arches of freshwater potamotrygonid stingrays (Paratrygon aiereba and Potamotrygon sp.). Both species exhibit similar mass-specific gill area, 89.8 ± 6.6 and 91.5 ± 4.3 mm² g⁻¹ for P. aiereba and Potamotrygon sp., respectively. The density of Na⁺/K⁺-ATPase-rich MRCs and Na⁺/K⁺-ATPase activity was higher in the 4th gill arch in both species. The Na⁺/K⁺-ATPase activity was positively correlated to the Na⁺/K⁺-ATPase-rich Na⁺/K⁺-ATPase rich) mitochondrion-rich cell (MRC) distribution among the gill arches of P. aiereba but not in Potamotrygon sp. The levels Na⁺/K⁺-ATPase activity were not correlated to the gill surface area among the arches for both rays' species. Considering that the Na⁺/K⁺-ATPase-rich MRC is the main site for active ion transport in the gill epithelia and Na⁺/K⁺-ATPase activity plays a crucial role in osmoionoregulatory function, we suggesting that 4th gill arch is more relevant for osmoregulation and ion balance in these potamotrygonids.
Galíndez, E J; Díaz-Andrade, M C; Avaca, M S; Estecondo, S
The oviductal gland is an exclusive structure of cartilaginous fishes that produces the egg jelly, forms the tertiary egg envelopes and stores sperm. The biological importance of this structure is related to the special features of the reproductive strategy of the group and to its phylogeny, considering that egg-laying is the ancestral condition in this fish (Dulvy and Reynolds, 1997). This gland of the smallnose fanskate shows four morphofunctional zones. The lining epithelium along the gland is columnar with secretory and ciliated cells. Secretions are mucous and/or proteic according to the zone, and to their specific functions. This is the first report about the microanatomy of the female reproductive tract of S. bonapartii with evidence of sperm storage in the genus.
Tanzola, Ruben D; Sardella, Norma H
The purpose of this study was to study and redescribe Terranova galeocerdonis (Thwaite, 1927) from Carcharias taurus off Argentina. Its fourth larval stage was described, measured and illustrated for the first time. The host and geographical range of this species is extended into the southwestern Atlantic Ocean. When the present material was compared with T. rochalimai (Pereira, 1935) and T. ginglymostomae Olsen, 1952, it was considered that both morphological and morphometrical differences between the three species did not justify differentiation at the specific level. As a result, T. rochalimai and T. ginglymostomae are considered to be junior synonyms of T. galeocerdonis.
Burreson, E M; Kearn, G C
A new genus and species of piscicolid leech in the Platybdellinae inhabits the oral cavity of Dasyatis akajei in the northwestern Pacific Ocean near Tanabe, Japan. The genus Rhopalobdella n. gen. is characterized externally by very small oral and caudal suckers and a smooth body that is widest just posterior to the clitellum. Eyespots and ocelli are lacking. The coelom is spacious with large segmental connecting sinuses between dorsal and ventral sinuses. There are 5 pairs of testisacs, an unusually extensive epididymis, and a very large bursa. Conducting tissue is absent. There are 2 pairs of esophageal diverticula and very well developed nephridia. Rhopalobdella japonica n. gen. n. sp. is characterized by a urosome that tapers strongly to the caudal sucker and by a single gonopore; the common oviduct opens into the posterior portion of the bursa. The coelomic and excretory systems resemble Aestabdella, but in other respects the genera are quite different. This is the first marine leech reported from rays in the northwestern Pacific.
Pauliv, Victor E; Dias, Eliseu V; Sedor, Fernando A; Ribeiro, Ana Maria
The Brazilian records on Xenacanthiformes include teeth and cephalic spines from the Parnaíba, Amazonas and Paraná basins. This work describes a new species of Xenacanthidae, collected in an outcrop of Serrinha Member of Rio do Rasto Formation (Wordian to Wuchiapingian), Paraná Basin, municipality of Jacarezinho, State of Paraná. The teeth of the new species are two or three-cuspidated and the aboral surface show a smooth concavity and one rounded basal tubercle. The coronal surface presents one semi-spherical and subcircular coronal button, and also two lateral main cusps and one central (when present) with less than one fifth of the size of the lateral cusps in the labial portion. The lateral cusps are asymmetric or symmetric, rounded in transversal section, lanceolate in longitudinal section, devoid of lateral carinae and lateral serrations, and with few smooth cristae of enameloid. In optical microscope the teeth show a trabecular dentine (osteodentine) base, while the cusps are composed by orthodentine, and the pulp cavities are non-obliterated by trabecular dentine. The fossil assemblage in the same stratigraphical level and in the whole Rio do Rasto Formation indicates another freshwater record for xenacanthid sharks.
Soares, Karla D A; Gomes, Ulisses L; Carvalho, Marcelo R De
Sharks of the genus Scyliorhinus from the southwestern Atlantic are reviewed; identification problems and taxonomic misinformation given in the literature are rectified. After extensive examination of the external and internal morphology of specimens collected mostly off southeastern and southern Brazil, Scyliorhinus besnardi Springer & Sadowsky, 1970 is placed in the synonymy of S. haeckelii (Miranda Ribeiro, 1907), which is thoroughly redescribed. Additionally, a new species, Scyliorhinus cabofriensis, sp. nov., is described from the state of Rio de Janeiro, distinguished from all southwestern Atlantic congeners by its color pattern, clasper and neurocranial morphology, and proportional measurements. A key to Scyliorhinus species occurring in the southwestern Atlantic is also provided.
Ontogenetic changes in neuropeptide Y-like immunoreactivity (NPY-LI) were studied in chromaffin tissue of the cloudy dogfish, Scyliorhinus torazame. In adults and post-hatching juveniles, NPY-LI was demonstrated in chromaffin cells, but not in ganglion cells and supporting cells. Immunoreactive fibers were also found in the axillary body (the major chromaffin tissue) of the adult fish. During the embryonic period, NPY-LI was found at first in chromaffin tissue in the 34-mm stage. In this stage, cells in the periphery of the tissue were positive for NPY. Afterwards, changes were not observed in the topography and relative dominance of labelled cells in the tissue. Transmission electron microscopy of chromaffin tissue of the 26-mm stage showed an early phase of histogenesis in rudimental cell clusters composed of agranular cells and a few granular cells, i.e. pheochromoblasts. In the 43-mm stage, differentiation of the chromaffin tissue enabled ultrastructural classification of adrenalin-producing cells, noradrenalin-producing cells, ganglion cells, supporting cells, and unmyelinated nerve fibers. These results suggest that in the dogfish the appearance of NPY-LI in the developing sympathoadrenal system is related to differentiation of chromaffin cells.
Marques, F; Brooks, D R; Ureña, H M
Two new species of tetraphyllidean cestodes inhabiting Himantura pacifica from the northwest coast of Costa Rica are apparently most closely related to species inhabiting Himantura schmardae from the Atlantic coast of Colombia. Acanthobothroides pacificus n. sp. differs from Acanthobothroides thorsoni, the only other species in the genus, primarily by having smaller lateral (98-123 microns rather than 168-198 microns long) and medial (handles 92-116 microns rather than 162-168 microns long) hooks, and more testes (up to 125 rather than up to 97) per proglottis. The generic diagnosis of Acanthobothroides is modified to include the presence of a small inner prong on the large medial bothridial hooks. Rhinebothrium geminum n. sp. and Rhinebothrium magniphallum are the only 2 species in the genus possessing unusually long cirrus sacs, extending from the genital atrium all the way to the ovarian isthmus; R. geminum averages 12 (12-14) loculi per bothridium and 11 (9-12) testes, whereas R. magniphallum averages 17 (16-18) loculi and 14 (10-16) testes per proglottis.
Rocco, L; Stingo, V; Bellitti, M
A repetitive HindIII fragment of DNA from Raja montagui (Rajiformes) was cloned and sequenced for the first time in cartilaginous fishes. This element, which comprises approximately 5% of the whole genome of the spotted ray, is absent in long tandem arrays, being typical of satellite DNA. It appeared constituted by 311 AT-rich bp (61%). The clone was hybridized to the genomic DNA of species with varying phyletic distances, revealing a high degree of conservation.
Griffiths, Andrew Mark; Miller, Dana D; Egan, Aaron; Fox, Jennifer; Greenfield, Adam; Mariani, Stefano
Skates are widely consumed across the globe, but many large species are subject to considerable concern regarding their conservation and management. Within Europe such issues have recently driven policy changes so that, for the first time, reports of skate landings now have to be made under species-specific names. Total allowable catches have also been established for many groups, which have been set to zero for a number of the most vulnerable species (e.g., Dipturus batis, Raja undulata and Rostoraja alba). Whilst accurate species identification has become an important issue for landings, the sale of skates is still usually made under a blanket term of "skate" or "ray". The matter of identifying species of skate is further complicated by their morphologically conservative nature and the fact that they are commercially valued for their wings. Thus, before sale their bodies are usually discarded (i.e., "winged") and often skinned, making morphological identification impossible. For the first time, DNA barcoding (of the mitochondrial COI gene) was applied to samples of skate wings from retail outlets across the British Isles, providing insight into which species are sold for consumption. A total of 98 wing samples were analysed, revealing that six species were sold; blonde ray (Raja brachyura), spotted ray (Raja montagui), thornback ray (Raja clavata), cuckoo ray (Leucoraja naevus) small-eyed ray (Raja microocellata) and shagreen ray (Leucoraja fullonica). Statistical testing demonstrated that there were significant differences in the species sold in the distinct retail groups which suggests complex drivers behind the patterns of sale in skates. The results also indicate that endangered species are not commonly being passed on to consumers. In addition, the practice of selling skate wings under ambiguous labels is highlighted as it makes it extremely difficult for consumers to exercise a right to avoid species of conservation concern. Interestingly, a single retailer chain labelled their wings as originating from three smaller-growing species (generally to be considered of lower conservation concern); of the six samples analysed from this company a third were mislabelled and originated from the thornback ray (a larger species that is currently undergoing population declines).
Dunn, Katherine A; McEachran, John D; Honeycutt, Rodney L
Mitochondrial DNA sequences from the 12S rRNA gene, four tRNA genes, and a portion of two protein coding genes were used to investigate the relationship of myliobatoid genera. In addition, we conducted an investigation of the sister group to the freshwater stingrays by sampling additional DNA sequences from GenBank. Consequently, two datasets were used to examine myliobatoid relationships. The first consisted of the genes sequenced in this study. The second dataset was compiled by combining the first dataset with cytochrome b sequences from GenBank. The second dataset, however, included a number of missing characters due to differences in sampling. The effect of the missing characters on both maximum parsimony and maximum likelihood analysis was investigated by conducting a simulation study. Results of the simulation study indicated that maximum likelihood was not sensitive to the missing data, whereas the accuracy of maximum parsimony analysis was expected to decrease. Phylogenetic analysis of this group had several areas concordant with morphological studies, however, the analysis also revealed two novel relationships. In addition, placement of two taxa (Gymnura and Himantura) were dependent both on the dataset and analytical method used.
Ivanov, Verónica A
Examination of the spiral intestines of 44 freshwater stingrays, Potamotrygon motoro, from tributary rivers of the Parana River in Argentina, allowed for the collection of specimens of an undescribed species of Acanthobothrium. Acanthobothrium ramiroi n. sp. can be distinguished from all other congeners by the combination of the following characters: asymmetrical hooks (medial and lateral hooks conspicuously different in size and form, with axial prong of medial hooks stouter than abaxial prong), hook size (total length of medial hooks up to 242 microm, total length of lateral hooks up to 239 microm), bothridia not fused to the scolex proper at posterior ends, worm size (51-84 mm long), and the presence of a conspicuous vaginal sphincter. The new species is different from all other species of Acanthobothrium in freshwater potamotrygonids, except Acanthobothrium terezae, in having conspicuous asymmetrical hooks. The main differences that allow for the distinction between A. ramiroi and A. terezae include hook size, the way the bothridia are attached to the scolex proper, and the shape of the older gravid segments. The discovery of a new species of Acanthobothrium from a potamotrygonid extends our understanding of the diversity of the genus in freshwater stingrays in South America.
De La Cruz-Agüero, José; García-Rodríguez, Francisco Javier; Cota-Gómez, Víctor Manuel; Melo-Barrera, Felipe Neri; González-Armas, Rogelio
Fresh and preserved (type material) specimens of the black ghost chimaera Hydrolagus melanophasma were compared for morphometric characteristics. A molecular comparison was also performed on two mitochondrial gene sequences (12S rRNA and 16S rRNA gene sequences). While significant differences in measurements were found, the differences were not attributable to sexual dimorphism or the quality of the specimens, but to the sample size and the type of statistical tests. The result of the genetic characterization showed that 12S rRNA and 16S rRNA genes represented robust molecular markers that characterized the species.
An annotated checklist of the chondrichthyan fishes (sharks, batoids and chimaeras) of the world is presented. As of 7 November 2015, the number of species totals 1188, comprising 16 orders, 61 families and 199 genera. The checklist includes nine orders, 34 families, 105 genera and 509 species of sharks; six orders, 24 families, 88 genera and 630 species of batoids (skates and rays); one order, three families, six genera and 49 species of holocephalans (chimaeras). The most speciose shark orders are the Carcharhiniformes with 284 species, followed by the Squaliformes with 119. The most species-rich batoid orders are the Rajiformes with 285 species and the Myliobatiformes with 210. This checklist represents the first global checklist of chondrichthyans to include information on maximum size, geographic and depth distributions, as well as comments on taxonomically problematic species and recent and regularly overlooked synonymizations. Furthermore, a detailed analysis of the biogeographical diversity of the species across 10 major areas of occurrence is given, including updated figures for previously published hotspots of chondrichthyan biodiversity, providing the detailed numbers of chondrichthyan species per major area, and revealing centres of distribution for several taxa.
Carvalho, Marcelo R De; Rosa, Ricardo S; Araújo, Maria Lúcia G De
A new species of Potamotrygon is described from the Rio Negro drainage, Amazonas, Brazil. In spite of being cited or pictured several times in the scientific and aquarium fish literature since the 19th Century, it had been misidentified and still lacked a scientific name. Potamotrygon wallacei, n. sp., is diagnosed by the following characters: dorsal surface of disc light brown, with black irregularly-shaped vermiculate markings forming an amphora- or Ω-shaped figure on mid-disc, delimiting light brown reniform areas at disc center, and with subcircular light brown ocellate markings on disc margins; small body size (smallest known Potamotrygon species; largest examined specimen measured 310 mm DW); dorsal spines on tail usually rather low, without broad bases, in one to rarely three irregular rows, but extending posteriorly only to tail mid-length and not to caudal stings, with altogether relatively few spines; denticles on posterior mid-disc and tail base Y-shaped, with a central, anterior, bulbous cusp and usually two posterior pairs of smaller, rounded cusps; and single (anterior) angular cartilage. The new species is similar to P. orbignyi and other "reticulated" species in having a single (anterior) angular cartilage and in the color pattern of the tail, but is easily distinguished based on its size, dorsal tail spine arrangement, and specific details of color pattern.
Moro, G; Charvet, P; Rosa, R S
Potamotrygon signata is an endemic freshwater stingray species in the Parnaíba River basin, Brazil. After its original description, only citations in systematic lists were recorded in the literature and the biology of the species remains unknown, including the feeding habits. The aim of this study is to characterize the overall diet of P. signata based on analysing stomach contents and to provide preliminary information on intraspecific diet variability between sexes and maturity stages. The stomach contents of 56 specimens of P. signata were analyzed. The taxonomic identification of food items showed the presence of 13 prey orders, including insects, mollusks, crustaceans and teleost fish. The Index of Relative Importance (IRI%) indicated P. signata as an insectivorous species, with a dominance of Diptera larvae (60.64%) and Ephemeroptera nymphs (34.68%). Differences in diet were observed between sexes, as well as between mature and immature individuals. The IRI% of females showed a similar occurrence of Diptera and Ephemeroptera (47.12% and 47.86%, respectively), whereas for males, Ephemeroptera was the main item (79.56%). Immature individuals showed a dominance of Diptera (76.20%) while mature individuals showed a similar occurrence of Diptera (46.95%) and Ephemeroptera (47.23%). The observed sexual and ontogenetic differences in diet may be related to distinct nutritional requirements of males and females, and to the variation of morphological aspects of the oral apparatus and dentition of males and females and of immature individuals and adults. The essentially insectivorous diet of the species is possibly adaptively advantageous in the Caatinga semi-arid environment, where the availability of fish as prey may be subject to strong seasonal variation.
Fontenelle, João Pedro; Da Silva, João Paulo C B; De Carvalho, Marcelo R
Potamotrygon limai, sp. nov., is described from the Jamari River, upper Madeira River system (Amazon basin), state of Rondônia, Brazil. This new species differs from congeners by presenting unique polygonal or concentric patterns formed by small whitish spots better defined over the posterior disc and tail-base regions. Potamotrygon limai, sp. nov., can be further distinguished from congeners in the same basin by other characters in combination, such as two to three rows of midtail spines converging to a single irregular row at level of caudal sting origin, proportions of head, tail and disc, patterns of dermal denticles on rostral, cranial and tail regions, among other features discussed herein. Potamotrygon limai, sp. nov., is most similar to, and occurs sympatrically with, P. scobina, and is distinguished from it by lacking ocellated spots on disc, by its characteristic polygonal pattern on posterior disc, a comparatively much shorter and broader tail, greater intensity of denticles on disc, more midtail spine rows at tail-base, and other features including size at maturity and meristic characters. Potamotrygon limai, sp. nov., is also distinguished from other species of Potamotrygon occurring in the Amazon region, except P. scobina, by presenting three angular cartilages (vs. two or one). This new species was discovered during a detailed taxonomic and morphological revision of the closely related species P. scobina, and highlights the necessity for thorough and all-embracing taxonomic studies, particularly in groups with pronounced endemism and morphological variability.
Szabó, Márton; Kocsis, László
A new Middle Miocene (Langhian - early Serravallian) assemblage with shark and ray teeth from Nyirád (Hungary, Transdanubia, Veszprém County) consists of nine families, with 15 different species. The assemblage shares many common genera with other Middle Miocene assemblages in the Paratethys (Notorynchus, Carcharias, Otodus, Cosmopolitodus, Hemipristis, Galeocerdo, Carcharhinus, and Aetobatus), and reflects a subtropical climate and a close connection with the Mediterranean Sea. However, a detailed faunal compilation of Miocene selachians reveals that several taxa that were still present in the Mediterranean or lived in the Paratethys during the Lower Miocene disappeared or became very rare by the Middle Miocene in the Central Paratethys (e.g., Isistius, Centrophorus, Mitsukurina, Carcharoides, Parotodus, Alopias). The taxa that went locally extinct in the Paratethys are mainly represented by deep-water or pelagic forms. Their disappearance is most probably related to the gradual separation of the Paratethys from the Mediterranean. The common presence of some large, rather pelagic sharks (e.g., Otodus, Cosmopolitodus) in the Central Paratethys during the Middle Miocene is explained here by the widespread occurrence of their potential prey represented by marine mammals (e.g., whales and dolphins).
Berman, R; Brooks, D R
Cestodes collected in spiral valves of the stingray Urotrygon chilensis from the Pacific coast of Costa Rica represent an undescribed species of Tetraphyllidea. By possessing more than 2 loculi as well as an apical sucker on each bothridium, the new species is diagnosably distinct from all other tetraphyllidean genera; therefore, a new genus is proposed for it. The new species also possesses globular structures irregularly arranged on the surface of the bothridia. We found similar structures on the bothridial faces of Trilocularia acanthiaevulgaris, possibly indicating phylogenetic relationships with the new species. This possibility is enhanced by the observation that the bothridia of T. acanthiaevulgaris comprise 2 loculi and an apical sucker, rather than 3 loculi.
Brooks, D R; McCorquodale, S
A new species of Acanthobothrium in Aetobatus narinari from the Gulf of Nicoya, Costa Rica, most closely resembles Acanthobothrium colombianum in the same host and A. urotrygoni in Urotrygon venezuelae from Cartagena, Colombia, by having relatively few proglottides per strobila, spinose cephalic peduncles, bothridial margins free at their posterior ends, and irregularly shaped rather than spherical or elongate cirrus sacs. Acanthobothrium colombianum differs from the new species by being as much as 35 mm rather than no more than 4.7 mm long and by having 31-48 rather than 13-19 proglottides, an average of 46 rather than 15 testes per proglottis, and bothridial hooks averaging 185 microns rather than 137 microns in total length. Acanthobothrium urotrygoni differs from the new species by being as much as 15 mm rather than no more than 4.7 mm long and by having V-shaped rather than H-shaped ovaries, bothridial hooks averaging 95 microns rather than 137 microns in total length, by having an average of 28 rather than 15 testes per proglottis, and by having poral ovarian arms extending anteriorly to the posterior margin of the cirrus sac and aporal arms extending to the lateral margin of the cirrus sac.
Menoret, Adriana; Ivanov, Verónica A
Examination of the type material of Progrillotia dollfusi Carvajal et Rego, 1983, and of new specimens recently collected off the coast of Argentina (including plerocerci from 10 species of teleosts and adults from Squatina guggenheim Marini), allowed a detailed redescription of this species and the evaluation of its current taxonomic status. The following characters that have been treated inconsistently by different authors have been herein corrected or confirmed: band of hooklets on external surface restricted to the base of the tentacle, external surface of metabasal region with 3-5 intercalary hooks arranged in a single row merging immediately to a cluster of 3-4 hooklets arranged in two rows; retractor muscle originating in the posterior third of the bulb, hollow hooks, and posterior margin of bothria notched. These features along with the presence of postovarian testes in the adults clearly confirm the placement of P. dollfusi in the genus Grillotia Guiart, 1927. In order to avoid the homonymy with Grillotia dollfusi Carvajal, 1971, a new name, Grillotia carvajalregorum nom. n., is proposed. This species differs from the 16 valid species in the genus in the combination of the following characters: number and morphology of hooks in principal rows in proximal metabasal region of the tentacle, number and distribution of intercalary hooks, presence of clusters of hooklets, extent of band of hooklets on external surface of basal armature, site of origin of the retractor muscle, and features of the terminal genitalia. The present study describes the plerocerci and adult worms, and provides detailed description of the microthrix pattern and histology of this species for the first time.
Adnet, Sylvain; Salas Gismondi, Rodolfo; Antoine, Pierre-Olivier
Endemic South American river stingrays (Potamotrygonidae), which include the most diversified living freshwater chondrichthyans, were conspicuously absent from pre-Neogene deposits in South America despite the fact that recent phylogenetic analyses strongly suggest an older origination for this clade. To date, the rare representatives of this family were mostly represented by ambiguous isolated remains. Here, we report 67 isolated fossil teeth of a new obligate freshwater dasyatoid (Potamotrygon ucayalensis nov. sp) from the fossiliferous level CTA-27 (Yahuarango Formation), near Contamana, in the Peruvian Amazonia. We assigned this sample to a new representative of Potamotrygon by comparison with numerous fresh jaws of living specimens of Potamotrygonidae, thus providing the first detailed review of dental morphology for this poorly understood clade. These new fossils fill a long stratigraphic gap by extending the family range down to the middle Eocene (~41 Mya). Moreover, the relative modernity and diversity in tooth morphology among Eocene freshwater stingrays (including Potamotrygon ucayalensis nov. sp. and coeval North American dasyatoids) indicate that the hypothetically marine ancestor of potamotrygonids probably invaded the rivers earlier than in the middle Eocene. The first potamotrygonids and affiliates were possibly more generalized and less endemic than now, which is consistent with an opportunistic filling of vacated ecospace.
Solbakken, J.E.; Palmork, K.H.
The fate of polycyclic hydrocarbons (PAH) in marine animals has received increasing attention in the last decade. The present studies dealing with spiny dogfish (Squalus acanthias) and rainbow trout (Salmo gairdneri) are part of a series of experiments with different marine organisms. All the experiments were performed under the same laboratory conditions using intragastric administration of the PAH-component, /sup 14/C-labelled phenanthrene. Thus it is possible to compare species differences of disposition of PAH in various marine organisms. The most pronounced differences in the disposition of phenanthrene between bony fish and cartilaginous fish in our studies are that the maximum value of radioactivity in the liver of cartilaginous fish occurred several days later than the corresponding value in bony fish. Furthermore, the radioactivity in cartilaginous fish was retained at a high level beyond 672 h (28 days), a time at which the radioactivity in bony fish is near the background values.
Adnet, S.; Hosseinzadeh, R.; Antunes, M. T.; Balbino, A. C.; Kozlov, V. A.; Cappetta, H.
Little is known about the extinct Xiphodolamia, a peculiar lamnid shark which inhabited the Eocene seas. The reexamination of a large set of fossilized teeth specimens from the Ypresian of Kazakhstan has enabled the reconstitution of the tooth series of this enigmatic taxa of lamnid shark. Five distinct tooth morphologies seem to occur in X. ensis Leidy [Leidy, J., 1877. Description of vertebrate remains, chiefly from the phosphate beds of South Carolina. Journal of the Academy of Natural Sciences of Philadelphia 8, 209-261] species revealing a weak ontogenetic variation. Such specific variation in tooth shape means that the other described species may be their junior synonyms. Dental morphology perfectly conforms with a Lamniforme but does not prove the current attribution to the Lamnidae family due to some inconsistent dental features observed, such as the presence of symphysial teeth. This genus could be regarded as an old lineage branched from the stem group of Lamnidae, close to the Isuroids sharks. Several Xiphodolamia teeth, originating both from old collections and new acquisitions, are reported and illustrated in order to provide information about a new species described here: Xiphodolamia serrata nov. sp. This species, currently limited to deposits in Angola, Jordan and Iran and dated at the Late Eocene, is easily distinguishable from the Early-Middle Eocene material belonging to the genus by the presence of serrated cutting edges. Adding to the type species considered here as the only valid taxa during the Early-Middle Eocene period, the temporal range of this genus extends to the Late Eocene, thus setting its upper stratigraphic limit prior to its disappearance as enigmatic as its appearance in the Early Eocene was.
Reiss, Katie L; Bonnan, Matthew F
The shark heterocercal caudal fin and its contribution to locomotion are of interest to biologists and paleontologists. Current hydrodynamic data show that the stiff dorsal lobe leads the ventral lobe, both lobes of the tail are synchronized during propulsion, and tail shape reflects its overall locomotor function. Given the difficulties surrounding the analysis of shark caudal fins in vivo, little is known about changes in tail shape related to ontogeny and sex in sharks. A quantifiable analysis of caudal fin shape may provide an acceptable proxy for inferring gross functional morphology where direct testing is difficult or impossible. We examined ontogenetic and sex-related shape changes in the caudal fins of 115 Squalus acanthias museum specimens, to test the hypothesis that significant shape changes in the caudal fin shape occur with increasing size and between the sexes. Using linear and geometric morphometrics, we examined caudal shape changes within the context of current hydrodynamic models. We found no statistically significant linear or shape difference between sexes, and near-isometric scaling trends for caudal dimensions. These results suggest that lift and thrust increase linearly with size and caudal span. Thin-plate splines results showed a significant allometric shape change associated with size and caudal span: the dorsal lobe elongates and narrows, whereas the ventral lobe broadens and expands ventrally. Our data suggest a combination of caudal fin morphology with other body morphology aspects, would refine, and better elucidate the hydrodynamic factors (if any) that underlie the significant shape changes we report here for S. acanthias.
Aichino, D R; Pastori, M C; Roncati, H A; Ledesma, M A; Swarça, A C; Fenocchio, A S
The Potamotrygonidae family represents the only freshwater group of specialized elasmobranchs and is composed of 4 genera: Plesiotrygon, Paratrygon, Potamotrygon, and Heliotrygon. Individuals of Potamotrygon motoro were collected from the Paraná River at Ituzaingó (Province of Corrientes) in Argentina. Mitotic preparations were obtained using direct techniques and lymphocyte cultures. Chromosomes were studied with conventional Giemsa, C-band and nucleolus organizer region stainings. The diploid number and karyotype formulae were 2n = 66 with 33 homomorphic pairs (14M + 16SM + 22ST + 14A) in females and 2n = 65 with 31 homomorphic pairs plus 3 heteromorphic chromosomes (13M + 15SM + 23ST + 14A) in males. Heterochromatin was distributed at the pericentromeric regions of almost all chromosomes and in the telomeric and interstitial positions of some chromosomes. nucleolus organizer regions were multiple and located at telomeric regions. Because of the clear karyotype differences between the 2 sexes and the presence of 3 unpaired chromosomes in males, it is possible to suggest the occurrence of a multiple sex chromosome system, with male heterogamety (X1X1X2X2/X1X2Y). Further cytogenetic studies are required to develop a hypothesis about the origin of the multiple sex chromosome system in P. motoro.
Rocha, F; Gadig, O B F
The reproductive biology of the guitarfish Rhinobatos percellens was studied from 751 specimens caught by bottom pair trawlers off the coast of São Paulo, Brazil, between c. 24° 00' S; 45° 15' W and c. 25° 10' S; 47° 52' W, from September 2007 to August 2009. The total length (L(T)) and total mass (M(T)) relationship for males and females combined was M(T) = 1·29E-06 L(T) (3·15) (r = 0·99, n = 751). The mean L(T) of sexually mature specimens was 548 mm for males and 583 mm for females. Clasper growth was allometric and showed three distinct phases. Most claspers were calcified in specimens of c. 550 mm L(T). The mean diameter of the largest oocyte was 29·8 mm, the mean ovarian fecundity was seven oocytes and ovulation occurred between August and November. Uterine fecundity ranged from two to 13 embryos (mean of five embryos). Larger females had higher litter sizes and larger embryos; the size-at-birth was c. 200 mm L(T). The hepato-somatic index oscillated seasonally for males and females; the gonado-somatic index had little variation in males, but varied seasonally in females. The presence of many non-pregnant adult females and of encapsulated eggs during two consecutive seasons suggests a resting period between gestations and the possibility of diapause.
Soares, Mateus C; de Carvalho, Marcelo R
The order Hexanchiformes currently comprises two families, Chlamydoselachidae (frilled sharks) and Hexanchidae (six- and seven-gill sharks), but its monophyly and relationships with other elasmobranchs are still discussed. Previous studies of hexanchiforms addressing these issues were based mainly on external morphology, teeth, skeletal features, and molecular data, whereas the employment of characters derived from variations in muscles has not been significantly explored. Dissections of four species of Hexanchiformes (including Chlamydoselachus anguineus) are reported here describing the mandibular (musculus adductor mandibulae dorsalis, m. adductor mandibulae ventralis, m. levator labii superioris, m. intermandibularis, and m. constrictor dorsalis) and hyoidean (m. constrictor hyoideus dorsalis and ventralis) arch muscles. Our results provide new data concerning the relationships of hexanchiforms to other elasmobranchs. The m. adductor mandibulae superficialis is described and illustrated in C. anguineus, contradicting previous accounts in which is was considered absent. The anteroposterior orientation of the m. adductor mandibulae superficialis in Chlamydoselachus is similar to the pattern found in hexanchids, squaloids, and hypnosqualeans (including batoids), suggesting it was secondarily lost in Echinorhinus. This muscle therefore provides further support for the inclusion of the Chlamydoselachidae and Hexanchidae in the Squalomorphi, and not basal to all other elasmobranchs or nested within an all-shark collective, as has been previously proposed. However, the m. adductor mandibulae superficialis originating at the jaw joint and with an aponeurotic insertion in hexanchids, squaliforms, and hypnosqualeans, may be a separate derived feature uniting these taxa. The insertion of the m. constrictor dorsalis is restricted to the postorbital articulation in hexanchids, whereas it extends farther anteriorly in C. anguineus. The insertion of the m. constrictor hyoideus dorsalis solely on the palatoquadrate is found exclusively in the Hexanchidae. We conclude that no specific pattern of mandibular or hyoid arch muscles support the monophyly of hexanchiforms (i.e., including Chlamydoselachus).
Wagner, C M; Rice, P H; Pease, A P
The first recorded incidence of dicephalia in a bull shark Carcharhinus leucas is reported from a foetus collected by a fisherman in the Gulf of Mexico near Florida, U.S.A. External examination, Radiography and magnetic resonance imaging revealed a case of monosomic dicephalia where the axial skeleton and internal organs were found to divide into parallel systems anterior to the pectoral girdle resulting in two well-developed heads.
Ebert, David A; Wilms, Hana A
A new species of sawshark, Pristiophorus lanae sp. nov., is described from off the Philippine Islands. The new species is the second member of the genus Pristiophorus described from the western North Pacific and can be separated from its closest geographic congener, P. japonicus, by having fewer rostral teeth in front of rostral barbels (17-26 versus 25-32), mouth at corners extending forward to below the rear margin of the eye versus extending below the rear one-third of eye margin, a greater mouth width at 6.9-7.8 times into pre-oral length (versus 5.8-6.9), eye length into head length (15.6-15.9 versus 9.8-13.2), mouth width into head length 9.0-10.0 versus 7.4-8.5 times, head width at nostrils 5.2-6.1 times into pre-orbital length versus 3.9-4.9 times, shorter prebarbel length (from snout tip to barbel) of 50.7-54.5% of preoral length versus 53.6-59.2%, a snout angle of 10.6-13.0 degrees versus 12.4 degrees - 14.6 degrees, and lateral trunk denticles with flat crowns that are imbricated versus erect crowns that are not imbricated. The number of monospondylous vertebrae is slightly lowe in P. lanae (43-48) versus P. japonicus (51-52). The genus is reviewed, with a revised key to its species presented.
A new species of Acanthobothrium van Beneden, 1849 (Eucestoda:Tetraphyllidea: Onchobothriidae) in Dasyatis longus Garman (Chondrichthyes:Myliobatiformes:Dasyatididae) from Chamela Bay, Jalisco, Mexico.
Monks, S; Brooks, D R; de León, G P
A new species of Acanthobothrium in Dasyatis longus from Chamela Bay, Jalisco, Mexico, is a member of a presumed clade of species diagnosed by being anapolytic or nearly so, having more than 100 testes per proglottis, with immature and mature proglottides wider than long to square, aspinose scolex, muscular bothridia fused to the scolex at their posterior ends, H- to V -shaped ovaries, relatively short symmetrical to asymmetrical ovarian arms that extend anteriorly to, or nearly to, the cirrus sac, and vitellaria arranged in fields rather than a single row of follicles. The new species most closely resembles Acanthobothrium terezae from the freshwater stingray Potamotrygon motoro in the following characters: bothridial hooks longer than 200 microns with inner hooks having bent asymmetrical prongs, an average of 130-140 testes per proglottis, and shallow genital atria located posterior to midline of proglottis. The new species differs from A. terezae by having outer hooks approximately the same size and shape as the inner hooks, inner hooks averaging 230 microns rather than 313 microns in total length, and cirrus sacs averaging 255 microns rather than 450 microns in length. The new species is unique among all described species of Acanthobothrium by having a cleft in the posterior margin of each apical bothridial pad. The apparent close relationship of the new species to one inhabiting a Neotropical freshwater stingray provides support for the hypothesized Pacific marine ancestry of Neotropical freshwater stingrays and raises the possibility that the Neotropical freshwater stingrays may not be monophyletic.
Echinocephalus janzeni n. sp. (Nematoda: Gnathostomatidae) in Himantura pacifica (Chondrichthyes: Myliobatiformes) from the Pacific coast of Costa Rica and Mexico, with historical biogeographic analysis of the genus.
Hoberg, E P; Brooks, D R; Molina-Ureña, H; Erbe, E
Echinocephalus janzeni n. sp. in the stingray, Himantura pacifica, is described from the eastern Pacific Ocean off the coasts of Costa Rica and southern Mexico. On the basis of the presence of 6 postanal caudal papillae, and modified annules anterior to the caudal alae in males, E. janzeni is most similar to Echinocephalus daileyi and Echinocephalus diazi. Specimens of E. janzeni are distinguished from those of E. daileyi by bilobed caudal alae and long cervical sacs that extend up to 65% of the length of the esophagus; E. janzeni is differentiated from E. diazi by the number of rows of cephalic spines (30-38 vs. 26-27), arrangement of the postanal caudal papillae, 3 rather than 2 preanal papillae, relative position and distance between the anus and vulva (395-460 microm vs. 70 microm), the digitiform female tail with a terminal cuticular fold, and the length of the female tail (450-480 microm vs. 270 microm). Cladistic analysis of the 10 Echinocephalus spp. resulted in a single most parsimonious tree (consistency index=0.893) and placed E. janzeni in a highly derived subclade where E. daileyi is the sister species of E. diazi + E. janzeni. Historical biogeographic analysis of hosts and parasites provides support for origins in the Pacific rather than the Atlantic for the potamotrygonid stingrays.
Pasolini, Paola; Costagliola, Domenico; Rocco, Lucia; Tinti, Fausto
The genomic and gene organisation of 5S rDNA clusters have been extensively characterized in bony fish and eukaryotes, providing general issues for understanding the molecular evolution of this multigene DNA family. By contrast, the 5S rDNA features have been rarely investigated in cartilaginous fish (only three species). Here, we provide evidence for a dual 5S rDNA gene system in the Rajidae by sequence analysis of the coding region (5S) and adjacent nontranscribed spacer (NTS) in five Mediterranean species of rays (Rajidae), and in a large number of piscine taxa including lampreys and bony fish. As documented in several bony fish, two functional 5S rDNA types were found here also in the rajid genome: a short one (I) and a long one (II), distinguished by distinct 5S and NTS sequences. That the ancestral piscine genome had these two 5S rDNA loci might be argued from the occurrence of homologous dual gene systems that exist in several fish taxa and from 5S phylogenetic relationships. An extensive analysis of NTS-II sequences of Rajidae and Dasyatidae revealed the occurrence of large simple sequence repeat (SSR) regions that are formed by microsatellite arrays. The localization and organization of SSR within the NTS-II are conserved in Rajiformes since the Upper Cretaceous. The direct correlation between the SSRs extension and the NTS length indicated that they might play a role in the maintenance of the larger 5S rDNA clusters in rays. The phylogenetic analysis indicated that NTS-II is a valuable systematic tool limited to distantly related taxa of Rajiformes.
Serendip deborahae n. gen. and n. sp. (Eucestoda: Tetraphyllidea: Serendipidae n. fam.) in Rhinoptera steindachneri Evermann and Jenkins, 1891 (Chondrichthyes: Myliobatiformes: Myliobatidae) from southeastern Ecuador.
Brooks, D R; Barriga, R
Cestodes collected in spiral valves of Rhinoptera steindachneri from the southern coast of Ecuador represent an undescribed species of Tetraphyllidea. The new species has bothridia possessing septa but lacking apical suckers. It is diagnosably distinct from all other tetraphyllidean genera by possessing a scolex comprising 4 triangular bothridia that are fused together forming a platelike structure, each of which is subdivided by 2 simple and 1 bifurcating septa radiating from its base and ringed by marginal loculi; therefore, a new genus is proposed for it. By exhibiting some degree of bothridial fusion, testes arranged in 2 layers in the proglottis and postovarian testes, the new species appears to be a member of a clade containing Dioecotaenia, Duplicibothrium, and Glyphobothrium. The new species possesses vitelline fields that converge dorsally in each proglottis, except for the ovarian and terminal genitalia areas, a feature that has been reported previously only in Duplicibothrium and Glyphobothrium. Furthermore, Duplicibothrium and Glyphobothrium, like the new species, are markedly protandric. Therefore, we propose that Duplicibothrium, Glyphobothrium, and the new species comprise the sister group of the Dioecotaeniidae, and propose a new family name for the clade. Tritaphros is rejected as a possible sister group for the clade; suggested alternatives include some species of Caulobothrium, Rhodobothrium, or some members of the Phyllobothrium centrurum group.
Last, Peter R; Séret, Bernard; Naylor, Gavin J P
A new guitarfish, Rhinobatos borneensis sp. nov., is described from material collected at fish markets in Malaysian Borneo (South China Sea). This ray, which is almost plain coloured with faint orange blotches in adults, has a more colourful embryo marked with small pale ocelli with dark centres. Confused with R. schlegelii (Japan to Taiwan) and its junior synonym R. formosensis, new molecular data suggests it is more closely related to a subgroup of Rhinobatos from the Indo-Malay Archipelago that includes R. jimbaranensis, R. sainsburyi and R. whitei. Based on evidence from recent phylogenetic studies, the genus Rhinobatos is non-monophyletic, nor is the Rhinobatidae a monophyletic family-level group. Former subgenera of Rhinobatos, Acroteriobatus and Glaucostegus, are valid genus-level taxa supported by both morphological and molecular evidence. Moreover, amphi-American members of Rhinobatos, assigned herein to a new genus Pseudobatos, are not monophyletic with Rhinobatos, Acroteriobatus and Glaucostegus and its position within the newly erected order Rhinopristiformes needs to be reassessed. Several molecular studies have suggested that the family Rhinobatidae is polyphyletic and needs to be redefined. We propose a revised classification of the order Rhinopristiformes based on molecular analyses and supported by morphological data, making strong use of oronasal morphology. The group now contains 5 family-level taxa: three valid nominal taxa, Pristidae (2 genera, 5 species), Rhinidae (incorporating Rhynchobatidae, 2 genera, 9 species), Rhinobatidae (3 genera, 31 species); and two new taxa, Glaucostegidae (single genus, 6 species) and Trygonorrhinidae (3 genera, 8 species).
Grace, Mark A; Doosey, Michael H; Bart, Henry L; Naylor, Gavin J P
The description of the pocket shark genus Mollisquama (M. parini Dolganov, 1984) is based on a single known specimen collected from the Nazca Ridge of the southeast Pacific Ocean. A second Mollisquama specimen has been captured in the central Gulf of Mexico establishing a considerable range extension and a parturition locality because the specimen has a healed vitelline scar. Both the holotype of M. parini and the Gulf of Mexico specimen possess the remarkable pocket gland with its large slit-like external opening located just above the pectoral fin. Features found on the Gulf of Mexico specimen that were not noted in the description of M. parini include a series of ventral abdominal photophore agglomerations and a modified dermal denticle surrounded by a radiating arrangement of denticles just posterior to the mouth. Based on a morphometric and meristic comparison of the Gulf of Mexico specimen with information in the description of M. parini, the Gulf of Mexico specimen is identified as Mollisquama sp. due to differences in tooth morphology and vertebral counts. Phylogenetic analysis of NADH2 gene sequences places Mollisquama sister to Dalatias plus Isistius within the family Dalatiidae.
Towards sustainable fishery management for skates in South America: The genetic population structure of Zearaja chilensis and Dipturus trachyderma (Chondrichthyes, Rajiformes) in the south-east Pacific Ocean
Bustamante, Carlos; Bennett, Michael B.; Ovenden, Jennifer R.
The longnose skates (Zearaja chilensis and Dipturus trachyderma) are the main component of the elasmobranch fisheries in the south-east Pacific Ocean. Both species are considered to be a single stock by the fishery management in Chile however, little is known about the level of demographic connectivity within the fishery. In this study, we used a genetic variation (560 bp of the control region of the mitochondrial genome and ten microsatellite loci) to explore population connectivity at five locations along the Chilean coast. Analysis of Z. chilensis populations revealed significant genetic structure among off-shore locations (San Antonio, Valdivia), two locations in the Chiloé Interior Sea (Puerto Montt and Aysén) and Punta Arenas in southern Chile. For example, mtDNA haplotype diversity was similar across off-shore locations and Punta Arenas (h = 0.46–0.50), it was significantly different to those in the Chiloé Interior Sea (h = 0.08). These results raise concerns about the long-term survival of the species within the interior sea, as population resilience will rely almost exclusively on self-recruitment. In contrast, little evidence of genetic structure was found for D. trachyderma. Our results provide evidence for three management units for Z. chilensis, and we recommend that separate management arrangements are required for each of these units. However, there is no evidence to discriminate the extant population of Dipturus trachyderma as separate management units. The lack of genetic population subdivision for D. trachyderma appears to correspond with their higher dispersal ability and more offshore habitat preference. PMID:28207832
Vögler, Rodolfo; Beier, Emilio; Ortega-García, Sofía; Santana-Hernández, Heriberto; Valdez-Flores, J Javier
Regional ecological patterns, distribution and population structure of Prionace glauca were analyzed based on samples collected on-board two long-line fleets operating in oceanic waters (1994-96/2000-02) and in coastal oceanic waters (2003-2009) of the eastern tropical Pacific off México. Generalized additive models were applied to catch per unit of effort data to evaluate the effect of spatial, temporal and environmental factors on the horizontal distribution of the life stages (juvenile, adult) and the sexes at the estimated depth of catch. The presence of breeding areas was explored. The population structure was characterized by the presence of juveniles' aggregations and pregnant females towards coastal waters and the presence of adult males' aggregations towards oceanic waters. The species exhibited horizontal segregation by sex-size and vertical segregation by sex. Distribution of the sex-size groups at oceanic waters was seasonally affected by the latitude; however, at coastal oceanic waters mainly females were influenced by the longitude. Latitudinal changes on the horizontal distribution were coupled to the seasonal forward and backward of water masses through the study area. Adult males showed positive relationship with high temperatures and high-salinities waters (17.0°-20.0 °C; 34.2-34.4) although they were also detected in low-salinities waters. The distribution of juvenile males mainly occurred beyond low temperatures and low-salinities waters (14.0°-15.0 °C; 33.6-34.1), suggesting a wide tolerance of adult males to explore subartic and subtropical waters. At oceanic areas, adult females were aggregated towards latitudes <25.0°N, mainly associated to subtropical waters during summer. The distribution of juvenile females indicated its preference by lower temperatures and more saline waters. Presence of pregnant females suggests that the eastern tropical Pacific off México represents an ecological key region to the reproductive cycle of P. glauca.
Adel, Milad; Oliveri Conti, Gea; Dadar, Maryam; Mahjoub, Masoud; Copat, Chiara; Ferrante, Margherita
Together with several health benefits, fish meat could lead to heavy metal intoxication of consumers. In this study, we discuss Zn, Cu, Pb, Hg and Cd concentrations in fillets of forty specimens of Carcharhinus dussumieri, analyzed with atomic adsorption spectroscopy (AAS). The potential human health risks due to consumption of C. dussumieri was assessed by estimating average daily intake (EDI) and target hazard quotient (THQ) of metals. The average concentrations of metals measured in this study were (ppm dry weight): Cu 7.49 ± 0.25; Zn 3.47 ± 0.26; Pb 0.12 ± 0.03; Hg 0.028 ± 0.02; Cd 0.11 ± 0.03. Our results showed that no metal exceeded the EC and FAO limits. Cu and Cd accumulate in muscles with a body length (age)-dependent manner. The exposure daily intake of all toxic metals analyzed was found lower than the PTDI provided by WHO and the THQ resulted lower than 1, suggesting no risk for human health derived from consumption.
Potamotrygon rex, a new species of Neotropical freshwater stingray (Chondrichthyes: Potamotrygonidae) from the middle and upper rio Tocantins, Brazil, closely allied to Potamotrygon henlei (Castelnau, 1855).
Carvalho, Marcelo R De
A systematic revision of the rio Tocantins stingrays has confirmed the occurrence of a new species of Potamotrygon first discovered more than two decades ago but which lacked material for a thorough description. Field surveys since undertaken in the middle and upper rio Tocantins have assembled significant material that forms the basis of an ongoing revision of the diverse Tocantins potamotrygonid assemblage. Potamotrygon rex, sp. nov., is a very large, "black stingray" species from the mid and upper rio Tocantins that is closely related to P. henlei (Castelnau), which occurs in the lower Tocantins basin and in rio Araguaia; both species do not co-occur. Potamotrygon rex, sp. nov., has a unique blackish to dark brown dorsal color with numerous small, yellow to orange irregular spots usually forming distinct clusters on dorsal disc, with ocelli in center of clusters on posterior and outer disc, dorsal tail also with clusters but lateral tail with ocelli, and a dark brownish to gray color covering most of ventral surface except nasoral region, gill slits and anterior snout in some specimens, with small whitish spots on ventral disc, pelvic fins and tail. Potamotrygon rex, sp. nov., can be further distinguished by its broad pelvic-fin apices, lack of labial grooves, irregular double row of dorsal tail thorns, and in having two angular cartilages associated with each hyomandibula. Potamotrygon rex, sp. nov., P. henlei, P. leopoldi Castex & Castello, and another new Potamotrygon species from the rio Tapajós (in description) form a species-group (the "black stingrays") occurring in rivers draining the central Brazilian shield, characterized by their black to dark brown but highly ornate dorsal color, wide pelvic fins with broadly convex apices, among other features. Potamotrygon rex, sp. nov., is the 25th species of Potamotrygon, and highlights that very large new species of fishes still await discovery and description in the Neotropical region.
Cruz, V P; Oliveira, C; Foresti, F
5S rDNA genes of the stingray Potamotrygon motoro were PCR replicated, purified, cloned and sequenced. Two distinct classes of segments of different sizes were obtained. The smallest, with 342 bp units, was classified as class I, and the largest, with 1900 bp units, was designated as class II. Alignment with the consensus sequences for both classes showed changes in a few bases in the 5S rDNA genes. TATA-like sequences were detected in the nontranscribed spacer (NTS) regions of class I and a microsatellite (GCT) 10 sequence was detected in the NTS region of class II. The results obtained can help to understand the molecular organization of ribosomal genes and the mechanism of gene dispersion.
Effects of exposure to coplanar polychlorinated biphenyls (PCBs) and other dioxin-like chemicals on developing vertebrates involve many organ systems, including the skeletal and cardiovascular systems. Apex predators, including those from the class Chondrichthyes (sharks, skates,...
Effects of exposure to coplanar polychlorinated biphenyls (PCBs) and other dioxin-like chemicals on developing vertebrates involve many organ systems, including the skeletal and cardiovascular systems. Apex predators, including those from the class Chondrichthyes (sharks, skates,...
Morphological and ultrastructural redescription of Chloromyxum leydigi Mingazzini, 1890 (Myxozoa: Myxosporea), type species of the genus, infecting the gall bladder of the marine cartilaginous fish Torpedo marmorata Risso (Chondrichthyes: Torpedinidae), from the Portuguese Atlantic Coast.
Rocha, Sónia; Casal, Graça; Al-Quraishy, Saleh; Azevedo, Carlos
Chloromyxum leydigi Mingazzini, 1890, the type species of Chloromyxum Mingazzini, 1890, is redescribed based on material found in the gall bladder of the cartilaginous fish Torpedo marmorata Risso collected from the Portuguese Atlantic coast and its sporogonic development is described. Plasmodia and mature spores were floating free in the bile. Plasmodia are polysporic and highly polymorphic in shape and organization. Mature spores are spherical to subspherical with a pointed anterior end, measuring 12.3 +/- 0.5 microm in length and 9.0 +/- 0.5 microm in width. The spore wall is composed of two asymmetric shell valves, each bearing 4-5 elevated surface ridges. A bundle of 40-50 tapering caudal filaments extends from the basal portion of the shell valves. Four pyriform equal-sized polar capsules, measuring about 5.3 x 3.2 microm, are observed at the same level in the anterior pole of the spores, each containing a polar filament coiled in 8-9 (rarely 10) turns. Spore morphology, tissue tropism, host species and sequences of the SSU rRNA gene supported species identification. Since its discovery, this species has been dubiously reported from several cartilaginous hosts, namely due to the poor description of its features.
Cestode parasites in Potamotrygon motoro (Natterer) (Chondrichthyes: Potamotrygonidae) from southwestern Brazil, including Rhinebothroides mclennanae n. sp. (Tetraphyllidea: Phyllobothriidae), and a revised host-parasite checklist for helminths inhabiting neotropical freshwater stingrays.
Brooks, D R; Amato, J F
Specimens of 5 species of cestodes were collected in 6 specimens of the freshwater stingray species Potamotrygon motoro (Natterer), collected in the vicinity of Corumba, Mato Grosso do Sul, Brazil. Acanthobothrium regoi, Potamotrygonocestus orinocoensis, Rhinebothroides venezuelensis, and Rhinebothrium paratrygoni are reported from P. motoro and from southwestern Brazil for the first time. Rhinebothroides mclennanae n. sp. appears to be the sister species of Rhinebothroides glandularis, the only other member of the genus exhibiting darkly staining glandular cells lying free in the parenchyma surrounding the terminal genitalia. The new species resembles Rhinebothroides glandularis, Rhinebothroides freitasi, and Rhinebothroides scorzai by having poral ovarian arms that extend anteriorly beyond the posterior margin of the cirrus sac, coiled vaginae, and vitelline follicles not interrupted on the poral side in the vicinity of the genital pore. It differs from all 6 previously described members of the genus by possessing an average of 31 testes per proglottid, compared with an average of 45 for R. glandularis, 55 for R. freitasi and R. venezuelensis, 77 for Rhinebothroides circularisi and Rhinebothroides moralarai, and 80 for R. scorzai. An updated phylogenetic tree for Rhinebothroides is presented.
Antarctic fishes are represented by sharks, skates (Chondrichthyes) and bony fishes (Teleostei). Teleosts play an important role in the completion of life cycles of many helminth species. They serve as either definitive or intermediate and paratenic hosts. Chondrichthyes are definitive hosts only. Seventy three helminth species occur as the adult stage in fishes: Digenea (45), Cestoda (14), Nematoda (6), Acanthocephala (8), Also, 11 larval stages of Cestoda (7) and Nematoda (4) are known, together with 7 species of Acanthocephala in the cystacanth stage. One digenean species, Otodistomum cestoides, matures in skates. Among cestodes maturing in fishes only one, Parabothriocephalus johnstoni, occurs in a bony fish, Macrourus whitsoni. Antarctic Chondrichthyes are not infected with nematodes and acanthocephalans. Cestode larvae from teleosts belong to Tetraphyllidea (parasites of skates), and Tetrabothriidae and Diphyllobothriidae (parasites of birds and mammals). Larval nematodes represent Anisakidae, parasites of fishes, birds and mammals. Acanthocephalan cystacanths mature in pinnipeds and birds. The majority of parasites maturing in Antarctic fishes are endemics. Only 4 digenean and one nematode species, Hysterothylacium aduncum, are cosmopolitan. All acanthocephalans, almost all digeneans, the majority of cestodes and some nematodes occur mainly or exclusively in benthic fishes. Specificity of the majority of helminths utilizing teleosts as intermediate and/or paratenic hosts is low. Among parasites using fishes as definitive hosts, all Cestoda, most Digenea and Nematoda, and almost all Acanthocephala have a range of hosts restricted to one order or even to 1-2 host species.
Chahud, Artur; Petri, Setembrino
The taphonomy of Early Permian vertebrates from a sandy facies at the base of the Taquaral Member, Irati Formation, was surveyed in order to acquire data for the interpretation of the sedimentary processes and paleoenvironment of deposition. Six outcrops from the Rio Claro municipality and surrounding areas, from the Brazilian State of São Paulo, were investigated. The vertebrate groups are Chondrichthyes (Xenacanthiformes, Ctenacanthiformes and Petalodontiformes), Osteichthyes (Actinopterygii and Sarcopterygii) and Tetrapodomorpha. They occur as loose teeth, scales, spines and bone remains. The sandy facies is characterized by fining upward deposition. The coarser sandstone immediately above the underlying Tatuí Formation is rich in Chondrichthyes. However, the fine sandstone above, immediately beneath the silty shale facies, is devoid of Chondrichthyes, though Osteichthyes scales, teeth and bones were present. The taphonomy is important for inferring sedimentary processes and then the paleoenvironments. The poor sorting of the sandstone and the presence of fossils that are mostly abraded or worn are indicative of a high energy environment. In contrast, the presence of fossils in a good state of preservation, some without abrasion and breakages are indicative of only limited transport. Differences of fossil spatial density, numbers of specimens and taxa may be explained by the dynamics of deposition, from details of the palaeoenvironment can be obtained.
Chapman, Demian D; Shivji, Mahmood S; Louis, Ed; Sommer, Julie; Fletcher, Hugh; Prodöhl, Paulo A
Parthenogenesis has been documented in all major jawed vertebrate lineages except mammals and cartilaginous fishes (class Chondrichthyes: sharks, batoids and chimeras). Reports of captive female sharks giving birth despite being held in the extended absence of males have generally been ascribed to prior matings coupled with long-term sperm storage by the females. Here, we provide the first genetic evidence for chondrichthyan parthenogenesis, involving a hammerhead shark (Sphyrna tiburo). This finding also broadens the known occurrence of a specific type of asexual development (automictic parthenogenesis) among vertebrates, extending recently raised concerns about the potential negative effect of this type of facultative parthenogenesis on the genetic diversity of threatened vertebrate species.
Hallström, Björn M; Janke, Axel
The relationship between the Chondrichthyes (cartilaginous fishes), the Actinopterygii (ray-finned fishes), and the piscine Sarcopterygii (lobe-finned fishes) and how the Tetrapoda (four-limbed terrestrial vertebrates) are related to these has been a contentious issue for more than a century. A general consensus about the relationship of these vertebrate clades has gradually emerged among morphologists, but no molecular study has yet provided conclusive evidence for any specific hypothesis. In order to examine these relationships on the basis of more extensive sequence data, we have produced almost 1,000,000 bp of expressed sequence tags (ESTs) from the African marbled lungfish, Protopterus aethiopicus. This new data set yielded 771 transcribed nuclear sequences that had not been previously described. The lungfish EST sequences were combined with EST data from two cartilaginous fishes and whole genome data from an agnathan, four ray-finned fishes, and four tetrapods. Phylogenomic analysis of these data yielded, for the first time, significant maximum likelihood support for a traditional gnathostome tree with a split between the Chondrichthyes and remaining (bone) gnathostomes. Also, the sister group relationship between Dipnoi (lungfishes) and Tetrapoda received conclusive support. Previously proposed hypotheses, such as the monophyly of fishes, could be rejected significantly. The divergence time between lungfishes and tetrapods was estimated to 382-388 Ma by the current data set and six calibration points.
Gustafsson, Ola S E; Ekström, Peter; Kröger, Ronald H H
Crystalline lenses with multiple focal lengths in monochromatic light (multifocal lenses) are present in many vertebrate groups. These lenses compensate for chromatic aberration and create well-focused color images. Stabilization of the lens within the eye and the ability to adjust focus are further requirements for vision in high detail. We investigated the occurrence of multifocal lenses by photorefractometry and lens suspension structures by light and electron microscopy in sturgeons (Acipenseriformes, Chondrostei) as well as sharks and rays (Elasmobranchii, Chondrichthyes). Multifocal lenses were found in two more major vertebrate groups, the Chondrostei represented by Acipenseriformes and Chondrichthyes represented by Elasmobranchii. The lens suspension structures of sturgeons, sharks, and rays are more complex than described previously. The lens is suspended by many delicate suspensory fibers in association with a ventral papilla in all groups studied. The arrangements of the suspensory fibers are most similar between sturgeons and sharks. In rays, the lens is suspended by a smaller ventral papilla and the suspensory fibers are arranged more concentrically to the lens.
Castro, L Filipe C; Gonçalves, Odete; Mazan, Sylvie; Tay, Boon-Hui; Venkatesh, Byrappa; Wilson, Jonathan M
The stomach, a hallmark of gnathostome evolution, represents a unique anatomical innovation characterized by the presence of acid- and pepsin-secreting glands. However, the occurrence of these glands in gnathostome species is not universal; in the nineteenth century the French zoologist Cuvier first noted that some teleosts lacked a stomach. Strikingly, Holocephali (chimaeras), dipnoids (lungfish) and monotremes (egg-laying mammals) also lack acid secretion and a gastric cellular phenotype. Here, we test the hypothesis that loss of the gastric phenotype is correlated with the loss of key gastric genes. We investigated species from all the main gnathostome lineages and show the specific contribution of gene loss to the widespread distribution of the agastric condition. We establish that the stomach loss correlates with the persistent and complete absence of the gastric function gene kit--H(+)/K(+)-ATPase (Atp4A and Atp4B) and pepsinogens (Pga, Pgc, Cym)--in the analysed species. We also find that in gastric species the pepsinogen gene complement varies significantly (e.g. two to four in teleosts and tens in some mammals) with multiple events of pseudogenization identified in various lineages. We propose that relaxation of purifying selection in pepsinogen genes and possibly proton pump genes in response to dietary changes led to the numerous independent events of stomach loss in gnathostome history. Significantly, the absence of the gastric genes predicts that reinvention of the stomach in agastric lineages would be highly improbable, in line with Dollo's principle.
Coates, Michael I; Gess, Robert W; Finarelli, John A; Criswell, Katharine E; Tietjen, Kristen
Chimaeroid fishes (Holocephali) are one of the four principal divisions of modern gnathostomes (jawed vertebrates). Despite only 47 described living species, chimaeroids are the focus of resurgent interest as potential archives of genomic data and for the unique perspective they provide on chondrichthyan and gnathostome ancestral conditions. Chimaeroids are also noteworthy for their highly derived body plan. However, like other living groups with distinctive anatomies, fossils have been of limited use in unravelling their evolutionary origin, as the earliest recognized examples already exhibit many of the specializations present in modern forms. Here we report the results of a computed tomography analysis of Dwykaselachus, an enigmatic chondrichthyan braincase from the ~280 million year old Karoo sediments of South Africa. Externally, the braincase is that of a symmoriid shark and is by far the most complete uncrushed example yet discovered. Internally, the morphology exhibits otherwise characteristically chimaeroid specializations, including the otic labyrinth arrangement and the brain space configuration relative to exceptionally large orbits. These results have important implications for our view of modern chondrichthyan origins, add robust structure to the phylogeny of early crown group gnathostomes, reveal preconditions that suggest an initial morpho-functional basis for the derived chimaeroid cranium, and shed new light on the chondrichthyan response to the extinction at the end of the Devonian period.
Castro, L. Filipe C.; Gonçalves, Odete; Mazan, Sylvie; Tay, Boon-Hui; Venkatesh, Byrappa; Wilson, Jonathan M.
The stomach, a hallmark of gnathostome evolution, represents a unique anatomical innovation characterized by the presence of acid- and pepsin-secreting glands. However, the occurrence of these glands in gnathostome species is not universal; in the nineteenth century the French zoologist Cuvier first noted that some teleosts lacked a stomach. Strikingly, Holocephali (chimaeras), dipnoids (lungfish) and monotremes (egg-laying mammals) also lack acid secretion and a gastric cellular phenotype. Here, we test the hypothesis that loss of the gastric phenotype is correlated with the loss of key gastric genes. We investigated species from all the main gnathostome lineages and show the specific contribution of gene loss to the widespread distribution of the agastric condition. We establish that the stomach loss correlates with the persistent and complete absence of the gastric function gene kit—H+/K+-ATPase (Atp4A and Atp4B) and pepsinogens (Pga, Pgc, Cym)—in the analysed species. We also find that in gastric species the pepsinogen gene complement varies significantly (e.g. two to four in teleosts and tens in some mammals) with multiple events of pseudogenization identified in various lineages. We propose that relaxation of purifying selection in pepsinogen genes and possibly proton pump genes in response to dietary changes led to the numerous independent events of stomach loss in gnathostome history. Significantly, the absence of the gastric genes predicts that reinvention of the stomach in agastric lineages would be highly improbable, in line with Dollo's principle. PMID:24307675
Wyffels, Jennifer; L. King, Benjamin; Vincent, James; Chen, Chuming; Wu, Cathy H.; Polson, Shawn W.
Chondrichthyan fishes are a diverse class of gnathostomes that provide a valuable perspective on fundamental characteristics shared by all jawed and limbed vertebrates. Studies of phylogeny, species diversity, population structure, conservation, and physiology are accelerated by genomic, transcriptomic and protein sequence data. These data are widely available for many sarcopterygii (coelacanth, lungfish and tetrapods) and actinoptergii (ray-finned fish including teleosts) taxa, but limited for chondrichthyan fishes. In this study, we summarize available data for chondrichthyes and describe resources for one of the largest projects to characterize one of these fish, Leucoraja erinacea, the little skate. SkateBase ( http://skatebase.org) serves as the skate genome project portal linking data, research tools, and teaching resources. PMID:25309735
Noch häufig, vor allem im englischen Sprachraum, wird für die fischartigen Wirbeltiere mit Knochenskelett, also die Actinopterygii und Sarcopterygii, der Begriff "Osteichthyes" (Knochenfische) verwendet. Da sich jedoch aus einem Subtaxon der Sarcopterygier die Tet rapoda entwickelten (S. 322), würde diese Gruppierung ein paraphyletisches Taxon darstellen. Hier wird daher dem Vorschlag W. Hennigs (1983) gefolgt und die Schwestergruppe der Chondrichthyes Osteognathostomata genannt: Sie enthält alle weiteren kiefertragenden Wirbeltiere mit Knochenskelett (Name!) (Abb. 201). Die Sarcopterygii umfassen demnach verschiedene fossile Gruppen, die rezenten Reliktgruppen der Dipnoi (Lungenfische) und Actinistia (Hohlstachler) sowie die Tetrapoda und ihre Stammgruppenvertreter. (Neuerdings wird in der Literatur aus denselben Gründen einer konsequent phylogenetischen Systematisierung wieder die Gruppierung Osteichthyes, aber unter Einschluss der Tetrapoda, verwendet!).
Chen, Xiao; Ai, Weiming; Pan, Lianghao; Shi, Xiaofang
The whale shark Rhincodon typus (Pisces: Chondrichthyes, Orectolobiformes, Rhincodontidae) is the largest living fish on Earth. In this study, we presented its complete mitogenome. It is 16,928 bp in length, contains 13 protein-coding genes, 2 rRNA genes, 22 tRNA genes and one control region with the typical gene order and transcriptional direction in the vertebrates. Overall base composition of the R. typus mitogenome is 33.5% A, 24.3% C, 12.8% G and 29.5% T. Two start codon (GTG and ATG) and two stop codon patterns (TAG and TAA/T) were found in protein-coding genes. The tRNA-Ser2 could not be folded into the typical cloverleaf secondary structure because of the replacement of its dihydrouridine arm by a simple loop. A termination associated sequences (TAS) and three conserved sequence blocks (CSB1-3) were identified in the control region.
Lane, David P; Madhumalar, Arumugam; Lee, Alison P; Tay, Boon-Hui; Verma, Chandra; Brenner, Sydney; Venkatesh, Byrappa
Analysis of the genome of the elephant shark (Callorhinchus milii), a member of the cartilaginous fishes (Class Chondrichthyes), reveals that it encodes all three members of the p53 gene family, p53, p63 and p73, each with clear homology to the equivalent gene in bony vertebrates (Class Osteichthyes). Thus, the gene duplication events that lead to the presence of three family members in the vertebrates dates to before the Silurian era. It also encodes Mdm2 and Mdm4 genes but does not encode the p19(Arf) gene. Detailed comparison of the amino acid sequences of these proteins in the vertebrates reveals that they are evolving at highly distinctive rates, and this variation occurs not only between the three family members but extends to distinct domains in each protein.
Dores, Robert M; Majeed, Qais; Komorowski, Leanne
At the close of the Devonian Period the rapid decline in the diversity of the lobe-finned fishes was countered by the emergence and diversification of the ray-finned fishes and the cartilaginous fishes that now dominate marine and freshwater ecosystems. All of these jawed vertebrates were derived from the ancestral gnathostomes; a chordate lineage that had experienced two genome duplication events during the evolution of the phylum. This review analyzes trends in the phylogeny of the opioid/orphanin gene family (four prohormone/neuropeptide precursor-coding genes) in the major classes of gnathostomes that survived the extinction events at the close of the Devonian Period and focuses on some features of this gene family that appear to set the cartilaginous fishes (class Chondrichthyes) apart from class Sarcopterygii (lobe-finned fishes and tetrapods) and class Actinopterygii (the ray-finned fishes).
Chen, Xiao; Ai, Weiming; Xiang, Dan; Chen, Yunyun; Chen, Shaobo
The complete mitogenome of the pale-edged stingray (Dasyatis zugei) was first confirmed in this study. The mitogenome is 18,264 bp in length and contains 13 protein-coding genes, 2 rRNAs, 22 tRNAs and 1 control region, with the typical gene order in vertebrates. Similar to nucleotide composition of most vertebrate mitogenomes, the nucleotide composition of the pale-edged stingray demonstrates low G and high A+T components. The control region of the pale-edged stingray is 2523 bp in length, the longest known in Chondrichthyes. The termination-associated sequence and two short conserved blocks (CSB II and CSB III) are found in the control region.
Yang, Chao-Pin; Zhi, Ting-Ting; Zhang, Shuai; Yan, Shuai; Yang, Tingbao
The pelagic stingray Pteroplatytrygon violacea is the only pelagic species of the Dasyatidae (Chondrichthyes: Elasmobranchii), which is widely distributed in all tropical, subtropical and temperate oceans. In this study, the complete mitochondrial genome of Pteroplatytrygon violacea was determined. It is 17,665 bp in length and contains 13 protein-coding genes, 2 ribosomal RNA genes, 22 transfer RNA genes and 1 control region, with the typical gene order and direction of transcription of vertebrates. The overall nucleotide compositions of the whole mitogenome are 30.8% A, 26.9% C, 28.6% T and 13.7% G. The ND2 and CO1 sequences are highly similar to the corresponding sequences of this species available in NCBI collected from the Atlantic sea.
Opazo, Juan C.; Toloza-Villalobos, Jessica; Burmester, Thorsten; Venkatesh, Byrappa; Storz, Jay F.
Comparative analyses of vertebrate genomes continue to uncover a surprising diversity of genes in the globin gene superfamily, some of which have very restricted phyletic distributions despite their antiquity. Genomic analysis of the globin gene repertoire of cartilaginous fish (Chondrichthyes) should be especially informative about the duplicative origins and ancestral functions of vertebrate globins, as divergence between Chondrichthyes and bony vertebrates represents the most basal split within the jawed vertebrates. Here, we report a comparative genomic analysis of the vertebrate globin gene family that includes the complete globin gene repertoire of the elephant shark (Callorhinchus milii). Using genomic sequence data from representatives of all major vertebrate classes, integrated analyses of conserved synteny and phylogenetic relationships revealed that the last common ancestor of vertebrates possessed a repertoire of at least seven globin genes: single copies of androglobin and neuroglobin, four paralogous copies of globin X, and the single-copy progenitor of the entire set of vertebrate-specific globins. Combined with expression data, the genomic inventory of elephant shark globins yielded four especially surprising findings: 1) there is no trace of the neuroglobin gene (a highly conserved gene that is present in all other jawed vertebrates that have been examined to date), 2) myoglobin is highly expressed in heart, but not in skeletal muscle (reflecting a possible ancestral condition in vertebrates with single-circuit circulatory systems), 3) elephant shark possesses two highly divergent globin X paralogs, one of which is preferentially expressed in gonads, and 4) elephant shark possesses two structurally distinct α-globin paralogs, one of which is preferentially expressed in the brain. Expression profiles of elephant shark globin genes reveal distinct specializations of function relative to orthologs in bony vertebrates and suggest hypotheses about
Theodosiou, Nicole A; Hall, Daniel A; Jowdry, Andrea L
The digestive tract of vertebrates is a complex organ system required for the digestion of food and the absorption of nutrients. The colon evolved as a water absorption organ essential for vertebrates to survive on land. In contrast to land vertebrates, the Chondrichthyes (sharks, skates and rays) are nearly iso-osmotic with their ocean environment and do not reabsorb water from food waste. To understand the origin of the vertebrate colon, we examined the distribution of sulfated and sialyated mucus-producing cells in the little skate, Raja erinacea, as an indication of water absorption function in the chondrichthian digestive tract. The percentage of acid mucin producing goblet cells was analyzed in the spiral valve and hindgut of little skate and the small intestine and colon of mouse embryos. Levels of acid mucins in the hindgut of the little skate was comparable to that of the small intestines of terrestrial vertebrates, whereas the distal region of the spiral valve contained high levels of acid mucin producing cells similar to the colon of mouse and chick. The low numbers of acid mucins in the little skate hindgut confirms that a functional colon for water absorption is absent in the Chondrichthyes. Interestingly, the presence of high levels of acid mucins in the posterior spiral valve provides evidence for a possible primordial water-absorbing organ in the elasmobranchs. Hoxd13 patterns acid mucins in the colons of terrestrial vertebrates. Expression of Hoxd13 and Hoxa13 in R. erinacea suggests conserved roles for Hox genes in patterning the early hindgut.
Baker, Michael E; Nelson, David R; Studer, Romain A
Many responses to adrenal and sex steroids are mediated by receptors that belong to the nuclear receptor family of transcription factors. We investigated the co-evolution of these vertebrate steroid receptors and the enzymes that synthesize adrenal and sex steroids through data mining of genomes from cephalochordates [amphioxus], cyclostomes [lampreys, hagfish], chondrichthyes [sharks, rays, skates], actinopterygii [ray-finned fish], sarcopterygii [coelacanths, lungfishes and terrestrial vertebrates]. An ancestor of the estrogen receptor and 3-ketosteroid receptors evolved in amphioxus. A corticoid receptor and a progesterone receptor evolved in cyclostomes, and an androgen receptor evolved in gnathostomes. Amphioxus contains CYP11, CYP17, CYP19, 3β/Δ5-4-HSD and 17β-HSD14, which suffice for the synthesis of estradiol and Δ5-androstenediol. Amphioxus also contains CYP27, which catalyzes the synthesis of 27-hydroxy-cholesterol, another estrogen. Lamprey contains, in addition, CYP21, which catalyzes the synthesis of 11-deoxycortisol. Chondrichthyes contain, in addition, CYP11A, CYP11C, CYP17A1, CYP17A2. Coelacanth also contains CYP11C1, the current descendent from a common ancestor with modern land vertebrate CYP11B genes, which catalyze the synthesis of cortisol, corticosterone and aldosterone. Interestingly, CYP11B2, aldosterone synthase, evolved from separate gene duplications in at least old world monkeys and two suborders of rodents. Sciurognathi (including mice and rats) and Hystricomorpha (including guinea pigs). Thus, steroid receptors and steroidogenic enzymes co-evolved at key transitions in the evolution of vertebrates. Together, this suite of receptors and enzymes through their roles in transcriptional regulation of reproduction, development, homeostasis and the response to stress contributed to the evolutionary diversification of vertebrates. This article is part of a Special Issue entitled 'Steroid/Sterol signaling'.
Mahaut, Marie-Laure; Geistdoerfer, Patrick; Sibuet, Myriam
Trophic relationships between fish species have been analyzed as a contribution to the construction of an energy transfer model between various groups in the benthic ecosystem of Meriadzek Terrace, located at 170 miles off the west French coast at a depth of 2100m. Attention was given to the carnivorous megafaunal compartment. The importance of the carnivore megafaunal biomass and its part in energy transfer is still unresolved. On the Meriadzek Terrace, numerous Chondrichthyes (sharks and chimeroids) were frequently observed from the manned submersible Cyana or by baited camera; their biomass appears to be exceptionally large. Results of a photographic survey conducted using the unmanned free vehicle Epaulard have given estimates of 22 per 10 4m 2 of teleost fishes (belonging to 8 different families and one suborder) but included no Chondrichthyes (except one specimen of Rajidae). From baited camera observations, however, we conclude that carcasses falling to the bottom on the Terrace are exploited only by selacians as the bait was never seen to be eaten by macrourids, morids or synaphobranchids although they always attended the baits before the arrival of large scavengers. Trophic specialization strategies occur in this deep-sea ecosystem and our further studies on the energy transfer model for the Meriadzek Terrace will differentiate between strategies exploiting two sources of organic input to the bottom environment: organic particles and large carcasses. In one case, carbon transfer is via the whole benthic food web in which each link is specified by size and trophic behaviour. This pathway ends in the carnivorous megafaunal compartment, which includes benthic fishes, consumers of the local epibenthic and sometimes inbenthic, macro- and megafauna. The second pathway originates with carcass falls, and carbon transfer is direct to the benthopelagic scavengers observed frequently at the Meriadzek Terrace.
Parton, Angela; Bayne, Christopher J; Barnes, David W
Elasmobranchs are the most commonly used experimental models among the jawed, cartilaginous fish (Chondrichthyes). Previously we developed cell lines from embryos of two elasmobranchs, Squalus acanthias the spiny dogfish shark (SAE line), and Leucoraja erinacea the little skate (LEE-1 line). From these lines cDNA libraries were derived and expressed sequence tags (ESTs) generated. From the SAE cell line 4303 unique transcripts were identified, with 1848 of these representing unknown sequences (showing no BLASTX identification). From the LEE-1 cell line, 3660 unique transcripts were identified, and unknown, unique sequences totaled 1333. Gene Ontology (GO) annotation showed that GO assignments for the two cell lines were in general similar. These results suggest that the procedures used to derive the cell lines led to isolation of cell types of the same general embryonic origin from both species. The LEE-1 transcripts included GO categories "envelope" and "oxidoreductase activity" but the SAE transcripts did not. GO analysis of SAE transcripts identified the category "anatomical structure formation" that was not present in LEE-1 cells. Increased organelle compartments may exist within LEE-1 cells compared to SAE cells, and the higher oxidoreductase activity in LEE-1 cells may indicate a role for these cells in responses associated with innate immunity or in steroidogenesis. These EST libraries from elasmobranch cell lines provide information for assembly of genomic sequences and are useful in revealing gene diversity, new genes and molecular markers, as well as in providing means for elucidation of full-length cDNAs and probes for gene array analyses. This is the first study of this type with members of the Chondrichthyes.
Opazo, Juan C; Lee, Alison P; Hoffmann, Federico G; Toloza-Villalobos, Jessica; Burmester, Thorsten; Venkatesh, Byrappa; Storz, Jay F
Comparative analyses of vertebrate genomes continue to uncover a surprising diversity of genes in the globin gene superfamily, some of which have very restricted phyletic distributions despite their antiquity. Genomic analysis of the globin gene repertoire of cartilaginous fish (Chondrichthyes) should be especially informative about the duplicative origins and ancestral functions of vertebrate globins, as divergence between Chondrichthyes and bony vertebrates represents the most basal split within the jawed vertebrates. Here, we report a comparative genomic analysis of the vertebrate globin gene family that includes the complete globin gene repertoire of the elephant shark (Callorhinchus milii). Using genomic sequence data from representatives of all major vertebrate classes, integrated analyses of conserved synteny and phylogenetic relationships revealed that the last common ancestor of vertebrates possessed a repertoire of at least seven globin genes: single copies of androglobin and neuroglobin, four paralogous copies of globin X, and the single-copy progenitor of the entire set of vertebrate-specific globins. Combined with expression data, the genomic inventory of elephant shark globins yielded four especially surprising findings: 1) there is no trace of the neuroglobin gene (a highly conserved gene that is present in all other jawed vertebrates that have been examined to date), 2) myoglobin is highly expressed in heart, but not in skeletal muscle (reflecting a possible ancestral condition in vertebrates with single-circuit circulatory systems), 3) elephant shark possesses two highly divergent globin X paralogs, one of which is preferentially expressed in gonads, and 4) elephant shark possesses two structurally distinct α-globin paralogs, one of which is preferentially expressed in the brain. Expression profiles of elephant shark globin genes reveal distinct specializations of function relative to orthologs in bony vertebrates and suggest hypotheses about
Takagi, Wataru; Kajimura, Makiko; Bell, Justin D; Toop, Tes; Donald, John A; Hyodo, Susumu
Cartilaginous fish comprise two subclasses, the Holocephali (chimaeras) and Elasmobranchii (sharks, skates and rays). Little is known about osmoregulatory mechanisms in holocephalan fishes except that they conduct urea-based osmoregulation, as in elasmobranchs. In the present study, we examined the ornithine urea cycle (OUC) enzymes that play a role in urea biosynthesis in the holocephalan elephant fish, Callorhinchus milii (cm). We obtained a single mRNA encoding carbamoyl phosphate synthetase III (cmCPSIII) and ornithine transcarbamylase (cmOTC), and two mRNAs encoding glutamine synthetases (cmGSs) and two arginases (cmARGs), respectively. The two cmGSs were structurally and functionally separated into two types: brain/liver/kidney-type cmGS1 and muscle-type cmGS2. Furthermore, two alternatively spliced transcripts with different sizes were found for cmgs1 gene. The longer transcript has a putative mitochondrial targeting signal (MTS) and was predominantly expressed in the liver and kidney. MTS was not found in the short form of cmGS1 and cmGS2. A high mRNA expression and enzyme activities were found in the liver and muscle. Furthermore, in various tissues examined, mRNA levels of all the enzymes except cmCPSIII were significantly increased after hatching. The data show that the liver is the important organ for urea biosynthesis in elephant fish, but, extrahepatic tissues such as the kidney and muscle may also contribute to the urea production. In addition to the role of the extrahepatic tissues and nitrogen metabolism, the molecular and functional characteristics of multiple isoforms of GSs and ARGs are discussed.
Maisey, J G
The Subclass Elasmobranchii is widely considered nowadays to be the sister group of the Subclass Holocephali, although chimaeroid fishes were originally classified as elasmobranchs along with modern sharks and rays. While this modern systematic treatment provides an accurate reflection of the phylogenetic relationships among extant taxa, the classification of many extinct non-holocephalan shark-like chondrichthyans as elasmobranchs is challenged. A revised, apomorphy-based definition of elasmobranchs is presented in which they are considered the equivalent of neoselachians, i.e. a monophyletic group of modern sharks and rays which not only excludes all stem and crown holocephalans, but also many Palaeozoic shark-like chondrichthyans and even close extinct relatives of neoselachians such as hybodonts. The fossil record of elasmobranchs (i.e. neoselachians) is reviewed, focusing not only on their earliest records but also on their subsequent distribution patterns through time. The value and limitations of the fossil record in answering questions about elasmobranch phylogeny are discussed. Extinction is seen as a major factor in shaping early elasmobranch history, especially during the Triassic. Extinctions may also have helped shape modern lamniform diversity, despite uncertainties surrounding the phylogenetic affinities of supposedly extinct clades such as cretoxyrhinids, anacoracids and odontids. Apart from these examples, and the supposed Cretaceous extinction of 'sclerorhynchids', elasmobranch evolution since the Jurassic has mostly involved increased diversification (especially during the Cretaceous). The biogeographical distribution of early elasmobranchs may be obscured by sampling bias, but the earliest records of numerous groups are located within the Tethyan realm. The break-up of Gondwana, and particularly the opening of the South Atlantic Ocean (together with the development of epicontinental seaways across Brazil and Africa during the Cretaceous
Poddubnaya, Larisa G; Reed, Cecile; Gibson, David I
A scanning electron microscopical study, incorporating some transmission electron microscopical observations, was undertaken on the surface topography of the gill parasite Callorhynchocotyle callorhynchi (Manter, 1955) (Monogenea: Hexabothriidae) from the Cape elephant fish Callorhinchus capensis (Holocephali) off the western coast of South Africa. The study revealed the presence of several new characteristics for this species. These include the presence of regularly distributed, knob-shaped projections on the surface of the haptor, haptoral appendix and sucker peduncles measuring 0.2 μm and in concentrations of approximately 100 per 10 μm(2) and the existence of a ridge which bisects each sucker lumen, forming two different loculi. We also report, for the first time for any monogenean, the presence of 'true spines'; these occur on the luminal surface of the haptoral suckers and have all of the characteristics of the tegumental spines of digeneans, i.e. they are situated within the distal syncytial tegumental cytoplasm, rest on the basal plasma membrane, have a uniform structure and are covered apically by the tegumental surface plasma membrane. These spines are simple, straight and single-pointed. Under the scanning electron microscopy (SEM), within an area of 20 μm in diameter, 23 such spines were counted, but their concentration and arrangement varies in different regions of the sucker. At their base, they measure about 1.5 μm in width and reach approximately 2 μm in height above the general level of the tegument, but transmission electron microscopy (TEM) measurements of an entire spine indicate that they may reach 3 μm in total length. The presence of spines, possessing similar morphological characteristics in both basal polyopisthocotylean monogeneans and digeneans, represents another characteristic which may prove useful in understanding the evolutionary relationships within the Neodermata.
Davies, Angela J; Hosein, Shazia; Merrett, Nigel R
Archived blood smears from 32 of 113 fishes in 18 families and 12 orders, trawled from deep North Atlantic waters off the Cape Verde Islands in 1999 and over the Porcupine Seabight in 2001 were found to harbour haematozoans. These included four species of haemogregarines (Adeleorina, Haemogregarinidae) and a species of trypanosome (Trypanosomatina, Trypanosomatidae) located in Porcupine Seabight fishes. Also present were Haemohormidium-like structures of uncertain status found in samples from this location and from the Cape Verde Islands. Although material was limited, two of the haemogregarines were provisionally named Desseria harriottae sp. n. from Harriotta raleighana Goode et Bean (Chimaeriformes, Rhinochimaeridae), and Haemogregarina bathysauri sp. n. from Bathysaurus ferox Günther (Aulopiformes, Bathysauridae). The two remaining haemogregarines were identified as Desseria marshalllairdi (Khan, Threlfall et Whitty, 1992) from Halosauropsis macrochir (Günther) (Notacanthiformes, Halosauridae), and Haemogregarina michaeljohnstoni (Davies et Merrett, 2000) from Cataetyx laticeps Koefoed (Ophidiformes, Bythitidae). The name H. michaeljohnstoni was proposed to replace Haemogregarinajohnstoni Davies et Merrett, 2000 from C. laticeps and to avoid confusion with Hepatozoon johnstoni (Mackerras, 1961) Smith, 1996 from varanid lizards, originally named Haemogregarina johnstoni Mackerras, 1961. The trypanosome formed a mixed parasitaemia with D. harriottae in H. raleighana and was provisionally named Trypanosoma harriottae sp. n. No blood parasites had been described previously from cartilaginous fishes of the Holocephali, making the finds in H. raleighana unique. Haemohormidium-like structures were located in erythrocytes in one fish, Coryphaenoides armatus (Hector), among the Cape Verde Islands samples and in 12 species of fishes from the Porcupine Seabight; all these hosts were bony fishes. Finally, the haemogregarine species listed in the genus Desseria Siddall
Priede, I G; Froese, R
Analysis of maximum depth of occurrence of 11 952 marine fish species shows a global decrease in species number (N) with depth (x; m): log10N = −0·000422x + 3·610000 (r2 = 0·948). The rate of decrease is close to global estimates for change in pelagic and benthic biomass with depth (−0·000430), indicating that species richness of fishes may be limited by food energy availability in the deep sea. The slopes for the Classes Myxini (−0·000488) and Actinopterygii (−0·000413) follow this trend but Chondrichthyes decrease more rapidly (−0·000731) implying deficiency in ability to colonize the deep sea. Maximum depths attained are 2743, 4156 and 8370 m for Myxini, Chondrichthyes and Actinopterygii, respectively. Endemic species occur in abundance at 7–7800 m depth in hadal trenches but appear to be absent from the deepest parts of the oceans, >9000 m deep. There have been six global oceanic anoxic events (OAE) since the origin of the major fish taxa in the Devonian c. 400 million years ago (mya). Colonization of the deep sea has taken place largely since the most recent OAE in the Cretaceous 94 mya when the Atlantic Ocean opened up. Patterns of global oceanic circulation oxygenating the deep ocean basins became established coinciding with a period of teleost diversification and appearance of the Acanthopterygii. Within the Actinopterygii, there is a trend for greater invasion of the deep sea by the lower taxa in accordance with the Andriashev paradigm. Here, 31 deep-sea families of Actinopterygii were identified with mean maximum depth >1000 m and with >10 species. Those with most of their constituent species living shallower than 1000 m are proposed as invasive, with extinctions in the deep being continuously balanced by export of species from shallow seas. Specialized families with most species deeper than 1000 m are termed deep-sea endemics in this study; these appear to persist in the deep by virtue of global distribution enabling
Priede, I G; Froese, R
Analysis of maximum depth of occurrence of 11 952 marine fish species shows a global decrease in species number (N) with depth (x; m): log10 N = -0·000422x + 3·610000 (r(2) = 0·948). The rate of decrease is close to global estimates for change in pelagic and benthic biomass with depth (-0·000430), indicating that species richness of fishes may be limited by food energy availability in the deep sea. The slopes for the Classes Myxini (-0·000488) and Actinopterygii (-0·000413) follow this trend but Chondrichthyes decrease more rapidly (-0·000731) implying deficiency in ability to colonize the deep sea. Maximum depths attained are 2743, 4156 and 8370 m for Myxini, Chondrichthyes and Actinopterygii, respectively. Endemic species occur in abundance at 7-7800 m depth in hadal trenches but appear to be absent from the deepest parts of the oceans, >9000 m deep. There have been six global oceanic anoxic events (OAE) since the origin of the major fish taxa in the Devonian c. 400 million years ago (mya). Colonization of the deep sea has taken place largely since the most recent OAE in the Cretaceous 94 mya when the Atlantic Ocean opened up. Patterns of global oceanic circulation oxygenating the deep ocean basins became established coinciding with a period of teleost diversification and appearance of the Acanthopterygii. Within the Actinopterygii, there is a trend for greater invasion of the deep sea by the lower taxa in accordance with the Andriashev paradigm. Here, 31 deep-sea families of Actinopterygii were identified with mean maximum depth >1000 m and with >10 species. Those with most of their constituent species living shallower than 1000 m are proposed as invasive, with extinctions in the deep being continuously balanced by export of species from shallow seas. Specialized families with most species deeper than 1000 m are termed deep-sea endemics in this study; these appear to persist in the deep by virtue of global distribution enabling recovery
Sunyer, J Oriol
The evolutionary origins of Ig-producing B cells appear to be linked to the emergence of fish in this planet. There are three major classes of living fish species, which from most primitive to modern they are referred to as agnathan (e.g., lampreys), Chondrichthyes (e.g., sharks), and teleost fish (e.g., rainbow trout). Agnathans do not have immunoglobulin- producing B cells, however these fish contain a subset of lymphocytes-like cells producing type B variable lymphocyte receptors (VLRBs) that appear to act as functional analogs of immunoglobulins. Chondrichthyes fish represent the most primitive living species containing bona-fide immunoglobulin-producing B cells. Their B cells are known to secrete three types of antibodies, IgM, IgW and IgNAR. Teleost fish are also called bony fish since they represent the most ancient living species containing true bones. Teleost B cells produce three different immunoglobulin isotypes, IgM, IgD and the recently described IgT. While teleost IgM is the principal player in systemic immunity, IgT appears to be a teleost immunoglobulin class specialized in mucosal immune responses. Thus far, three major B cell lineages have been described in teleost, those expressing either IgT or IgD, and the most common lineage which co-expresses IgD and IgM. A few years ago, the study of teleost fish B cells revealed for the first time in vertebrates the existence of B cell subsets with phagocytic and intracellular bactericidal capacities. This finding represented a paradigm shift as professional phagocytosis was believed to be exclusively performed by some cells of the myeloid lineage (i.e., macrophages, monocytes, neutrophils). This phagocytic capacity was also found in amphibians and reptiles, suggesting that this innate capacity was evolutionarily conserved in certain B cell subsets of vertebrates. Recently, the existence of subsets of B cells with phagocytic and bactericidal abilities have also been confirmed in mammals. Moreover, it has
da Silva, Nelson Jorge; Clementino Ferreira, Kalley Ricardo; Leite Pinto, Raimundo Nonato; Aird, Steven Douglas
Freshwater stingrays cause many serious human injuries, but identification of the offending species is uncommon. The present case involved a large freshwater stingray, Potamotrygon motoro (Chondrichthyes: Potamotrygonidae), in the Araguaia River in Tocantins, Brazil. Appropriate first aid was administered within ~15 min, except that an ice pack was applied. Analgesics provided no pain relief, although hot compresses did. Ciprofloxacin therapy commenced after ~18 h and continued seven days. Then antibiotic was suspended; however, after two more days and additional tests, cephalosporin therapy was initiated, and proved successful. Pain worsened despite increasingly powerful analgesics, until debridement of the wound was performed after one month. The wound finally closed ~70 days after the accident, but the patient continued to have problems wearing shoes even eight months later. Chemistry and pharmacology of Potamotrygon venom and mucus, and clinical management of freshwater stingray envenomations are reviewed in light of the present case. Bacterial infections of stingray puncture wounds may account for more long-term morbidity than stingray venom. Simultaneous prophylactic use of multiple antibiotics is recommended for all but the most superficial stingray wounds. Distinguishing relative contributions of venom, mucus, and bacteria will require careful genomic and transcriptomic investigations of stingray tissues and contaminating bacteria. PMID:26094699
Falcón, Jack; Coon, Steven L; Besseau, Laurence; Cazaméa-Catalan, Damien; Fuentès, Michaël; Magnanou, Elodie; Paulin, Charles-Hubert; Boeuf, Gilles; Sauzet, Sandrine; Jørgensen, Even H; Mazan, Sylvie; Wolf, Yuri I; Koonin, Eugene V; Steinbach, Peter J; Hyodo, Susumu; Klein, David C
Melatonin (N-acetyl-5-methoxytrypamine) is the vertebrate hormone of the night: circulating levels at night are markedly higher than day levels. This increase is driven by precisely regulated increases in acetylation of serotonin in the pineal gland by arylalkylamine N-acetyltransferase (AANAT), the penultimate enzyme in the synthesis of melatonin. This unique essential role of AANAT in vertebrate timekeeping is recognized by the moniker the timezyme. AANAT is also found in the retina, where melatonin is thought to play a paracrine role. Here, we focused on the evolution of AANAT in early vertebrates. AANATs from Agnathans (lamprey) and Chondrichthyes (catshark and elephant shark) were cloned, and it was found that pineal glands and retinas from these groups express a form of AANAT that is compositionally, biochemically, and kinetically similar to AANATs found in bony vertebrates (VT-AANAT). Examination of the available genomes indicates that VT-AANAT is absent from other forms of life, including the Cephalochordate amphioxus. Phylogenetic analysis and evolutionary rate estimation indicate that VT-AANAT evolved from the nonvertebrate form of AANAT after the Cephalochordate-Vertebrate split over one-half billion years ago. The emergence of VT-AANAT apparently involved a dramatic acceleration of evolution that accompanied neofunctionalization after a duplication of the nonvertebrate AANAT gene. This scenario is consistent with the hypotheses that the advent of VT-AANAT contributed to the evolution of the pineal gland and lateral eyes from a common ancestral photodetector and that it was not a posthoc recruitment.
Milewski, Antoni V; Dierenfeld, Ellen S
Tapirs (Perissodactyla: Tapiridae) are the only living vertebrates, beyond the order Proboscidea, found to possess a true proboscis, defined as a flexible tubular extension of the joint narial and upper labial musculature that serves, at least in part, to grasp food. Tapirs show only partial homology and analogy with elephants in the narial and upper labial structures, as well as in the skull bones and teeth. However, superficially similar extensions in other extant vertebrates differ greatly in anatomy and function. Therefore, they deserve new names: prorhiscis (e.g. Mammalia: Saiga tatarica), prorhinosis (e.g. Chondrichthyes: Callorhinchus spp.), prorhynchis (e.g. Osteichthyes: Campylomormyrus spp.) and progeneiontis (e.g. Osteichthyes: Gnathonemus spp.). Among non-mammalian vertebrates, no bird or reptile is known to possess a proboscis. Among fishes, there are various extensions of the rostrum, jaws, 'nose' and 'chin' that lack the required narial involvement. The skulls of extinct mammals within (e.g. deinotheres) and beyond (e.g. astrapotheres) the Proboscidea confirm that a proboscis evolved independently in several mammalian lineages before the Pliocene. This convergence with tapirs presumably reflects, in part, the advantages of concentrating the olfactory sensor on what is, effectively, the tip of a long mobile upper lip. However, the proboscis does not appear to have arisen de novo in any vertebrate post-Pliocene, and its continued evolution has apparently depended on the further development of its length, flexibility and innervations, as epitomized by elephants.
Fortibuoni, Tomaso; Libralato, Simone; Raicevich, Saša; Giovanardi, Otello; Solidoro, Cosimo
The understanding of fish communities' changes over the past centuries has important implications for conservation policy and marine resource management. However, reconstructing these changes is difficult because information on marine communities before the second half of the 20th century is, in most cases, anecdotal and merely qualitative. Therefore, historical qualitative records and modern quantitative data are not directly comparable, and their integration for long-term analyses is not straightforward. We developed a methodology that allows the coding of qualitative information provided by early naturalists into semi-quantitative information through an intercalibration with landing proportions. This approach allowed us to reconstruct and quantitatively analyze a 200-year-long time series of fish community structure indicators in the Northern Adriatic Sea (Mediterranean Sea). Our analysis provides evidence of long-term changes in fish community structure, including the decline of Chondrichthyes, large-sized and late-maturing species. This work highlights the importance of broadening the time-frame through which we look at marine ecosystem changes and provides a methodology to exploit, in a quantitative framework, historical qualitative sources. To the purpose, naturalists' eyewitness accounts proved to be useful for extending the analysis on fish community back in the past, well before the onset of field-based monitoring programs. PMID:21103349
Smith, Moya Meredith; Riley, Alex; Fraser, Gareth J; Underwood, Charlie; Welten, Monique; Kriwet, Jürgen; Pfaff, Cathrin; Johanson, Zerina
In classical theory, teeth of vertebrate dentitions evolved from co-option of external skin denticles into the oral cavity. This hypothesis predicts that ordered tooth arrangement and regulated replacement in the oral dentition were also derived from skin denticles. The fossil batoid ray Schizorhiza stromeri (Chondrichthyes; Cretaceous) provides a test of this theory. Schizorhiza preserves an extended cartilaginous rostrum with closely spaced, alternating saw-teeth, different from sawfish and sawsharks today. Multiple replacement teeth reveal unique new data from micro-CT scanning, showing how the 'cone-in-cone' series of ordered saw-teeth sets arrange themselves developmentally, to become enclosed by the roots of pre-existing saw-teeth. At the rostrum tip, newly developing saw-teeth are present, as mineralized crown tips within a vascular, cartilaginous furrow; these reorient via two 90° rotations then relocate laterally between previously formed roots. Saw-tooth replacement slows mid-rostrum where fewer saw-teeth are regenerated. These exceptional developmental data reveal regulated order for serial self-renewal, maintaining the saw edge with ever-increasing saw-tooth size. This mimics tooth replacement in chondrichthyans, but differs in the crown reorientation and their enclosure directly between roots of predecessor saw-teeth. Schizorhiza saw-tooth development is decoupled from the jaw teeth and their replacement, dependent on a dental lamina. This highly specialized rostral saw, derived from diversification of skin denticles, is distinct from the dentition and demonstrates the potential developmental plasticity of skin denticles.
Simpfendorfer, Colin A; Dulvy, Nicholas K
Sharks, rays and chimeras (class Chondrichthyes; herein 'sharks') today face possibly the largest crisis of their 420 million year history. Tens of millions of sharks are caught and traded internationally each year, many populations are overfished to the point where global catch peaked in 2003, and a quarter of species have an elevated risk of extinction [1-3]. To some, the solution is to simply stop taking them from our oceans, or prohibit carriage, sale or trade in shark fins . Approaches such as bans and alternative livelihoods for fishers (e.g. ecotourism) may play some role in controlling fishing mortality but will not solve this crisis because sharks are mostly taken as incidental catch and play an important role in food security [5-7]. Here, we show that moving to sustainable fishing is a feasible solution. In fact, approximately 9% of the current global catch of sharks, from at least 33 species with a wide range of life histories, is biologically sustainable, although not necessarily sufficiently managed.
Hagey, Lee R; Møller, Peter R; Hofmann, Alan F; Krasowski, Matthew D
Bile salts are the major end metabolites of cholesterol and are also important in lipid and protein digestion, as well as shaping of the gut microflora. Previous studies had demonstrated variation of bile salt structures across vertebrate species. We greatly extend prior surveys of bile salt variation in fish and amphibians, particularly in analysis of the biliary bile salts of Agnatha and Chondrichthyes. While there is significant structural variation of bile salts across all fish orders, bile salt profiles are generally stable within orders of fish and do not correlate with differences in diet. This large data set allowed us to infer evolutionary changes in the bile salt synthetic pathway. The hypothesized ancestral bile salt synthetic pathway, likely exemplified in extant hagfish, is simpler and much shorter than the pathway of most teleost fish and terrestrial vertebrates. Thus, the bile salt synthetic pathway has become longer and more complex throughout vertebrate evolution. Analysis of the evolution of bile salt synthetic pathways provides a rich model system for the molecular evolution of a complex biochemical pathway in vertebrates.
Priede, Imants G; Froese, Rainer; Bailey, David M; Bergstad, Odd Aksel; Collins, Martin A; Dyb, Jan Erik; Henriques, Camila; Jones, Emma G; King, Nicola
The oceanic abyss (depths greater than 3000 m), one of the largest environments on the planet, is characterized by absence of solar light, high pressures and remoteness from surface food supply necessitating special molecular, physiological, behavioural and ecological adaptations of organisms that live there. Sampling by trawl, baited hooks and cameras we show that the Chondrichthyes (sharks, rays and chimaeras) are absent from, or very rare in this region. Analysis of a global data set shows a trend of rapid disappearance of chondrichthyan species with depth when compared with bony fishes. Sharks, apparently well adapted to life at high pressures are conspicuous on slopes down to 2000 m including scavenging at food falls such as dead whales. We propose that they are excluded from the abyss by high-energy demand, including an oil-rich liver for buoyancy, which cannot be sustained in extreme oligotrophic conditions. Sharks are apparently confined to ca 30% of the total ocean and distribution of many species is fragmented around sea mounts, ocean ridges and ocean margins. All populations are therefore within reach of human fisheries, and there is no hidden reserve of chondrichthyan biomass or biodiversity in the deep sea. Sharks may be more vulnerable to over-exploitation than previously thought. PMID:16777734
Rasmussen, Ann-Sofie; Arnason, Ulfur
The Chondrichthyes (cartilaginous fishes) are commonly accepted as being sister group to the other extant Gnathostomata (jawed vertebrates). To clarify gnathostome relationships and to aid in resolving and dating the major piscine divergences, we have sequenced the complete mtDNA of the starry skate and have included it in phylogenetic analysis along with three squalomorph chondrichthyans—the common dogfish, the spiny dogfish, and the star spotted dogfish—and a number of bony fishes and amniotes. The direction of evolution within the gnathostome tree was established by rooting it with the most closely related non-gnathostome outgroup, the sea lamprey, as well as with some more distantly related taxa. The analyses placed the chondrichthyans in a terminal position in the piscine tree. These findings, which also suggest that the origin of the amniote lineage is older than the age of the oldest extant bony fishes (the lungfishes), challenge the evolutionary direction of several morphological characters that have been used in reconstructing gnathostome relationships. Applying as a calibration point the age of the oldest lungfish fossils, 400 million years, the molecular estimate placed the squalomorph/batomorph divergence at ≈190 million years before present. This dating is consistent with the occurrence of the earliest batomorph (skates and rays) fossils in the paleontological record. The split between gnathostome fishes and the amniote lineage was dated at ≈420 million years before present. PMID:10051614
Jones, R C
This review examines the structure and function of the extratesticular sperm ducts of vertebrates in terms of their evolutionary development and adaptive significance. The primitive extratesticular duct system of Chondrichthyes is described as an example of the vertebrate archetype. Adaptations of the duct system in higher vertebrates have involved a loss of some structures and specialization of others. The duct system probably evolved as a homeostatic mechanism to facilitate fertilization and some embryological development under conditions protected from the external environment. However, it is argued that the ducts also play an important role in the competition between males to achieve paternity. In vertebrates that practise internal fertilization the ducts are involved in post-testicular maturation and storage of spermatozoa. The biological significance of post-testicular sperm maturation has not been resolved. By contrast, sperm storage is essential in most male vertebrates because of the slow rate of spermatogenesis, particularly in ectotherms. Sperm storage is also important in the competition between males for paternity as it enables a male to mate a 'partner' a number of times during an oestrus in order to reduce the prospect of being cuckolded by another male. The extent of sperm maturation and storage in the epididymis of particular vertebrates depends on the relative roles of the testis and its extragonadal ducts in the competition between males for paternity. These roles depend on a number of factors, including allometric limitations to testis size, metabolic rate and the development of endothermy, and the reproductive strategy of females of the species.
Tomita, Taketeru; Toda, Minoru; Ueda, Keiichi; Uchida, Senzo; Nakaya, Kazuhiro
We conducted an ultrasonographic experiment on a pregnant manta ray, Manta alfredi (Chondrichthyes, Batoidea). This study showed how the embryo of the live-bearing elasmobranchs respires in the body of the female. In the embryonic stage, the manta ray embryo takes in uterine fluid by buccal-pumping. After birth, the manta ray shifts its respiratory mode from buccal-pumping to ram-ventilation. The rapid reduction of the spiracle size in the young manta ray may reflect this shift of respiratory mode. Unlike mammals or some carcharhinid sharks that acquire oxygen through a placenta and umbilical cord, the manta ray embryo does not have a direct connection with the mother. Thus, the manta ray embryo obtains oxygen by buccal-pumping of the uterine fluid, in the same way that the embryos of egg-laying species obtain oxygen from the water in the egg case. This finding extends our understanding of the diversity of embryonic respiratory systems in live-bearing vertebrates.
Lopes-Marques, Mónica; Ruivo, Raquel; Delgado, Inês; Wilson, Jonathan M.; Aluru, Neelakanteswar; Castro, L. Filipe C.
The uptake and transport of vitamin B12 (cobalamin; Cbl) in mammals involves a refined system with three evolutionarily related transporters: transcobalamin 1 (Tcn1), transcobalamin 2 (Tcn2), and the gastric intrinsic factor (Gif). Teleosts have a single documented binder with intermediate features to the human counterparts. Consequently, it has been proposed that the expansion of Cbl binders occurred after the separation of Actinopterygians. Here, we demonstrate that the diversification of this gene family took place earlier in gnathostome ancestry. Our data indicates the presence of single copy orthologs of the Sarcopterygii/Tetrapoda duplicates Tcn1 and Gif, and Tcn2, in Chondrichthyes. In addition, a highly divergent Cbl binder was found in the Elasmobranchii. We unveil a complex scenario forged by genome, tandem duplications and lineage-specific gene loss. Our findings suggest that from an ancestral transporter, exhibiting large spectrum and high affinity binding, highly specific Cbl transporters emerged through gene duplication and mutations at the binding pocket. PMID:25552533
Schnetz, Lisa; Pfaff, Cathrin; Kriwet, Jürgen
The dentition of lamniforme sharks exhibits several characters that have been used extensively to resolve the phylogenetic relationships of extant taxa, yet some uncertainties remain. Also, the development of different teeth of a tooth file within the jaws of most extant lamniforms has not been documented to date. High-resolution micro-computed tomography is used here to re-evaluate the importance of two dental characters within the order Lamniformes, which were considered not to be phylogenetically informative, the histotype and the number of teeth per tooth file. Additionally, the development and mineralization patterns of the teeth of the two osteodont lamniforms Lamna nasus and Alopias superciliosus were compared. We discuss the importance of these dental characters for phylogenetic interpretations to assess the quality of these characters in resolving lamniform relationships. The dental characters suggest that (1) Lamniformes are the only modern-level sharks exhibiting the osteodont histotype, (2) the osteodont histotype in lamniform sharks is a derived state in modern-level sharks (Elasmobranchii), (3) the osteodont type, conversely is convergently achieved when the clade Chondrichthyes is considered and thus might comprise a functional rather than a phylogenetic signal, and (4) there is an increase in the number of teeth per file throughout lamniform phylogeny. Structural development of the teeth of L. nasus and A. superciliosus is congruent with a previous investigation of the lamniform shark Carcharodon carcharias. J. Morphol. 277:1584-1598, 2016. © 2016 Wiley Periodicals, Inc.
Smolka, A J; Lacy, E R; Luciano, L; Reale, E
Virtually all vertebrates acidify their gastric contents to a pH between 0.8 and 2.0. In mammals, acid secretion is mediated by a K-stimulated proton-translocating adenosine triphosphatase (H,K-ATPase), which establishes a million-fold gradient of protons across the apical membrane of the gastric parietal cell. The earliest phylogenetic appearance of gastric acid secretion is in cartilaginous fish, and we sought to verify in this class (Chondrichthyes) the presence and distribution of H,K-ATPase in gastric epithelial cells. An antibody against a synthetic peptide based on the C-terminus of pig H,K-ATPase alpha-subunit was localized in the gastric glands of the Atlantic stingray Dasyatis sabina. The C-terminal antibody stained all cells with tubulovesicles and the apical membrane domain of mucous neck cells. In proximal stomach, gastric glands showed the strongest immunoreactivity in cells close to the isthmus; in the distal stomach, strongest immunoreactivity was found in cells at the base of the glands. Oxyntic cells were more intensely immunoreactive than oxynticopeptic cells. This antibody labeled a single band of M(r) 100,600 on immunoblots of D. sabina gastric microsomes. These results show the earliest phylogenetic occurrence of a gastric ATPase in putative acid-secreting cells and suggest that this enzyme shares structural features with mammalian H,K-ATPase.
Verde, Cinzia; De Rosa, M Cristina; Giordano, Daniela; Mosca, Donato; De Pascale, Donatella; Raiola, Luca; Cocca, Ennio; Carratore, Vitale; Giardina, Bruno; Di Prisco, Guido
Cartilaginous fish are very ancient organisms. In the Antarctic sea, the modern chondrichthyan genera are poorly represented, with only three species of sharks and eight species of skates; the paucity of chondrichthyans is probably an ecological consequence of unusual trophic or habitat conditions in the Southern Ocean. In the Arctic, there are 26 species belonging to the class Chondrichthyes. Fish in the two polar regions have been subjected to different regional histories that have influenced the development of diversity: Antarctic marine organisms are highly stenothermal, in response to stable water temperatures, whereas the Arctic communities are exposed to seasonal temperature variations. The structure and function of the oxygen-transport haem protein from the Antarctic skate Bathyraja eatonii and from the Arctic skate Raja hyperborea (both of the subclass Elasmobranchii, order Rajiformes, family Rajidae) is reported in the present paper. These species have a single major haemoglobin (Hb 1; over 80% of the total). The Bohr-proton and the organophosphate-binding sites are absent. Thus the haemoglobins of northern and southern polar skates appear functionally similar, whereas differences were observed with several temperate elasmobranchs. Such evidence suggests that, in temperate and polar habitats, physiological adaptations have evolved along distinct pathways, whereas, in this case, the effect of the differences characterizing the two polar environments is negligible.
Walsh, Cathy J; Toranto, Jason D; Gilliland, C Taylor; Noyes, David R; Bodine, Ashby B; Luer, Carl A
Reactive nitrogen intermediates, such as nitric oxide (NO), are important immunomodulators in vertebrate immune systems, but have yet to be identified as mediators of host defence in any member of class Chondrichthyes, the cartilaginous fishes. In the present study, production of NO by nurse shark (Ginglymostoma cirratum) peripheral blood leucocytes (PBL) stimulated with bacterial cell wall lipopolysaccharide (LPS) was investigated. PBL were cultured for 24 to 96 h following stimulation with LPS at concentrations ranging from 0 to 25 microg ml(-1), in both serum-supplemented and serum-free culture conditions. Production of NO was measured indirectly using the Griess reaction, with maximal NO production occurring after 72 h using 10% FBS and 10 microg LPS ml(-1). Application of these culture conditions to PBL from another cartilaginous fish (clearnose skate, Raja eglanteria) resulted in a similar NO response. Addition of a specific inhibitor of inducible nitric oxide synthase (iNOS), L-N(6)-(1-iminoethyl)lysine (L-NIL), resulted in a significant decrease in the production of NO by PBL from both species.
Rocco, Lucia; Morescalchi, Maria A; Costagliola, Domenico; Stingo, Vincenzo
Different approaches can be used to elucidate the unsolved questions concerning taxonomic evolution in cartilaginous fish. The study of the karyological characteristics of these vertebrates by combining molecular and traditional techniques of chromosome preparation and banding has been demonstrated to be a very effective method. In this paper we studied the localization and the composition of the constitutive heterochromatin by using C- and restriction endonuclease-banding in four selachian species, belonging to two of the four superorders. We also characterized two different types of repetitive genomic sequences in these species: satellite DNA and (TTAGGG)(n) telomeric sequences. Finally, we analysed the nuclear ribosomal gene to determine the number of the nucleolar organizers and their position on chromosomes by using silver staining, chromomycin A(3), and FISH (fluorescent in situ hybridization). The results showed a prevailingly telomeric localization of constitutive heterochromatin in the Galeomorphii, the presence of additional nucleolar organizer sites in Raja asterias, an exclusively telomeric localization of the (TTAGGG)(n) sequences in Scyliorhinus stellaris and both telomeric and interstitial in Taeniura lymma. These data, together with those concerning the conservation of the satellite DNA, seem to support the hypothesis that Chondrichthyes have an evolutionary history leading them to the acquisition of large genomes rich in highly repeated sequences and subjected to some selective pressures favoring the conservation of this DNA fraction.
Matsuda, K; Yoshida, T; Nagano, Y; Kashimoto, K; Yatohgo, T; Shimomura, H; Shioda, S; Arimura, A; Uchiyama, M
Pituitary adenylate cyclase activating polypeptide (PACAP) was isolated from ovine hypothalami and found to exist as two amidated forms with 38 (PACAP 38) and 27 (PACAP 27) residues. The amino acid sequences of PACAPs isolated from the vertebrates, such as a bird, a frog and teleost fish, appear to be well conserved. In the present study, we attempted to isolate PACAP from the brain of an elasmobranch fish, Dasyatis akajei (stingray), which belongs to the Chondrichthyes (cartilaginous fish), by extraction of the acetone-dried powder with acetic acid, followed by successive high-performance liquid chromatography (HPLC) on a gel-filtration, a cation-exchange and two reverse-phase columns. Purification was monitored by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE) and Western blotting analysis using an anti-PACAP 27 serum. The PACAP thus obtained consisted of 44 residues. The amino acid sequence of the comparable portion of its N-terminal 38 residues showed 92%, 89%, 89%, and 82% identity with those of mammalian, chicken, frog and teleost PACAPs with 38 residues, respectively. The extra six C-terminal residues of the stingray resembled those of tetrapod and teleost PACAP precursors which were deduced from the respective cDNAs. These results indicate that PACAP, which has an amino acid sequence showing high similarity with those of tetrapod and teleost PACAPs, is present in the elasmobranch brain.
Marino, Katia; Boschetto, Loredana; de Pascale, Donatella; Cocca, Ennio
An extensive investigation of the organisation of globin genes has greatly contributed to the understanding of universal mechanisms of gene evolution and expression. Cartilaginous fish are the first organisms that have evolved the tetrameric form of hemoglobin (Hb). So far, there has been absolute lack of data about globin genes in chondrichthyans. Bathyraja is the dominant rajid south of 60 degrees S. In the framework of the investigations on globin genes of Antarctic red-blooded and Hb-less fish we obtained the cloning of the alpha- and beta-globin cDNAs of the main Hb (Hb 1) of the skate Bathyraja eatonii. Then, a genomic fragment of 6.2 kb was isolated where the Hb 1 alpha and beta genes are linked in a tail-to-head (3' to 5') orientation. The beta-globin gene promoter region and the chromosomal organisation of the Hb 1 genes of B. eatonii have been compared to their homologues in other vertebrates. The finding of a tail-to-head linkage of the Hb 1 alpha- and beta-globin genes in B. eatonii is the first characterisation of the organisation of globin genes in chondrichthyes; such finding offers a novel contribution to the understanding of the evolution of this class of genes. Moreover, the characterisation of chondrichthyan genes is very important for gaining insight into the ancestral state of vertebrate genomes.
Nah, Giselle Sek Suan; Lim, Zhi Wei; Tay, Boon-Hui; Osato, Motomi; Venkatesh, Byrappa
The Runx family genes encode transcription factors that play key roles in hematopoiesis, skeletogenesis and neurogenesis and are often implicated in diseases. We describe here the cloning and characterization of Runx1, Runx2, Runx3 and Runxb genes in the elephant shark (Callorhinchus milii), a member of Chondrichthyes, the oldest living group of jawed vertebrates. Through the use of alternative promoters and/or alternative splicing, each of the elephant shark Runx genes expresses multiple isoforms similar to their orthologs in human and other bony vertebrates. The expression profiles of elephant shark Runx genes are similar to those of mammalian Runx genes. The syntenic blocks of genes at the elephant shark Runx gene loci are highly conserved in human, but represented by shorter conserved blocks in zebrafish indicating a higher degree of rearrangements in this teleost fish. Analysis of promoter regions revealed conservation of binding sites for transcription factors, including two tandem binding sites for Runx that are totally conserved in the distal promoter regions of elephant shark Runx1-3. Several conserved noncoding elements (CNEs), which are putative cis-regulatory elements, and miRNA binding sites were identified in the elephant shark and human Runx gene loci. Some of these CNEs and miRNA binding sites are absent in teleost fishes such as zebrafish and fugu. In summary, our analysis reveals that the genomic organization and expression profiles of Runx genes were already complex in the common ancestor of jawed vertebrates. PMID:24699678
Robinson-Rechavi, Marc; Boussau, Bastien; Laudet, Vincent
Vertebrates originated in the lower Cambrian. Their diversification and morphological innovations have been attributed to large-scale gene or genome duplications at the origin of the group. These duplications are predicted to have occurred in two rounds, the "2R" hypothesis, or they may have occurred in one genome duplication plus many segmental duplications, although these hypotheses are disputed. Under such models, most genes that are duplicated in all vertebrates should have originated during the same period. Previous work has shown that indeed duplications started after the speciation between vertebrates and the closest invertebrate, amphioxus, but have not set a clear ending. Consideration of chordate phylogeny immediately shows the key position of cartilaginous vertebrates (Chondrichthyes) to answer this question. Did gene duplications occur as frequently during the 45 Myr between the cartilaginous/bony vertebrate split and the fish/tetrapode split as in the previous approximately 100 Myr? Although the time interval is relatively short, it is crucial to understanding the events at the origin of vertebrates. By a systematic appraisal of gene phylogenies, we show that significantly more duplications occurred before than after the cartilaginous/bony vertebrate split. Our results support rounds of gene or genome duplications during a limited period of early vertebrate evolution and allow a better characterization of these events.
Smith, W Leo; Stern, Jennifer H; Girard, Matthew G; Davis, Matthew P
Venom and its associated delivery systems have evolved in numerous animal groups ranging from jellyfishes to spiders, lizards, shrews, and the male platypus. Building off new data and previously published anatomical and molecular studies, we explore the evolution of and variation within venomous fishes. We show the results of the first multi-locus, ordinal-level phylogenetic analysis of cartilaginous (Chondrichthyes) and ray-finned (Actinopterygii) fishes that hypothesizes 18 independent evolutions of this specialization. Ancestral-states reconstruction indicates that among the 2386-2962 extant venomous fishes, envenomed structures have evolved four times in cartilaginous fishes, once in eels (Anguilliformes), once in catfishes (Siluriformes), and 12 times in spiny-rayed fishes (Acanthomorpha). From our anatomical studies and phylogenetic reconstruction, we show that dorsal spines are the most common envenomed structures (∼95% of venomous fish species and 15 independent evolutions). In addition to envenomed spines, fishes have also evolved venomous fangs (2% of venomous fish species, two independent evolutions), cleithral spines (2% of venomous fish species, one independent evolution), and opercular or subopercular spines (1% of venomous fish species, three independent evolutions).
Ferrando, Sara; Gallus, Lorenzo; Amaroli, Andrea; Gambardella, Chiara; Waryani, Baradi; Di Blasi, Davide; Vacchi, Marino
Sharks belonging to the family Hexanchidae have six or seven gill slits, unlike all other elasmobranchs, which have five gill slits. Their olfactory organs have a round shape, which is common for holocephalans, but not for elasmobranchs. Thus, the shape of the olfactory organ represents a further, less striking, peculiarity of this family among elasmobranchs. Despite that, the microscopic anatomy and histology of the olfactory organ have not yet been studied in any species of this family. Here, an anatomical and histological description of the olfactory organ of the sharpnose sevengill shark Heptranchias perlo is given. The organ is a rosette, with a central raphe and 31-34 primary lamellae, which bear secondary lamellae with a more or less branched shape. The elastic connective capsule which envelops the olfactory rosette possibly changes its shape along with water influx. In the olfactory epithelium, the supporting cells also have a secretory function, while no specialized mucous cells are visible; regarding this feature the olfactory epithelium of H. perlo differs from that of other chondrichthyan species. The immunohistochemical investigation of the sensory epithelium shows the absence of immunoreactivity for Gαolf in receptor neurons, which confirms previous observations in Chondrichthyes.
Tanaka, Keiko; Tomita, Taketeru; Suzuki, Shingo; Hosomichi, Kazuyoshi; Sano, Kazumi; Doi, Hiroyuki; Kono, Azumi; Inoko, Hidetoshi; Kulski, Jerzy K.; Tanaka, Sho
Hexanchiformes is regarded as a monophyletic taxon, but the morphological and genetic relationships between the five extant species within the order are still uncertain. In this study, we determined the whole mitochondrial DNA (mtDNA) sequences of seven sharks including representatives of the five Hexanchiformes, one squaliform, and one carcharhiniform and inferred the phylogenetic relationships among those species and 12 other Chondrichthyes (cartilaginous fishes) species for which the complete mitogenome is available. The monophyly of Hexanchiformes and its close relation with all other Squaliformes sharks were strongly supported by likelihood and Bayesian phylogenetic analysis of 13,749 aligned nucleotides of 13 protein coding genes and two rRNA genes that were derived from the whole mDNA sequences of the 19 species. The phylogeny suggested that Hexanchiformes is in the superorder Squalomorphi, Chlamydoselachus anguineus (frilled shark) is the sister species to all other Hexanchiformes, and the relations within Hexanchiformes are well resolved as Chlamydoselachus, (Notorynchus, (Heptranchias, (Hexanchus griseus, H. nakamurai))). Based on our phylogeny, we discussed evolutionary scenarios of the jaw suspension mechanism and gill slit numbers that are significant features in the sharks. PMID:24089661
Priede, Imants G; Froese, Rainer; Bailey, David M; Bergstad, Odd Aksel; Collins, Martin A; Dyb, Jan Erik; Henriques, Camila; Jones, Emma G; King, Nicola
The oceanic abyss (depths greater than 3000 m), one of the largest environments on the planet, is characterized by absence of solar light, high pressures and remoteness from surface food supply necessitating special molecular, physiological, behavioural and ecological adaptations of organisms that live there. Sampling by trawl, baited hooks and cameras we show that the Chondrichthyes (sharks, rays and chimaeras) are absent from, or very rare in this region. Analysis of a global data set shows a trend of rapid disappearance of chondrichthyan species with depth when compared with bony fishes. Sharks, apparently well adapted to life at high pressures are conspicuous on slopes down to 2000 m including scavenging at food falls such as dead whales. We propose that they are excluded from the abyss by high-energy demand, including an oil-rich liver for buoyancy, which cannot be sustained in extreme oligotrophic conditions. Sharks are apparently confined to ca 30% of the total ocean and distribution of many species is fragmented around sea mounts, ocean ridges and ocean margins. All populations are therefore within reach of human fisheries, and there is no hidden reserve of chondrichthyan biomass or biodiversity in the deep sea. Sharks may be more vulnerable to over-exploitation than previously thought.
Williams, Donna A; Flood, Mary H; Lewis, Debra A; Miller, Virginia M; Krause, William J
The stable metabolite of nitric oxide in plasma is NOx, the sum of nitrite plus nitrate. Measures of plasma NOx may provide information about the nitric oxide tonus of the entire endothelium including capillary microvessels. Although data are available for mammalian species, plasma NOx measurements in early vertebrate species are scarce. The purpose of this study was to test the hypothesis that plasma NOx would be similar to the NOx in the water environment for fish in early classes (Agnatha and Chondrichthye) and would exceed water NOx levels in the known nitrite-sensitive fish (Osteichthye). Plasma samples were obtained from 18 species of adult fish (n = 167) and from their housing or natural water environment. NOx was measured by using chemiluminescence. Plasma NOx was detected in all species and ranged from 0.5 nmol/ml (skate) to 453.9 nmol/ml (shortnose gar). Average plasma NOx was significantly higher in sea lamprey than in Atlantic hagfish whereas that of little skate was 3-fold lower than in spiny dogfish shark. Plasma NOx differed significantly among early bony fish (paddlefish, pallid sturgeon, gar) yet was similar among modern bony fish, with the exception of rainbow trout. Plasma NOx reflected water NOx in only 2 species (hagfish and shark), and levels did not coincide with nitrite sensitivity. This study provides an expanded comparative view of plasma NOx levels across 3 groups of early fish. The data obtained suggest a nitric oxide system in early and modern fish. PMID:19004368
Effects of exposure to coplanar polychlorinated biphenyls (PCBs) and other dioxin-like chemicals on developing vertebrates involve many organ systems, including the skeletal and cardiovascular systems. Apex predators, including those from the class Chondrichthyes (sharks, skates, and rays), accumulate high body burdens of PCBs through biomagnification of chemicals moving through food webs. There are no published reports of the effects of dioxin-like chemicals on the development of sharks, skates, or rays. A study was undertaken to assess developmental effects of 3, 3’, 4, 4’, 5 pentachlorobiphenyl (PCB 126) exposure in little skate, Leucoraja erinacea, a model for oviparous elasmobranchs. Skate embryos cultured outside of their egg cases were exposed to 0.02 - 20 ng/ml PCB 126 for 6 days and then grown in clean seawater for up to 29 days. Gas chromatography was used to measure PCB 126 in the exposures water and quantify its accumulation in the embryo. Digital still and video imaging was performed to assess growth, identify developmental abnormalities, and cardiovascular function. Embryos accumulated approximately 50% of PCB 126 exposure mass in the embryonic tissues and yolk sac. All embryos in the control and 0.02 ng/ml treatment survived; mortality rates were 14, 52, and 40% of embryos exposed to 0.2, 2.0, and 20.0 ng/ml, respectively. PCB 126 exposure induced yolk sac edema, deformities of the jaw, cranium, and fins, and cardiovascular system failure in
Cerdà, Joan; Finn, Roderick Nigel
Aquaporins are a superfamily of integral membrane proteins that facilitate the rapid and yet highly selective flux of water and other small solutes across biological membranes. Since their discovery, they have been documented throughout the living biota, with the majority of research focusing on mammals and plants. Here, we review available data for piscine aquaporins, including Agnatha (jawless fish), Chondrichthyes (chimaeras, sharks, and rays), Dipnoi (lungfishes), and Teleostei (ray-finned bony fishes). Recent evidence suggests that the aquaporin superfamily has specifically expanded in the chordate lineage consequent to serial rounds of whole genome duplication, with teleost genomes harboring the largest number of paralogs. The selective retention and dichotomous clustering of most duplicated paralogs in Teleostei, with differential tissue expression profiles, implies that novel or specialized physiological functions may have evolved in this clade. The recently proposed new nomenclature of the piscine aquaporin superfamily is discussed in relation to the phylogenetic signal and genomic synteny, with the teleost aquaporin-8 paralogs used as a case study to illustrate disparities between the underlying codons, molecular phylogeny, and physical locus. Structural data indicate that piscine aquaporins display similar channel restriction residues found in the tetrapod counterparts, and hence their functional properties seem to be conserved. However, emerging evidence suggests that regulation of aquaporin function in teleosts may have diverged in some cases. Cell localization and experimental studies imply that the physiological roles of piscine aquaporins extend at least to osmoregulation, reproduction, and early development, although in most cases their specific functions remain to be elucidated.
Stephen, J N; Sharp, M F; Ruethers, T; Taki, A; Campbell, D E; Lopata, A L
Allergy to bony fish is common and probably increasing world-wide. The major heat-stable pan-fish allergen, parvalbumin (PV), has been identified and characterized for numerous fish species. In contrast, there are very few reports of allergic reactions to cartilaginous fish despite widespread consumption. The molecular basis for this seemingly low clinical cross-reactivity between these two fish groups has not been elucidated. PV consists of two distinct protein lineages, α and β. The α-lineage of this protein is predominant in muscle tissue of cartilaginous fish (Chondrichthyes), while β-PV is abundant in muscle tissue of bony fish (Osteichthyes). The low incidence of allergic reactions to ingested rays and sharks is likely due to the lack of molecular similarity, resulting in reduced immunological cross-reactivity between the two PV lineages. Structurally and physiologically, both protein lineages are very similar; however, the amino acid homology is very low with 47-54%. Furthermore, PV from ancient fish species such as the coelacanth demonstrates 62% sequence homology to leopard shark α-PV and 70% to carp β-PV. This indicates the extent of conservation of the PV isoforms lineages across millennia. This review highlights prevalence data on fish allergy and sensitization to fish, and details the molecular diversity of the two protein lineages of the major fish allergen PV among different fish groups, emphasizing the immunological and clinical differences in allergenicity.
Rasmussen, A S; Arnason, U
The Chondrichthyes (cartilaginous fishes) are commonly accepted as being sister group to the other extant Gnathostomata (jawed vertebrates). To clarify gnathostome relationships and to aid in resolving and dating the major piscine divergences, we have sequenced the complete mtDNA of the starry skate and have included it in phylogenetic analysis along with three squalomorph chondrichthyans-the common dogfish, the spiny dogfish, and the star spotted dogfish-and a number of bony fishes and amniotes. The direction of evolution within the gnathostome tree was established by rooting it with the most closely related non-gnathostome outgroup, the sea lamprey, as well as with some more distantly related taxa. The analyses placed the chondrichthyans in a terminal position in the piscine tree. These findings, which also suggest that the origin of the amniote lineage is older than the age of the oldest extant bony fishes (the lungfishes), challenge the evolutionary direction of several morphological characters that have been used in reconstructing gnathostome relationships. Applying as a calibration point the age of the oldest lungfish fossils, 400 million years, the molecular estimate placed the squalomorph/batomorph divergence at approximately 190 million years before present. This dating is consistent with the occurrence of the earliest batomorph (skates and rays) fossils in the paleontological record. The split between gnathostome fishes and the amniote lineage was dated at approximately 420 million years before present.
Caputi, Angel A; Aguilera, Pedro A; Carolina Pereira, Ana; Rodríguez-Cattáneo, Alejo
Electroreception is a sensory modality present in chondrichthyes, actinopterygii, amphibians, and mammalian monotremes. The study of this non-intuitive sensory modality has provided insights for better understanding of sensory systems in general and inspired the development of innovative artificial devices. Here we review evidence obtained from the analysis of electrosensory images, neurophysiological data from the recording of unitary activity in the electrosensory lobe, and psychophysical data from analysis of novelty responses provoked in well-defined stimulus conditions, which all confirm that active electroreception has a short range, and that the influence of exploratory movements on object identification is strong. In active electric images two components can be identified: a "global" image profile depending on the volume, shape and global impedance of an object and a "texture" component depending on its surface attributes. There is a short range of the active electric sense and the progressive "blurring" of object image with distance. Consequently, the lack of precision regarding object location, considered together, challenge the current view of this sense as serving long range electrolocation and the commonly used metaphor of "electric vision". In fact, the active electric sense shares more commonalities with human active touch than with teleceptive senses as vision or audition. Taking into account that other skin exteroceptors and proprioception may be congruently stimulated during fish exploratory movements we propose that electric, mechanoceptive and proprioceptive sensory modalities found in electric fish could be considered together as a single haptic sensory system. This article is part of a Special Issue entitled Neural Coding 2012.
Flammang, B E
The adult morphology of the tail varies greatly among extant fishes despite sharing both ontogenetic similarities and the functional need to propel the body through a fluid medium. Both sharks (Chondrichthyes) and ray-finned fishes (Actinopterygii) control caudal fin musculature independently of axial body myomere activity to modify the stiffness and shape of their tails. For example, sharks and bony fishes possess different structural elements and muscles and move their tails in different ways, resulting in different locomotory hydrodynamic effects and a range of performance variables including speed and maneuverability. The stiffness of the heterocercal, lobate tail of the shark can be modulated during the tail beat resulting in nearly continuous thrust production. In contrast, the highly flexible tail of ray-finned fishes can be manipulated into many different shape conformations enabling increased maneuverability for these fishes. Consequently, the developmental, morphological, and functional derivation of the tail from the axial trunk has resulted in a diversity of form, the attributes of which may be of ecological and evolutionary significance.
Klug, Stefanie; Kriwet, Jürgen
Palaeospinacids are a group of basal galeomorph sharks and are placed in the order Synechodontiformes (Chondrichthyes, Neoselachii) ranging from the Permian to the Eocene. Currently, there is a controversy concerning the identity of diagnostic characters for distinguishing palaeospinacid genera because of very similar dental morphologies and the scarcity of articulated skeletal material. The most notable character for distinguishing species within the Palaeospinacidae is, however, the dental morphology. The main dental character uniting all palaeospinacids is the very specialised pseudopolyaulacorhize root vascularisation. A re-examination of articulated neoselachian skeletons from the Lower Jurassic of Lyme Regis (England) and Holzmaden (S Germany), and recently discovered specimens from the Upper Jurassic of the Solnhofen area and Nusplingen (S Germany) has yielded several hitherto unrecognised complete skeletons of the palaeospinacids Synechodus and Paraorthacodus enabling a re-evaluation of characters. These specimens indicate that the number of dorsal fins and the presence or absence of dorsal fin spines represent important features for identifying palaeospinacids. Synechodus bears two dorsal fins without fin spines, whereas Paraorthacodus only has a single dorsal fin lacking a fin spine directly in front of the caudal fin. All palaeospinacids from the Early Jurassic have two spines supporting the dorsal fins and are consequently assigned to a new genus, Palidiplospinax nov. gen. Three species are placed into the new taxon: Synechodus enniskilleni, S. occultidens and S. smithwoodwardi.
Diaz, James H
A descriptive analysis and review of the world's salient scientific literature on stingray injuries was conducted in light of recent high-profile cases of fatal and near-fatal thoracic stingray injuries to guide clinicians in evaluating and managing stingray injuries. Data was extracted from observational and longitudinal studies over the period, 1950-2006, to permit (1) a stratification of stingray injuries as bites, penetrating lacerations with and without envenoming, and combinations of deeply penetrating and envenoming wounds; and (2) an assessment of new management strategies for thoracoabdominal penetrating trauma and non-healing, necrotic stingray wounds. Unlike their Chondrichthyes classmates, the sharks, stingrays are docile and non-aggressive; and will not attack with their spined tails, unless provoked. Although some occupations are predisposed to stingray injuries, most stingray injuries can be avoided by observing seafloors and adopting simple practices when wading, swimming, diving, or fishing in temperate oceans and some tropical freshwater river systems. All stingray injuries should be managed initially with wound irrigation to dislodge retained spine fragments and envenoming tissues and warm water immersion to inactivate heat-labile toxins.
da Silva, Nelson Jorge; Ferreira, Kalley Ricardo Clementino; Pinto, Raimundo Nonato Leite; Aird, Steven Douglas
Freshwater stingrays cause many serious human injuries, but identification of the offending species is uncommon. The present case involved a large freshwater stingray, Potamotrygon motoro (Chondrichthyes: Potamotrygonidae), in the Araguaia River in Tocantins, Brazil. Appropriate first aid was administered within ~15 min, except that an ice pack was applied. Analgesics provided no pain relief, although hot compresses did. Ciprofloxacin therapy commenced after ~18 h and continued seven days. Then antibiotic was suspended; however, after two more days and additional tests, cephalosporin therapy was initiated, and proved successful. Pain worsened despite increasingly powerful analgesics, until debridement of the wound was performed after one month. The wound finally closed ~70 days after the accident, but the patient continued to have problems wearing shoes even eight months later. Chemistry and pharmacology of Potamotrygon venom and mucus, and clinical management of freshwater stingray envenomations are reviewed in light of the present case. Bacterial infections of stingray puncture wounds may account for more long-term morbidity than stingray venom. Simultaneous prophylactic use of multiple antibiotics is recommended for all but the most superficial stingray wounds. Distinguishing relative contributions of venom, mucus, and bacteria will require careful genomic and transcriptomic investigations of stingray tissues and contaminating bacteria.
Mizusawa, Kanta; Amiya, Noriko; Yamaguchi, Yoko; Takabe, Souichirou; Amano, Masafumi; Breves, Jason P; Fox, Bradley K; Grau, E Gordon; Hyodo, Susumu; Takahashi, Akiyoshi
Melanin-concentrating hormone (MCH) is a neuromodulator, synthesized in the hypothalamus, that regulates both appetite and energy homeostasis in mammals. MCH was initially identified in teleost fishes as a pituitary gland hormone that induced melanin aggregation in chromatophores in the skin; however, this function of MCH has not been observed in other vertebrates. Recent studies suggest that MCH is involved in teleost feeding behavior, spurring the hypothesis that the original function of MCH in early vertebrates was appetite regulation. The present study reports the results of cDNAs cloning encoding preproMCH and two MCH receptors from an elasmobranch fish, Sphyrna lewini, a member of Chondrichthyes, the earliest diverged class in gnathostomes. The putative MCH peptide is composed of 19 amino acids, similar in length to the mammalian MCH. Reverse-transcription polymerase chain reaction revealed that MCH is expressed in the hypothalamus in S. lewini MCH cell bodies and fibers were identified by immunochemistry in the hypothalamus, but not in the pituitary gland, suggesting that MCH is not released via the pituitary gland into general circulation. MCH receptor genes mch-r1 and mch-r2 were expressed in the S. lewini hypothalamus, but were not found in the skin. These results indicate that MCH does not have a peripheral function, such as a melanin-concentrating effect, in the skin of S. lewini hypothalamic MCH mRNA levels were not affected by fasting, suggesting that feeding conditions might not affect the expression of MCH in the hypothalamus.
Chapman, Demian D; Prodöhl, Paulo A; Gelsleichter, James; Manire, Charles A; Shivji, Mahmood S
There is growing interest in the mating systems of sharks and their relatives (Class Chondrichthyes) because these ancient fishes occupy a key position in vertebrate phylogeny and are increasingly in need of conservation due to widespread overexploitation. Based on precious few genetic and field observational studies, current speculation is that polyandrous mating strategies and multiple paternity may be common in sharks as they are in most other vertebrates. Here, we test this hypothesis by examining the genetic mating system of the bonnethead shark, Sphyrna tiburo, using microsatellite DNA profiling of 22 litters (22 mothers, 188 embryos genotyped at four polymorphic loci) obtained from multiple locations along the west coast of Florida. Contrary to expectations based on the ability of female S. tiburo to store sperm, the social nature of this species and the 100% multiple paternity observed in two other coastal shark species, over 81% of sampled bonnethead females produced litters sired by a single male (i.e. genetic monogamy). When multiple paternity occurred in S. tiburo, there was an indication of increased incidence in larger mothers with bigger litters. Our data suggest that sharks may exhibit complex genetic mating systems with a high degree of interspecific variability, and as a result some species may be more susceptible to loss of genetic variation in the face of escalating fishing pressure. Based on these findings, we suggest that knowledge of elasmobranch mating systems should be an important component of conservation and management programmes for these heavily exploited species.
Pajuelo, J. G.; Seoane, J.; Biscoito, M.; Freitas, M.; González, J. A.
The structure and composition of deep-sea fish assemblages living on the middle slope off NW Africa (26-33° N) were investigated. Data were collected by six commercial trawlers during experimental fishing (1027 hauls) at depths between 800 and 1515 m. A total of 1,115,727 fish specimens, belonging to 37 families and 96 species (24 Elasmobranchii, 5 Holocephali, and 67 Actinopteri) were collected with bottom trawls. The deep-sea demersal fish fauna off NW Africa is dominated by fishes of the family Macrouridae, followed by the Moridae and Alepocephalidae families. The main abundant species were Trachyrincus scabrus, Bathygadus favosus, Mora moro, Alepocephalus productus, Nezumia aequalis and Bathygadus melanobranchus. PERMANOVA analysis showed differences in demersal fish assemblages among bottom types, depth strata and between areas (north and south of parallel 30° N), with the area being the most influential factor followed by the type of substrate. PERMANOVAs computed separately for each area showed significant differences among the bottom types and depths in both areas. SIMPER analysis revealed that B. melanobranchus and B. favosus, which occurred at higher abundances in the area ≥30° N, were the species that were best discriminated between areas; whilst T. scabrus and M. moro occurred at higher abundances in the area <30° N. N. aequalis, B. favosus, B. melanobranchus, Deania hystricosa, Aphanopus intermedius, Coelorinchus labiatus and Halosaurus johnsonianus were restricted or more abundant in the area ≥30° N, and functioned as the discriminating species that most contributed to the average dissimilarity between areas. T. scabrus, M. moro, Alepocephalus productus and Alepocephalus bairdii were more abundant in the area <30° N. The standardized mean abundance (in number of individuals/km2) showed a decreasing pattern: i) with depth in both areas, north and south of parallel 30° N, and ii) with depth on each type of substrate, except on cold coral
Fraser, Gareth J; Smith, Moya Meredith
Classically the oral dentition with teeth regulated into a successional iterative order was thought to have evolved from the superficial skin denticles migrating into the mouth at the stage when jaws evolved. The canonical view is that the initiation of a pattern order for teeth at the mouth margin required development of a sub-epithelial, permanent dental lamina. This provided regulated tooth production in advance of functional need, as exemplified by the Chondrichthyes. It had been assumed that teeth in the Osteichthyes form in this way as in tetrapods. However, this has been shown not to be true for many osteichthyan fish where a dental lamina of this kind does not form, but teeth are regularly patterned and replaced. We question the evolutionary origin of pattern information for the dentition driven by new morphological data on spatial initiation of skin denticles in the catshark. We review recent gene expression data for spatio-temporal order of tooth initiation for Scyliorhinus canicula, selected teleosts in both oral and pharyngeal dentitions, and Neoceratodus forsteri. Although denticles in the chondrichthyan skin appear not to follow a strict pattern order in space and time, tooth replacement in a functional system occurs with precise timing and spatial order. We suggest that the patterning mechanism observed for the oral and pharyngeal dentition is unique to the vertebrate oro-pharynx and independent of the skin system. Therefore, co-option of a successional iterative pattern occurred in evolution not from the skin but from mechanisms existing in the oro-pharynx of now extinct agnathans.
Bininda-Emonds, Olaf RP; Jeffery, Jonathan E; Sánchez-Villagra, Marcelo R; Hanken, James; Colbert, Matthew; Pieau, Claude; Selwood, Lynne; ten Cate, Carel; Raynaud, Albert; Osabutey, Casmile K; Richardson, Michael K
Background Tetrapods exhibit great diversity in limb structures among species and also between forelimbs and hindlimbs within species, diversity which frequently correlates with locomotor modes and life history. We aim to examine the potential relation of changes in developmental timing (heterochrony) to the origin of limb morphological diversity in an explicit comparative and quantitative framework. In particular, we studied the relative time sequence of development of the forelimbs versus the hindlimbs in 138 embryos of 14 tetrapod species spanning a diverse taxonomic, ecomorphological and life-history breadth. Whole-mounts and histological sections were used to code the appearance of 10 developmental events comprising landmarks of development from the early bud stage to late chondrogenesis in the forelimb and the corresponding serial homologues in the hindlimb. Results An overall pattern of change across tetrapods can be discerned and appears to be relatively clade-specific. In the primitive condition, as seen in Chondrichthyes and Osteichthyes, the forelimb/pectoral fin develops earlier than the hindlimb/pelvic fin. This pattern is either retained or re-evolved in eulipotyphlan insectivores (= shrews, moles, hedgehogs, and solenodons) and taken to its extreme in marsupials. Although exceptions are known, the two anurans we examined reversed the pattern and displayed a significant advance in hindlimb development. All other species examined, including a bat with its greatly enlarged forelimbs modified as wings in the adult, showed near synchrony in the development of the fore and hindlimbs. Conclusion Major heterochronic changes in early limb development and chondrogenesis were absent within major clades except Lissamphibia, and their presence across vertebrate phylogeny are not easily correlated with adaptive phenomena related to morphological differences in the adult fore- and hindlimbs. The apparently conservative nature of this trait means that changes in
Smith, Moya Meredith; Riley, Alex; Fraser, Gareth J.; Underwood, Charlie; Welten, Monique; Kriwet, Jürgen; Pfaff, Cathrin; Johanson, Zerina
In classical theory, teeth of vertebrate dentitions evolved from co-option of external skin denticles into the oral cavity. This hypothesis predicts that ordered tooth arrangement and regulated replacement in the oral dentition were also derived from skin denticles. The fossil batoid ray Schizorhiza stromeri (Chondrichthyes; Cretaceous) provides a test of this theory. Schizorhiza preserves an extended cartilaginous rostrum with closely spaced, alternating saw-teeth, different from sawfish and sawsharks today. Multiple replacement teeth reveal unique new data from micro-CT scanning, showing how the ‘cone-in-cone’ series of ordered saw-teeth sets arrange themselves developmentally, to become enclosed by the roots of pre-existing saw-teeth. At the rostrum tip, newly developing saw-teeth are present, as mineralized crown tips within a vascular, cartilaginous furrow; these reorient via two 90° rotations then relocate laterally between previously formed roots. Saw-tooth replacement slows mid-rostrum where fewer saw-teeth are regenerated. These exceptional developmental data reveal regulated order for serial self-renewal, maintaining the saw edge with ever-increasing saw-tooth size. This mimics tooth replacement in chondrichthyans, but differs in the crown reorientation and their enclosure directly between roots of predecessor saw-teeth. Schizorhiza saw-tooth development is decoupled from the jaw teeth and their replacement, dependent on a dental lamina. This highly specialized rostral saw, derived from diversification of skin denticles, is distinct from the dentition and demonstrates the potential developmental plasticity of skin denticles. PMID:26423843
Martinez, Christopher M; Rohlf, F James; Frisk, Michael G
Batoids (Chondrichthyes: Batoidea) are a diverse group of cartilaginous fishes which comprise a monophyletic sister lineage to all neoselachians or modern sharks. All species in this group possess anteroposteriorly expanded-pectoral fins, giving them a unique disc-like body form. Reliance on pectoral fins for propulsion ranges from minimal (sawfish) to almost complete dependence (skates and rays). A recent study on the diversity of planform pectoral fin shape in batoids compared overall patterns of morphological variation within the group. However, inconsistent pectoral homology prevented the study from accurately representing relationships within and among major batoid taxa. With previous work in mind, we undertook an independent investigation of pectoral form in batoids and evaluated the implications of shape diversity on locomotion and lifestyle, particularly in the skates (Rajoidei) and rays (Myliobatoidei). We used geometric morphometrics with sliding semilandmarks to analyze pectoral fin outlines and also calculate fin aspect ratios (AR), a functional trait linked to locomotion. In agreement with previous work, our results indicated that much of the evolution of batoid pectoral shape has occurred along a morphological axis that is closely related to AR. For species where kinematic data were available, both shape and AR were associated with swimming mode. This work further revealed novel patterns of shape variation among batoids, including strong bimodality of shape in rays, an intermediate location of skate species in the morphospace between benthic/demersal and pelagic rays, and approximately parallel shape trajectories in the benthic/demersal rays and skates. Finally, manipulation of landmarks verified the need for a consistent and accurate definition of homology for the outcome and efficacy of analyses of pectoral form and function in batoids.
Pilgrim, Brettney L; Franz-Odendaal, Tamara A
Many vertebrates have an ocular skeleton composed of cartilage and/or bone situated within the sclera of the eye. In this study we investigated whether modern and fossil sharks have an ocular skeleton, and whether it is conserved in morphology. We describe the scleral skeletal elements of three species of modern sharks and compare them to those found in fossil sharks from the Cleveland Shale (360 Mya). We also compare the elements to contemporaneous arthrodires from the same deposit. Surprisingly, the morphology of the skeletal support of the eye was found to differ significantly between modern and fossil sharks. All three modern shark species examined (spiny dogfish shark Squalus acanthias, porbeagle shark Lamna nasus and blue shark Prionace glauca) have a continuous skeletal element that encapsulates much of the eyeball; however, the tissue composition is different in each species. Histological and morphological examination revealed scleral cartilage with distinct tesserae in parts of the sclera of the porbeagle and blue shark, and more diffuse calcification in the dogfish. Strengthening of the scleral cartilage by means of tesserae has not been reported previously in the shark eye. In striking contrast, the ocular skeleton of fossil sharks comprises a series of individual elements that are arranged in a ring, similar to the arrangement in modern and fossil reptiles. Fossil arthrodires also have a multi-unit sclerotic ring but these are composed of fewer elements than in fossil sharks. The morphology of these elements has implications for the behaviour and visual capabilities of sharks that lived during the Devonian Period. This is the first time that such a dramatic variation in the morphology of scleral skeletal elements has been observed in a single lineage (Chondrichthyes), making this lineage important for broadening our understanding of the evolution of these elements within jawed vertebrates. PMID:19538630
Guizouarn, H; Musch, M W; Goldstein, L
Anion exchangers (AE) are transmembrane proteins catalyzing electroneutral exchange of Cl(-) for HCO3-. To date, three different genes coding for this protein, AE1, AE2 and AE3, have been identified in many species. AE1 is considered to be the unique anion exchanger expressed in erythrocytes. In this paper we propose the presence of three different AEs in skate erythrocytes, a skAE1, a skAE2 and a skAE3, cloned by RT-PCR (reverse-transcriptase polymerase chain reaction). These three skAE have a similar predicted secondary structure. All three skAE are divided in two main domains: a hydrophilic cytoplasmic N-terminal domain and a C-terminal domain crossing the lipid bilayer at least 12 times. The greatest similarity is found in the membrane-spanning domain of the three skAE. The size as well as the amino-acid sequence of the cytoplasmic domain differ significantly among three anion exchangers. Functional expression studies in Xenopus oocytes led to the conclusion that skAE-1 and -2 share some functional features (Cl-dependence and DIDS sensitivity). The skAE3 could not be expressed in Xenopus oocytes. These data are in agreement with expression data obtained with AEs of different species utilizing the oocyte system. It is highly probable that these three new AE sequences come from three different genes, thus suggesting for the first time the presence of the three AE genes in Chondrichthyes.
Calvin, J L; Slater, C H; Bolduc, T G; Laudano, A P; Sower, S A
These studies investigated brains of skate, Raja erinacea (order Rajiformes, class Chondrichthyes), for gonadotropin-releasing hormone (GnRH) peptides by chromatograph and immunoreactivity with region-specific antisera raised against mammalian GnRH and lamprey GnRH. The region-specific antibody to lamprey GnRH-I was produced following conjugation to bovine serum albumin using the bis-diazotized benzidine method. This antibody was characterized by assaying a range of increasing dilutions of the known vertebrate GnRHs, as well as analogs to lamprey GnRH-I. Two analogs, lamprey [Phe2]GnRH-I and lamprey [Leu7]GnRH-I, were synthesized by solid phase peptide synthesis using a benzhydrylamine resin as the supporting medium and purified by chromatography. This antibody demonstrated less than 0.01% cross-reactivity with all GnRH peptides tested, suggesting a highly specific antibody with a region of amino acids 2-8 that appears essential for binding. In the skate brain, five immunoreactive (IR) GnRH forms were detected, four of which eluted in the same positions as synthetic mammal and chicken GnRH-I (which coelute): lamprey GnRH-I, salmon and chicken GnRH-II, and one that was an unidentified form. A minor peak coeluted with lamprey GnRH-III. The major form in the skate brain is considered to have eluted with synthetic mammalian GnRH. These studies confirm an earlier report of an IR-mammalian GnRH peptide and provide new evidence for IR-lamprey GnRH in the brain of an elasmobranch.
Zhao, Tong-Jin; Liu, Yang; Chen, Zhao; Yan, Yong-Bin; Zhou, Hai-Meng
Creatine kinase, a key enzyme in vertebrate excitable tissues that require large energy fluxes, catalyzes the reversible transfer of phosphate between adenosine triphosphate and creatine. Sequence alignment indicated that the 146th amino acid is cysteine in the muscle creatine kinase of higher vertebrates including Amphibia, Reptilia, Aves and Mammalia. In fishes, it is cysteine in Agnatha and Chondrichthyes, and asparagine or threonine in Osteichthyes, which is the ancestor of Amphibia, Reptilia, Aves and Mammalia. To explore the structural and functional role of this special residue, a series of site-directed mutants of rabbit muscle creatine kinase were constructed, including C146S, C146N, C146T, C146G, C146A, C146D and C146R. A detailed comparison was made between wild-type creatine kinase and the mutants in catalytic activity, physico-chemical properties and structural stability against thermal inactivation and guanidine hydrochloride denaturation. It was found that except for C146S, the mutants had relatively lower catalytic activity and structural stability than Wt-CK. Wt-CK and C146S were the most stable ones, followed by C146N and C146T, and then C146G and C146A, and C146D and C146R were the least stable mutants. These results suggested that the 146th residue plays a crucial role in maintaining the structural stability of creatine kinase, and that the evolution in this amino acid from asparagine or threonine to cysteine contributes to the generation of a more efficient and more stable form of creatine kinase in higher vertebrates.
Pilgrim, Brettney L; Franz-Odendaal, Tamara A
Many vertebrates have an ocular skeleton composed of cartilage and/or bone situated within the sclera of the eye. In this study we investigated whether modern and fossil sharks have an ocular skeleton, and whether it is conserved in morphology. We describe the scleral skeletal elements of three species of modern sharks and compare them to those found in fossil sharks from the Cleveland Shale (360 Mya). We also compare the elements to contemporaneous arthrodires from the same deposit. Surprisingly, the morphology of the skeletal support of the eye was found to differ significantly between modern and fossil sharks. All three modern shark species examined (spiny dogfish shark Squalus acanthias, porbeagle shark Lamna nasus and blue shark Prionace glauca) have a continuous skeletal element that encapsulates much of the eyeball; however, the tissue composition is different in each species. Histological and morphological examination revealed scleral cartilage with distinct tesserae in parts of the sclera of the porbeagle and blue shark, and more diffuse calcification in the dogfish. Strengthening of the scleral cartilage by means of tesserae has not been reported previously in the shark eye. In striking contrast, the ocular skeleton of fossil sharks comprises a series of individual elements that are arranged in a ring, similar to the arrangement in modern and fossil reptiles. Fossil arthrodires also have a multi-unit sclerotic ring but these are composed of fewer elements than in fossil sharks. The morphology of these elements has implications for the behaviour and visual capabilities of sharks that lived during the Devonian Period. This is the first time that such a dramatic variation in the morphology of scleral skeletal elements has been observed in a single lineage (Chondrichthyes), making this lineage important for broadening our understanding of the evolution of these elements within jawed vertebrates.
Long, John A.; Burrow, Carole J.; Ginter, Michal; Maisey, John G.; Trinajstic, Kate M.; Coates, Michael I.; Young, Gavin C.; Senden, Tim J.
Background Living gnathostomes (jawed vertebrates) comprise two divisions, Chondrichthyes (cartilaginous fishes, including euchondrichthyans with prismatic calcified cartilage, and extinct stem chondrichthyans) and Osteichthyes (bony fishes including tetrapods). Most of the early chondrichthyan (‘shark’) record is based upon isolated teeth, spines, and scales, with the oldest articulated sharks that exhibit major diagnostic characters of the group—prismatic calcified cartilage and pelvic claspers in males—being from the latest Devonian, c. 360 Mya. This paucity of information about early chondrichthyan anatomy is mainly due to their lack of endoskeletal bone and consequent low preservation potential. Methodology/Principal Findings Here we present new data from the first well-preserved chondrichthyan fossil from the early Late Devonian (ca. 380–384 Mya) Gogo Formation Lägerstatte of Western Australia. The specimen is the first Devonian shark body fossil to be acid-prepared, revealing the endoskeletal elements as three-dimensional undistorted units: Meckel’s cartilages, nasal, ceratohyal, basibranchial and possible epibranchial cartilages, plus left and right scapulocoracoids, as well as teeth and scales. This unique specimen is assigned to Gogoselachus lynnbeazleyae n. gen. n. sp. Conclusions/Significance The Meckel’s cartilages show a jaw articulation surface dominated by an expansive cotylus, and a small mandibular knob, an unusual condition for chondrichthyans. The scapulocoracoid of the new specimen shows evidence of two pectoral fin basal articulation facets, differing from the standard condition for early gnathostomes which have either one or three articulations. The tooth structure is intermediate between the ‘primitive’ ctenacanthiform and symmoriiform condition, and more derived forms with a euselachian-type base. Of special interest is the highly distinctive type of calcified cartilage forming the endoskeleton, comprising multiple layers
Tolimieri, Nick; Anderson, Marti J.
Background Large-scale patterns or trends in species diversity have long interested ecologists. The classic pattern is for diversity (e.g., species richness) to decrease with increasing latitude. Taxonomic distinctness is a diversity measure based on the relatedness of the species within a sample. Here we examined patterns of taxonomic distinctness in relation to latitude (ca. 32–48 °N) and depth (ca. 50–1220 m) for demersal fishes on the continental shelf and slope of the US Pacific coast. Methodology/Principal Findings Both average taxonomic distinctness (AvTD) and variation in taxonomic distinctness (VarTD) changed with latitude and depth. AvTD was highest at approximately 500 m and lowest at around 200 m bottom depth. Latitudinal trends in AvTD were somewhat weaker and were depth-specific. AvTD increased with latitude on the shelf (50–150 m) but tended to decrease with latitude at deeper depths. Variation in taxonomic distinctness (VarTD) was highest around 300 m. As with AvTD, latitudinal trends in VarTD were depth-specific. On the shelf (50–150 m), VarTD increased with latitude, while in deeper areas the patterns were more complex. Closer inspection of the data showed that the number and distribution of species within the class Chondrichthyes were the primary drivers of the overall patterns seen in AvTD and VarTD, while the relatedness and distribution of species in the order Scorpaeniformes appeared to cause the relatively low observed values of AvTD at around 200 m. Conclusions/Significance These trends contrast to some extent the patterns seen in earlier studies for species richness and evenness in demersal fishes along this coast and add to our understanding of diversity of the demersal fishes of the California Current. PMID:20498727
Dombkowski, Ryan A; Russell, Michael J; Schulman, Alexis A; Doellman, Meredith M; Olson, Kenneth R
Hydrogen sulfide (H(2)S) is a recently identified endogenous vasodilator in mammals. In steelhead/rainbow trout (Oncorhynchus mykiss, Osteichthyes), H(2)S produces both dose-dependent dilation and a unique dose-dependent constriction. In this study, we examined H(2)S vasoactivity in all vertebrate classes to determine whether H(2)S is universally vasoactive and to identify phylogenetic and/or environmental trends. H(2)S was generated from NaHS and examined in unstimulated and precontracted systemic and, when applicable, pulmonary arteries (PA) from Pacific hagfish (Eptatretus stouti, Agnatha), sea lamprey (Petromyzon marinus, Agnatha), sandbar shark (Carcharhinus milberti, Chondrichthyes), marine toad (Bufo marinus, Amphibia), American alligator (Alligator mississippiensis, Reptilia), Pekin duck (Anas platyrhynchos domesticus, Aves), and white rat (Rattus rattus, Mammalia). In otherwise unstimulated vessels, NaHS produced 1) a dose-dependent relaxation in Pacific hagfish dorsal aorta; 2) a dose-dependent contraction in sea lamprey dorsal aorta, marine toad aorta, alligator aorta and PA, duck aorta, and rat thoracic aorta; 3) a threshold relaxation in shark ventral aorta, dorsal aorta, and afferent branchial artery; and 4) a multiphasic contraction-relaxation-contraction in the marine toad PA, duck PA, and rat PA. Precontraction of these vessels with another agonist did not affect the general pattern of NaHS vasoactivity with the exception of the rat aorta, where relaxation was now dominant. These results show that H(2)S is a phylogenetically ancient and versatile vasoregulatory molecule that appears to have been opportunistically engaged to suit both organ-specific and species-specific homeostatic requirements.
Anderson, M. E.; Almond, J. E.; Evans, F. J.; Long, J. A.
Four major groups of fish are represented by fragmentary remains from South Africa's Lower Bokkeveld Group of Early to Middle Devonian age: the Acanthodii, Chondrichthyes, Placodermi and Osteichthyes. These represent the oldest known occurrences of these groups in southern Africa, as well as an important addition to the very meagre record of earlier Devonian fish from the Malvinokaffric Province of southwestern Gondwana. Bokkeveld fish material comes from the Gydo (Late Emsian) and Tra Tra (Middle Eifelian) Formations of the Western Cape and Eastern Cape Provinces. The cosmopolitan marine acanthodian Machæracanthus is represented only by isolated fin spines which may belong to two different species on the basis of their external ornamentation, cross-sectional outline and internal histology. The elasmobranchs are represented by four elements: (1) a flattened chondrocranium which bears affinity to the Late Devonian-Carboniferous symmoriid (protacrodont) 'cladodont' sharks. It is probably the earliest known (Emsian) shark chondrocranium; (2) an isolated, primitive scapulocoracoid with a very short coracoidal ridge; (3) ankylosed and isolated radials, interpreted as parts of pterygial plates of a paired fin of an unknown chondrichthyan bearing affinity to the Middle Devonian Zamponiopteron from Bolivia; and (4) isolated barlike structures, perhaps gill arch or a jaw elements, thought to be from the same taxon as (3). The placoderms are represented by an incomplete trunk armour and fragmentary, finely ornamented plates of a primitive antiarch. The Osteichthyes are represented by a single large scale of an unidentified dipnoan from the Eifelian of the Cedarberg range, as well as a probable sarcopterygian dermal plate from the Emsian of the Prince Albert area. These are among the earliest sarcopterygian remains recorded from the Malvinokaffric Province.
Habegger, Maria L; Motta, Philip J; Huber, Daniel R; Dean, Mason N
Evaluations of bite force, either measured directly or calculated theoretically, have been used to investigate the maximum feeding performance of a wide variety of vertebrates. However, bite force studies of fishes have focused primarily on small species due to the intractable nature of large apex predators. More massive muscles can generate higher forces and many of these fishes attain immense sizes; it is unclear how much of their biting performance is driven purely by dramatic ontogenetic increases in body size versus size-specific selection for enhanced feeding performance. In this study, we investigated biting performance and feeding biomechanics of immature and mature individuals from an ontogenetic series of an apex predator, the bull shark, Carcharhinus leucas (73-285cm total length). Theoretical bite force ranged from 36 to 2128N at the most anterior bite point, and 170 to 5914N at the most posterior bite point over the ontogenetic series. Scaling patterns differed among the two age groups investigated; immature bull shark bite force scaled with positive allometry, whereas adult bite force scaled isometrically. When the bite force of C. leucas was compared to those of 12 other cartilaginous fishes, bull sharks presented the highest mass-specific bite force, greater than that of the white shark or the great hammerhead shark. A phylogenetic independent contrast analysis of anatomical and dietary variables as determinants of bite force in these 13 species indicated that the evolution of large adult bite forces in cartilaginous fishes is linked predominantly to the evolution of large body size. Multiple regressions based on mass-specific standardized contrasts suggest that the evolution of high bite forces in Chondrichthyes is further correlated with hypertrophication of the jaw adductors, increased leverage for anterior biting, and widening of the head. Lastly, we discuss the ecological significance of positive allometry in bite force as a possible
Romano, Carlo; Koot, Martha B; Kogan, Ilja; Brayard, Arnaud; Minikh, Alla V; Brinkmann, Winand; Bucher, Hugo; Kriwet, Jürgen
significant reduction in osteichthyan body size. Neopterygii, the clade that encompasses the vast majority of extant fishes, underwent another diversification phase in the Late Triassic. The Triassic radiation of Osteichthyes, predominantly of Actinopterygii, which only occurred after severe extinctions among Chondrichthyes during the Middle-Late Permian, resulted in a profound change within global fish communities, from chondrichthyan-rich faunas of the Permo-Carboniferous to typical Mesozoic and Cenozoic associations dominated by actinopterygians. This turnover was not sudden but followed a stepwise pattern, with leaps during extinction events.
Yopak, Kara E; Lisney, Thomas J
In cartilaginous fishes (Chondrichthyes; sharks, skates and rays (batoids), and holocephalans), the midbrain or mesencephalon can be divided into two parts, the dorsal tectum mesencephali or optic tectum (analogous to the superior colliculus of mammals) and the ventral tegmentum mesencephali. Very little is known about interspecific variation in the relative size and organization of the components of the mesencephalon in these fishes. This study examined the relative development of the optic tectum and the tegmentum in 75 chondrichthyan species representing 32 families. This study also provided a critical assessment of attempts to quantify the size of the optic tectum in these fishes volumetrically using an idealized half-ellipsoid approach (method E), by comparing this method to measurements of the tectum from coronal cross sections (method S). Using species as independent data points and phylogenetically independent contrasts, relationships between the two midbrain structures and both brain and mesencephalon volume were assessed and the relative volume of each brain area (expressed as phylogenetically corrected residuals) was compared among species with different ecological niches (as defined by primary habitat and lifestyle). The relatively largest tecta and tegmenta were found in pelagic coastal/oceanic and oceanic sharks, benthopelagic reef sharks, and benthopelagic coastal sharks. The smallest tecta were found in all benthic sharks and batoids and the majority of bathyal (deep-sea) species. These results were consistent regardless of which method of estimating tectum volume was used. We found a highly significant correlation between optic tectum volume estimates calculated using method E and method S. Taxon-specific variation in the difference between tectum volumes calculated using the two methods appears to reflect variation in both the shape of the optic tectum relative to an idealized half-ellipsoid and the volume of the ventricular cavity. Because the
Gilmour, Kathleen M; Shah, Bina; Szebedinszky, Cheryl
-bound carbonic anhydrase activity may be a generalised elasmobranch characteristic. Ratfish, which also belong to the class Chondrichthyes, exhibited a similar pattern. Unlike skate and ratfish, bullhead exhibited high plasma non-bicarbonate buffering capacity and lacked an endogenous carbonic anhydrase inhibitor in the absence of plasma and gill membrane-bound carbonic anhydrase activities.
Baker, Michael E; Funder, John W; Kattoula, Stephanie R
Mineralocorticoid receptors (MR) and glucocorticoid receptors (GR) are descended from an ancestral corticoid receptor (CR). To date, the earliest CR have been found in lamprey and hagfish, two jawless fish (cyclostomes) that evolved at the base of the vertebrate line. Lamprey CR has both MR and GR activity. Distinct orthologs of the GR and MR first appear in skates and sharks, which are cartilaginous fishes (Chondrichthyes). Aldosterone, the physiological mineralocorticoid in terrestrial vertebrates, first appears in lobe-finned fish, such as lungfish and coelacanth, forerunners of terrestrial vertebrates, but not in sharks, skates or ray-finned fish. Skate MR are transcriptionally activated by glucocorticoids, such as corticosterone and cortisol, as well as by mineralocorticoids such as deoxycorticosterone and (experimentally) aldosterone; skate GR have low affinity for all human corticosteroids and 1α-OH-corticosterone, which has been proposed to be biologically active glucocorticoid. In fish, cortisol is both physiological mineralocorticoid and glucocorticoid; in terrestrial vertebrates, cortisol or corticosterone are the physiological glucocorticoids acting through GR, and aldosterone via MR as the physiologic mineralocorticoid. MR have equally high affinity for cortisol, corticosterone and progesterone. We review this evolutionary process through an analysis of changes in sequence and structure of vertebrate GR and MR, identifying changes in these receptors in skates and lobe-fined fish important in allowing aldosterone to act as an agonist at epithelial MR and glucocorticoid specificity for GR. hMR and hGR have lost a key contact between helix 3 and helix 5 that was present in their common ancestor. A serine that is diagnostic for vertebrate MR, and absent in terrestrial and fish GR, is present in lamprey CR, skate MR and GR, but not in coelacanth GR, marking the transition of the GR from MR ancestor. Based on the response of the CR and skate MR and GR to
Summers, Adam P; Ketcham, Richard A; Rowe, Timothy
The horn sharks (Heterodontidae: Chondrichthyes) represent one of four independent evolutions of durophagy in the cartilaginous fishes. We used high-resolution computed tomography (CT scanning) to visualize and quantify the mineralized tissue of an ontogenetic series of horn sharks. CT scanning of neonatal through adult California horn sharks (Heterodontus francisci) confirmed that this technique is effective for examining mineralized tissue in even small (<10 mm) specimens. The jaw joint is among the first areas to become mineralized and is the most heavily mineralized area in the cranium of a neonatal horn shark. The hyoid is also well mineralized, although the poorly mineralized molariform teeth indicate that the neonatal animal may be a suction feeder on softer prey. The symphysis of the jaws never mineralizes, in sharp contrast to the condition in the hard prey-crushing stingrays. Digitally reslicing the CT scans along the jaws allowed measurement of the second moment of area (Ina). Assuming that the jaws are made of the same material at all ages, Ina is an indicator of the flexural stiffness of the jaws. In all sizes of shark the lower jaws were stiffer than the upper and the stiffness increased in the area of the molariform teeth. The central region of the jaws, where the rami meet, support cuspidate grasping teeth and has the lowest Ina. The spotted eagle ray (Aetobatus narinari), a hard prey-crushing stingray, shows a different pattern of flexural stiffness, with the peak at the central part of the jaws where the prey is reduced between flattened tooth plates. Although the eagle ray jaws have a higher Ina than the horn shark, they are also far more heavily mineralized. When the relative amounts of mineralization are taken into account, horn sharks do better with what mineral they have than does the eagle ray. With a tight jaw joint and loose mandibular symphysis, as well as nearly opposite patterns of stiffness in the jaws, it is clear that two of the
vertebrate groups not examined here, such as Chondrichthyes or Actinopterygii. An online database to type in developmental events for different stages and species could be a basis for further studies in comparative embryology. By documenting developmental events with the standard code, sequence heterochrony studies (i.e. Parsimov) and studies on variability can use this broad comparative data set.
for other vertebrate groups not examined here, such as Chondrichthyes or Actinopterygii. An online database to type in developmental events for different stages and species could be a basis for further studies in comparative embryology. By documenting developmental events with the standard code, sequence heterochrony studies (i.e. Parsimov) and studies on variability can use this broad comparative data set. PMID:19521537
Cardoso, João C R; Félix, Rute C; Trindade, Marlene; Power, Deborah M
The secretin receptor (SCTR) is a member of Class 2 subfamily B1 GPCRs and part of the PAC1/VPAC receptor subfamily. This receptor has long been known in mammals but has only recently been identified in other vertebrates including teleosts, from which it was previously considered to be absent. The ligand for SCTR in mammals is secretin (SCT), an important gastrointestinal peptide, which in teleosts has not yet been isolated, or the gene identified. This study revises the evolutionary model previously proposed for the secretin-GPCRs in metazoan by analysing in detail the fishes, the most successful of the extant vertebrates. All the Actinopterygii genomes analysed and the Chondrichthyes and Sarcopterygii fish possess a SCTR gene that shares conserved sequence, structure and synteny with the tetrapod homologue. Phylogenetic clustering and gene environment comparisons revealed that fish and tetrapod SCTR shared a common origin and diverged early from the PAC1/VPAC subfamily group. In teleosts SCTR duplicated as a result of the fish specific whole genome duplication but in all the teleost genomes analysed, with the exception of tilapia (Oreochromis niloticus), one of the duplicates was lost. The function of SCTR in teleosts is unknown but quantitative PCR revealed that in both sea bass (Dicentrarchus labrax) and tilapia (Oreochromis mossambicus) transcript abundance is high in the gastrointestinal tract suggesting it may intervene in similar processes to those in mammals. In contrast, no gene encoding the ligand SCT was identified in the ray-finned fishes (Actinopterygii) although it was present in the coelacanth (lobe finned fish, Sarcopterygii) and in the elephant shark (holocephalian). The genes in linkage with SCT in tetrapods and coelacanth were also identified in ray-finned fishes supporting the idea that it was lost from their genome. At present SCTR remains an orphan receptor in ray-finned fishes and it will be of interest in the future to establish why SCT was