Dorsal Fin Spines Research Articles

Morphology and histology of dorsal spines of the xenacanthid shark Orthacanthus platypternus from the Lower Permian of Texas, USA: palaeobiological and palaeoenvironmental implications

Detailed studies on Carboniferous species of the xenacanth Orthacanthus have shown that the xenacanth dorsal fin spine can be used for skeletochronological analyses and provides valuable information about development, growth and environmental life conditions of those extinct sharks. We report here for the first time the histology and skeletochronology of Permian specimens, dorsal spines of Orthacanthus platypternus from the Craddock Bone Bed (lower Clear Fork Formation; Early Permian, Leonardian age) of northern Baylor County (north-central Texas, USA). Twelve dorsal spines of O. platypternus preserve a highly vascularized wall mainly composed of centrifugally growing dentine in a succession of dentine layers, probably deposited with an annual periodicity. As expected, spines of individuals with 1–2 dentine layers, presumably juveniles, present the smallest sizes. However, spines of individuals showing at least 3–4 dentine layers and interpreted to be subadults/young adults, are distributed in two spine-s...

A new species of Corydoras Lacépède (Siluriformes: Callichthyidae) from the Rio Tapajós basin and its phylogenetic implications

A new species of Corydoras is described from tributaries of the rio Arinos, rio Teles Pires and rio Preto, all in the rio Tapajós basin. The new species is a member of a group that includes 36 species with spots on the body. Within this group, the new species can be readily distinguished by having a smaller dorsal-fin spine than the first three subsequent soft dorsal-fin rays; pectoral, pelvic and anal fins hyaline; dorsal-fin interradial membrane hyaline; rounded spots on trunk restricted to dorsolateral body plates and dorsal portion of ventrolateral body plates, not reaching the base of pelvic and anal fins. The new species can be further distinguished from Corydoras xinguensis by having spots with diffuse edges, and from all other species of spotted Corydoras except C.multimaculatus, by the absence of ventral platelets. A phylogenetic analysis recovered the new species plus Corydoras metae and C.araguaiensis in a clade sharing the presence of a pointed process on the maxilla for insertion of the retractor tentaculi muscle. In addition, the presence in the new species of an elongated anterior portion of the mesethmoid and a triangular uncinate process of the epibranchial 3 suggests a close relationship with Corydoras metae.

New record of Juvenile Stethojulis trilineata (Perciformes: Labridae) from Korea, Revealed by Molecular Analysis

A single specimen of a juvenile Stethojulis trilineata was first collected from the coastal waters of Ulsan, Korea, in October 2012. This species is characterized by IX dorsal fin spines, 26 lateral line scales, 25 vertebrae, dark spots between the 10th and 11th dorsal fin rays, and a caudal peduncle region. The new Korean name proposed is "Se-jul-mu-ji-gae-nol-rae-gi" for S. trilineata.

Chriolepis bilix, a new species of goby (Teleostei: Gobiidae)from deep waters of the western Atlantic.

A new species of seven-spined goby of the genus Chriolepis is described from four specimens from four widely separate western Atlantic localities (Little Bahama Bank; off southwestern Florida; Tobago Island; and northeastern Colombia) from depths ranging from 62 to 138 m. The species is distinct from all other western Atlantic species currently assigned to the genus Chriolepis in having a fully scaled body, the first two dorsal-fin spines greatly elongated in both sexes, especially so in females, and two anal-fin pterygiophores inserted anterior to the first haemal spine. It differs from members of the similar genus Varicus in having branched pelvic-fins rays, a longer fifth pelvic-fin ray and more numerous meristic elements. It closely resembles Chriolepis atrimelum, known from a similar depth at Isla del Coco in the eastern Pacific Ocean.

Assessment of radiometric dating for age validation of deep-water dogfish (Order: Squaliformes) finspines

Vertebrae of most deep-water sharks are too poorly calcified to record visible growth bands and therefore are not useful for age determination. Most dogfish species (Order: Squaliformes) possess dorsal finspines and several recent studies have shown that these structures offer potential for age determination. Age validation should be central to any age determination study, yet to date no age and growth study of deep-water sharks has included a complete validation of age estimates. In this study we sought to age two deep-water dogfish species by analyzing 210Pb and 226Ra incorporated into the internal dentin of the finspines. These radiometric age estimates were compared with counts of internal growth bands observed in the finspines. A pilot study indicated that dorsal finspines of Centroselachus crepidater are too small and thus offer insufficient mass for the radiometric techniques employed in this study. For ageing larger finspines of Centrophorus squamosus, the lead–radium disequilibria method (ingrowth of 210Pb from 226Ra) was found to be inapplicable due to exogenous uptake of 210Pb in the finspine. Therefore, to approximate age, we measured the decay of 210Pb within the dentin material at the tip of the finspine (formed in utero), relative to the terminal material at the base of the finspine. Results with this method proved to be inconsistent and did not yield reliable age estimates. Hence the use of 210Pb and 226Ra for radiometric age determination and validation using dorsal finspines from these deep-water dogfishes was deemed unsuccessful. This outcome was likely due to violations of the consistent, life-long isotopic uptake assumption as well as the provision that the finspine must function as a closed system for these radioisotopes. Future improvements in analytical precision will allow for smaller samples to be analyzed, potentially yielding a better understanding of the fate of these radioisotopes within finspine dentin throughout the life of the shark.

Shark faunas from the Late Jurassic—Early Cretaceous of northeastern Thailand

A revision of the freshwater shark fauna from the Phu Kradung Formation in NE Thailand allows the recognition of a new species of Acrodus, which represents the youngest occurrence of the genus and confirms its displacement in freshwater environments after the Toarcian. The rest of the shark fauna includes teeth of Hybodus sp., aff. Hybodus sp., hybodontid dermal denticles, Jiaodontus sp., Lonchidion sp. A, Lonchidion sp. B, Heteroptychodus cf. H. kokutensis and dorsal fin spines. The presence of Jaiodontus and of unusual hybodontid dermal denticles suggests a Jurassic age for most of the Phu Kradung Formation, whereas the presence of Heteroptychodus suggests an Early Cretaceous age for the top of the Formation. However, the age of the Phu Kradung Formation is still uncertain, with contradictory signals coming from palynology, detrital zircon thermochronology and vertebrate palaeontology. In any case, it appears that this is the oldest occurrence of the genus Heteroptychodus, and suggests a Thai origin for this genus, which may have replaced Acrodus in the Thai freshwater palaeoecosystems. Together with Acrodus, the presence of Lonchidion sp. A suggests some European affinities for the shark fauna from the Phu Kradung Formation.

Late Albian chimaeroid fishes (Holocephali, Chimaeroidei) from Annopol, Poland

Remains of Late Albian chimaeroid fishes (Holocephali, Chimaeroidei) are described from the mid-Cretaceous condensed succession of the Annopol anticline, Poland. The described material consists of dental plates, dorsal-fin spines and a single frontal clasper. These remains are assigned to five genera and seven species of ‘edaphodontids’, namely Ischyodus thurmanni, Ischyodus aff. bifurcatus, ‘Ischyodus incisus’, Elasmodus sp., Elasmodectes sp., Lebediodon oskolensis and Edaphodon sedgwickii. Most of these taxa are recorded from Poland for the first time, documenting a much greater regional chimaeroid diversity than previously recognised. In terms of taxonomic composition, the Annopol chimaeroid fauna is intermediate between coeval assemblages from the Cambridge Greensand (England) and from Belgorod Province, Russia, having more taxa in common with the latter.

New Record of Sillago sinica (Pisces: Sillaginidae) in Korean Waters, and Re-identification of Sillago parvisquamis Previously Reported from Korea as S. sinica

A single specimen of the genus Sillago, collected from Gwangyang, Korea, in May 2009, is characterized by XI first dorsal fin spines, 3 or 4 rows of melanophore pattern along the second dorsal fin membrane, and a darkish posterior margin of the caudal fin. Our specimen was identified as Sillago sinica reported as a new species; this identification is confirmed by mitochondrial DNA cytochrome oxidase subunit I sequences, which show that our specimen corresponds to S. sinica (d=0.000) and differs from the congeneric species Sillago parvisquamis (d=0.170). Comparisons of Korean specimens previously reported as S. parvisquamis with specimens of S. sinica show that the S. parvisquamis specimens are actually S. sinica. We propose the new Korean name "buk-bang-jeom-bo-ri-myeol" for S. sinica.

Morphological Discrimination between the Dorsal-fin Spines of the Blue Marlin Makaira nigricans: Reducing Biases in Age and Growth Estimations

Morphological Discrimination between the Dorsal-fin Spines of the Blue Marlin Makaira nigricans: Reducing Biases in Age and Growth Estimations

First Record of the Stichaeid Fish Chirolophis saitone (Perciformes: Stichaeidae) from Korea

One specimen of Chirolophis saitone, belonging to the family Stichaeidae, was collected by a bottom trawl in the southern area of the Yellow Sea. The present specimen was characterized by 52 dorsal fin spines, 38 anal fin spines, a caudal fin with four vertical dark bands and an orbital region with three pairs of branched cirri. We propose a new Korean name, "Jak-eun-goe-do-ra-chi', for C. saitone.

A new goatfish of the genus Upeneus (Mullidae) from Angoche, northern Mozambique.

A new goatfish, Upeneus saiab n. sp. (Mullidae), is described from six specimens collected off Angoche, northern Mozambique, during a research cruise of the RV Dr. F. Nansen in August 2009. Upeneus saiab n. sp. differs from all congeneric species in the following combination of characteristics: seven dorsal-fin spines, 29 total gill rakers, body depth at anal-fin origin 17-19% SL, and pectoral-fin length 20-21% SL. Detailed comparisons with the eight other species of the japonicus group are made and a key for Western Indian Ocean species is provided. A new record of Upeneuspori for Kwa-Zulu-Natal, South Africa, is reported based on in situ photographs. The need for further exploration of the rather long and ecologically diverse Mozambican coast and adjacent areas of southeastern Africa for the occurrence of yet undescribed or unreported goatfish species is emphasized.

An early fossil remora (Echeneoidea) reveals the evolutionary assembly of the adhesion disc

The adhesion disc of living remoras (Echeneoidea: Echeneidae) represents one of the most remarkable structural innovations within fishes. Although homology between the spinous dorsal fin of generalized acanthomorph fishes and the remora adhesion disc is widely accepted, the sequence of evolutionary-rather than developmental-transformations leading from one to the other has remained unclear. Here, we show that the early remora †Opisthomyzon (Echeneoidea: †Opisthomyzonidae), from the early Oligocene (Rupelian) of Switzerland, is a stem-group echeneid and provides unique insights into the evolutionary assembly of the unusual body plan characteristic of all living remoras. The adhesion disc of †Opisthomyzon retains ancestral features found in the spiny dorsal fins of remora outgroups, and corroborates developmental interpretations of the homology of individual skeletal components of the disc. †Opisthomyzon indicates that the adhesion disc originated in a postcranial position, and that other specializations (including the origin of pectination, subdivision of median fin spines into paired lamellae, increase in segment count and migration to a supracranial position) took place later in the evolutionary history of remoras. This phylogenetic sequence of transformation finds some parallels in the order of ontogenetic changes to the disc documented for living remoras.

Redescription of Parexus recurvus, an Early Devonian acanthodian from the Midland Valley of Scotland

Parexus Agassiz was one of the first Early Devonian ‘spiny sharks’ to be described. The genus is readily recognized by the large size and ornament of its anterior dorsal fin spine. Although two species were erected, reappraisal of all known specimens indicate they should be synonymized in the type species Parexus recurvus. Farnellia tuberculata Traquair, originally described as a vertebral column, is actually tooth rows of jaw dentition, and is also now considered to be a junior synonym of P. recurvus. Parexus has a perichondrally ossified scapulocoracoid of typical acanthodian shape, and diagnostic features of the family Climatiidae, but has distinctive scales comprising appositional growth zones that closely resemble those of the putative stem chondrichthyan Seretolepis elegans Karatajute-Talimaa.

Australoheros sanguineus sp. n. - a new cichlid species from the rio Cubatão basin, southern Brazil (Cichlidae: Heroini)

A new species of Australoheros is herein described from the rio Cubatão basin, southern Brazil. The new species differs from all its congeners mainly by the following character states: presence of a conspicuous rounded caudal-fin base; presence of two blood red regions on the corners of caudal-fin posterior margin; absence of conspicuous metallic blotches on anal-fin base; absence of a red pigmented line on dorsal-fin margin; presence of one conspicuous blue iridescence bar on dorsal-margin; more pectoral-fin rays (14); fewer proximal radials on dorsal-fin base (24 – 25); more proximal radials on anal-fin base (13); anal-fin base squamation beginning at 7th anal-fin spine; and dorsal-fin base squamation beginning between 11th and 12th dorsal-fin spine.

Larval and juvenile development of dusky grouper Epinephelus marginatus reared in mesocosms

The larval development of the dusky grouper Epinephelus marginatus up to the benthic juvenile stage is described in detail to establish a reference for their larval identification. Development is described in terms of ontogenetic changes in morphology, growth, pigmentation, fin structure and skeletal structure. Larvae were reared in mesocosms at a mean temperature of 24·3° C, salinity of 36·5, dissolved oxygen of 6·4 mg l(-1) and pH of 8·2. Newly hatched larvae had an estimated total length (LT ) of 2·3 mm. On the second day post hatching the yolk was almost fully absorbed with traces of the oil globule still present, the eyes were already pigmented and mouth and gut functional. At this stage the cranial skeletal elements for feeding and breathing (mouth and gills) and the pectoral-fin support were already present. About 50% of the observed larvae had food in their guts. Pigmentation was very characteristic, consisting of two large chromatophores visible on the edge of the primordial fin, close to the midpoint of the post-anal region of the body and over the midgut and hindgut and post-anal portion of the body. At 2·9 mm LT the emergence of the second dorsal-fin spine, characteristic of the Epinephilinae, was clearly visible. The pre-flexion stage started in larva of 3·2 mm LT . At 5·5 mm LT the larvae possessed posterior preopercular angle spines, and the dorsal and pelvic spines presented serrated edges and were pigmented. The water surface-tension-related death of the yolk sac and pre-flexion larvae described in the rearing of several other grouper species did not occur during E. marginatus culture. Notochord flexion, with initial ossification of the caudal-fin supporting elements, started at 6·6 mm LT . At this stage the major melanophores, preopercular, dorsal and pelvic spines and mandibular teeth were already present. Transformation of larvae into juveniles occurred when larvae averaged 13·8 mm LT . Juveniles with a mean LT of 20·1 mm started to settle and most of them were benthic with a mean LT of 26·8 mm.

Rhabdosargus niger (Perciformes: Sparidae), a new sparid species from Indonesia, with taxonomic status of the nominal species synonymized under Rhabdosargus sarba

A new sparid Rhabdosargus niger is described on the basis of three type specimens collected from off Kalimantan, Indonesia. The species can be differentiated from all known congeners by the following combination of characters: dorsal-fin rays XI, 13, anal-fin rays III, 11, scale rows below lateral line 11½–12½, scale rows between the fifth dorsal-fin spine base and lateral line 5½, pored lateral-line scales 53–55, head and body silvery-black, pelvic and anal fins dusky gray, and no golden longitudinal lines on the body. Partial sequences of mitochondrial COI gene (571 bp) strongly supported the distinctiveness of R. niger within the genus. Taxonomic status of the nominal species synonymized under Rhabdosargus sarba (Forsskal 1775) is discussed and the key to the species of Rhabdosargus is provided.

Review of theAcanthopagrus latuscomplex (Perciformes: Sparidae) with descriptions of three new species from the Indo‐West Pacific Ocean

Acanthopagrus latus, long considered a single valid Indo-West Pacific Ocean species, characterized by having yellow pelvic, anal and caudal fins, is reviewed and separated into A. latus (east Asian shelf) and Acanthopagrus longispinnis (Bengal Bay), and three new species: Acanthopagrus morrisoni sp. nov. (north-western Australia), Acanthopagrus arabicus sp. nov. [Middle East (except for the Red Sea) to coasts of Iran and Pakistan, and western Indian coast] and Acanthopagrus sheim sp. nov. (The Gulf). Although A. latus as redefined considerably varies in morphology and colouration, it can be recognized as a discrete east Asian endemic, with the following nominal species being junior synonyms: Chrysophrys auripes, Chrysophrys xanthopoda, Chrysophrys rubroptera and Sparus chrysopterus. Chrysophrys novaecaledoniae, known only from the holotype (type locality: Nouméa, New Caledonia), is a questionable junior synonym of A. latus, the lack of subsequent collections suggesting that the type locality is erroneous. Acanthopagrus longispinnis is differentiated from the other species in the complex by consistently having 12 dorsal-fin spines and a much larger second anal-fin spine, 21-26% (mean 23%) of standard length (LS ) (v. 14-24%, mean 18-21% in the other four species). Acanthopagrus morrisoni sp. nov. has the entire caudal fin yellow with a wide black posterior margin (persisting in preserved specimens) and consistently 3 ½ scale rows between the fifth dorsal-fin spine base and the lateral line. Acanthopagrus sheim sp. nov. has the pelvic, anal and lower caudal fins vivid yellow, with two (rarely three) small black blotches on the lower inter-radial membranes between the spinous and soft dorsal-fin rays. Acanthopagrus arabicus sp. nov. consistently has 4 ½ scale rows between the fifth dorsal-fin spine base and the lateral line, whereas A. latus always has black streaks proximally on the inter-radial membranes between the yellow anal-fin rays. A neotype and lectotye, respectively, are designated for A. latus and A. longispinnis. The p-distance (net nucleotide substitutions per site) of partial mitochondrial 16s ribosomal RNA genes (538 bp) among the above species (except A. longispinnis) and three other congeners (Acanthopagrus berda, Acanthopagrus pacificus and Acanthopagrus bifasciatus) strongly indicates that each is a distinct species. A key is provided for the 20 species of Acanthopagrus currently known from the Indo-West Pacific Ocean.

A new Haptoclinus blenny (Teleostei, Labrisomidae) from deep reefs off Curaçao, southern Caribbean, with comments on relationships of the genus

A second species of the blenniiform genus Haptoclinus is described from deep reefs off Curaçao, southern Caribbean. Haptoclinus dropi sp. n. differs from the northwestern Caribbean Haptoclinus apectolophus Böhlke and Robins, 1974, in having 29 total dorsal-fin elements—III-I-XIII, 12 (vs. 31—III-I-XIV, 13 or III-I-XIII, 14); 19 anal-fin soft rays (vs. 20-21); 12 pectoral-fin rays (vs. 13); 12 precaudal vertebrae (vs. 13); and the first dorsal-fin spine longer than the second (vs. the second longer than the first). It further differs from Haptoclinus apectolophus in lacking scales (vs. three-quarters of body densely scaled), in having a distinctive pattern of spotting on the trunk and fins in preservative (vs. no spotting), and in lacking a fleshy flap on the anterior rim of the posterior nostril (vs. flap present). Color in life is unknown for Haptoclinus apectolophus, and the color description presented for the new species constitutes the first color information for the genus. Familial placement of Haptoclinus remains questionable, but the limited relevant information obtained from morphological examination of the new species provides additional support for a close relationship with the Chaenopsidae. Haptoclinus dropi represents one of numerous new teleost species emerging from sampling to 300 m off Curaçao as part of the Smithsonian Institution’s Deep Reef Observation Project (DROP).

New species of Eugerres from the Usumacinta Province, México and Guatemala with a redescription of E. mexicanus (Steindachner, 1863) (Teleostei: Gerreidae)

Eugerres castroaguirrei, new species is described from the río Grijalva-Usumacinta basin of southeastern Mexico and northern Guatemala. Eugerres castroaguirrei and E. mexicanus are distinguishable from their marine estuarine congeners by the dorsal-fin origin posterior to the insertion of the pectoral and pelvic fins, a shorter and broad based supraoccipital crest, and a distinct geographic distribution restricted to freshwater habitats. Eugerres castroaguirrei differs from E. mexicanus by diagnostic characters of the body skeleton: anterior process of supraoccipital convex, infraorbital 1 with foramen, premaxillary ascending process developed with margins curved, pharyngeal plate granular and not serially arranged, and dorsal and anal fin-rays reduced. Likewise, E. castroaguirrei is characterized by an oblong and laterally thicker body (37.6-58.5% HL); greater body depth (33.8-42.1% SL), and eye diameter (23.3-31.6% HL); in addition to 16 significant morphometric characters: length of the second dorsal-fin spine 23.2-34.2% SL; depressed second dorsal-fin spine (extending to base of third to fourth dorsal-fin rays); length of second anal-fin spine 11.1-20.6% SL, depressed second anal-fin spine extending to the base of third to fourth anal-fin rays not reaching the distal point of last anal-fin ray; pelvic-fin spine length 49.7-65.0% in the first pelvic-fin ray length

First ever record of a threatened onespot barb fish, Puntius terio (Hamilton) from Arunachal Pradesh, India: A biodiversity hot spot

Arunachal Pradesh is geographically the largest state in North-East region of India with rich lentic and lotic water resources. The state has more than 7000 ha of lentic water and 2000 km of lotic water resources. Arunachal Pradesh is the 18th hot spot of the world in view of the richness of biological diversity. It constitutes high endemism and comparatively higher incidence of rare and threatened taxa. Available literature suggests that Puntius terio has not been reported earlier from the aquatic habitat of Arunachal Pradesh except in West Bengal, Assam, Manipur and Tripura in India, Bangladesh and Pakistan. This fish has incomplete lateral line with 22 to 24 scales on the lateral line, barbels absent, dorsal fin spine smooth and osseous and round golden-edged black blotch on 16th to 18th scales. The present finding of the threatened fish, P. terio requires its conservation in the water system of the biodiversity hot spot, Arunachal Pradesh. Key words: First ever record, threatened, Puntius terio, Tango Epong stream, Arunachal Pradesh.