Hypostomus sertanejo (Siluriformes: Loricariidae), new armoured catfish species from north‐eastern Brazil

A re‐evaluation of the armoured catfish species of Hypostomus in the Rio Jaguaribe, north‐eastern Brazil, was prompted by the discovery of specimens with pale spots on a dark background collected from that basin c. 1936 and deposited at the Academy of Natural Sciences of Philadelphia. Recent field collections in the Rio Jarguaribe basin confirmed the presence of the pale‐spotted specimens and its distinctiveness as a new species. Hypostomus sertanejo n. sp. is diagnosed from other species of Hypostomus by having fins and dermal‐plated regions of head and body with pale spots or vermiculations on darker background, teeth slender, asymmetrically bicuspid and numerous (34–75) on dentary and premaxilla, depressed dorsal‐fin spine not reaching adipose spine, unbranched pectoral‐fin spine longer than unbranched pelvic‐fin ray, seven branched dorsal‐fin rays and one (rarely two) predorsal plate(s) bordering supraoccipital. Ancistrus salgadae Fowler 1941 is hypothesized to be a junior synonym of Hypostomus carvalhoi (Miranda‐Ribeiro, 1937), a dark‐spotted Hypostomus described from the Rio Granjeiro, a tributary to the upper Rio Salgado.     

Hemimyzon sheni, a new species of balitorid fish (Teleostei: Balitoridae) from Taiwan

A new balitord fish, Hemimyzon sheni n. sp. was collected from the Tar-Ju River basin, Taitung County, southeast Taiwan. The new endemic species can be distinguished from other congeneric species by a combination of the following features: (1) dorsal fin rays 3 + 8, pectoral fin rays 13+11 (total 24); (2) lateral-line scales 78–80 and predorsal scales 31–32; (3) somewhat pointed head shape; (3) small pelvic fin which does not extend to rear vertical of dorsal fin; (4) position of anus close to anal fin base; and (5) predorsal region with many very small light brown marks and unmarked pectoral fin. A diagnostic key to three nominal, endemic species of Hemimyzon from Taiwan is also provided in this paper.     

Hyphessobrycon platyodus (Teleostei: Characiformes), a new species from the Rio Madeira basin,Brazil, with comments on how multicuspid teeth relate to feeding habits in Characidae

A new species of Hyphessobrycon is described from the Rio Juma, a tributary of the lower Rio Aripuanã–Rio Madeira basin, Amazonas, Brazil. Hyphessobrycon platyodus can be distinguished from its congeners by the: presence of an elongated dorsal fin in adult males, 25–28 branched anal‐fin rays and absence of dark blotches from the dorsal fin and caudal peduncle. The presence of multicuspid teeth in species of Characidae and its relation with feeding habits are briefly commented on.     

A new species of the genusamblyeleotris (pisces: Gobiidae) from Japan

A new shrimp-associated goby,Amblyeleotris melanocephala, is described on the basis of specimens from Okinoshima Island. Kochi Prefecture, and Okinawa Island, Okinawa Prefecture, Japan. The species is distinguished from other members of the genus by the following combination of characters: head dark brown, a few yellow spots on pectoral fin base and opercular margin, 13 second dorsal and 13 anal fin soft rays, 20 pectoral fin rays, longitudinal scales 92–101, proportional length of interpelvic connecting membrane relative to longest pelvic fin ray (CM-value) 0.46–0.55, presence of a ventral frenum, midline of nape naked, sides scaled above midpoint between preopercle and opercle.     

Taxonomic revision of Hypostomus albopunctatus (Siluriformes: Loricariidae) reveals a new piece of the Hypostomus jigsaw in the upper Rio Paraná basin

Hypostomus albopunctatus was described from the Rio Piracicaba, a tributary of the Rio Tietê, upper Rio Paraná basin. Nevertheless, specimens attributed to this species are commonly found throughout other river systems in the upper Rio Paraná basin and present varying degrees of morphological variation. A taxonomic review of H. albopunctatus based on large series of specimens from many localities throughout the upper Rio Paraná basin was carried out. Results support H. lexi, H. niger and H. scaphyceps as junior synonyms. Hypostomus albopunctatus differs from all congeners except H. heraldoi by having pectoral-fin spine equal to or shorter than pelvic-fin spine (v. longer); it differs from H. heraldoi by having white or light yellow spots on the body and fins (v. dark brown or black spots). Despite conspicuous variation related to the shape and size of the spots and snout morphology, both spot and snout patterns overlapped among the examined populations, thus this variation was inferred to be intraspecific within a widely distributed H. albopunctatus.     

Atrosalarias hosokawai, a new species of blenny (perciformes: Blenniidae) from the western pacific

A new species of blenny,Atrosalarias hosokawai is described on the basis of 15 specimens from the western Pacific. It is distinguished from the only known congeneric species,A. fuscus (=A. fuscus fuscus+A. fuscus holomelas), by the following: supraorbital cirrus broad and flat (vs. slender and thread-like inA. fuscus); dorsal fin broadly contacting caudal fin (vs. narrow contact); anal fin narrowly contacting caudal fin (vs. usually free or (rarely) very narrow contact); posteriormost dorsal and anal fin rays long (vs. short); first or posteriormost soft dorsal fin ray shortest (vs. posteriormost ray shortest); first soft anal fin ray shortest (vs. posteriormost ray shortest); caudal fin rays branched in specimens over 36.0 mm SL (vs. unbranched); a large dark spot on base of pectoral fin absent (vs. present or absent); a red margin on anterior dorsal fin absent (vs. present). Futhermore,A. hosokawai differs fromA. f. fuscus in having a lower number of dorsal fin spines (ten vs. eleven) and geographical distribution (western Pacific Ocean vs. Indian Ocean and Red Sea). AlthoughA. hosokawai occurs sympatrically withA. f. holomelas, it can be further distinguished from the latter in lacking a large dark spot on base of pectoral fin.     

A new rheophilic South American darter (Crenuchidae: Characidium) from the rio Juruena basin,Brazil, with comments on morphological adaptations to life in fast-flowing waters

Characidium iaquira, a new species from the upper rio Juruena, rio Tapajós basin, Brazil, is described. The new species can be promptly distinguished from all congeners by having a unique v-shaped dark mark lying along the caudal-fin extension, in medium- and large-sized specimens, and a remarkable iridescent green colouration in life. Characidium iaquira is closely related to Characidium crandellii and Characidium declivirostre by sharing unambiguous synapomorphies such as branchiostegal membranes united to each other across the isthmus, a scaleless area extending from the isthmus to the pectoral girdle, and dermal flaps surrounding anterior and posterior naris independent, but touching each other distally. Morphological specializations of the paired fins in the three riffle-dwellers species are discussed, including the wing-like shape, robustness, and inclination of the pectoral fin.     

When destruction comes first: Two new species of Hypostomus Lacépède, 1803 (Siluriformes: Loricariidae) from a deeply-impacted river in the Rio São Francisco basin in Brazil

Environmental disasters affecting Brazilian rivers have been frequent recently, especially involving mining activities. Two recent dam-rupture events suddenly released millions of cubic meters of iron tailings downstream into two major Brazilian watersheds. These events generated major losses to the environment and human life. Additionally, the biodiversity in both watersheds was still incompletely known. Two new species of the armoured catfish genus Hypostomus were discovered in the Rio Paraopeba and surrounding rivers of the Rio São Francisco Basin. The species share some main characteristics including a depressed body, large dark spots on a clearer background and the absence of keels on flanks. However, while one species (Hypostomus freirei sp. n.) has a large mandibular ramus and numerous slender teeth, the other (Hypostomus guajupia sp. n.) has a shorter mandibular ramus and few robust teeth. The discovery of these two new mid-sized fish species emphasizes the presumption that the effects of major environmental disasters cannot be fully estimated as local biodiversity is not completely known. This discovery in a recently devastated area also shows that tough environmental laws for the protection, supervision and mitigation of major impacts are urgently needed in developing countries.     

Redescription of a rare bothid,Asterorhombus bleekeri (Macleay), and description of a new species ofAsterorhombus from northwestern Australia (Teleostei: Pleuronectiformes)

A rare Australian bothid flounder.Asterorhombus bleekeri (Macleay), is redescribed from the holotype and ten additional specimens from the east coast of Qeensland, Gulf of Carpentaria and Rowly Shoal (Western Australia). The species is transferred fromArnoglossus Bleeker toAsterorhombus Tanaka because of the lack of obvious sexual dimorphism in the interorbital width and pectoral fin length, the lack of rostral and orbital spines, the yellow-white blind side body coloration, and the deeply cleft parhypural and hypural plates. The definition ofAsterorhombus was emended as follows: the first dorsal fin ray continuous with or separated from remaining fin rays and gill rakers slender or stubby, with or without serrations.Asterorhombus osculus sp. nov., formerly briefly described in the literature as unidentified species ofEngyprosopon, was described from eight specimens from the northwestern coast of Australia. The new species is most similar toA. bleekeri in lacking sexual dimorphism, and having the caudal skeleton with deep clefts, two or three rows of teeth on the upper jaw and a pair of conspicuous black spots on the caudal fin, in addition to a similar general appearance, but is distinguished from the latter by shorter gill rakers, a very small mouth and feebly ctenoid scales on the ocular side. Both species clearly differed fromA. intermedius andA. fijiensis in having two (or three) rows of teeth on the upper jaws, slender gill rakers without serrations, first dorsal fin ray continuous with the other fin rays, and a pair of conspicuous black spots on the caudal fin.     

Species delimitation in annual killifishes from the Brazilian Caatinga,the Hypsolebias flavicaudatus complex (Cyprinodontiformes: Rivulidae): implications for taxonomy and conservation

The organisms investigated are members of the Hypsolebias flavicaudatus species complex; a clade of morphologically similar annual killifishes endemic to the semi-arid savannah of north-eastern Brazil in the São Francisco River basin, which is a tropical area under intensive process of habitat loss. A taxonomic revision was conducted combining two different approaches for species delimitation – a tree-based approach using mt-DNA (cytochrome b) and a character-based approach using morphological variation (colour patterns, fin morphology, meristic and morphometric data). Nine species are recognised, of which five are new species: H. flagellatus (Costa), H. flavicaudatus (Costa & Brasil), H. gilbertobrasili sp. nov., H. guanambi (Costa & Amorim), H. janaubensis (Costa), H. nitens sp. nov., H. pterophyllus sp. nov., H. radiseriatus sp. nov. and H. sertanejo sp. nov. On the basis of 17 years of field studies, preliminary conservation status assessments indicate that two species are highly threatened with extinction, at least one is endangered and another is vulnerable, whereas the others are not endangered. This result deeply contrasts with a previous assessment 10 years ago, when the whole H. flavicaudatus complex was considered as a single species of no conservation concern. Discrepancies in the assessment of conservation among closely related species living in similar habitats are a consequence of heterogeneous human occupation and disproportionate recent development throughout the São Francisco River basin.     

Species limits and phylogenetic relationships of red‐finned cryptic species of the seasonal killifish genus Hypsolebias from the Brazilian semi‐arid Caatinga (Teleostei: Cyprinodontiformes: Rivulidae)

Members of the Hypsolebias antenori species group comprise a diverse clade of morphologically similar seasonal killifishes occurring in a vast region of the semi‐arid savannah of northeastern Brazil. The present paper focuses on an assemblage of three allopatric cryptic species (H. antenori from isolated coastal river drainages, Hypsolebias igneus from the São Francisco River basin and Hypsolebias coamazonicus sp. nov. from the Parnaíba River basin) sharing almost identical colour patterns, including the presence of an orangish red anal fin in males, thus herein named as the red‐finned assemblage. A tree‐based approach using mt‐DNA (cytochrome b) supports delimitation of all three species, but indicates that the red‐finned assemblage is paraphyletic – H. igneus and H. coamazonicus are closely related to Hypsolebias nudiorbitatus, whereas H. antenori is the sister group to a clade comprising all 13 species of the H. antenori group included in the analysis. Morphological characters are useful to diagnose species, but are not informative for most clades highly supported by molecular data. H. coamazonicus is distinguished from all other congeners by the possession of a dark grey or black stripe on the dorsal fin in males. The basal position of H. antenori is related to uplift episodes involving the Araripe‐Borborema plateau during the Miocene, which isolated the coastal area inhabited by H. antenori from the remaining areas of the Caatinga. The sister group relationship between H. igneus and H. coamazonicus is attributed to a past connection between the São Francisco and Paranaíba River until the Tertiary.     

The length-weight relationship of four fish species captured in the Ibicuí River,southern Brazil

Length-Weight relationship (LWRs) were estimated for four fish species occurring in the Ibicuí River drainage basin, southern Brazil. Samples were captured monthly during the spring and summer seasons (October 2018 to March 2019). The fish were caught with gillnets of different meshes (15, 20, 25, 30, 40 mm between adjacent nodes) and a trawl net (5 mm mesh between adjacent nodes) Eighteen excursions were realized in three sites, with a length of approximately 100 km, in third-order flux, all distributed in sub-basin Ibicuí River. The captured tools were installed at the end of the day (6 p.m.) and removed around 6 a.m. the next day. The present study provides the length-weight relationship for four species (Astyanax dissensos, Galeocharax humeralis, Hypostomus roseopunctatus e Hypostomus uruguayensis).     

A comparison of pectoral fin ray morphology and its impact on fin ray flexural stiffness in labriform swimmers

The organization of tissues in appendages often affects their mechanical properties and function. In the fish family Labridae, swimming behavior is associated with pectoral fin flexural stiffness and morphology, where fins range on a continuum from stiff to relatively flexible fins. Across this diversity, pectoral fin flexural stiffness decreases exponentially along the length of any given fin ray, and ray stiffness decreases along the chord of the fin from the leading to trailing edge. In this study, we examine the morphological properties of fin rays, including the effective modulus in bending (E), second moment of area (I), segmentation, and branching patterns, and their impact on fin ray stiffness. We quantify intrinsic pectoral fin ray stiffness in similarly sized fins of two closely related species that employ fins of divergent mechanics, the flapping Gomphosus varius and the rowing Halichoeres bivittatus. While segmentation patterns and E were similar between species, measurements of I and the number of fin ray branch nodes were greater in G. varius than in H. bivittatus. A multiple regression model found that of these variables, I was always significantly correlated with fin ray flexural stiffness and that variation in I always explained the majority of the variation in flexural stiffness. Thus, while most of the morphological variables quantified in this study correlate with fin ray flexural stiffness, second moment of area is the greatest factor contributing to variation in flexural stiffness. Further, interspecific variation in fin ray branching pattern could be used as a means of tuning the effective stiffness of the fin webbing to differences in swimming behavior and hydrodynamics. The comparison of these results to other systems begins to unveil fundamental morphological features of biological beams and yields insight into the role of mechanical properties in fin deformation for aquatic locomotion.     

A new loach, Cobitis shikokuensis (Teleostei: Cobitidae), from Shikoku Island, Japan

A new species of spinous loach, Cobitis shikokuensis, is described based on 297 specimens from Shikoku Island, Japan. The new species was formerly known as the Shikoku group of Cobitis takatsuensis. It can be distinguished from other species of Cobitis and closely related genera by a combination of the following characters: dorsal fin with 6 branched soft rays; anal fin with 5 branched soft rays; one brownish streak across eye from the tip of nose, no streak on cheek; a black spot smaller than eye diameter near the dorsal corner of the caudal fin base; 3–5 small brownish speckles on ventral side of caudal peduncle; high caudal peduncle with well-developed fleshy keels on dorsal and ventral side; a lamina circularis at base of dorsal part of pectoral fin absent; first branched soft ray of pectoral fin broad in males; pectoral soft rays widely branched from the approximate midpoint; last anal fin ray with 2 elements; interorbital width 11.2–17.1% of head length.     

Knodus dorsomaculatus (Characiformes: Characidae), a new species from Teles Pires River,Tapajós River basin,Brazil

Knodus dorsomaculatus, a new species, is described from Teles Pires River, a tributary of the Tapajós River, Brazil. It can be distinguished from its congeners by the presence of a conspicuous dark blotch on the base of the first five branched dorsal fin rays and the presence of ii,9 dorsal fin rays. Additional comparisons between K. dorsomaculatus and its congeners are presented.     

Balitora eddsi,a new species of hillstream loach (Ostariophysi: Balitoridae) from Nepal

A new species of hillstream loach Balitora eddsi is described from the Karnali River drainage in south‐western Nepal. The new species is distinguished from all its congeners by possessing the following combination of characters: six to seven unbranched pectoral‐fin rays, pelvic‐fin length 12–14% standard length (L_S), dorsal surface without circular or irregular shaped dark blotches, snout pointed, median lobe between anterior rostral barbels pointed posteriorly, dorsal‐fin origin posterior to pelvic‐fin origin, lateral line scales 66–67, caudal peduncle length 22–23·2% L_S, caudal peduncle depth 4·1–4·2 times its length.     

Enteromius thespesios (Teleostei: Cyprinidae): a new minnow species with a remarkable sexual dimorphism from the south-eastern part of the Upper Congo River

A new minnow species, Enteromius thespesios, is described from the south-eastern part of the upper Congo River; that is, the Kalule Nord, the Luvilombo and the Chambeshi Rivers. Enteromius thespesios belongs to the group of the soft-rayed species of Enteromius from the Congo Basin; that is, those with a weakly ossified, flexible last unbranched dorsal-fin ray that lacks serrations along its posterior edge. Within this group, E. thespesios is most similar to E. humeralis, from which it is distinguished by a higher number of circumpeduncular scales and shorter anterior and posterior barbels. Enteromius thespesios is a rheophilic and territorial species. It exhibits a marked sexual dimorphism, with males having: a red band towards the distal edge of dorsal, caudal and, to a lesser degree, anal fin; nuptial tubercles; a longer snout; longer pectoral fins; a shorter anal fin. This study gives extensive consideration to sexual shape differences for a species of Enteromius and also briefly reviews the current knowledge of sexual dimorphism in the species of Enteromius from the Congo Basin. Some conservation issues related to the new species are also highlighted.     

A new species of Sturisoma Swainson, 1838 (Loricariidae: Loricariinae), from the Madeira River basin,with a discussion of historical biogeography of western Amazonas and Paraguay River basins

A new loricariin species of Sturisoma is described from the Cautário, Guaporé, Mamoré, Machado and Soteiro rivers, Madeira River basin, in Bolivia and Brazil. The new species is distinguished from its congeners by the presence of a middorsal longitudinal, thin dark brown stripe on the caudal peduncle, extending from two or three plates posterior to the dorsal-fin base, reaching the origin of the caudal fin, or one or two plates anterior to the origin of the caudal fin; small squarish anteriormost abdominal plates; and a middorsal longitudinal dark-brown stripe from first predorsal plate to near the dorsal-fin origin. Furthermore, the new species is diagnosed from congeners by plate morphology, counts on the median series, coalescent plates and ventrolateral thoracic plates, in addition to measurements related to body and head structures. An analysis of genetic distances using cytochrome C oxidase subunit 1 gene marker of the mitochondrial genome between the new species and several congeners is presented, in addition to a likelihood analysis to illustrate the position of the new taxon within Sturisoma. An identification key for species of the genus currently recorded at the upper Amazonas River basin is provided.     

New Ecuadorian records of the eyeless banjo catfish Micromyzon akamai (Siluriformes: Aspredinidae) expand the species range and reveal intraspecific morphological variation

Two specimens of Micromyzon akamai, an eyeless and miniaturized species previously known only from the deep channels of the eastern Amazon basin in Brazil, are reported from the Curaray River, a tributary of the Napo River in Ecuador. The new specimens are the first records of Micromyzon in the headwaters of the Amazon River and the first records of M. akamai outside Brazil. External morphological characters and a phylogenetic analysis of cytochrome c oxidase I (coI) gene support the identification of the new specimens as M. akamai. Nevertheless, the new specimens also indicate that some features previously hypothesized to be apomorphic for M. akamai are intraspecifically variable.     

Callionymus omanensis,a new species of dragonet from Oman,north‐western Indian Ocean (Teleostei: Callionymidae)

A new species of deep‐living dragonet Callionymus omanensis from Oman is described on the basis of a single male specimen collected in a trawl from 500 m depth off the coast of Oman. The new species is characterized within the subgenus Bathycallionymus by having a small branchial opening; head short (3·9 in proportion to standard length); eye large (2·4 in proportion to head length); preopercular spine with a long, upcurved main tip, with a small antrorse barb and a larger antrorse spine, and with a strong antrorse spine laterally at the preopercular‐spine base, ventral margin smooth; first dorsal fin slightly higher than second dorsal fin (male); second dorsal fin distally straight; 17 pectoral fin rays; distal end of caudal fin slightly pointed, with two median unbranched rays bearing short filaments; first dorsal fin with basal black spot reaching from first to fourth membranes, third membrane with an ocellated distal black blotch; second dorsal fin with vertical dark grey bars; distal three‐fourths of anal fin black; upper half of caudal fin with oblique dark grey bars; pelvic fin dark grey, second ray basally with a black blotch. The new species is compared with similar species. Revised keys to callionymid species of the western Indian Ocean and the Red Sea, as well as species of the subgenus Bathycallionymus, are presented.