A New Species of the Blind Cave Loach Genus Protocobitis (Cypriniformes: Cobitidae), Protocobitis longicostatus sp. nov., from Guangxi, China.

Protocobitis species are typical cave-dwelling fish, exhibiting distinctive morphological adaptations such as colorless body, lack of eyes, and reduced scales and ribs in response to their extreme cave habitats. Distinct from the recorded species, P. anteroventris, P. polylepis, and P. typhlops, a new species, Protocobitis longicostatus sp. nov., is described from Guangxi Zhuang Autonomous Region, China. Protocobitis longicostatus sp. nov. can easily be distinguished from all known congeners by the following characteristics: whole body covered by scales except head, 12 branched caudal fin rays, and long ribs. These species face threats from habitat degradation, hydrological changes, and environmental pollution. Thus, the conservation of cavefish in China has become an urgent issue.

Scale Characteristics of Six Fish Species of the Genus Cyprinion (Teleostei: Cypriniformes): A Microscopic Analysis.

This study investigated the morphological characteristics of scales in six Cyprinion species, using light and scanning electron microscopy focusing on key features such as scale type, key scales, lateral line scales, radius/radii, rostral margin, focus, circuli, lepidonts, tubercles, and scale indices. The research analyzed the scales using ultramicroscopy and light microscopy imaging, categorizing them based on size classes and body regions. The morphological variations in scale characteristics were examined across different species, regions, and size classes. Notable findings included the tetra-sectioned form of scales, representing a unique characteristic of the Cyprinion genus. Morphological changes in scale features were observed with fish growth, particularly in the overall shape, focus shape, and size. Quantitative analysis revealed variations in average relative scale length and width among different species, regions, and size classes. The study utilized canonical discriminant analysis for multivariate assessment, classifying the species into distinct groups based on morphometric indices. The findings contribute to the understanding of scale morphology in Cyprinion species and exploring morphological variation between the examined species.

Descriptions of two new species of the botiid genus Leptobotia Bleeker, 1870 (Teleostei: Cypriniformes) from South China.

Two new species of Leptobotia are here described as L. rotundilobus from the Xin'an-Jiang of the upper Qiantang-Jiang basin in both Anhui and Zhejiang Provinces and the Cao'e-Jiang in Zhejiang Province, and L. paucipinna from the Qing-Jiang of the middle Chang-Jiang basin in Hubei Province, South China. Both have a plain brown body as found in L. bellacauda Bohlen & Slechtová, 2016, L. microphthalma Fu & Ye, 1983, L. posterodorsalis Chen & Lan, 1992 and L. tientainensis (Wu, 1930). The two new species are distinct from these species in vertebral counts, further from L. posterodorsalis in vent placement and further from the other three species in pectoral-fin length. Both differ in caudal-fin coloration and shape, and dorsal-fin location and coloration, and also in internal morphology. Their validity is confirmed by their own monophyly recovered in a phylogenetic analysis based on the mitochondrial cyt b and COI genes.

A new cavefish of Sinocyclocheilus (Teleostei: Cypriniformes: Cyprinidae) from the Nanpanjiang River in Guizhou, China.

A new species, Sinocyclocheilus xingyiensis, is described based on specimens collected from a karst cave in Guizhou Province, China. The authors used an integrated taxonomic approach, including morphological and molecular data, to identify the new species as a member of the Sinocyclocheilu angularis group, and it can be distinguished from all other members of this group by a combination of the following features: two pairs of long barbels and long pectoral fins, 42-46 lateral-line scales, 7 (13-14) on outer (inner) side of the first gill arch and 35 (14-15 + 4 + 16 - 17) vertebrae. Phylogenetic analyses based on the cytochrome b (cyt b) gene fragment suggest that S. xingyiensis is a sister lineage to Sinocyclocheilus flexuosdorsalis. The genetic distance (Kimura 2-parameter) between the S. xingyiensis and S. angularis groups of Sinocyclocheilus species based on cyt b gene fragment ranged from 1.2% to 15.4%.

Schistura sonarengaensis, a new species of cave-dwelling loach (Teleostei: Nemacheilidae) from Meghalaya, northeast India.

A new species of nemacheilid loach, Schistura sonarengaensis sp. nov., is described from three cave-dwelling populations (Barak-Surma-Meghna drainage) in the South Garo Hills district of Meghalaya, India. The new species possesses prominent eyes but is easily distinguished from all the congeners of the genus Schistura from Barak-Surma-Meghna and adjacent rivers drainages of northeast Indian (except S. syngkai) in having 13-26 vertically elongated to circular mid-lateral black blotches (brownish in life) overlayered on a grayish-black mid-lateral stripe on a dull white or pale-beige (golden brown in life) body. However, it can be easily distinguished from S. syngkai in having a complete (vs. incomplete) lateral line with more 72-89 (vs. 19-42) lateral-line pored scales, greater pre-dorsal length (48.5-53.1 vs. 41.9-44.1 %SL), a wider body at dorsal-fin origin (11.3-16.7 vs. 9.4-10.3 %SL), greater dorsal (18.1-21.1 vs. 15.1-17.0 %SL) and lateral (20.9-24.1 vs. 17.4-18.9 %SL) head length, a wider head (14.5-18.5 vs. 11.6-13.3 %SL), and moderately forked (vs. emarginated) caudal fin. Further, molecular analysis confirms the distinctiveness of S. sonarengaensis sp. nov. from its congeners found in northeast India by significant divergences with uncorrected genetic distance ranging from 3.7% to 17.3% in the mitochondrial cytochrome c oxidase subunit I (COI) gene dataset. The phylogenetic position of the new species with its sister species was evaluated using maximum likelihood and Bayesian analysis. The species delimitation approaches assemble species by automatic partitioning (ASAP) and Poisson tree processes (PTP) utilized for testing species assignments consistently identified our test group as a distinct species from its sister species. Although the new species lacks typical morphological adaptations usually associated with a subterranean life, such as complete absence (or vestigial presence) of eyes and pigmentation, it exhibits a reduction of pigmentation when compared to the epigean congeners.

Review of the spotted lizard loaches, Pseudohomaloptera (Cypriniformes: Balitoridae) with a re-description of Pseudohomaloptera sexmaculata and description of a new species from Sumatra.

A review of the six recognized species of Pseudohomaloptera is provided. Counts in the original description of Pseudohomaloptera sexmaculata Fowler (1934) were incorrect and led to confusion in identifying populations of Pseudohomaloptera in mainland Southeast Asia, and the species is re-described. The validity of Homaloptera septemmaculata Fowler (1934) is investigated and confirmed as a junior synonym of P. sexmaculata. P. sexmaculata and Pseudohomaloptera leonardi, similar morphologically and often misidentified, are widely distributed in mainland Southeast Asia, with P. sexmaculata in the Chao Phraya, Mae Klong and Pran Buri River basins, and P. leonardi in the Malay Peninsula and the Chao Phraya and Mekong River basins. Pseudohomaloptera yunnanensis and Pseudohomaloptera vulgaris have been reported from the Mekong basin of Thailand and Laos but appear to be restricted to Yunnan Province, China. A new species of Pseudohomaloptera is described from Sumatra. This is the southern-most species and first record for the genus from the Indonesian island. An identification key is provided for all species of the genus.

The Legacy of Sexual Ancestors in Phenotypic Variability, Gene Expression, and Homoeolog Regulation of Asexual Hybrids and Polyploids.

Hybridization and polyploidization are important evolutionary processes whose impacts range from the alteration of gene expression and phenotypic variation to the triggering of asexual reproduction. We investigated fishes of the Cobitis taenia-elongatoides hybrid complex, which allowed us to disentangle the direct effects of both processes, due to the co-occurrence of parental species with their diploid and triploid hybrids. Employing morphological, ecological, and RNAseq approaches, we investigated the molecular determinants of hybrid and polyploid forms. In contrast with other studies, hybridization and polyploidy induced relatively very little transgressivity. Instead, Cobitis hybrids appeared intermediate with a clear effect of genomic dosing when triploids expressed higher similarity to the parent contributing two genome sets. This dosage effect was symmetric in the germline (oocyte gene expression), interestingly though, we observed an overall bias toward C. taenia in somatic tissues and traits. At the level of individual genes, expression-level dominance vastly prevailed over additivity or transgressivity. Also, trans-regulation of gene expression was less efficient in diploid hybrids than in triploids, where the expression modulation of homoeologs derived from the "haploid" parent was stronger than those derived from the "diploid" parent. Our findings suggest that the apparent intermediacy of hybrid phenotypes results from the combination of individual genes with dominant expression rather than from simple additivity. The efficiency of cross-talk between trans-regulatory elements further appears dosage dependent. Important effects of polyploidization may thus stem from changes in relative concentrations of trans-regulatory elements and their binding sites between hybridizing genomes. Links between gene regulation and asexuality are discussed.

Resolving an unnoticed diversity within the Schistura robertsi species complex (Teleostei: Nemacheilidae) using molecules and morphology.

The Schistura robertsi species complex is a group of freshwater fish inhabiting streams in southeast Myanmar as well as in western and southern Thailand. In southern Thailand, the distribution exceeds the biogeographically important 'Surat Thani - Krabi line'. The complex is believed to include five described and one undescribed species, but monophyly and systematics of the group have never been studied explicitly. The present study aims to resolve the number of species within the Schistura robertsi group as well as their distribution areas and phylogenetic relations. We analysed mitochondrial and nuclear sequence data of 86 specimens from 47 localities and 18 morphological characters of 193 specimens. The phylogenetic analyses revealed the S. robertsi complex to be monophyletic and to be composed of ten major lineages. Six of them correspond to the known described or undescribed species, but another four newly identified clades reveal the existence of an overlooked diversity within the group. All genetic lineages are statistically highly supported and all are morphologically diagnosable, suggesting that they represent distinct species. The distribution areas of several clades overlap, the cases of direct co-occurrence show no sign of hybridisation.

Psilorhynchus nahlongthai, a new fish species (Teleostei: Psilorhynchidae) from the Brahmaputra drainage, northeast India.

Psilorhynchus nahlongthai, a new psilorhynchid fish, is described from the Diyung River, a tributary to the Kopili River (itself a southern tributary of the Brahmaputra drainage) in Assam, northeast India. It is placed in the Psilorhynchus balitora species group and can be easily distinguished from all other members of this group by a combination of the following characters: dense and prominent tuberculation on the head region; thick and long pre- and post-epiphyseal fontanelles on the neurocranium; 9 + 8 caudal-fin rays; and 34 (24 + 10) vertebrae. Genetic divergence between P. nahlongthai and members of the P. balitora species group from the Brahmaputra and neighbouring drainages, with K2P distances ranging 3.7%-14.7% and 7.4%-20.7% in the mitochondrial COI and cyt b gene datasets respectively, support its report as a new species.

Oreonectes guilinensis (Teleostei, Cypriniformes, Nemacheilidae), a new loach species from Guangxi, China.

A new loach Oreonectes guilinensis sp. nov. is described from Guangxi Zhuang Autonomous Region, China. It is the second surface-dwelling fish identified in the genus Oreonectes after the type species Oreonectes platycephalus. This new species can be distinguished from other species within the genus by the combination of the following features: a round caudal fin, 13-14 branched rays, an incomplete lateral line with 4-6 pores, a short pelvic fin located some distance from the anus, a scale-covered body, a stout build (body width 14.0%-16.7% of standard length), a posterior chamber of well-developed airbladder and a yellowish-brown body with a lateral dark brown strip. The maximum likelihood phylogenetic analysis based on cytb gene recovered this new species in a well-supported clade with the type species O. platycephalus, sister to the Lefua clade. Morphological comparisons as well as our phylogenetic tree support Oreonectes shuilongensis, Oreonectes daqikongensis, Oreonectes jiarongensis as species of Troglonectes. Based on our results there are 6 valid species in the genus Oreonectes.

Oxynoemacheilus cemali, a new species of stone loach (Teleostei: Nemacheilidae) from the Çoruh River drainage, Turkey.

Oxynoemacheilus cemali sp. nov. is described from the Çoruh River drainage in the eastern Black Sea basin. One molecular marker (coI), 25 morphometric and four meristic characters were analysed. Oxynoemacheilus cemali is distinguished from O. kosswigi, O. banarescui, O. samanticus and O. angorae in the Black Sea basin by having a suborbital groove in males, an axillary lobe at the pelvic-fin base, no dorsal adipose crest on the caudal peduncle, a slightly-forked caudal fin and 7-15 dark grey dorsal saddles. Morever, Oxynoemacheilus cemali is distinguished by commonly having 9-15 irregularly-shaped dark-grey bars on the flank posterior to the dorsal-fin origin or, rarely having a mottled pattern or 4-6 irregularly shaped dark-grey bars on the flank posterior to the dorsal-fin origin. Oxynoemacheilus cemali is also distinguished from the closely related species O. araxensis and O. cyri, distributed outside the Black Sea basin, by having 15 and 31 diagnostic nucleotide substitutions in the coI barcode region, respectively.

Light Microscopy of Development of the Olfactory Organ of European Weatherfish Misgurnus fossilis (Тeleostei: Cobitidae).

We studied the formation of the olfactory organ of European weatherfish Misgurnus fossilis (Linnaeus, 1758) from the formation of its placodes to the formation of lamellae using light microscopy. The aim of the present investigation was to determine which morphogenetic features of the olfactory organ ate associated with the demersal lifestyle. The olfactory organ of European weatherfish goes through such developmental stages as olfactory placode, olfactory pit, and olfactory chamber with lamellae. Formation of the olfactory pit occurs in prolarvae, but a considerable increase in size takes place during the switch to exogenous feeding. In late larva, lamellae are formed in the aboral part olfactory chamber as an outward fold at its bottom. At the same time, incurrent and excurrent nostrils start being formed as the result of approximation of lateral and medial margins in the rostal part above the olfactory cavity. In contrast to other fishes, the peculiarity of morphogenesis of olfactory organ of M. fossilis is its late formation followed by intensive postembryonic development.

Description of a new species of Triplophysa (Teleostei: Nemacheilidae) from Guizhou Province, China.

A new cave-dwelling fish species Triplophysa guizhouensis is described based on specimens collected from Guizhou, China, in a subterranean system interconnected with the Hongshui River drainage. The species can be distinguished from its congeners by a combination of characters: eyes present; caudal fin with 14 branched rays; inner gill rakers of first gill arch 8-10; posterior chamber of air bladder developed; and body posterior of dorsal fin scaled. A key to species of Triplophysa in the Pearl River basin is provided.

Selection and constraint underlie irreversibility of tooth loss in cypriniform fishes.

The apparent irreversibility of the loss of complex traits in evolution (Dollo's Law) has been explained either by constraints on generating the lost traits or the complexity of selection required for their return. Distinguishing between these explanations is challenging, however, and little is known about the specific nature of potential constraints. We investigated the mechanisms underlying the irreversibility of trait loss using reduction of dentition in cypriniform fishes, a lineage that includes the zebrafish (Danio rerio) as a model. Teeth were lost from the mouth and upper pharynx in this group at least 50 million y ago and retained only in the lower pharynx. We identified regional loss of expression of the Ectodysplasin (Eda) signaling ligand as a likely cause of dentition reduction. In addition, we found that overexpression of this gene in the zebrafish is sufficient to restore teeth to the upper pharynx but not to the mouth. Because both regions are competent to respond to Eda signaling with transcriptional output, the likely constraint on the reappearance of oral teeth is the alteration of multiple genetic pathways required for tooth development. The upper pharyngeal teeth are fully formed, but do not exhibit the ancestral relationship to other pharyngeal structures, suggesting that they would not be favored by selection. Our results illustrate an underlying commonality between constraint and selection as explanations for the irreversibility of trait loss; multiple genetic changes would be required to restore teeth themselves to the oral region and optimally functioning ones to the upper pharynx.

A new cave-dwelling loach, Triplophysa xichouensis sp. nov. (Teleostei Nemacheilidae) from Yunnan, China.

A new cave-dwelling loach of the genus Triplophysa, T. xichouensis, is described from an outlet of a subterranean river in Xisa Town, Xichou County, Yunnan Province, China. It can be distinguished from its congeners by the following characters: dorsal-fin rays iii, 8; anal-fin rays ii, 6; pectoral-fin rays i, 9 or 10; pelvic-fin rays i, 5 or 6; branched caudal-fin rays 16(8+8); eyes highly degenerated to a very tiny black dot; dorsal-fin origin closer to snout tip than to caudal-fin base and anterior to vertical line of pelvic-fin origin; pectoral fin length about two-thirds the distance between pectoral-fin origin to pelvic-fin origin; caudal peduncle slender, its length about three times its depth; caudal fin emarginate; body smooth and scaleless; lateral line complete and straight; anterior chamber of air bladder wrapped in dumbbell-shaped bony capsule and the posterior one well developed, long, oval; intestine short, bending in zigzag shape behind stomach. A key for the cave-dwelling species of Triplophysa is provided. urn:lsid:zoobank.org:pub:9162FFB1-7911-47C3-AE50-6A00E9590327.

Description of Triplophysa luochengensis sp. nov. (Teleostei: Nemacheilidae) from a karst cave in Guangxi, China.

A new cave-dwelling fish Triplophysa luochengensis is described based on specimens collected from a karst cave in Guangxi Zhuang Autonomous Region, China, that is interconnected to the Hongshui River drainage. The species can be distinguished from its congeners by a combination of characters: eyes degenerated, anal fin with six branched rays, caudal fin with 16-17 branched rays, pectoral-fin length 72·4-95·8% of the distance between pectoral-fin origin and pelvic-fin origin, lateral head length 26·2-28·2% of standard length (LS ), eye diameter 7·5-8·6 of LS , body covered by sparse scales, lateral line complete and 7-8 pre-operculo-mandibular pores. Dark pigments irregularly present on dorsum of head, dorsum and flank.

Molecular and morphological analyses revealed a cryptic species of dojo loach Misgurnus anguillicaudatus (Cypriniformes: Cobitidae) in Japan.

Although it has been reported that populations of the Japanese dojo loach Misgurnus anguillicaudatus (Cypriniformes: Cobitidae) belong to two distinct mitochondrial (mt)DNA (Type I and Type II), the taxonomic status of the species remains unresolved. To address this question, nuclear DNA and morphological analyses were performed on M. anguillicaudatus population in the Nakaikemi Wetland, where Type I and Type II lineages are sympatric. Results suggest the existence of a cryptic species (Type I) within the Japanese dojo loach.

Morphological characteristics of visual cells in the endemic Korean loach Kichulchoia multifasciata (Pisces; Cobitidae) by microscopy.

The visual cell of the retina in the Korean loach Kichulchoia multifasciata, a bottom-dwelling freshwater loach in shallow water, contains double cones and large rods. With light microscopy, the cones form a row mosaic pattern in which the partners of double cones are linearly oriented with a large rod. In a double cone or twin cone, the two members are unequal such that one cone may be longer than the other. An anatomical unit is apparent which consists of 5 rod cells and 15 double cone cells per 20 × 20 µm area. We found that the cone cells of outer segments are linked to the inner segment by so-called "calyceal process" using a scanning electron microscopy, unlike rod cells. In the transmission electron microscopy, the outer membrane shows piles of membrane discs surrounded by double membranes.

Multivariate heritability of shape in June sucker (Chasmistes liorus) and Utah sucker (Catostomus ardens): shape as a functional trait for discriminating closely related species.

Molecular genetic data suggest that June sucker (Chasmistes liorus) is only shallowly diverged from the co-occurring but phenotypically distinct Utah sucker (Catostomus ardens) in Utah Lake. Phenotypes representing both extreme morphologies (June sucker and Utah sucker) are observed in the small wild population, but relatively large numbers of intermediate phenotypes are also present. This relatively continuous variation between the two putative species could result from extensive hybridization (including reticulate evolutionary patterns) of genetically based phenotypes or incomplete divergence among lineages and extensive phenotypic plasticity with little genetic basis. To help inform the evolutionary history of June sucker and to provide critical information for management and restoration of June sucker populations, we evaluated the distribution of shape phenotypes among purebreds of each species and their hybrids and determined the heritability of shape and ecological performance between June sucker (C. liorus) and its sister species Utah sucker (C. ardens). Mouth shape of purebred June sucker and Utah sucker are located at the extremes, and hybrids are located midway between the purebreds. Multivariate heritability was relatively high for mouth shape at 0.27. Heritability for growth rate was high at 0.32-0.42, but variation was not associated with cross type. Genetically based variation in mouth shape has evolved fairly rapidly or has been maintained in the face of ongoing hybridization between the two species. Currently, there seems to be little evidence for differential selection between species that would maintain shape variation.

Transforming growth factor-ß1 expression in endangered age-0 shortnose suckers (Chasmistes brevirostris) from Upper Klamath Lake, OR relative to histopathology, meristic, spatial, and temporal data.

During July-September of 2008, 2009, and 2010 endangered age-0 juvenile shortnose suckers were sampled from Upper Klamath Lake, OR in a health evaluation that included the measurement of transforming growth factor - beta (TGF-ß) expression in spleen in combination with a histopathology assessment. This analysis was performed to determine if the expression of this immuno-regulator could be used as a component of a larger health evaluation intended to identify potential risk-factors that may help to explain why very few of these fish survive to age-1. Potential associations between TGF-ß1 expression, histopathological findings, meristic data as well as temporal and spatial data were evaluated using analysis-of-variance. In this analysis, the absence or presence of opercula deformity and hepatic cell necrosis were identified as significant factors in accounting for the variance in TGF-ß1 expression observed in age-0 shortnose suckers (n = 122, squared multiple R = 0.989). Location of sample collection and the absence or presence of anchor worms (Lernaea spp.) were identified as significant cofactors. The actual mechanisms involved with these relationships have yet to be determined. The strength, however, of our findings support the concept of using TGF-ß1 expression as part of a broader fish health assessment and suggests the potential for using additional immunologic measures in future studies. Specifically, our results indicate that the measure of TGF-ß1 expression in age-0 shortnose sucker health assessments can facilitate the process of identifying disease risks that are associated with the documented lack of recruitment into the adult population.