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The chubbyhead barbs, a distinct group of fishes endemic to southern Africa, currently include eight valid species. Historically, Enteromius anoplus was the most widespread freshwater fish in South Africa due to synonymizations in the 1960s. It occurred in nearly every river system except coastal systems in the Cape Fold Ecoregion and the lower Orange River. However, a recent revision utilizing molecular and morphological analyses has led to significant taxonomic updates. Enteromius anoplus is restricted to the Gouritz River system, whereas Enteromius cernuus and Enteromius oraniensis have been revalidated and respectively confined to the Olifants and Orange River systems. Additionally, a new species Enteromius mandelai was described, with its range currently considered to encompass several river systems in the Eastern Cape. Despite these advances, the taxonomic status of fish previously assigned to E. anoplus from KwaZulu‐Natal remained uncertain. In this study, an integrative approach, combining genetic analysis, morphological characteristics, and geographic data, was employed to resurrect Enteromius karkensis as a distinct species from E. anoplus. Enteromius karkensis is deeply genetically differentiated (3.99%–8.07% p‐distance) from its congeners within the chubbyhead group. Morphologically, E. karkensis is easily distinguishable from its counterparts due to possession of a terminal mouth (vs. inferior in E. amatolicus), one pair of maxillary barbels (vs. two conspicuous pairs in E. motebensis, E. treurensis, and E. gurneyi), and a complete lateral line (vs. incomplete in E. anoplus and E. oraniensis). Furthermore, E. karkensis is differentiated from E. mandelai and E. cernuus by its long maxillary barbels that extend beyond the midpoint of the orbit. These findings highlight a consistent pattern from previous studies that show many freshwater fishes in South Africa have narrow geographic ranges. This emphasizes the importance of targeted conservation and management efforts, and our understanding of the biogeographic and evolutionary history of freshwater fishes in southern Africa. [ABSTRACT FROM AUTHOR]

Advancements in genome sequencing technology have brought unprecedented accessibility of high-throughput sequencing to species of conservation interest. The potential knowledge gained from application of these techniques is maximized by availability of high-quality, annotated reference genomes for endangered species. However, these vital resources are often lacking for endangered minnows of North America (Cypriniformes: Leuciscidae). One such endangered species, Colorado pikeminnow (Ptychocheilus lucius), is the largest North American minnow and the top-level native aquatic predator in the Colorado River Basin of the southwestern United States and northwestern Mexico. Over the past century, Colorado pikeminnow has suffered habitat loss and population declines due to anthropogenic habitat modifications and invasive species introductions. The lack of genetic resources for Colorado pikeminnow has hindered conservation genomic study of this unique organism. This study seeks to remedy this issue by presenting a high-quality reference genome for Colorado pikeminnow developed from Pacific Biosciences HiFi sequencing and Hi-C scaffolding. The final assembly was a 1.1 Gb genome comprised of 305 contigs including 25 chromosome-sized scaffolds. Measures of quality, contiguity, and completeness met or exceeded those observed for Danio rerio (Danionidae) and 2 other Colorado River Basin leuciscids (Meda fulgida and Tiaroga cobitis). Comparative genomic analyses identified enrichment of gene families for growth, development, immune activity, and gene transcription; all of which are important for a large-bodied piscivorous fish living in a dynamic environment. This reference genome will provide a basis for important conservation genomic study of Colorado pikeminnow and help efforts to better understand the evolution of desert fishes. [ABSTRACT FROM AUTHOR]

This study analyzes the species composition, length–weight relationship (LWR), condition factor, and morphometric and meristic characteristics of eleven freshwater fish species in Kota Panjang Reservoir, Indonesia. Fresh specimens were collected from September 2023 to February 2024. Results show that among the sampled species, two belong to Order Anabantiformes, three to Order Siluriformes, and six to Order Cypriniformes. The Order Siluriformes has the lowest species composition, with Hemibagrus wyckii at 3.09%, while the Order Cypriniformes has the highest, with Barbonymus schwanefeldii at 15.25%. The LWR coefficient b ranges from 1.693 to 3.151. Of the species studied, only Hemisilurus heterorhynchus (b = 2.174), Clarias teijsmanni (b = 2.046), Anabas testudineus (b = 2.375), Labiobarbus festivus (b = 2.305), and Rasbora argyrotaenia (b = 1.693) fall outside the expected range of 2.5 < b less than < 3.5. One species exhibits a positive allometric growth (+), seven show a negative allometric growth (−), and three display an isometric growth (I). Fulton's condition factor (Kc) averages between 0.73 ± 0.15 and 4.96 ± 0.63, indicating morphological variation. The allometric condition factor (Ka) ranges from 0.87 ± 0.18 to 26.25 ± 4.05, reflecting differences in resource availability and competition. Relative condition factor (Kn) values range from 1.00 ± 0.09 to 2.51 ± 0.55, indicating good growth. Morphometric analysis shows that Rasbora argyrotaenia has the smallest average total length, head length, and body depth, while Hemibagrus wyckii has the largest. The results provide new data on the LWR, condition factor, and morphometric characteristics of eleven selected freshwater fish species in Kota Panjang Reservoir, Indonesia, and offer up‐to‐date information on the remaining species in the study area. These findings could have a significant impact on species stock assessments and help identify priority species for domestication. [ABSTRACT FROM AUTHOR]

Control and elimination of invasive fishes, like carps (Order Cypriniformes), may be possible by using chemical stimuli to congregate them for removal. To this end, we tested behavioral responses of grass (Ctenopharyngodon idella), bighead (Hypophthalmichthys nobilis), and silver carp (H. molitrix) to L‐alanine, L‐arginine, L‐glutamic acid, and L‐aspartic acid. In grass carp, the first three amino acids have been shown to be beneficial for growth, and all four produce a strong olfactory response in this species. This study used pairs of conspecific fish in a video‐recorded, sound‐insulated, clear acrylic, tube‐shaped tank; during trials, an amino acid stimulus was delivered at one end of that tank. Changes in space use, velocity, and acceleration across all amino acids differed significantly among species. Changes in space use by grass carp indicated avoidance of only two amino acids, L‐alanine and L‐aspartic acid. There was no evidence for attraction to amino acids for grass or silver carp. For bighead carp, change in spatial use on exposure to amino acids indicated attraction across the four amino acids. This attraction was enhanced by lowered velocity. Our results suggested that olfactory sensitivity does not directly translate to behavioral responses. Other sensory cues, for example tactile, visual, and/or taste, may mediate the selective foraging of grass carp. Amino acids may serve as a better olfactory attractant for bighead carp compared to grass or silver carp. [ABSTRACT FROM AUTHOR]

A growing body of evidence indicates that the global diversity of freshwater fishes has not been fully documented. Studies of freshwater fishes that were previously thought to be morphologically variable have revealed the existence of deeply divergent lineages, with many distinct species. In southern Africa a number of Enteromius species exhibit either exceedingly wide or divided distribution patterns that should be rare for freshwater fishes with limited dispersal opportunities between river systems. One such species is the sidespot barb, Enteromius neefi. As currently defined, E. neefi has a disjunct distribution that is divided between rivers in the northeast escarpment in South Africa and Eswatini, and tributaries of the Upper Zambezi in Zambia and southern Congo in the Democratic Republic of Congo, with a large geographic gap between these two populations. With the use of molecular and morphological methods, the level of divergence between the two populations was examined, and a new species was described from the Steelpoort River in the Limpopo River system of South Africa. Findings from this study provide further evidence for a number of taxonomic problems within the goldie barbs of southern Africa, and some taxonomic rearrangements are proposed for this group. [ABSTRACT FROM AUTHOR]

Psilorhynchus kosygini, a new species, is described from the Tepuiki River, a tributary of the Barak drainage in Nagaland, north-east India. The new species, belonging to the P. homaloptera species group, is characterised by possessing a unique pattern of 3–4 scales positioned along the mid-ventral region between the posterior base of the pelvic fin and the anal opening, body elongate with 41–42 scales along the lateral line, 14 scales in the pre-dorsal region, 8 scales around the caudal peduncle and 9–10 branched pectoral-fin rays. [ABSTRACT FROM AUTHOR]

A fundamental assumption in animal telemetry is that the behavior and performance of tagged animals do not substantially deviate from that of untagged animals. For fish, swimming behavior is fundamental for every part of a fish post-hatch life, influencing predator-prey interactions, movement ecology, and habitat choice. Here, we study the effects of PIT-tagging on survival and a range of swimming behaviors for South European nase (Protochondrostoma genei) and brook barbel (Barbus caninus), two small-sized, stream-dwelling cypriniforms native to the Italian peninsula. Effects on volitional swimming activity (sustained swimming) and maximum swimming speed (escape response; burst swimming) were tested in arena trials. Tagging effects on the prolonged swimming performance were tested in South European nase in an increasing velocity time-to-fatigue test, while a barrier passage test was designed to further investigate tagging effects in brook barbel. Both species displayed very high survival (95–100%), with no difference between tagged and control fish. No fish lost a tag during the 64 days of the study, and no tagging effect on swimming activity, prolonged swimming performance, barrier passage rate, or escape response was detected. Our results indicate that PIT-telemetry is a suitable tool to study the tested fish species. [ABSTRACT FROM AUTHOR]

In this study, the complete mitochondrial genome of Triplophysa erythraea was determined for the first time. Results showed the mitogenome was 16 565 bp, including 2 ribosomal RNA genes, 22 transfer RNA genes, 13 protein-coding genes and 2 non-coding regions. The overall base composition of its mitochondrial genome was 28.9% A, 25.2% T, 28.7% C and 17.2% G. Phylogenetic tree revealed that Triplophysa erythraea had the closest relationship with Triplophysa xiangxiensis, which was also found in Xiangxi Tujia and Miao Nationality Autonomous Prefecture, Hunan province. In general, this study provided valuable information for conservation genetics analyses of Triplophysa erythraea and further displayed the evolution of species within the genus Triplophysa. [ABSTRACT FROM AUTHOR]

The taxonomy of the Parachela–Oxygaster–Macrochirichthys clade of Xenocyprididae has been confused since the original descriptions of Parachela oxygastroides and Parachela hypophthalmus in the mid‐19th century. The confusion seems attributable to the substantial intraspecific variation in color and other morphological characteristics of species of Oxygaster and Parachela. Morphological data on 401 specimens from throughout the range of Parachela and molecular phylogenetic analyses indicate that six available species names for Parachela are valid: Parachela cyanea, P. hypophthalmus, Parachela ingerkongi, Parachela johorensis (removed from the synonymy of P. oxygastroides), P. oxygastroides, and Parachela williaminae. In addition, two new species of Parachela, Parachela melanosticta and Parachela microlepis, are described. Chela pointoni is a synonym of P. oxygastroides, not a valid species of Oxygaster as previously hypothesized, and Parachela maculicauda is a synonym of Parachela johorensis. Considerable morphological and genetic variation is present in all well‐sampled species of Parachela. [ABSTRACT FROM AUTHOR]

The additional record of Hypselobarbus kushavali is reported from Thunga River, Karnataka, India and a new species of Hypselobarbus from Bhadra River, Karnataka is described herein. Hypselobarbus arunachalami sp. nov. is diagnosed from all its congeners in the genus by having fewer lateral-line scales and fewer circumferential scale rows [ABSTRACT FROM AUTHOR]

Two new species, Beaufortia granulopinna and Beaufortia viridis, are described from the upper Pearl River system in southwest China. Both species share the characteristics of the Beaufortia pingi species group, including prominent vertical stripes on the lateral body and pinnate-type lower lips, distinguishing them from other Beaufortia species. Beaufortia granulopinna is differentiated from other species in the group by possessing a unique set of characteristics: the presence of well-developed prominent tubercles on the first 6–9 pectoral fin rays in adults; and a significant proportion (54.76%) of individuals experiencing blurriness or absence of vertical stripes in the mid-section of the lateral body upon reaching adulthood. The minimum interspecific genetic distance within the genus based on mitochondrial cytb gene sequences is 10.80%. Beaufortia viridis is distinguished from other species in the group by consistently exhibiting vertical stripes of uniform length, width, and spacing across all stages of growth; the absence of tubercles on the branched rays of pectoral fins; and a body coloration of dark cyan to green. The minimum interspecific genetic distance within the genus based on mitochondrial cytb gene sequences is 4.60%. Molecular phylogenetic results confirm that the Beaufortia pingi species group forms a monophyletic clade, which is congruent with morphological classification findings. This study also addresses and resolves the taxonomic ambiguity surrounding Beaufortia pingi and Beaufortia zebroida, providing a redescription of these taxa. [ABSTRACT FROM AUTHOR]

The morphology, phylogenetic position, and distribution of a recently revalidated species of leuciscid minnow, Phoxinus isetensis, were substantially clarified. The species was described in the late 18th century from the Middle Urals but later synonymized with Phoxinus phoxinus. As believed, P. isetensis is distributed in the Arctic Ocean catchment from the Murman coast via West and East Siberia until the Pacific Ocean catchment in Far East and Northeastern Asia. Our study, with the use of mtDNA markers coupled with extensive morphological data, showed that the distribution of P. isetensis is greatly different. Currently, this is the most widespread Phoxinus species in Europe, distributed in Northern and Eastern Europe and on the western edge of Siberia (Iset and Ural basins). In particular, P. isetensis inhabits the basins of the Caspian, Baltic, White, Barents, and Kara seas, possibly occurring in the North Sea basin. The species was redescribed, and the type locality and neotype were designated. The main morphological difference from other Phoxinus spp. is the large total number of vertebrae (39–43, mode 41) due to an increase in the number of caudal vertebrae (16–21, mode 19). Phylogenetically, P. isetensis is a sister to the Caucasian species P. colchicus (p-distance = 5%). The wide distribution of P. isetensis within the area of the Last Glacial Maximum suggests rapid colonization of deglaciated regions, probably due to its adaptation to a cold climate. [ABSTRACT FROM AUTHOR]

The pale chub Zacco platypus (Cypriniformes; Xenocyprididae; Jordan & Evermann, 1902) is widely distributed across freshwater ecosystems in East Asia and has been recognized as a potential model fish species for ecotoxicology and environmental monitoring. Here, a high-quality de novo genome assembly of Z. platypus was constructed through the integration of a combination of long-read Pacific Bioscience (PacBio) sequencing, short-read Illumina sequencing, and Hi-C sequencing technologies. Z. platypus has the smallest genome size compared to other species belonging to the order Cypriniformes. The assembled genome encompasses 41.45% repeat sequences. As shown in other fish, a positive correlation was observed between genome size and the composition of transposable elements (TE) in the genome. Among TEs, a relatively higher rate of DNA transposon was observed, which is a common pattern in the members of the order Cypriniformes. Functional annotation was processed using four representative databases, identifying a core set of 12,907 genes shared among them. Orthologous gene family analysis revealed that Z. platypus has experienced more gene family contraction rather than expansion compared to other Cypriniformes species. Among the uniquely expanded gene families in Z. platypus, detoxification and stress-related gene families were identified, suggesting that this species could represent a promising model for ecotoxicology and environmental monitoring. Taken together, the Z. platypus genome assembly will provide valuable data for omics-based health assessments in aquatic ecosystems, offering further insights into the environmental and ecological facets within this species. [ABSTRACT FROM AUTHOR]

Simple Summary: Myxozoa is an important metazoan parasite, with approximately 2600 species reported around the world. However, their diversity is still largely underestimated, particularly for those of the Culters, where only 15 species have been previously reported in China. Thus, an investigation into the diversity of myxozoans in Culters was conducted, and a new species belonging to Myxobolus was found. Through comprehensive morphological comparisons and molecular analyses with closely related species, we designated it a new Myxobolus species and named it Myxobolus darbryi n. sp. Culters are a popular and economically important carnivorous freshwater fish, widely distributed in rivers, lakes, and reservoirs in China. An investigation of Myxozoa was conducted to enhance the understanding of Myxozoan diversity in Culters in China, as only 15 Myxosporean species have been previously reported in 6 Culters species. A new species with typical Myxobolus characteristics was discovered exclusively in the gills of Chanodichthys dabryi, Bleeker, 1871, and no other species were found in other Culters fish or organs. The new species elicited whitish plasmodia in the serosa layer of the gill arch, with no distinct inflammatory reaction observed. This species is morphologically different from all reported Myxobolus spp. from Culters, differing in plasmodium and spore size, as well as the coils of polar filaments. Molecular analysis further supports that it does not match any sequences available in GenBank. Therefore, we identified it as a new species and named it Myxobolus dabryi n. sp. [ABSTRACT FROM AUTHOR]

The Pseudogastromyzon genus, consisting of species predominantly distributed throughout southeastern China, has garnered increasing market attention in recent years due to its ornamental appeal. However, the overlapping diagnostic attributes render the commonly accepted criteria for interspecific identification unreliable, leaving the phylogenetic relationships among Pseudogastromyzon species unexplored. In the present study, we undertake molecular phylogenetic and morphological examinations of the Pseudogastromyzon genus. Our phylogenetic analysis of mitochondrial genes distinctly segregated Pseudogastromyzon species into two clades: the Pseudogastromyzon clade and the Labigastromyzon clade. A subsequent morphological assessment revealed that the primary dermal ridge (specifically, the second ridge) within the labial adhesive apparatus serves as an effective and precise interspecific diagnostic characteristic. Moreover, the distributional ranges of Pseudogastromyzon and Labigastromyzon are markedly distinct, exhibiting only a narrow area of overlap. Considering the morphological heterogeneity of the labial adhesive apparatus and the substantial division within the molecular phylogeny, we advocate for the elevation of the Labigastromyzon subgenus to the status of a separate genus. Consequently, we have ascertained the validity of the Pseudogastromyzon and Labigastromyzon species, yielding a total of six valid species. To facilitate future research, we present comprehensive descriptions of the redefined species and introduce novel identification keys. [ABSTRACT FROM AUTHOR]

Triplophysa grahami Regan 1906 is a member of the family Nemacheilidae, Cypriniformes, and native loach in Yunnan. In this study, the complete mitochondrial genome (mitogenome) of T. grahami Regan 1906 was firstly reported and analyzed. The mitogenome of T. grahami Regan 1906 is 16,566 bp in length, including 13 protein-coding genes (PCGs), 22 transfer RNAs (tRNAs), two ribosomal RNAs (rRNAs), and one control region (D-loop). The arrangement and orientation of protein coding genes and RNAs in T. grahami Regan 1906 are identical to other species of Nemacheilidae. The base composition of T. grahami Regan 1906 mitogenome was 29.25% A, 28.55% T, 25.03% C, and 17.17% G. The phylogenetic analysis based on the mitogenome showed that T. grahami Regan 1906 belongs to the clade of genus Triplophysa and the monophyly of Triplophysa is identified. This study contributed valuable genetic data for T. grahami Regan 1906 and explored the phylogenetic relationships in Nemacheilidae. [ABSTRACT FROM AUTHOR]

This study assessed the functional effectiveness in terms of passage proportion of three fishways, one nature‐like bypass, one partly nature‐like bypass and partly technical pool‐type and one completely technical, on the Pinka Stream and Rába River in Western Hungary. Radio frequency identification with passive integrated transponder tagging was used to collect data on the upstream passage. A total of 2976 tagged individuals were included in the study; 2863 individuals were either barbel (Barbus barbus), nase (Chondrostoma nasus) or chub (Squalius cephalus), which were chosen as model species, and 113 individuals belonged to four other species. There were 540 individuals of the model species and 18 individuals of the other species detected while successfully ascending one of the fishways. The time‐to‐event (survival) analysis of the data of the model species revealed significant species‐specific differences in passage probability between the fishways. The passage probabilities of the barbel were the highest, and those of the nase were the lowest at all three fishways. The findings demonstrate that single‐species evaluations can lead to incorrect conclusions on fishway effectiveness. Technical fishways can be as effective as nature‐like ones, and hybrid solutions (technical fishways combined with nature‐like bypasses) can function as well. The limitations of the study and recommendations for further evaluations are also discussed. [ABSTRACT FROM AUTHOR]

The Leuciscidae (minnows, shiners and relatives) is a diverse family of freshwater fishes with many species endangered due to anthropogenic stressors. Notropis oxyrhynchus and Notropis buccula are two shiners found only in the upper Brazos River basin in Texas, USA and listed as endangered due to contracted habitat. The complete mitochondrial genome was sequenced for two vouchered specimens for each species; Notropis oxyrhynchus having a total mitogenome length of 16,711 bp and N. buccula having a total mitogenome length 16685–16686 bp, with both including 13 protein-coding genes, 22 transfer RNAs genes, and 2 ribosomal RNA genes. Phylogenetic analysis supports previous hypotheses regarding placement of these species.

In this study, the complete mitochondrial genome of Triplophysa erythraea was determined for the first time. Results showed the mitogenome was 16 565 bp, including 2 ribosomal RNA genes, 22 transfer RNA genes, 13 protein-coding genes and 2 non-coding regions. The overall base composition of its mitochondrial genome was 28.9% A, 25.2% T, 28.7% C and 17.2% G. Phylogenetic tree revealed that Triplophysa erythraea had the closest relationship with Triplophysa xiangxiensis, which was also found in Xiangxi Tujia and Miao Nationality Autonomous Prefecture, Hunan province. In general, this study provided valuable information for conservation genetics analyses of Triplophysa erythraea and further displayed the evolution of species within the genus Triplophysa.

Variations in molecular evolutionary rate have been widely investigated among lineages and genes. However, it remains an open question whether fast rate of molecular evolution is driven by natural selection or random drift, and how the fast rate is linked to metabolic rate. Additionally, previous studies on fast molecular evolution have been largely restricted to concatenated matrix of genes or a few specifically selected genes, but less is known for individual genes at the genome-wide level. Here we addressed these questions using more than 5000 single-copy orthologous (SCO) genes through comparative genomic and phylogenetic analyses among fishes, with a special focus on a newly-sequenced clupeocephalan fish the Chinese hook snout carp Opsariichthys bidens. We showed O. bidens displays significantly higher mean substitution rate and more fast-evolving SCO genes (2172 genes) than most fishes studied here. The rapidly evolving genes are enriched in highly conserved and very basic functions such as translation and ribosome that are critical for biological fitness. We further revealed that ∼25 % of these fast-evolving genes exhibit a constant increase of substitution rate from the common ancestor down to the present, suggesting a neglected but important contribution from ancestral states. Model fitting showed that ∼85 % of fast-evolving genes exclusive to O. bidens and related species follow the adaptive evolutionary model rather than random-drift model, and 7.6 % of fast-evolving genes identified in O. bidens have experienced positive selection, both indicating the reflection of adaptive selection. Finally, metabolic rate was observed to be linked with substitution rate in a gene-specific manner. Overall, our findings reveal fast molecular evolution of SCO genes at genome-wide level in O. bidens, and uncover the evolutionary and ecological contributors to it.

The ecological characteristics of the eight-barbel loach Lefua tokaiensis Ito, Hosoya, and Miyazaki were elucidated. Ecological field research was conducted at two localities: the montane stream of Houraiji and the Arao River of the Toyo River system in the Tokai region of Japan. The two localities showed high population density of L. tokaiensis, consisting of young-to-aged individuals. Loaches were likely to reproduce and migrate both upstream and downstream throughout year. Their lifespan was over 10 years, and loaches of more than ten generations simultaneously lived together. Growth rates slowed down strikingly with increasing age. The montane stream of Houraiji was suitable for the population of L. tokaiensis. The results of this study contribute to the protection of this endangered species. [ABSTRACT FROM AUTHOR]

An increasing presence of instream structures such as weirs, dams, culverts and reservoirs degrades habitats, fragments rivers and blocks fish movements worldwide. Longitudinal river movements are fundamental for many fish species and the most widespread solution to restore longitudinal connectivity is the implementation of different fish passage solutions. Fishway functionality, however, is highly variable. To design a functional fishway, several aspects of the fish's interaction with its environment need to be taken into consideration. Artificial light at night (ALAN) can affect a range of different behaviours in fish, from activity and movement to feeding and predator–prey relationships. In a fish passage setting, fish are exposed to artificial light at night (ALAN) in the form of light pollution, but, sometimes, also as part of the fish passage solution. Although likely highly species specific, the effect of artificial light on fish passage behaviour has been little explored. Here we study the passage behaviour of two small‐sized fish species, European gudgeon (Gobio gobio) and Italian riffle dace (Telestes muticellus), over a scaled deep side notch weir in a hydraulic flume in three different light conditions: daylight, darkness and ALAN. Although both species passed the obstacle at high efficiencies under all light conditions, their passage behaviours were influenced by light, particularly at the higher levels. While ALAN reduced passage success and resulted in delayed passage for gudgeon, riffle dace passed at higher rates under the artificial light compared to night treatment. Both results indicate a risk of negative effects from ALAN on passage performance at real fishways—or movement rates in lit areas of natural streams—for both species. Independent of light conditions, individuals of both species also passed faster after repeated trials, demonstrating learning in a fish passage context. [ABSTRACT FROM AUTHOR]

Nepal holds a high ichthyofaunal diversity, nevertheless, the molecular study of Nepalese fish is still in its early stages. The first record of a cyprinid fish species the Garra kempi Hora, 1921 for Nepal was reported from eastern Nepal's Lohandra River. Both morphology and molecular data affirmed the existence of G. kempi in Nepal's aquatic system. This species was previously reported from China (Tibet) and northern India. The maximum likelihood phylogenetic analysis and pairwise genetic distance based on Kimura 2 parameters using cytochrome oxidase subunit 1 (COI) segment sequences (665 bp) also confirmed the identity of the species as G. kempi. The COI sequences of specimens from Nepal formed a monophyletic clade with the sequence of G. kempi from northeastern India and the two contained a pairwise genetic distance of 1.8% only. The new record of G. kempi from Nepal warrants a detailed ichthyofaunal survey for documenting the fish diversity in Nepal. [ABSTRACT FROM AUTHOR]

With 75 known species, the freshwater fish genus Sinocyclocheilus is the largest cavefish radiation in the world and shows multiple adaptations for cave‐dwelling (stygomorphic adaptations), which include a range of traits such as eye degeneration (normal‐eyed, micro‐eyed and eyeless), depigmentation of skin, and in some species, the presence of "horns". Their behavioural adaptations to subterranean environments, however, are poorly understood. Wall‐following (WF) behaviour, where an organism remains in close contact with the boundary demarcating its habitat when in the dark, is a peculiar behaviour observed in a wide range of animals and is enhanced in cave dwellers. Hence, we hypothesise that wall‐following is also present in Sinocyclocheilus, possibly enhanced in eyeless species compared to eye bearing (normal‐/micro‐eyed species). Using 13 species representative of Sinocyclocheilus radiation and eye morphs, we designed a series of assays, based on pre‐existing methods for Astyanax mexicanus behavioural experiments, to examine wall‐following behaviour under three conditions. Our results indicate that eyeless species exhibit significantly enhanced intensities of WF compared to normal‐eyed species, with micro‐eyed forms demonstrating intermediate intensities in the WF distance. Using a mtDNA based dated phylogeny (chronogram with four clades A–D), we traced the degree of WF of these forms to outline common patterns. We show that the intensity of WF behaviour is higher in the subterranean clades compared to clades dominated by normal‐eyed free‐living species. We also found that eyeless species are highly sensitive to vibrations, whereas normal‐eyed species are the least sensitive. Since WF behaviour is presented to some degree in all Sinocyclocheilus species, and given that these fishes evolved in the late Miocene, we identify this behaviour as being ancestral with WF enhancement related to cave occupation. Results from this diversification‐scale study of cavefish behaviour suggest that enhanced wall‐following behaviour may be a convergent trait across all stygomorphic lineages. [ABSTRACT FROM AUTHOR]

Members of the genus Cyprinion (Cypriniformes: Cyprinidae) are found in the Indus River basin west to the Arabian Peninsula and the Tigris‐Euphrates River drainages (Persian Gulf basin). The taxonomic status of Cyprinion including Cyprinion muscatense is poorly understood when compared to other cyprinid genera. C. muscatense has been considered as a member of the Cyprinion watsoni‐microphthalmum group and a valid species endemic to the Arabian Peninsula. Here, we redescribe C. muscatense based on an integrative morphological and molecular approach and freshly sampled material from several localities in the Oman Mountains ecoregion. The results showed that C. muscatense is distinguished from the other Cyprinion species in the Arabian Peninsula by having a short, thin, and slightly serrated last unbranched dorsal fin ray; the lower number of circumpeduncular scales; lateral line scales; and also scales between the lateral line and the dorsal‐fin origin. Subterminal mouth, presence of one pair of small barbels at the mouth corner, 3–4 unbranched and 9½–10½ dorsal‐fin branched rays, 12–14 pectoral‐fin rays, 7–8 pelvic‐fin rays, 2–3 unbranched and 6½–7½ branched anal‐fin rays, and 37–40 lateral line scales are other morphological characteristics of C. muscatense. C. muscatense is also well distinguished by molecular characters among its congeners. The first molecular phylogenetic analysis of the genus, covering all currently recognized Cyprinion species except for C. watsoni, is also presented. C. muscatense is resolved as the sister species to another endemic fish of the Arabian Peninsula Cyprinion mhalense, with a Kimura‐2‐Parameter model distance of 5.3%. [ABSTRACT FROM AUTHOR]

Climate change is having a major impact on species distribution and habitat loss, especially for species with restricted ranges. The genus Seminemacheilus is endemic to Türkiye and includes six species. This study investigated the current distribution of the genus Seminemacheilus and its possible distribution in 2050 and 2070 using the Wallace platform, a Maxent modeling method. Simulations of future projections indicated that bioclimatically suitable habitats of Seminemacheilus spp. will be limited in 2050 and nearly extinct in 2070. The model is primarily affected by temperature and precipitation, which are directly associated with the phenomenon of global warming. It has been established that conservation strategies must be developed to protect the species of the genus and avoid habitat deterioration. [ABSTRACT FROM AUTHOR]

One of the commonest pesticides used in agriculture is the fungicide carbendazim, which can cause deleterious effects on the physiology and behaviour of acutely and chronically exposed animals. However, few studies have evaluated the effects of carbendazim on fish behaviour and our main objective was to evaluate behavioural changes on adult zebrafish (Danio rerio) exposed to this fungicide. We studied 177 fishes, divided into control groups (not exposed) and treatment groups, exposed to a concentration of 120 µg/L for 7, 14, 21 and 28. Behavioural data were collected using the scan sampling, with instantaneous recording every 30 s. We evaluated and compared fish behaviours and aquarium occupancy between treatments and controls using Generalized Linear Mixed Models. The results indicate that carbendazim initially elicited slow swimming and later fast swimming, decreased aggressiveness, and caused behavioural changes indicative of distress, like abnormal swimming and the gulping of air in water surface. In the wild, this behavioural change can result in an increased predation risk and consequent decrease or extinction of populations, revealing important ecological issues for animal communities living in polluted water bodies. [ABSTRACT FROM AUTHOR]

In this study, a comprehensive analysis is presented on the complete mitochondrial genome and phylogenetic relationships of Devario shanensis, an endemic species to the Irrawaddy drainage in southwestern China. The complete mitogenome sequence of D. shanensis was sequenced to be 16,860 bp long and encompassed 13 protein-coding genes, 22 tRNA genes, two rRNA genes and a non-coding control region. The overall AT content (61.1%) was much higher than GC content (38.9%). Phylogenetic analyses employing maximum-likelihood and Bayesian inference methods on the complete mitogenomes, including D. shanensis and 13 other species, unveiled a close genomic relationship between D. shanensis and Devario interruptus. This work will contribute to the genetic resource enrichment and phylogenetic researches on genus Devario. [ABSTRACT FROM AUTHOR]

Oxynoemacheilus chaboras, new species, from the stream Beyazsu in the Euphrates drainage, belongs to the O. persa species group, being closely related to O. shehabi from the Orontes, O. sarus from the Seyhan and Ceyhan, O. euphraticus from the Euphrates and Tigris, O. karunensis from the Karkheh, and O. persa from Central Iran. The new species is distinguished from others in the O. persa group by having 8–9 pores in the supraorbital canal, two distinct black blotches at the caudal-fin base, a rudimentary and shallow pelvic axillary lobe, 6–10 irregularly shaped bars on the flank, and a deep head, body, and caudal peduncle. Oxynoemacheilus chaboras sp. nov. is most closely related to O. euphraticus, from which it is differentiated by a mean uncorrected p-distance of 3.24% (min. 3.09%) in its COI barcode gene. [ABSTRACT FROM AUTHOR]

A new species of Yunnanilus is described from the Nanpanjiang River, Yunnan, China. The new species, Yunnanilus polylepis, can be distinguished from other species of Yunnanilus by the following combination of characteristics: Processus dentiformis absent; eye diameter smaller than interorbital width; outer gill raker absent and 10 inner gill rakers on first gill arch; whole trunk covered by scales; nine branched dorsal-fin rays; 10 or 11 branched pectoral-fin rays; six branched pelvic-fin rays. Despite our phylogenetic analysis, which sheds light on the complex relationships among Yunnanilus species, the majority of Yunnanilus species are restricted to more localized environments and habitats. It is urgent to address the environmental threats that jeopardize their survival, especially given their generally restricted distribution. [ABSTRACT FROM AUTHOR]

The blind cavefish genus Karstsinnectes, established in 2023, is the subject of taxonomic revision in the present study. Five valid species are recognized, including one new species, Karstsinnectes longzhouensis sp. nov., described from Guangxi, China, based on a combination of morphological evidence. Karstsinnectes longzhouensis sp. nov. can be distinguished from all other congeners based on the presence of a lateral line, 11–12 branched pectoral fin rays, and five branched pelvic fin rays. Additionally, due to the loss of the type specimens, a neotype is designated for K. parvus. The lateral line of K. hyalinus is revised as lacking in this study. A key to all valid Karstsinnectes species is provided. Blind cavefish serve as a valuable natural framework for investigating convergent and adaptive evolutionary processes. The survival of cavefish is under significant threat due to human activities, climate change, water pollution, and invasive species. Thus, to preserve these valuable species, it is crucial to implement various conservation measures, such as habitat protection, artificial breeding, and fundamental research. [ABSTRACT FROM AUTHOR]

Geometric morphometrics is an efficient way to quantify biological shape variation and its covariation with other biotic or abiotic factors. The geometric information of an object is measured in a non-linear shape space after removing size, orientation, and position-related effects. This study was aimed to determine sexual dimorphism and morphological variation in body shape using landmark- based morphometrics by means of relative warp analysis. The indigenous freshwater fish Puntius sophore (Hamilton, 1822) (Cyprinidae) was selected as the model organism for the study. Adult male and female individuals were collected during July--August 2019 (breeding season) and March--April 2019 (non-breeding season) from the ponds of Bolpur, West Bengal, India. Prior to analysis, the images were digitised using the appropriate fourteen landmarks and relative wrap analysis was performed using appropriate soft ware. The results were then analysed, and the maximum relative displacements of adjacent landmarks were interpreted using canonical variate analysis (CVA) and principal component analysis (PCA). Significant body shape differences were found to be present in the non-breeding season and breeding season (male and female) populations of the species. Thus, geometric morphometrics can be used to understand the sexual dimorphism in natural populations of small fish species. [ABSTRACT FROM AUTHOR]

Molecular data from samples encompassing 22 nominal species of Poropuntius indicate that the species-level diversity in the genus has been vastly overestimated, likely due to inadequate taxon and geographic sampling and reliance on morphological characters that vary intra-specifically. The latter includes discrete mouth morphologies related to alternate feeding strategies (ecomorphs) within populations. One new species is described, Poropuntius anlaoensis Hoàng, Phạm & Trần, sp. nov., and 17 synonyms of six valid species names of Poropuntius, P. krempfi, P. alloiopleurus, P. huangchuchieni, P. laoensis, P. kontumensis, and P. deauratus, are recognised. Additional taxonomic changes in this widespread and generally poorly known genus are likely as more molecular and morphological data become available. [ABSTRACT FROM AUTHOR]

Transgenic ornamental fish that fluoresce are becoming popular in the aquarium trade worldwide. Some transgenic zebrafish (TZF) records in natural water bodies have been published, but there are no data on their biological attributes in the new areas. This study aimed to evaluate the distribution, trophic ecology, and reproductive condition of the non-native TZF in headwater creeks located in the largest Brazilian ornamental aquaculture center. Insect fragments – identified as chitinous material in the 'false stomach'- and aquatic insects were the most consumed item. TZF adults were found in breeding conditions during almost all sampling periods. The Gonadosomatic Index of females and males showed peaks during the rainy season and matched with the rising water levels. Breeding females and males were found at small body sizes, indicating early maturation, and these transgenic females produced a moderate amount of small oocytes. Sex-ratio assessment showed that females and males had the same frequencies in one site, while females were significantly more frequent than males at another location. Management recommendations, such as utilization of best management practices (e.g. screens on outlets), not using unapproved genetically modified organisms in aquaculture, and awareness with fish farmers about transgenic animals, are suggested to avoid new introductions. [ABSTRACT FROM AUTHOR]

The taxonomy and geographical distributions of Osteobrama species have historically posed challenges to ichthyologists, leading to uncertainties regarding their native ranges. While traditional taxonomy has proven valuable in classification, the utility of an integrated approach is restricted for this particular group due to limitations in combining information from biogeography, morphology, and genetic data. This study addresses the taxonomic puzzle arising from the recent identification of Osteobrama tikarpadaensis in the Mahanadi and Godavari Rivers, casting doubt on the actual distribution and systematics of both O. tikarpadaensis and Osteobrama vigorsii. The research reveals distinctions among specimens resembling O. vigorsii from the Krishna and Godavari riverine systems. Notably, specimens identified as O. vigorsii from the Indian Museum exhibit two pairs of barbels, while those from the Godavari River in this study are identified as O. tikarpadaensis. Inter-species genetic divergence and maximum likelihood phylogeny provide clear delineation between O. vigorsii and O. tikarpadaensis. The study suggests that O. vigorsii may be limited to the Krishna River system in southern India, while O. tikarpadaensis could potentially extend from the Mahanadi River in central India to the Godavari River in southern India. Proposed revision to morphological features for both species, accompanied by revised taxonomic keys, aim to facilitate accurate differentiation among Osteobrama congeners. The data generated by this research provide a resource for future systematic investigations into cyprinids in India and surrounding regions. Further, the genetic diversity information obtained from various riverine systems for Osteobrama species will be instrumental in guiding aquaculture practices and formulating effective conservation action plans. [ABSTRACT FROM AUTHOR]

Due to the detrimental effect of formaldehyde on DNA, ethanol has replaced formalin as the primary preservative for animal specimens. However, short-term formalin fixation of specimens might be applied during field collection. In an increasing number of studies, DNA extraction and sequencing have been successfully conducted from formalin-fixed specimens. Here the DNA from five specimens of Triplophysa dalaica (Kessler, 1876) were extracted and performed high-throughput sequencing. Four of the specimens underwent short-term fixation with formalin and were subsequently transferred to ethanol. One was continuously stored in ethanol. No significant difference of DNA quality and amount were observed among these samples. Followed by assembly and annotation, five mitochondrial genomes ranging in length from 16,569 to 16,572 bp were obtained. Additionally, previously published data of other individuals or species were included to perform phylogenetic analyses. In the reconstructed trees, all eight individuals of T. dalaica form a monophyletic group within the Triplophysa branch. The group is divided into three clades: (1) samples from the Yellow River, (2) those from the Yangtze River, and (3) those from the Haihe River, and the Lake Dali Nur. This study sheds initial light on the phylogeographic relationships among different populations of T. dalaica, and will support the research about its evolutionary history in the future. [ABSTRACT FROM AUTHOR]

Simple Summary: As an endemic and vulnerable fish from the upper Yangtze River in China, Schizothorax kozlovi holds significant scientific and ecological importance, yet it has received little attention so far. In this paper, we reported the characterization of the mitochondrial genome of S. kozlovi, and further investigated the phylogenetic relationships of Schizothorax. The results showed that the mitochondrial genome of S. kozlovi had a total size of 16,585 bp, a circular arrangement, and contained 13 PCGs, 22 tRNAs, two rRNAs, and two non-coding regions. Moreover, the phylogenetic analyses demonstrated that Schizothorax could be classified into four clades, and S. kozlovi was closely related to Schizothorax chongi. The present study enriched the basic biological data for S. kozlovi and provided fundamental references for the conservation of S. kozlovi and Schizothorax. Schizothorax kozlovi is an endemic and vulnerable fish species found in the upper Yangtze River in China. Over the past few years, the population resources of S. kozlovi have been nearly completely depleted owing to multiple contributing threats. While the complete mitochondrial genomes serve as important molecular markers for phylogenetic and genetic studies, the mitochondrial genome of S. kozlovi has still received little attention. In this study, we analyzed the characterization of the mitochondrial genome of S. kozlovi and investigated the phylogenetic relationships of Schizothorax. The complete mitochondrial genome of S. kozlovi was 16,585 bp in length, which contained thirty-seven genes (thirteen protein-coding genes (PCGs), two ribosomal RNA genes (rRNAs), twenty-two transfer RNA genes (tRNAs)) and two non-coding regions for the origin of light strand (OL) and the control region (CR). There were nine overlapping regions and seventeen intergenic spacers regions in the mitochondrial genome. The genome also showed a bias towards A + T content (55.01%) and had a positive AT-skew (0.08) and a negative GC-skew (−0.20). All the PCGs employed the ATG or GTG as the start codon and TAA, TAG, or single T as the stop codon. Additionally, all of the tRNAs displayed a typical cloverleaf secondary structure, except trnS1 which lacked the D arm. The phylogenetic analysis, based on the maximum likelihood (ML) and Bayesian inference (BI) methods, revealed that the topologies of the phylogenetic tree divided the Schizothorax into four clades and did not support the classification of Schizothorax based on morphology. The phylogenetic status of S. kozlovi was closely related to that of S. chongi. The present study provides valuable genomic information for S. kozlovi and new insights in phylogenetic relationships of Schizothorax. These data could also offer fundamental references and guidelines for the management and conservation of S. kozlovi and other species of Schizothorax. [ABSTRACT FROM AUTHOR]

The investigation examines the structure of diploid and polyploid populations within the spined loach group (Cobitis elongatoides-taenia-tanaitica) in the water systems of Western and Central Ukraine, including the Danube River, Dniester River, Southern Bug River, Vistula River, Middle and Upper Dnipro River basins. The study reveals a bipolarity in settlement structure, with a sharp prevalence of either diploids or polyploids, and no discernible geographical trends in spatial distribution. Clonal hybrid polyploids, which make up 70 % of the individuals studied in the region, are most common in settlements along the main river channels, as well as in the middle and lower reaches of first and second-order tributaries. Populations where diploid specimens of the parent species are predominant are located in accessory systems, tributaries of the third and higher orders, upper reaches of first and second-order tributaries, and lakes. This spatial segregation arises from historical circumstances rather than ecological preferences, primarily due to the distance from water corridors through which polyploids invaded in the 1960s-1970s. The displacement of diploid individuals by clonal hybrid polyploids is a universal phenomenon. This is due to the advantages of parthenogenetic reproduction and higher survival rates of polyploids in modern environmental situations. [ABSTRACT FROM AUTHOR]

We present a genome assembly from an individual Squalius cephalus (the European chub; Chordata; Actinopteri; Cypriniformes; Cyprinidae). The genome sequence is 1,101.9 megabases in span. Most of the assembly is scaffolded into 25 chromosomal pseudomolecules. The mitochondrial genome has also been assembled and is 16.61 kilobases in length.

A new loach species, Oreonectes andongensis sp. nov. is described from the Guangxi Zhuang Autonomous Region, China. The new species can be differentiated from other members of the genus by combinations of characters: a developed posterior chamber of the swim bladder, 13–14 branched caudal-fin rays, 8–16 lateral-line pores, body width 12–15% of standard length (SL), interorbital width 42–47% of head length (HL), and caudal peduncle length 11–16% of SL. Bayesian inference phylogenetic analysis based on mitochondrial Cyt b provided strong support for validity of O. andongensis sp. nov. (uncorrected p-distance 6.0–7.5%). [ABSTRACT FROM AUTHOR]

Introduction: The successful cryopreservation of common carp sperm is crucial for its application in aquaculture and selective breeding programs. This study investigates the efficacy of cryopreserving sperm in large containers (5 mL) with a low dilution rate (1:1) in three different cryoprotective media and thawing in different conditions. Methods: The developed method utilizes a low-ionic (hypotonic) cryoprotective medium, freezing with a controlled cooling rate, and high-temperature sperm thawing (60°C). The investigation employs a detailed spermatozoon motility assessment. Results: Post-thaw motility of 32.3% ± 14% and initial curvilinear velocity of 89 ± 20 mm/s across 30 males were observed. Principal component analysis of sperm kinematic characteristics revealed distinct populations of sperm cells exhibiting varying responses to cryopreservation. The developed method achieved successful fertilization comparable to that of the non-frozen control group using sperm from a single cryotube (2.5 mL, approximately 50 * 109 spermatozoa) to fertilize 200 g of eggs (1:120,000 egg:spz). Discussion: This novel approach demonstrates an effective cryopreservation protocol for common carp sperm in large-volume cryo-containers in combination with low-ionic cryomedia and high thawing temperature, providing methods well-suited for fisheries practices and selective breeding programs. Future studies of the biological properties of different sperm subpopulations in post-thaw sperm samples can contribute to a deeper understanding of sperm biology, improve cryopreservation techniques, and enhance the success rates of assisted reproductive technologies. [ABSTRACT FROM AUTHOR]

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%. [ABSTRACT FROM AUTHOR]

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 & Šlechtová, 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. [ABSTRACT FROM AUTHOR]

La loche aux yeux de feu Barbucca diabolica, rencontrée dans les eaux douces d’Asie du Sud-Est, est actuellement connue en Thaïlande, en Malaisie occidentale, à Sumatra et à Bornéo. Malgré cette large distribution, il n’y a pas de signalement publié sur cette espèce pour l’île de Belitung (Indonésie). Nous rapportons ici une première occurrence de B. diabolica pour cette île, sur la base de deux spécimens collectés dans la province orientale de Belitung. Ce nouvel enregistrement étend la distribution de l’espèce d’environ 600 km au sud-est de Johor (péninsule malaise, Malaisie), d’environ 400 km à l’est de la rivière Musi (Sumatra, Indonésie) et d’environ 500 km au sud-ouest de la rivière Kapuas (Bornéo, Indonésie). Il s’agit aussi de l’enregistrement de l’espèce sur une île supplémentaire dans la Région du Sundaland. [ABSTRACT FROM AUTHOR]

Guigarra cailaoensis is a member of family Cyprinidae, subfamily Labeoninae (Cypriniformes) which was recently discovered in southwestern China. Following its initial description, additional information on this species has remained notably scarce. In the current study, we assemble the complete mitochondrial genome (mitogenome) of G. cailaoensis using the Illumina sequencing platform. The mitogenome is identified as a circular, double-stranded DNA sequence of 16,593 base pairs, encompassing 13 protein-coding genes (PCGs), 22 transfer RNA genes, two ribosomal RNA genes, and a putative control region. Maximum-likelihood and Bayesian-inference approaches were used to construct phylogenetic trees for three datasets: (i) PCG sequences of the complete mitogenome (dataset 1); (ii) PCG sequences of the complete mitogenome combined with nuclear DNA (ncDNA) (Rag1) sequence (dataset 2); and (iii) ncDNA (Rag1) sequences (dataset 3). Phylogenetic analyses position G. cailaoensis as a sister taxon to the lineage consisting of Paraqianlabeo lineatus Zhao, Sullivan, Zhang & Peng, 2014 and Pseudogyrinocheilus prochilus Fang, 1933 in dataset 1, and to Pseudogyrinocheilus prochilus in dataset 2, species lacking an oral disc on the lower lip. However, G. cailaoensis showed a close relationship to the lineage consisting of Discogobio and Discocheilus in dataset 3, species possessing an oral disc on the lower lip. Nonetheless, a variety of species with an oral disc on the lower lip are clustered into different lineages across the three datasets that may indicate that the development of the oral disc is homoplastic within the subfamily Labeoninae. The outcomes of this study have the potential to support conservation efforts for this species and to enrich our understanding of genetic resources in the area. [ABSTRACT FROM AUTHOR]

The variability in the stenotopic miniature rasborine Boraras maculatus (Cypriniformes: Danionidae: Rasborinae) across acidic‐water habitats of Peninsular Malaysia (PM) was investigated using two molecular markers (the mitochondrial cytochrome c oxidase subunit I [COI] gene and the nuclear rhodopsin gene), as well as morphological evidence. Molecular phylogenetic analyses revealed differentiation among populations of B. maculatus in PM with the distinction of four allopatric lineages. Each of them was recognized as a putative species by automatic species delimitation methods. These lineages diverged from each other between 7.4 and 1.9 million years ago. A principal component analysis (PCA) was conducted to examine the multivariate variation in 11 morphometric measurements among three of these lineages. PCA results showed a significant overlap in morphological characteristics among these lineages. Additionally, a photograph‐based machine learning approach failed to fully differentiate these lineages, suggesting limited morphological differentiation. B. maculatus represents a case of morphological stasis in a stenotopic miniature species. Strong habitat preference, coupled with long‐term habitat fragmentation, may explain why each lineage of B. maculatus has a restricted distribution and did not disperse to other regions within and outside of PM, despite ample possibilities when the Sunda shelf was emerged and drained by large paleodrainages for most of the past 7 million years. The conservation status of B. maculatus and its peat swamp habitats are discussed, and it is concluded that peat swamps comprise several evolutionary units. Each of these units is considered a conservation unit and deserves appropriate protection. [ABSTRACT FROM AUTHOR]

Geological events can strongly affect the genetic structures and differentiation of fish populations. Especially, as an endemic fish of the genus Sinocyclocheilus in the Yunnan‐Guizhou Plateau, the effects of key geological events on the distributions and genetic structures remain poorly understood. Examining the phylogeographic patterns of Sinocyclocheilus fishes can be useful for elucidating the spatio‐temporal dynamics of their population size, dispersal history and extent of geographical isolation, thereby providing a theoretical basis for their protection. Here, we used single nucleotide polymorphisms (SNP) method to investigate the phylogeographic patterns of Sinocyclocheilus fishes. Our analysis supports the endemicity of Sinocyclocheilus, but the samples of different regions of Sinocyclocheilus contain multiple ancestral components, which displayed more admixed and diversified genetic components, this may be due to the polymorphism of the ancestors themselves, or gene infiltration caused by hybridization between adjacent species of Sinocyclocheilus. We estimate that the most recent common ancestor (MRCA) of Sinocyclocheilus fish in the Central Yunnan Basin at approximately 3.75~3.11 Ma, and infer that the evolution of Sinocyclocheilus in the central Yunnan Basin is closely related to the formation of plateau lakes (around 4.0~0.02 Ma), and identifies the formation of Dianchi Lake and Fuxian Lake as key geological events shaping Sinocyclocheilus population structure. It is also the first time to prove that the altitude change has a great influence on the genetic variation among the populations of Sinocyclocheilus. [ABSTRACT FROM AUTHOR]

Discogobio brachyphysallidos Huang 1989 is a Cyprinidae fish species that is endemic to the upper Pearl River. In the present study, the complete mitochondrial genome of D. brachyphysallidos collected from the Nanpanjiang River was sequenced and annotated. The mitochondrial genome encompassed 13 protein-coding genes, two ribosomal RNA (rRNA) genes, 22 transfer RNA (tRNA) genes, and the control region (D-loop). The total length of the mitochondrial genome was determined to be 16,594 base pairs (bp), with a GC content of 41.7%. Phylogenetic analyses revealed that D. brachyphysallidos may be a sister to D. longibarbatus and D. macrophysallidos. These findings provide insight into the genetic information and phylogenetic relationships of D. brachyphysallidos. [ABSTRACT FROM AUTHOR]

Understanding historical processes underlying lineage distribution patterns is a primary goal of phylogeography. We selected Gobio rivuloides (Cypriniformes: Gobionidae) as a model to improve our knowledge about how intraspecific genetic divergence of freshwater fishes arises in coastal drainages of northern China via statistical analysis using cytochrome b gene. The time-calibrated phylogeny of G. rivuloides showed the divergence of two major lineages (I and II) at ~0.98 Ma (million years ago). Lineage I can be divided into two sub-lineages (I-A and I-B) with a divergence time of ~0.83 Ma. Sub-lineage I-A inhabits the Amur River, and sub-lineage I-B lives in the Luan River and Liao River. Lineage II is distributed in the Yellow River and Hai River, with close genetic relationships between the two drainages, and can be split into two sub-lineages (II-C and II-D) with a divergence time of ~0.60 Ma. Our findings indicate that the splitting of lineages and sub-lineages could be attributed to geographic isolation caused by the formation of the Bohai Sea, river capture, and the episodic hydrologic closing of a paleolake during the late Lower–Middle Pleistocene. It is also the first report we know of displaying a clear phylogeographic break for freshwater fishes across coastal drainages in northern China. [ABSTRACT FROM AUTHOR]

Hemiculterella wui is an endemic small freshwater fish, distributed in the Pearl River system and Qiantang River, China. In this study, we identified and annotated the complete mitochondrial genome sequence of H. wui. The mitochondrial genome was 16,619 bp in length and contained 13 protein coding genes (PCGs), two rRNA genes, 22 tRNA genes, and one control region. The nucleotide composition of the mitochondrial genome was 29.9% A, 25.3% T, 27.4% C, and 17.5% G, respectively. Most PCGs used the ATG start codon, except COI and ATPase 8 started with the GTG start codon. Five PCGs used the TAA termination codon and ATPase 8 ended with the TAG stop codon, and the remaining seven genes used two incomplete stop codons (T and TA). Most of the tRNA genes showed classical cloverleaf secondary structures, except that tRNASer(AGY) lacked the dihydrouracil loop. The average Ka/Ks value of the ATPase 8 gene was the highest, while the average Ka/Ks value of the COI gene was the lowest. Phylogenetic analyses showed that H. wui has a very close relationship with Pseudohemiculter dispar and H. sauvagei. This study will provide a valuable basis for further studies of taxonomy and phylogenetic analyses in H. wui and Xenocyprididae. [ABSTRACT FROM AUTHOR]