Genus Sinocyclocheilus Research Articles

Wall-following - Phylogenetic context of an enhanced behaviour in stygomorphic Sinocyclocheilus (Cypriniformes: Cyprinidae) cavefishes.

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.

Sinocyclocheilusxiejiahuai (Cypriniformes, Cyprinidae), a new cave fish with extremely small population size from western Guizhou, China.

This study describes a new species, Sinocyclocheilusxiejiahuai sp. nov., discovered within a cave located in Hongguo Town, Panzhou City, Guizhou Province, southwestern China, with the type locality in the Nanpanjiang River basin. Phylogenetic trees reconstructed based on mitochondrial genes show that the new species represents an independent evolutionary lineage with large genetic differences, 1.9%-13.8% in mitochondrial Cyt b, from congeners. Morphologically, this species can be differentiated from the 79 species currently classified under the genus Sinocyclocheilus by several characteristics: absence of horn-like structures and indistinct elevation at the head-dorsal junction, absence of irregular black markings on the body lateral and scaleless, eyes large, eye diameter 13% of head length, dorsal-fin rays, iii, 6½, last unbranched ray strong, with serrations along posterior margin, pectoral-fin rays, i, 13, anal-fin rays, iii, 5, pelvic-fin rays, i, 7, lateral line pores 74, gill rakers well developed, nine on first gill arch, pectoral fins short, tip not reaching to pelvic-fin origin. The number of Sinocyclocheilus species has been increased from 79 to 80 since the description of this new species.

Expansion and contraction of lake basin shape the genetic structure of Sinocyclocheilus (Osteichthyes: Cypriniformes: Cyprinidae) populations in Central Yunnan, China.

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.

Four new hypogean species of the genus Triplophysa (Osteichthyes, Cypriniformes, Nemacheilidae) from Guizhou Province, Southwest China, based on molecular and morphological data

Recently described cave species of the genus Triplophysa have been discovered in southwestern China, suggesting that the diversity of the genus is severely underestimated and that there may be many undescribed species. In this work, four new species of the genus Triplophysa are described from southwestern Guizhou Province, China, namely Triplophysa cehengensis Luo, Mao, Zhao, Xiao & Zhou, sp. nov. and Triplophysa rongduensis Mao, Zhao, Yu, Xiao & Zhou, sp. nov. from Rongdu Town, Ceheng County, Guizhou, Triplophysa panzhouensis Yu, Luo, Lan, Xiao & Zhou, sp. nov. from Hongguo Town, Panzhou City, Guizhou, and Triplophysa anlongensis Song, Luo, Lan, Zhao, Xiao & Zhou, sp. nov. from Xinglong Town, Anlong County, Guizhou. These four new species can be distinguished from all recognized congeners by a combination of morphological characteristics and significant genetic divergences. The discovery of these species increases the number of known cave species within the genus Triplophysa to 39, making the genus the second most diverse group of cave fishes in China after the golden-line fish genus Sinocyclocheilus. Based on the non-monophyletic relationships of the different watershed systems in the phylogenetic tree, this study also discusses the use of cave species of the genus Triplophysa to determine the possible historical connectivity of river systems.

A long-ignored unique ecosystem of cavefishes in the southern karst: achievements, challenges, and prospects.

Cavefishes represent a taxon that has experienced natural selection pressures. This paper summarizes the results with respect to the taxonomy, diversity, phylogeny, and adaptation aspects of cavefishes research. It showed that: 1) These studies suggest that cavefishes play important roles in the study of geologic history and adaptation to extreme environments, but the mechanisms involved 168 species of cavefishes belonging to 17 genera, four families, and two orders have been recorded in China. Meanwhile, more new species are being discovered recently, and the species diversity of cavefishes are still underestimated, indicating the need to strengthen the survey in field. 2) The biogeography of cavefishes have focused on Sinocyclocheilus and Triplophysa, that have helped understand the geomorphology of karst areas in southern China and the spatial pattern of species diversity. These studies revealed the influences of evolution and geological history in Sinocyclocheilus, but there are still many species that have not been studied accordingly. 3) Some adaptive mechanistic studies have been conducted on cavefishes, primarily focusing on eye and body color degradation and energy metabolism in the genus Sinocyclocheilus to reveal adaptive mechanisms in the dark environment. 4) The IUCN list of protected cavefishes species in China only includes 21 species. The List of Key Protected Wild Animals for 2021 includes all species of Sinocyclocheilus as National Class II.It is necessary to strengthen the research on the biodiversity and adaptation and need consider the conservation actions for cavefishes.

Sensory evolution in a cavefish radiation: patterns of neuromast distribution and associated behaviour in Sinocyclocheilus (Cypriniformes: Cyprinidae).

The genus Sinocyclocheilus, comprising a large radiation of freshwater cavefishes, are well known for their presence of regressive features (e.g. variable eye reduction). Fewer constructive features are known, such as the expansion of the lateral line system (LLS), which is involved in detecting water movements. The precise relationship between LLS expansion and cave adaptation is not well understood. Here, we examine morphology and LLS-mediated behaviour in Sinocyclocheilus species characterized by broad variation in eye size, habitat and geographical distribution. Using live-staining techniques and automated behavioural analyses, we examined 26 Sinocyclocheilus species and quantified neuromast organ number, density and asymmetry within a phylogenetic context. We then examined how these morphological features may relate to wall-following, an established cave-associated behaviour mediated by the lateral line. We show that most species demonstrated laterality (i.e. asymmetry) in neuromast organs on the head, often biased to the right. We also found that wall-following behaviour was distinctive, particularly among eyeless species. Patterns of variation in LLS appear to correlate with the degree of eye loss, as well as geographical distribution. This work reveals that constructive LLS evolution is convergent across distant cavefish taxa and may mediate asymmetric behavioural features that enable survival in stark subterranean microenvironments.

Molecular phylogeny and historical biogeography of the cave fish genus Sinocyclocheilus (Cypriniformes: Cyprinidae) in southwest China.

Modern accumulations of genetic data offer unprecedented opportunities for understanding the systematic classification and origins of specific groups of organisms. The genus Sinocyclocheilus is among the most cave abundant genera in Cyprinidae, with 76 recognized species, belonging to 4 species groups. Recent phylogenetic studies have shown that the classification of species groups within the genus Sinocyclocheilus remains controversial. In this study, we constructed a sequence supermatrix of 26 species from 4 species groups of the genus Sinocyclocheilus using the mitochondrial genome to reveal phylogenetic relationships, historical biogeography and patterns of species diversification in the genus Sinocyclocheilus. Phylogenetic analysis strongly supports the monophyletic groups of the 3 species groups (S. jii, S. cyphotergous, and S. tingi groups) except the S. angularis group. Phylogenetic analysis showed that S. anshuiensis and S. microphthalmus, which were recognized as numbers of S. angularis group, formed a strongly supported independent clade. Therefore, we propose a new species group, the S. microphthalmus group, which contains S. anshuiensis and S. microphthalmus. Biogeographic reconstruction suggests that the living Sinocyclocheilus may have originated in north-central Guangxi at the late Eocene and dispersed outward after a vicariance at 32.31 Million years ago (Ma). Early diversification is focused on the late Oligocene (ca. 25 Ma), which is related to the second uplift of the Qinghai-Tibetan Plateau and the lateral extrusion of the Indochina at the Oligocene/Miocene boundary. Our results suggest that 2 uplifts of the Qinghai-Tibetan Plateau and climate change in the Miocene may have influenced the diversification of the Sinocyclocheilus lineage.

Evolving in the darkness: Phylogenomics of Sinocyclocheilus cavefishes highlights recent diversification and cryptic diversity

Troglomorphism—any morphological adaptation enabling life to the constant darkness of caves, such as loss of pigment, reduced eyesight or blindness, over-developed tactile and olfactory organs—has long intrigued biologists. However, inferring the proximate and ultimate mechanisms driving the evolution of troglomorphism (stygomorphism) in freshwater fish requires a sound understanding of the evolutionary relationships between surface and stygomorphic lineages. We use Restriction Site Associated DNA Sequencing (RADseq) to better understand the evolution of the Sinocyclocheilus fishes of China. With a remarkable array of derived stygomorphic traits, they comprise the largest cavefish diversification in the world, emerging as a multi-species model system to study evolutionary novelty. We sequenced a total of 120 individuals throughout the Sinocyclocheilus distribution. The data comprised a total of 646,497 bp per individual, including 4378 loci and 67,983 SNPs shared across a minimum of 114 individuals at a given locus. Phylogenetic analyses using either the concatenated RAD loci (RAxML) or the SNPs under a coalescent model (SVDquartets, SNAPP) showed a high degree of congruence with similar topologies and high node support (>95 for most nodes in the phylogeny). The major clades recovered conform to a pattern previously established using Sanger-based mt-DNA sequences, with a few notable exceptions. We now recognize six major clades in this group, elevating the blind cavefish S. tianlinensis and the micro-eyed S. microphthalmus as two new distinct clades due to their deep divergence from other clades. PCA plots of the SNP data also support the recognition of six major clusters of species congruent with the identified clades in ordination space. A Bayes factor delimitation (BFD) analysis showed support for 21 species, recognizing 19 previously described species and two putative new cryptic ones. Two species whose identities were previously disputed, S. furcodorsalis and S. tianeensis, are supported here as distinct species. In addition, our multi-species calibrated tree in SNAPP suggests that the genus Sinocyclocheilus originated around 10.16 Mya, with most speciation events occurring in the last 2 Mya, likely favored by the uplift of the Qinghai-Tibetan Plateau and cave occupation induced by climate-driven aridification during this period. These results provide a firm basis for future comparative studies on the evolution of Sinocyclocheilus and its adaptations to cave life.

The complete mitochondrial genome and phylogenetic analysis of Sinocyclocheilus angularis (Cypriniformes: Cyprinidae)

This is the first study to determine the complete mitochondrial genome of Sinocyclocheilus angularis, which is an endemic cavefish native to the Karst region of the Yunnan-Guizhou Plateau. The complete mitochondrial genome size of S. angularis was 16,586 bp, and it consisted of a control region, 13 protein-coding genes, 22 transfer RNA genes, and 2 ribosomal RNA genes. The base composition of the mitogenome was 25.14% A, 32.45% T, 27.10% G, and 15.31% C, with an overall GC content of 42.42%. Phylogenetic analysis revealed that all Sinocyclocheilus were clustered into one strong clade and S. angularis was very closely related to S. bicornutus. It will provide an essential genetic tool for the further evolutionary studies and conservation of genus Sinocyclocheilus.

The complete mitochondrial genomes of two Chinese endemic cave fishes, Sinocyclocheilus longibarbarus and Sinocyclocheilus punctatus (Cypriniformes: Cyprinidae)

Sinocyclocheilus longibarbarus and Sinocyclocheilus punctatus were collected from a karst cave Libo County, southwest of China. The two Sinocyclocheilus species can be distinguished obviously by external morphological characteristics. In this study, the complete mitochondrial genome sequences of two species were assembled, and both sequences reflected gene organization typical for mitochondrial DNA of the genus Sinocyclocheilus, comprising of 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs), 2 ribosomal RNA genes (rRNAs), and a large non-coding control region. Phylogenetic analysis showed that S. punctatus was first clustered together with S. mutipunctatus, and S. longibarbarus was closely related to S. yishanensis. The complete mitogenome of two species may provide useful information for the further taxonomic and phylogenetic studies.

Comparative Transcriptomics Reveals the Molecular Genetic Basis of Cave Adaptability in Sinocyclocheilus Fish Species

Cavefish evolved a series of distinct survival mechanisms for adaptation to cave habitat. Such mechanisms include loss of eyesight and pigmentation, sensitive sensory organs, unique dietary preferences, and predation behavior. Thus, it is of great interest to understand the mechanisms underlying these adaptability traits of troglobites. The teleost genus Sinocyclocheilus (Cypriniformes: Cyprinidae) is endemic to China and has more than 70 species reported (including over 30 cavefish species). High species diversity and diverse phenotypes make the Sinocyclocheilus as an outstanding model for studying speciation and adaptive evolution. In this study, we conducted a comparative transcriptomics study on the brain tissues of two Sinocyclocheilus species (surface-dwelling species – Sinocyclocheilus malacopterus and semi-cave-dwelling species – Sinocyclocheilus rhinocerous living in the same water body. A total of 425,188,768 clean reads were generated, which contributed to 102,839 Unigenes. Bioinformatic analysis revealed a total of 3,289 differentially expressed genes (DEGs) between two species Comparing to S. malacopterus, 2,598 and 691 DEGs were found to be respectively, down-regulated and up-regulated in S. rhinocerous. Furthermore, it is also found tens of DEGs related to cave adaptability such as insulin secretion regulation (MafA, MafB, MafK, BRSK, and CDK16) and troglomorphic traits formation (CEP290, nmnat1, coasy, and pqbp1) in the cave-dwelling S. rhinocerous. Interestingly, most of the DEGs were found to be down-regulated in cavefish species and this trend of DEGs expression was confirmed through qPCR experiments. This study would provide an appropriate genetic basis for future studies on the formation of troglomorphic traits and adaptability characters of troglobites, and improve our understanding of mechanisms of cave adaptation.

Ontogenetic development of the horn and hump of the Chinese cavefish Sinocyclocheilus furcodorsalis (Cypriniformes: Cyprinidae)

Cave adaptation has given rise to a diversity of unusual morphologies. One prominent character in Chinese cavefishes of the genus Sinocyclocheilus is the presence of a skull horn and a dorsal hump. These characters are present only in species that are troglobitic. Here we examine the osteological growth that underlies the horn and the hump of the species S. furcodorsalis using micro computed tomography. We tested the hypothesis that all structures grow isometrically, and found that the skull and the bony shelf that supports the horn grow isometrically in all dimensions. The neural spine of the first vertebrae, on the other hand, grew allometrically, getting taller and thinner with time. When comparing each structure with skull growth, the horn grew isometrically in the anterior-posterior and the medial-lateral dimensions. But the horn grew faster in height than the skull. The neural spine grew isometrically with the skull in the rostral-caudal dimension, but allometrically in the dorsal-ventral and medial-lateral dimensions. Even though the function of the horn and the hump are not known, our results suggest that heterochronic changes has led to allometric growth in these structures.

Length–weight relationships of four cavefish species from China

Length-weight relationships (LWRs) were estimated for four cavefish species belonging to the genus Sinocyclocheilus (Cypriniformes: Cyprinidae) occurring in the Nanpanjiang River and Hongshuihe River, which constitute the upstream of the species, S. angularis, S. furcodorsalis, S. rhinocerous, and S. tileihornes, were collected from 2011 to 2017. The b values of LWRs of these four species ranged from 2.830 to 3.719 and the correlation coefficient values (R2) were high for all species. This is the first record of LWRs for cavefish species with the horn in FishBase database.

Microscopic and Submicroscopic Gradient Variation of Olfactory Systems among Six Sinocyclocheilus Species Living in Different Environments.

The fish genus Sinocyclocheilus contains many different species that inhabit diverse natural environments, such as surface water layer, cave, or intermediate. As a result of these different habitats there are some differences in their sensory systems. Microscopic and submicroscopic structures of olfactory systems in six representative species of Sinocyclocheilus were studied, including one surface-dwelling species (S. grahami), two intermediate species (S. jii and S. macrophthalmus) and three cave-dwelling species (S. brevibarbatus, S. anshuiensis, and S. tianlinensis). Due to adaptive evolution under extreme environmental conditions, cave-dwelling species have more developed olfactory systems. We observed that, compared with surface-dwelling species, the olfactory sac of the cave-dwelling Sinocyclocheilus species has the following characteristics: higher density of cilia, greater length of sensory cilia, many other special structures (micro-ridge, olfactory islet, rod cilia). These results reveal different levels of olfactory system development, consistent with the view that that cave-dwelling species have more developed olfactory systems than intermediate and surface-dwelling species.

Testing the validity of two putative sympatric species from Sinocyclocheilus (Cypriniformes: Cyprinidae) based on mitochondrial cytochrome b sequences.

There are over 60 species within the freshwater fish genus Sinocyclocheilus (Cypriniformes: Cyprinidae) distributed throughout the Yunnan-Guizhou Plateau and its surrounding areas in China. In recent years, the increasing number of new species described has raised some controversy about the validity of several species within this genus, notably the putative sympatric species pair S. qiubeiensis and S. jiuchengensis. To test the validity of S. qiubeiensis and S. jiuchengensis, we analyzed the complete sequences of the mitochondrial cytochrome b (CYTB) gene of 20 identified species and one outgroup species. Phylogenetic relationships were reconstructed using CYTB with maximum likelihood (ML) and Bayesian inference (BI) methods. Our phylogenetic results showed that all individuals of S. qiubeiensis and S. jiuchengensis clustered in one clade with strong support. In addition, the genetic distance between the two species was 0.11%, within the range observed at the intraspecific level. The most recent common ancestor of S. qiubeiensis and S. jiuchengensis dated back to 0.13 million years ago, indicating little time for complete speciation to have occurred. These results clearly support the viewpoint that S. jiuchengensis is a synonym of S. qiubeiensis.

Characterization and phylogenetic analysis of the complete mitogenome of a rare cavefish, Sinocyclocheilus multipunctatus (Cypriniformes: Cyprinidae).

The genus Sinocyclocheilus is a representative group of cave creatures. However, genetic studies on Sinocyclocheilus are rare. The primary objective of this study was to explore the structure and feature of the complete mitochondrial genome of S. multipunctatus, and reconstruct the mitogenomic phylogeny of Sinocyclocheilus. The mitochondrial DNA of S. multipunctatus was amplified by overlapping PCR fragments. The mitogenome was assembled by the SeqMan and annotated using MitoAnnotator. The phylogenetic tree was established using the Bayesian inference and Maximum likelihood methods. The mitogenome of S. multipunctatus is a typical circular molecule of 16,586bp with base composition A (31.25%), T (25.90%), G (16.35%), and C (26.50%), and consists of 13 protein-coding genes (PCGs), 22 transfer RNAs (tRNAs) genes, two ribosomal RNAs, and a 931bp control region. Phylogenetic analysis reveals two clades in the Sinocyclocheilus with robust support. S. multipunctatus is close to a newly discovered cavefish, S. ronganensis. We obtained and described the complete mitogenome of S. multipunctatus, and investigated its phylogenetic status, which may provide a valuable resource for future phylogenetic analyses and population genetic studies in Sinocyclocheilus.

Brain of the blind: transcriptomics of the golden-line cavefish brain.

The genus Sinocyclocheilus (golden-line barbel) includes 25 species of cave-dwelling blind fish (cavefish) and more than 30 surface-dwelling species with normal vision. Cave environments are dark and generally nutrient-poor with few predators. Cavefish of several genera evolved convergent morphological adaptations in visual, pigmentation, brain, olfactory, and digestive systems. We compared brain morphology and gene expression patterns in a cavefish Sinocyclocheilus anophthalmus with those of a closely related surface-dwelling species S. angustiporus. Results showed that cavefish have a longer olfactory tract and a much smaller optic tectum than surface fish. Transcriptomics by RNA-seq revealed that many genes upregulated in cavefish are related to lysosomes and the degradation and metabolism of proteins, amino acids, and lipids. Genes downregulated in cavefish tended to involve “activation of gene expression in cholesterol biosynthesis” and cholesterol degradation in the brain. Genes encoding Srebfs (sterol regulatory element-binding transcription factors) and Srebf targets, including enzymes in cholesterol synthesis, were downregulated in cavefish brains compared with surface fish brains. The gene encoding Cyp46a1, which eliminates cholesterol from the brain, was also downregulated in cavefish brains, while the total level of cholesterol in the brain remained unchanged. Cavefish brains misexpressed several genes encoding proteins in the hypothalamus–pituitary axis, including Trh, Sst, Crh, Pomc, and Mc4r. These results suggest that the rate of lipid biosynthesis and breakdown may both be depressed in golden-line cavefish brains but that the lysosome recycling rate may be increased in cavefish; properties that might be related to differences in nutrient availability in caves.

The Sinocyclocheilus cavefish genome provides insights into cave adaptation.

BackgroundAn emerging cavefish model, the cyprinid genus Sinocyclocheilus, is endemic to the massive southwestern karst area adjacent to the Qinghai-Tibetan Plateau of China. In order to understand whether orogeny influenced the evolution of these species, and how genomes change under isolation, especially in subterranean habitats, we performed whole-genome sequencing and comparative analyses of three species in this genus, S. grahami, S. rhinocerous and S. anshuiensis. These species are surface-dwelling, semi-cave-dwelling and cave-restricted, respectively.ResultsThe assembled genome sizes of S. grahami, S. rhinocerous and S. anshuiensis are 1.75 Gb, 1.73 Gb and 1.68 Gb, respectively. Divergence time and population history analyses of these species reveal that their speciation and population dynamics are correlated with the different stages of uplifting of the Qinghai-Tibetan Plateau. We carried out comparative analyses of these genomes and found that many genetic changes, such as gene loss (e.g. opsin genes), pseudogenes (e.g. crystallin genes), mutations (e.g. melanogenesis-related genes), deletions (e.g. scale-related genes) and down-regulation (e.g. circadian rhythm pathway genes), are possibly associated with the regressive features (such as eye degeneration, albinism, rudimentary scales and lack of circadian rhythms), and that some gene expansion (e.g. taste-related transcription factor gene) may point to the constructive features (such as enhanced taste buds) which evolved in these cave fishes.ConclusionAs the first report on cavefish genomes among distinct species in Sinocyclocheilus, our work provides not only insights into genetic mechanisms of cave adaptation, but also represents a fundamental resource for a better understanding of cavefish biology.Electronic supplementary materialThe online version of this article (doi:10.1186/s12915-015-0223-4) contains supplementary material, which is available to authorized users.

The complete mitochondrial genome of horned Golden-line barbell, Sinocyclocheilus rhinocerous (Cypriniformes, Cyprinidae)

The horned Golden-line barbel, Sinocyclocheilus rhinocerous (Cypriniformes, Cyprinidae) is a species of ray-finned fish of the genus Sinocyclocheilus with specific features. For example, its forehead protrudes forward like a rhinoceros horn. Here, we first reported the complete mitochondrial genome of this semi-caved teleost. The whole mitochondrial genome was 16 588 bp, and composed of 13 protein-coding genes, 22 transfer RNAs, 2 ribosomal RNAs, and a 933 bp control region. A phylogenetic tree with the complete mitochondrial genome sequences of S. rhinocerous together with 10 other affinis species was constructed. The newly achieved mitochondrial genome sequence seem to be useful for addressing taxonomic issues and studying related evolution events, which would contribute to enrich the fish mitochondrial genome resource and promote the biological research.

A new cavefish species from Southwest China, Sinocyclocheilus gracilicaudatus sp. nov. (Teleostei: Cypriniformes: Cyprinidae).

One new species is added to the genus Sinocyclocheilus, the largest cyprinid genus in China and the largest cavefish genus in the world. Sinocyclocheilus gracilicaudatus sp. nov. is similar to S. donglanensis but differs to other congeners in having normal eyes and scaled body, curved lateral line with 59-64 lateral-line scale rows, half-hard dorsal fin spine, 8 gill rakers and 8 predorsal vertebrae. Compared to S. donglanensis, the new species has a longer and more narrow caudal peduncle (caudal peduncle length 21.3-22.7% vs. 16.8-20.4% of SL; caudal peduncle depth 10.5-12.0% vs. 12.5-15.5% of SL), smaller eyes (eye diameter 5.8-8.3% vs. 6.5-10.9% of SL) and longer barbels (maxillary barbel length 16.6-24.3% vs. 11.1-21.1 % of SL; rictal barbel length 19.5-21.6% vs. 11.3-21.1% of SL). The new species is distributed in a subterranean river, belonging to the Longjiang River system; S. donglanensis occurs in the Hongshuihe River system, a system separate from that where the former species occurs.