Yunnanilus chuanheensis, a new loach species(Cypriniformes: Nemacheilidae) from the upper Lixianjiang River in Yunnan, China

DEAR EDITOR,A new loach species(Cypriniformes: Nemacheilidae:Yunnanilini), Yunnanilus chuanheensis sp. nov., was caught from Chuanhe in the upper reaches of the Lixianjiang River, a tributary of the Red River in Nanjian County, Yunnan Province, China. This species is a member of the traditional Y.pleurotaenia species group based on the presence of a lateral line and cephalic lateral-line canals.

Comparative analysis and phylogenetic and evolutionary implications of mitogenomes of Chinese Sinocyclocheilus cavefish(Cypriniformes:Cyprinidae)

DEAR EDITOR,Cavefish are of considerable interest due to the remarkable morphological changes that occurred during their adaptation to cave or subterranean river habitats.These changes are thought to involve trade-offs in metabolic requirements and energy utilization.Mitochondria play a vital role in oxygen use and energy metabolism;thus,mitochondrial genes are likely to have experienced specific selective pressures during cavefish evolution.In this study,we assembled and annotated the mitogenome of Sinocyclocheilus sanxiaensis,a typical cavefish species in China.Using this sequence and other available mitogenomes from the NCBI database,we reconstructed an updated phylogeny of Sinocyclocheilus based on 29 species.Five species groups were revealed,with the recently erected S.microphthalmus species group supported.To determine whether divergent selective pressures have acted on the protein-coding genes(PCGs)of the 29 Sinocyclocheilus species exhibiting different morphological features(including eye shape and body color),the fish were classified into three groups according to their cave-related traits.The branch model test revealed higher nonsynonymous/synonymous substitution ratios(ω)in the cave-dwelling groups,potentially resulting from a balance between adaptive selection and relaxed functional constraints.Sophisticated analysis using site and branch-site models identified 24 highly credible positive selection sites located on nine PCGs,with most sites also showing radical changes in amino acid properties.This study sheds light on the phylogeny and mitogenomic evolution of Sinocyclocheilus cavefish,highlighting their successful adaptation and survival in subterranean environments.

A new species of sisorid catfish of the genus Exostoma from the Salween drainage, Yunnan, China

A new species of the sisorid catfish genus Exostoma Blyth, 1860 was collected from two hill-stream tributaries of the Nujiang （Salween River） drainage in Gaoligong Mountain, south-western Yunnan Province, China from 2003 to 2006 and from two tributaries of the Salween River in Cangyuan County Lingcang Prefecture, Yunnan Province, China （in 2007） and in Yongde County, Lingcang Prefecture, Yunnan Province, China （in 2015）. Exostoma gaoligongense sp. nov. is the 10th species of the genus and is most similar to E. vinciguerrae in morphology but can be distinguished by pelvic fin reaching anus vs. not reaching; maxillary barbels just reaching or slightly surpassing pectoral-fin origin vs. surpassing pectoral-fin origin or even reaching posterior end of gill membrane; abdominal vertebrae 23-25 vs. 25-27; length of dorsal fin/dorsal to adipose distance 90.3%-287.0% vs. 59.2-85.7. A key to Exostoma spp. is provided.

Sinocyclocheilus sanxiaensis, a new blind fish from the Three Gorges of Yangtze River provides insights into speciation of Chinese cavefish

DEAR EDITOR,A blind fish of Sinocyclocheilus (Cypriniformes: Cyprinidae)was caught in open water in the Three Gorges (Sanxia)reservoir, at a depth of 20 m in the mainstream of YangtzeRiver in Zigui County, Hubei Province, China. This fish can beeasily distinguished from all other congeners by externalmorphological characteristics, and is estimated to havediverged from its sister group about 0.55 million years ago(Ma). The geologically well separated locality of this specieshas expanded the distribution of Sinocyclocheilus cavefishfrom around N25°(latitude) to above N30°. Herein, wedescribe this new species as Sinocyclocheilus sanxiaensis sp.nov., and discuss the possible reasons why the speciesappears, surprisingly, in the Three Gorges reservoir.

What is the destiny of a threatened fish, Ptychobarbus chungtienensis, now that non-native weatherfishes have been introduced into Bita Lake, Shangri-La？

Biological invasion is a pervasive negative force of global change, especially in its effects on sensitive freshwater ecosystems. Even protected areas are usually not immune. Ptychobarbus chungtienensis is a threatened freshwater fish now almost confined to Bita Lake, in the Shangri-La region of Yunnan province, China. Its existence is threatened by the introduction of non-native weatherfishes （Misgumus anguillicaudatus and Paramisgurnus dabryanus） by an unusual method known as ＇prayer animal release＇ Periodic surveys revealed the ratio of invasive weatherfishes to P. chungtienensis has been increasing since the former species was first recorded from the lake in August, 2009. Ptychobarbus chungtienensis shows low genetic diversity in the relict Lake Bita population. Weatherfishes, however, have highly successful survival strategies. The degree of dietary overlap between the species is alarming and perhaps critical if food is found to be a limiting factor.

Effects of osmotic pressure, temperature and stocking density on survival and sexual reproduction of Craspedacusta sowerbii

The effects of osmotic pressure, temperature and stocking density on medusae survival of Craspedacusta sowerbii were examined. The medusae were shown to be sensitive to the variations of osmotic pressure. And the survival time was 〈90 h at 34 mOsm/L and it declined rapidly with rising osmotic pressure. The peak survival time of 〉200 h was recorded at 0.2 mOsm/L. Comparing with 27℃ and 32 ℃ treatments, 23 ℃ treatment yielded lower activities at a range of 8-13/min. However, there was a longer survival time. A non-linear relationship existed between survival time and stocking density. Lower density resulted in larger body size. And sexual reproduction resumed after breeding for 〉22 days. Newly-formed polyps and medusae appeared subsequently but only in the higher-density groups of 10, 14 and 18 ind./L. It suggested that the number of newly-formed polyps and medusae was highly dependent on stocking density. That is, a higher stocking density produced more organisms. However, newly-formed medusae died within one month and none grew a diameter of 〉5 mm.

Construction of a chromosome-level genome assembly for genome-wide identification of growth-related quantitative trait loci in Sinocyclocheilus grahami(Cypriniformes,Cyprinidae)

The Dianchi golden-line barbel,Sinocyclocheilus grahami(Regan,1904),is one of the“Four Famous Fishes”of Yunnan Province,China.Given its economic value,this species has been artificially bred successfully since 2007,with a nationally selected breed(“S.grahami,Bayou No.1”)certified in 2018.For the future utilization of this species,its growth rate,disease resistance,and wild adaptability need to be improved,which could be achieved with the help of molecular markerassisted selection(MAS).In the current study,we constructed the first chromosome-level genome of S.grahami,assembled 48 pseudo-chromosomes,and obtained a genome size of 1.49 Gb.We also performed QTL-seq analysis of S.grahami using the highest and lowest bulks(i.e.,largest and smallest size)in both a sibling and random population.We screened two quantitative trait loci(QTLs)(Chr3,14.9-39.1 Mb and Chr17,4.1-27.4 Mb)as major growth-related locations.Several candidate genes(e.g.,map2k5,stat1,phf21a,sox6,and smad6)were also identified,with functions related to growth,such as cell differentiation,neuronal development,skeletal muscle development,chondrogenesis,and immunity.These results built a solid foundation for in-depth MAS studies on the growth traits of S.grahami.