Background: Chinese clearhead icefish, Protosalanx hyalocranius, is a representative icefish species with economic importance and special appearance. Due to its great economic value in China, the fish was introduced into Lake Dianchi and several other lakes from the Lake Taihu half a century ago. Similar to the Sinocyclocheilus cavefish, the clearhead icefish has certain cavefish-like traits, such as transparent body and nearly scaleless skin. Here, we provide the whole genome sequence of this surface-dwelling fish and generated a draft genome assembly, aiming at exploring molecular mechanisms for the biological interests. Findings: A total of 252.1 Gb of raw reads were sequenced. Subsequently, a novel draft genome assembly was generated, with the scaffold N50 reaching 1.163 Mb. The genome completeness was estimated to be 98.39 % by using the CEGMA evaluation. Finally, we annotated 19 884 protein-coding genes and observed that repeat sequences account for 24.43 % of the genome assembly. Conclusion: We report the first draft genome of the Chinese clearhead icefish. The genome assembly will provide a solid foundation for further molecular breeding and germplasm resource protection in Chinese clearhead icefish, as well as other icefishes. It is also a valuable genetic resource for revealing the molecular mechanisms for the cavefish-like characters.

Background Seasonal migration is one of the most spectacular events in nature; however, the molecular mechanisms related to this phenomenon have not been investigated in detail. The Chinese tapertail, or Japanese grenadier anchovy, Coilia nasus, is a valuable migratory fish of high economic importance and special migratory dimorphism (with certain individuals as non-migratory residents). Results In this study, an 870.0-Mb high-quality genome was assembled by the combination of Illumina and Pacific Biosciences sequencing. Approximately 812.1 Mb of scaffolds were linked to 24 chromosomes using a high-density genetic map from a family of 104 full siblings and their parents. In addition, population sequencing of 96 representative individuals from diverse areas along the putative migration path identified 150 candidate genes, which are mainly enriched in 3 Ca2+-related pathways. Based on integrative genomic and transcriptomic analyses, we determined that the 3 Ca2+-related pathways are critical for promotion of migratory adaption. A large number of molecular markers were also identified, which distinguished migratory individuals and non-migratory freshwater residents. Conclusions We assembled a chromosome-level genome for the Chinese tapertail anchovy. The genome provided a valuable genetic resource for understanding of migratory adaption and population genetics and will benefit the aquaculture and management of this economically important fish.

No abstract

No abstract

Coilia nasus is a valuable commercial migratory fish species with ecological and economic importance in China. To explore the molecular mechanisms underlying the response to food intake, the stomach transcriptomes of feeding and non‐feeding C. nasus were analysed via RNA‐seq. A total of 610,640,864 clean reads were obtained, and annotation to six databases identified 63,567 unigenes. Comparative analysis of the gene expression in feeding and non‐feeding C. nasus identified 1,968 differentially expressed genes (p < .05), including 1,180 up‐regulated and 788 down‐regulated genes. Our results showed that stomach distention activated the vagal afferent neurons, resulting in satiation. Several of the most relevant appetite genes (e.g. leptin receptor [LepR], somatostatin [SS], nucleobindin‐2 [NUCB2], 5‐hydroxytryptamine receptor [5‐HTR], growth hormone receptor [GHR]) were also involved in the regulation of food intake and led to the termination of feeding. Furthermore, significant differences were observed in the genes encoding key enzymes involved in metabolism such as the tricarboxylic acid cycle (TCA) pathways, fatty acid synthesis and glycolysis, indicating that C. nasus utilizes food for its energy and nutrient contents to support life and gonadal development. These findings provide valuable insights into the mechanisms underlying appetite and metabolic regulation in anadromous fish and create a foundation for further research on C. nasus artificial breeding and migration energetics.

No abstract

No abstract

No abstract