Effects of starvation and refeeding on growth performance, appetite, growth hormone-insulin-like growth factor axis levels and digestive function of Acipenser dabryanus.

The aim of this study was to explore the effects and mechanisms of different starvation treatments on the compensatory growth of Acipenser dabryanus. A total of 120 fish (60·532 (sem 0·284) g) were randomly assigned to four groups (fasting 0, 3, 7 or 14 d and then refed for 14 d). During fasting, middle body weight decreased significantly with prolonged starvation. The whole-body and muscle composition, serum biochemical indexes, visceral indexes and digestive enzyme activities had been effected with varying degrees of changes. The growth hormone (GH) level in serum was significantly increased in 14D; however, insulin-like growth factor-1 (IGF-1) showed the opposite trend. The neuropeptide Y (npy) mRNA level in brain was significantly improved in 7D; peptide YY (pyy) mRNA level in intestine was significantly decreased during fasting. After refeeding, the final body weight, percentage weight gain, specific growth rate, feed intake, feed efficiency and protein efficiency ratio showed no difference between 0D and 3D. The changes of whole-body and muscle composition, serum biochemical indexes, visceral indexes and digestive enzyme activities had taken place in varying degrees. GH levels in 3D and 7D were significantly higher than those in the 0D; the IGF-1 content decreased significantly during refeeding. There was no significant difference in npy and pyy mRNA levels. These results indicated that short-term fasting followed by refeeding resulted in full compensation and the physiological and biochemical effects on A. dabryanus were the lowest after 3 d of starvation and 14 d of refeeding. Additionally, compensation in A. dabryanus may be mediated by appetite genes and GH, and the degree of compensation is also affected by the duration of starvation.

Transcriptome analysis identifies candidate genes associated with skin color variation in Triplophysa siluroides.

In vertebrates, skin pigmentation is the most diverse phenotypic trait, and it is produced by a complex biological process that is often genetically controlled. Recently, two different colors (the typical brown and orange varieties) of Triplophysa siluroides, a species restricted to Yellow River drainage in China, were discovered. In the present study, the skin, brain and liver transcriptomes of T. siluroides of both colors were sequenced to search for genes related to skin pigmentation. Transcriptome sequencing generated 1,484,197,774 clean reads, resulting in a total of 222.6 Gb of sequence. The reads were assembled into 470,788 unigenes with a mean length of 1550 bp and an N50 size of 2944 bp. Functional annotation of the unigene dataset showed that 214,507, 304,161, 112,886, 179,074, 180,064, 184,837 and 82,081 unigenes were significantly matched to entries in the Nr protein, Nt, KO, Swiss-Prot, Pfam, GO and KOG databases, respectively. A differential expression analysis revealed that 2774, 3552 and 1529 unigenes were upregulated and 2720, 2663 and 1103 unigenes were downregulated in the skin, brain and liver of orange-skinned T. siluroides, respectively. Several genes that play key roles in pigmentation, i.e., Agouti, Slc45a2, Cbs, Mift and Slc7a11, showed significantly differential expression between brown and orange fish. In addition, we detected 158,863 simple sequence repeats (SSRs) in the T. siluroides transcriptome, and a total of 201,338 single-nucleotide polymorphisms (SNPs) were discovered in the different transcriptomes. The present results will facilitate further study of the molecular mechanisms of skin pigmentation and marker-assisted breeding of fish with valuable skin colors.

Complete mitochondrial genome of the snakehead (Channa gachua) and its phylogeny.

In present study, the mitochondrial genome (mitogenome) of Channa gachua was determined and the phylogenetic relationship of Channidae fish was reconsidered. The mitogenome of the C. gachua is 16547 bp in length, containing 13 protein coding genes (PCGs), 22 transfer RNA genes (tRNAs), two ribosome RNA genes (rRNAs), a control region (D-loop) and an origin region of replication on the light-strand (OL). The overall nucleotide composition is 28.32% A, 26.58% T, 29.41% C, 15.69% G, with 54.90% AT, respectively. Phylogenetic analyses revealed that C. gachua belongs to the genus Channa and shares a close relationship with C. marulius and C. striata.

The complete mitochondrial genome of Schizothorax prenanti (Tchang) (Teleostei, Cyprinidae, Schizothoracinae).

The ya-fish, Schizothorax prenanti, is a well-known commercial cold-water fish species with the hexaploid karyotype distributed in the upper reaches of the Yangtze River and its tributaries on the western Sichuan Plateau in China. The complete mitogenome of S. prenanti is 16,587 bp in length, containing 37 genes of 13 protein-coding genes, 22 tRNA genes, 2 rRNA genes and a control region (D-loop). The gene nucleotide composition of S. prenanti is 29.6% A, 25.4% T, 27.1% C and 17.9% G, with a slight AT bias of 55.0%. The complete mitogenome sequence of S. prenanti could provide useful data for further studies on genetic structure and diversity, as well as the artificial cultivation and breeding of S. prenanti.