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Coilia nasus is an endangered fish species in the Yangtze River, and there is urgent need to know the genes related to its reproduction and fertility. The DAZ family including boule, daz and dazl, plays an important role in germ cells development. In this study, the cDNA sequence of boule (Cnbol) and dazl (Cndazl) genes were cloned and their expression patterns were characterized in Coilia nasus. RT-PCR showed that the expression of Cnbol and Cndazl mRNAs was restricted in adult gonads. The section in situ hybridization indicated that the temporospatial expression patterns of Cnbol and Cndazl were significantly different. In the testis, Cnbol was mainly detected in spermatocytes and spermatids, while Cndazl was prominently expressed in s permatogonia. In the ovary, Cnbol and Cndazl were highly expressed in the early stages of oocytes. Interestingly, Cndazl was also concentrated in perinuclear speckle and then localized to the Balbiani body in late stages of oocytes. In addition, Cnbol and Cndazl 3′ UTR can specifically label medaka Primordial Germ Cells (PGCs). According to our results, Cnbol and Cndazl are marker genes of germ cells and may play a vital role in the development and differentiation of germ cells in Coilia nasus.

This study was designed to generate the full-length transcriptome of Coilia nasus using single-molecule long read isoform sequencing (SMRT-seq) technology. RNAs of brains, ovaries, and testes of C. nasus conditioned in both seawater and freshwater except for gut which was only from the fish conditioned in freshwater, were isolated. All the RNAs were pooled together equally for SMRT sequencing. One SMRT cell produced 64.18 Gb clean data, including 765,184 circular consensus (CCS) reads and 616,126 full-length non-chimeric (FLNC) reads. Finally, 93,793 non-redundant transcripts were obtained after clustered and polished. Structural analysis of the 93,793 non-redundant transcripts predicted 8242 alternative splicing events, a total of 229,825 SSR and 72,037 complete CDS. A total of 8437 lncRNA were identified. 84,617 transcripts were annotated in NR, Swissprot, GO, COG, KOG, eggnog, Pfam and KEGG database totally. This is the first full-length transcriptome of Coilia nasus, including transcripts appeared in the case of seawater, which will facilitate exploration of genetic data and life story of Coilia nasus.

This study was carried out to determine the effects of abrupt salinity change on osmoregulatory ability of the spottedtail goby Synechogobius ommaturus. 720 juvenile fish (65.3 ± 11.8 g) were transferred to 200 L tanks (with 40 juveniles in each tank), in which salinities were abruptly changed from 10 to 20, 30, 40, 50 and freshwater. Survival rate, serum osmolality, electrolytes (Na+, Cl−, and K+) and gill Na+/K+-ATPase (NKA) activity were assessed successively in 528 h. Results showed serum osmolality, ion concentrations and gill Na+/K+-ATPase activity increased significantly when fish were transferred to salinity 40 and 50 and all fish in these groups died by the end of the experiment. Serum osmolality, Na+, Cl− and K+ in fish transferred to a salinity of 20, 30 and freshwater were not affected and no mortality was detected. Compared with the control group, a significantly decrease of NKA activity happened in the freshwater group, but the activity in 20 and 30 groups was not affected significantly. The results indicated that S. ommaturus could adapt rapidly and maintain homeostasis in a wide range of salinities (from freshwater to salinity 30) and this species may be suitable for aquaculture in estuarine and coastal areas where rapid salinity fluctuations commonly occur. Keywords: Osmolality, Gill, Na+/K+-ATPase, Synechogobius ommaturus