No abstract

Actinomycetes, as the main producers of a variety of active metabolites and enzymes, have received extensive attention in aquaculture. An actinomycete had been isolated from Haizhou Bay and been identified by morphological analysis and 16S rRNA sequencing. Results showed that the actinomycete had the highest similarity (99.65%) with Nocardiopsis sp. and was named strain E10. Strain E10 produced an exo-enzyme with proteinase effect that showed strong antibacterial activity against Vibrio anguillarum. This strain E10 was tested as a probiotic for the culture of Exopalaemon carinicauda. After having been fed with a diet supplemented with strain E10 for 30 days, the final body weight (Wt), weight gain rate (WGR), special growth rate (SGR), survival rate (SR) and digestive enzymes (chymotrypsin, α-amylase and lipase) of E. carinicauda in all experimental groups showed no significant differences (). However, the antioxidant enzymes (total superoxide dismutase, catalase and peroxidase) and the non-specific immune-related enzymes (acid phosphatase, alkaline phosphatase and lysozyme) in the treatment groups increased significantly () compared with the control group. The cumulative mortality of the treatment groups (35.56% in 5 × 109 CFU/100 g) was significantly lower than that of the control treatment (73.33%) () post challenge with V. anguillarum for 14 days. The results indicated that strain E10 had no significant effect on the growth, but a significant improvement on the immunity of E. carinicauda. This study provides the data for ecological aquaculture of E. carinicauda.

The Wnt family, the ligand of the Wnt signal pathway, is highly conserved and plays an important role in various cellular processes including reproduction and development. In this study, wnt5 was cloned from the ridgetail white prawn Exopalaemon carinicauda (Ec-wnt5) and its function in ovarian maturation was investigated. The results showed that the Ec-wnt5 cDNA was 2422 bp, including an ORF with 1116 bp encoding a polypeptide with 371 amino acids. Ec-WNT5 had the highest homology with WNT5 from Penaeus vannamei (93.1%). Ec-wnt5 was expressed in 9 tissues with the most expression in ovary and increased significantly () along with ovarian maturation, while decreased significantly () with vitellogenin and cathepsin L in E. carinicauda ovary post Ec-wnt5 RNA interference. All gonadosmatic indices of the RNAi group were significantly lower than those of the control (). The results suggest that Ec-WNT5 might be the key member of the Wnt family involved in ovarian maturation.

The Notch signalling pathway is widely present in organisms and is an essential factor involved in the developmental process. JAGGED-1, as an important ligand in the Notch signalling pathway, has been cloned from Exopalaemon carinicauda and its role in growth and development have been studied. The full length of the jagged-1 cDNA of E. carinicauda was 5148 bp encoding a protein composed of 1307 amino acids, which had the highest identity with JAGGED-1 of Procambarus clarkii. The expression of jagged-1 varied with development, with the highest expression at the gastrula stage of embryonic development, the Z2 stage of larval development, and the G4 stage of ovary development, respectively. The expression of jagged-1 in the interference group was significantly lower than that in the control group between 3 and 72 h post jagged-1 RNA interference. The expression of key genes in the Notch signalling pathway, including notch1 and delta, and genes related to growth and development, including chh, gih and mih, decreased significantly post jagged-1 RNA interference. After continuous jagged-1 RNA interference, the ovary of the interference group only developed to the G3 stage, while the ovary of the control group developed to the G4 stage. Further study found that there were 8 SNPs including one missense mutation (SNP 2389 T > C) and seven synonymous mutations, and the SNP 2389 T > C and SNP 2799 G > C might be related to the growth of E. carinicauda. The results showed that jagged-1 was involved in the growth and development of E. carinicauda.