16S rRNA gene sequencing analysis on changes in the intestinal flora of Procambarus clarkii with“Black May”disease

The morbidity and mortality peak of farmed Procambarus clarkii occurs around May every year,a phenomenon known as"Black May"disease(BMD).Increasing evidence shows that the intestinal flora is closely related to host health.We analyzed and compared the microbiota of healthy and BMDaffected P.clarkii intestines.The results show that there was no significant difference in bacterial a-diversity(richness P=0.59;evenness P=0.43;and diversity P=0.052)between the diseased group and the control group.Four dominant phyla in the intestines of crayfish in the control group,namely Tenericutes(30.86%),Bacteroidetes(29.99%),Firmicutes(22.23%),and Proteobacteria(15.23%),were identified.However,a striking shift in the microbial compo sition were found in the intestines of P.clarkii with BMD.Bacteroidetes was a dominant phylum in healthy P.clarkii,whereas the prevalence was low in diseased P.clarkii(1.87%).By contrast,the prevalence of Proteobacteria was significantly higher(P<0.05)in P.clarkii with BMD than in P.clarkii without BMD.Candidatus Bacilloplasma,Bacteroides,Vibrio,and Aeromonas showed significant differences(P<0.05)at the genus level.Tax4 Fun function prediction indicated that the relative abundance of genes involved in energy metabolism in the intestinal flora of P.clarkii with BMD was significantly reduced(P<0.05).Therefore,BMD can change the composition of the intestinal microbiota of P.clarkii.This study contributes to the understanding of the relationship between intestinal flora and host especially in aquatic animals.

Advances in Growth and Development in Crustaceans Induced by Eyestalk Ablation

Eyestalk ablation has been widely used in artificial breeding of crustaceans due to its significant promotion effect on gonadal development, which plays a certain role by directly affecting neuroendocrine function of X-organ sinus gland （XO-SG） complex in eyestalks. As an important endocrine organ, XO-SG complex of the eyestalk has become a hot issue in crustacean endocrinology. This paper introduced the biological structure and physiological functions of XO-SG complex and summarized the molecular mechanism of eyestalk neuroendocrine, which provided theoretical references for further revealing the regulatory mechanism of eyestalk neuroendocrine system.