Chinese mitten crab(Eriocheir sinensis)is one of the most commercially important aquaculture species in China. The androgenic gland (AG) of crustaceans plays pivotal roles in the regulation of male differentiation and in maintaining the male sexual characteristics. In order to reveal related mechanisms in AG, we compared transcriptomes of AG between proliferation and secretion phase. A total of 72,000 unigenes and 4,027 differentially expressed genes were obtained. Gene ontology enrichment analysis indicated that biological processes and metabolic pathways related to protein synthesis and secretion such as transcription, translation, and signal transduction were significantly enriched. Critical genes such asIAG, SXL, TRA-2, SRY, FTZ-F1, FOXL2, andFEM-1were identified and potentially involved in maintaining the testis development and spermatogenesis. Ribosomes pathway revealed the cause of insulin-like androgenic gland hormone secretion increase. Three insulin-like receptors were thought to be associated with growth and spermatogenesis. In the neuroactive ligand-receptor interaction pathway, the expression of octopamine receptor, 5-HT receptor 1, and melatonin receptor was significantly changed, which revealed the key regulation mechanism of aggressive and mating behavior of males. Comparative transcriptome analysis provided new insights into the genome-wide molecular mechanisms of AG development and the regulatory mechanisms of male development.

The intestinal microbiota of Penaeus vannamei is critical for its health and disease resistance, but imbalances can increase the risk of infections, especially by pathogenic Vibrio species. This study used the 2bRAD-M method to analyze the effects of dietary chitosan oligosaccharide (COS) supplementation on the gut microbiota of P. vannamei . Shrimp were fed diets with COS at 5‰ and 10‰ levels. Results showed that as COS concentration increased, beneficial microbial taxa (e.g., Bacteroidetes, Actinobacteria, and Campylobacter ) significantly increased, while harmful bacteria decreased. For example, Vibrio parahemolyticus abundance dropped from 0.084 in controls to 0.033 in the 5‰ group, and Vibrio rotiforianus decreased from 0.216 in controls to 0.121 and 0.021 in the 5‰ and 10‰ groups, respectively. Photobacterium damselae also declined from 0.244 in controls to 0.049 and 0.094 in the 5‰ and 10‰ groups. These findings indicate that COS supplementation can enhance beneficial microbes and reduce harmful bacteria in P. vannamei intestines. This study highlights COS as a sustainable dietary intervention to improve shrimp health and reduce antibiotic use in aquaculture. IMPORTANCE: This study demonstrates that dietary chitosan oligosaccharide (COS) supplementation can effectively modulate the intestinal microbiota of Penaeus vannamei . At 5‰ and 10‰ levels, COS increased beneficial bacteria (e.g., Bacteroidetes and Actinobacteria) while reducing harmful pathogens like Vibrio parahaemolyticus and Vibrio rotiferianus . This shift enhances nutrient absorption, immune function, and disease resistance in shrimp. COS thus offers a sustainable alternative to antibiotics in aquaculture, promoting healthy growth and reducing environmental impact.