17α-methyltestosterone (MT) is known for its ability to suppress ovaries and induce spermatogenesis; yet, its effects in crustaceans are underexplored. This study investigates the impact of varying MT concentrations on the gonadal development and intestinal microbiota of juvenile Macrobrachium rosenbergii. Feeds containing different MT doses were provided, and the sex ratios, histological observations, reproductive gene expression, and intestinal microbial composition were analyzed. The results revealed short-term feeding (60 days) of 1000 mg/kg MT resulted in the highest male ratio, while long-term feeding (150 days) of 500 mg/kg MT achieved the same outcome. Conversely, long-term feeding of 1500 mg/kg MT led to the lowest male ratio and retarded male germ cell development. An intestinal microbiota analysis showed that MT supplementation significantly increased microbial abundance and altered the intestinal microbial community structure. Additionally, MT suppressed the expression of female reproductive-related genes. This study provides insights into the effects of MT on reproductive development and gut microbiota in juvenile prawns, offering a valuable reference for the application of MT in crustacean aquaculture.

Macrobrachium rosenbergii is one of the largest and most economically significant freshwater prawns worldwide. Understanding its population genetic structure is essential for optimizing cross-breeding strategies, conserving germplasm resources, and supporting sustainable aquaculture. However, progress in this area has been hindered by the limited availability of reliable molecular markers. In this study, we developed 20 polymorphic microsatellite primer pairs and applied them to assess the genetic diversity of 11 populations collected from China and Southeast Asia (including Jiangsu, Zhejiang, Taiwan, Myanmar, Bangladesh, Sri Lanka, and Thailand). All loci exhibited high levels of polymorphism. The number of alleles (Na) ranged from 5 to 27, while the mean observed heterozygosity (Ho), expected heterozygosity (He), and polymorphism information content (PIC) were 0.570, 0.720, and 0.686, respectively. The genetic differentiation coefficient (Fst) among populations ranged from 0.017 to 0.289. UPGMA clustering revealed that the Myanmar population formed an independent branch, whereas the remaining ten populations clustered together, indicating relatively close genetic relationships among them. Beyond enriching the currently limited molecular marker resources for M. rosenbergii, this study provides essential baseline data for evaluating genetic diversity in existing populations and establishes a solid molecular foundation for future genetic monitoring and breeding programs.

The redclaw crayfish (Cherax quadricarinatus) features a unique intersex phenotype—functional males harboring a female (ZW) genotype. This study investigates the sexually dimorphic transcriptomic responses of the hepatopancreas to acute methyl farnesoate exposure to decouple genotypic from phenotypic sex. We found that normal males prioritize enzymatic detoxification and steroidogenesis, whereas normal females prioritize energy conservation for reproductive preparation. Strikingly, intersex individuals exhibited a massive transcriptomic burst and paradoxical hormone receptor dynamics, exposing a fragile endocrine network driven by their inherent genotypic–phenotypic conflict. To survive severe MF-induced pharmacological stress, the intersex hepatopancreas actively suppresses lysosomal and apoptotic pathways, which we hypothesize serves as a compensatory mechanism to mitigate severe tissue damage. Instead, it deploys a compensatory architecture by hyperactivating amino acid biosynthesis, sulfur relay systems, and gap junctions to manage proteotoxic and oxidative stress. Co-expression network analysis identified VCP, maf, and hdac8 as central regulatory hubs orchestrating this survival strategy through proteostasis, oxidative sensing, and epigenetic override. These findings suggest that the crustacean response to acute pharmacological challenge involves profound metabolic and epigenetic reprogramming, providing novel hypotheses for future functional studies.