The comparison of morphological characters, ovarian histology and gene expression levels between intersex and normal Eriocheir sinensis (Decapoda, Varunidae)

This study explores the primary characteristics of intersexuality in Eriocheir sinensis in aquacultural environments. We employed a variety of research methods, including morphological observations, histological analysis, transcriptome analysis, and 3D reconstruction techniques, to comprehensively examine the phenomenon of intersexuality in this species. Our findings indicate that most intersex E. sinensis in aquaculture may be genetically female crabs undergoing masculinization processes. These crabs exhibit a combination of both external and internal sexual characteristics, with the extent of intersexuality varying among individuals. While these intersex crabs may engage in normal mating behaviour, the structures of their abnormal internal reproductive system may impede proper fertilization, ovulation, or egg production. Additionally, we found that the androgenic gland (AG) in intersex crabs did not inhibit ovarian development. Our study provides insights into the potential mechanisms underlying intersex occurrence in E. sinensis and contributes to the improvement of aquaculture practices, a reduction in the incidence of intersex crabs, and the safeguarding of consumer health.