Fig. 2

Phenotypic features of normal mud crabs at stage I, stage II, and stage IV as well as “abnormal” crabs. a Diagram illustrating the developmental processes of ovaries in normal female mud crabs and “abnormal” crabs. Normal female mud crabs undergo a terminal molt prior to mating, after which they engage in mating with males. This process includes the transition of oocytes from the oogonia stage to the previtellogenesis stage. However, a small proportion of female crabs exhibit a disruption in oogenesis post-mating, resulting in an inability of oocytes to absorb vitellogenin. b–e Images of the anatomical structures showing the overall morphology of mud crabs at different ovarian developmental stages. Ovaries are outlined with dotted lines and indicated by arrowheads. f–i The details of ovarian differentiation, including oocyte development, were revealed by Hematoxylin and eosin (H&E) staining. I, stage I oocyte (diameter 35-50 μm); II, stage II oocyte (diameter 45–100 μm); IV, stage IV oocyte (diameter 120-200 μm); me, meiotic cells. Representative results of three independent experiments were shown. j–m The ovary sections showed vitellogenin absorption in the oocytes, as detected by immunohistochemical staining (Vtg). Asterisk, vitellogenin. Representative results of three independent experiments were shown. n–q The sections of the hepatopancreas showing the vitellogenin production, as revealed by immunohistochemical staining (Vtg). Ht, hepatopancreatic tubules; asterisk, vitellogenin. Representative results of three independent experiments were shown.