Vitellogenin and its receptor characterize exogenous vitellogenesis mode in the Pacific white shrimp Litopenaeus...

Vitellogenesis is a pivotal process of animal reproduction, characterized by yolk protein formation and accumulation in developing oocytes. Vitellogenin (Vg), the precursor of vitellin (Vn), serves as the primary yolk component. While animals employ both exogenous and endogenous vitellogenesis, the precise synthetic locus of Vg in the Pacific white shrimp Litopenaeus vannamei, the globally most important cultured shrimp, remains unclear. To characterize vitellogenesis and its regulatory mode, the present study examined ovarian morphology, gonadosomatic index (GSI) dynamics, hepatopancreatic and ovarian histology, as well as spatiotemporal expression and cellular localization of Vg and its receptor vitellogenin receptor (VgR), during gonadal development process. We discovered that L. vannamei ovarian cycle was categorized into five stages, marked by ovarian color transition from khaki to dark green and progressive GSI increase. In situ hybridization revealed Vg mRNA in hepatopancreatic Blasenzellen and Restzellen cells and ovarian follicular cells, but not in oocytes. Immunofluorescence showed Vg protein primarily in hepatopancreatic cells and oocytes, while VgR localized to the membrane of vitellogenic oocytes, forming complexes with exogenous Vg cytoplasmic internalization. Collectively, this study established a standardized ovarian staging system for L. vannamei, demonstrated an exogenous vitellogenesis mode, with hepatopancreas and ovarian follicle cells as the primary Vg synthesis sites, and elucidated the cooperative role of Vg and VgR in yolk protein uptake and deposition. These findings advance our understanding of crustacean reproductive biology and provide a theoretical foundation for optimizing shrimp fecundity and aquaculture practices.