Crustacean Vitellogenesis: Its Role in Oocyte Development

One of the major changes that occurs during the maturation ofoocytes is the accumulation of yolk protein, or vitellin (Vn).To better understand how this process is regulated, we characterizedthe Vn of the ridgeback shrimp, Sicyonia ingentis (Penaeoidea).This Vn is a 322 kDa molecule composed of three subunits. Usingpurified Vn, we developed an anti-Vn antiserum and used it tocharacterize vitellogenin by Western blot analysis. The antiserumwas also used in an ELISA to measure hemolymph levels of vitellogenin.Previous studies suggested the presence of vertebrate-type steroidsmight stimulate reproductive processes in decapod crustaceans.Treatment of sexually quiescent female shrimp with progesterone,hydroxyprogesterone, and estradiol did not increase hemolymphlevels of yolk protein precursor. The absence of a responseto these steroids may reflect the presence of other hormones(such as the gonad-inhibiting hormone) that prevent oocyte development.To examine the molecular basis for the regulation of vitellogenesis,ovarian and hepatopancreas expression cDNA libraries were screenedusing the anti-Vn antiserum. A 2.9 kilobase clone was isolatedfrom both cDNA libraries suggesting that both tissues are sitesof vitellogenin synthesis. These molecular tools should be usefulfor in vitro studies of vitellogenin synthesis.