Hemolymph vitellogenin levels during ovarian development in the kuruma prawn Penaeus japonicus

An enzyme immunoassay (EIA) system for kuruma prawn Penaeus japonicus vitel logenin (Vg) was developed and validated. In this assay, 96-well microtiter plates were coated with free vitellin (Vt). Assay conditions provided a de tectable Vg range of 1.56-100 ng/well. The dose-response curve for serially diluted vitellogenic female hemolymph was parallel to the Vg standard curv e. Male hemolymph produced absorbance values almost equal to background val ues, confirming the specificity of the assay. The intra- and interassay coe fficient of variations were 6.0% and 10.5%, respectively. Using this assay, it was determined that very low levels of hemolymph Vg were detectable in prawns with oocytes at the previtellogenic stage. The Vg levels in the hemo lymph rapidly increased at the endogenous vitellogenic stage and peaked at the early exogenous vitellogenic stage, but decreased at the late exogenous vitellogenic stage. Changes in hemolymph Vg levels preceded observed chang es in gonadosomatic indices.