INVITRO STIMULATION OF OOCYTES BY PRESUMPTIVE MANDIBULAR ORGAN SECRETIONS IN THE SHRIMP, PENAEUS-VANNAMEI

Several mandibular organ compounds and their derivatives were assayed in vitro to determine their effects on oocytes from the shrimp, Penaeus vannamei. Pieces of adult immature ovary were incubated for 24 h in modified Medium 199 supplemented with either a steroid or terpenoid hormone. The diameters of late perinucleolus stage oocytes were examined under light microscopy. Of the four steroids assayed, only 17-alpha-hydroxyprogesterone at concentrations of 1 pM-100 nM significantly increased oocyte diameter. Progesterone, 17-beta-estradiol and 17-alpha,20-beta-dihydroxyprogesterone had no effect. Terpenoids, methyl farnesoate and juvenile hormone III, also significantly increased oocyte diameter. Combinations of 17-alpha-hydroxyprogesterone and juvenile hormone III showed no additive effect. These data suggest that mandibular organ compounds and their derivatives may be potent in stimulating oocyte growth.