Effects of some steroids and other compounds on ovarian growth of the red swamp crayfish, Procambarus clarkii, during early vitellogenesis.

The effects of spiperone, a dopaminergic receptor blocker, the terpenoid JHIII, and the steroids 17alpha-hydroxyprogesterone and 17beta-estradiol (10(-7) mol/crayfish) were assayed in vivo on females of the red swamp crayfish, Procambarus clarkii, during early vitellogenesis. All these compounds were injected twice a week for 3 weeks. The rate of molting in response to these compounds was also determined. At the end of the experiment the ovaries were dissected out, in order to determine the gonadosomatic indexes and oocyte diameters. Spiperone, 17alpha-hydroxyprogesterone, and 17beta-estradiol produced a significant increase in the gonadosomatic index, while only the first two compounds were able to significantly increase the oocyte diameter; therefore, the effect of 17beta-estradiol the on gonadosomatic index could be merely due to increased water uptake by the ovary. Spiperone could be causing a decrease in secretion of the gonad and/or mandibular inhibiting hormones from the eyestalks, and 17alpha-hydroxyprogesterone could be having a direct stimulatory effect on vitellogenin production. Concerning molting, of the compound tested, only JHIII had a significant (P < 0.05) stimulatory effect, producing a 100% molting rate versus 66.7% among the controls. Copyright 2002 Wiley-Liss, Inc.