EFFECTS OF IMPREGNATION ON MATURATION, SPAWNING, AND ECDYSIS OF FEMALE SHRIMP PENAEUS-INDICUS

Impregnation of females (i.e., spermatophore transfer) is known to occ ur soon after ecdysis in closed thelycum penaeids, while no sign of fe male maturation is visible yet. The influence of impregnation on matur ation, spawning, and intermoult duration was assessed in Penaeus indic us females with or without unilateral eyestalk ablation. Impregnation, when occurring in unablated females, was found to significantly incre ase the percentages of maturing females (93-100% vs. 40-47%) and spawn ing females (86-100% vs. 20%), the number of spawns per female (1.46-1 .91 vs. 0.26-0.40), and the intermoult duration (13.16-13.53 vs. 11.36 -11.86 days). No remnants of impregnation was detected since its effec ts on the Various parameters studied were restricted to the moult cycl e where it occurred. Unilateral eyestalk ablation induced effects simi lar to those of impregnation on the reproduction parameters studied, b ut did not extend the length of the moult cycle. Impregnation of femal es that have been previously unilaterally ablated induced no change in any parameter studied including the intermoult duration. These findin gs suggest that impregnation interacts with certain physiological proc esses controlled by the X organ-sinus gland neuroendocrine complex, lo cated in the eyestalk. (C) 1994 Wiley-Liss, Inc.