Molting and its control in the female sand lobster Thenus orientalis (Lund)

Abstract

Thenus orientalis (Lund), the only species of the genus belonging to the family Scyllaridae, is found in the coastal waters of India where it breeds and molts throughout the year, with alternating peaks for molting and reproduction. Females mature at a carapace width (CW) of 7.3 ± 0.1 cm. The molting sequence of T. orientalis in the laboratory was observed and described. The lobster takes ≈ 30–45 min to complete ecdysis. The animal escapes from the old exoskeleton between the thorax and the abdomen. The anterior part, including the thorax, is shed gradually, but, at the end of shedding, the tail comes out quickly. Because of high pigmentation of the pleopods, the molting cycle could only be classified into five major stages (A-E). This, together with the morphological changes such as the appearance of ecdysial sutures and the changing of abdomen colour from yellowish-brown to pink, may help in predicting ecdysis. Eyestalk ablation affects molting more than reproduction; ablated animals molted faster than the controls. Eyestalk ablation in the intermolt condition produced accelerated molting compared to the premolt lobsters. However, there was no effect on ovarian growth although the lobsters with fully mature ovaries deposited eggs on pleopods instantaneously. In contrast, animals with developing ovaries at eyestalk ablation started oosorption.