EFFECTS OF PHOTOPERIOD ON SURVIVAL, FEEDING AND DEVELOPMENT OF LARVAEOF THE RED FROG CRAB, RANINA-RANINA

Ranina ranina zoea was reared from hatching to megalopa under five pho toperiods, from 0-h to 24-h light phase per day (0-24 L) with 6-h inte rvals, to test their effects on the survival rate, intermolt period, g rowth, external morphology, food consumption and cannibalism. Continuo us light had a negative effect on the larvae; however, continuous dark ness was advantageous, except during the final instar and metamorphosi s. The survival rate to the megalopa stage was significantly lower und er 0 and 24 L conditions than under 12 L conditions, but the rate to t he final instar under 0 L conditions was similar to that under 6-18 L conditions. The frequency of normal metamorphosis tended to be low und er 0 L conditions. The intermolt period was similar in each group, but accumulated zoeal duration was significantly longer under 24 L condit ions than in the other groups, at instars VI and VII. The carapace len gth was smaller with increasing photoperiod at instars III, V and VII. The number of setae on several appendages was similar in each group, but morphogenesis was retarded on the segmentation of several appendag es under 24 L conditions, at instar VII. The amount of food consumed d aily was significantly lower under 0 L conditions than under 18 and 24 L conditions at instars I, III and VII. Under 0 L condtions little ca nnibalism occurred, in contrast with those reared under 6-24 L conditi ons. A light-dark regime is recommended for the rearing of the larvae.