Inducing Molting by Eyestalk Ablation in the Red Swamp Crayfish, <i>Procambarus clarkii</i> from the Egyptian Freshwaters

Abstract

Eyestalk ablation was used for inducing molting in the freshwater crayfish, Procambarus clarkii at the laboratory conditions. The results exhibited that, both of unilateral and bilateral eyestalk removal accelerated molting rate than in non-ablated or intact individuals of this species. The use of unilateral eyestalk removal has low effect, induced molting at the 6th week and reached 100% at the end of the 16th week, compared with starting molting at the 8th week for control, which did not exceed than 40 % for molted individuals at the end of experiment, with 20% mortality for each. On contrast, the bilateral ablation has high effects and induced molting rapidly at the first and second weeks for the two experiments. It was associated with high mortality rates, averaged 28.33%for ablated individuals of the two experiments, increased gradually to 51.67%and 80.0% for individuals of the premolt stages, which showed signs of molting but were unable to complete molting cycle and died at the end of the last week of each experiment. Repeating molting was recorded for only one bilateral ablated animal after 11 days, but no molting was noticed for control group, with mortality of 20 %.The percentages of increments in body dimensions included body length, carapace length, chelae length and total body weight were calculated. Most ratios of increments, except only total body weight, were high in ablated males than ablated females, as well as clearly higher in normal molted males and females than ablated ones, but declined sharply to 3.30±2.91% in total body weight for bilateral ablated males.