EFFECT OF ACCLIMATION TEMPERATURE AND TEMPERATURE-CHANGES ON MOLTING AND SURVIVAL OF ABLATED AND NONABLATED CRAYFISH ORCONECTES VIRILIS

The effect of acclimation temperatures for producing soft-shell crayfi sh, and changes upward from acclimation temperature, were evaluated in crayfish Orconectes virilis subjected to either hemilateral or bilate ral eyestalk ablation. In each experiment, 60 juvenile O. virilis were reared for 21 d at temperatures ranging from 20 C to 30 C. Equal numb ers of male and female crayfish ranging in weight from 5.0 g to 16.0 g were used in each study. In the first three experiments, crayfish wer e acclimated and maintained at a constant temperature. In the remainin g experiments, crayfish were subjected to a step-wise increase in temp erature of either 5 or 10 C. Molting was highest in crayfish acclimate d to 25 C prior to experimentation at 25 C (experiment 2) and in crayf ish acclimated to 14 C prior to experimentation at 20 C (experiment 4) . Total molts during these two experiments were 51 (85.0%) and 56 (93. 3%), respectively. Bilateral eyestalk ablation resulted in significant reductions in the intermolt period in experiments 1 (acclimation temp erature 20 C, experimental temperature 20 C), 3 (acclimation temperatu re 30 C, experimental temperature 30 C) and 6 (acclimation temperature 15 C, experimental temperature 25 C), while hemilateral eyestalk abla tion had no effect on molting when compared to control (non-ablated) c rayfish. Bilateral eyestalk ablation resulted in a significant reducti on in survival in experiments 5 (acclimation temperature 20 C, experim ental temperature 25 C) and 6 (acclimation temperature 15 C, experimen tal temperature 25 C). Significantly more females molted in one experi ment (acclimation temperature 20 C, experimental temperature 25 C), bu t not in any others. The results of these studies demonstrate that bil ateral eyestalk ablation and water temperatures are effective methods of inducing molting in crayfish.