Reproduction and molt in previously spawned and first-time spawning red-claw crayfish Cherax quadricarinatus females following eyestalk ablation during the winter reproductive-arrest period

The effect of unilateral eyestalk ablation on reproduction, molting and quality of offspring was investigated in Cherax quadricarinatus females during the reproductive-arrest period (winter). At the end of the Autumn, females that had spawned for the first time had relatively uniform, early vitellogenic ovaries, while most females that had spawned previously had ovaries containing two distinctly sized and coloured oocyte populations. These included one population of small oocytes, similar to oocytes found in first-time spawners, while the other comprised of large oocytes. Winter reproduction of females that had spawned previously was not affected by eyestalk ablation, whereas significantly increased spawning activity was observed in eyestalk-ablated first-time spawners. Both females that had spawned previously and first-time spawners that were eyestalk ablated molted significantly more frequently than intact females. The size and number of offspring were not affected by eyestalk ablation. These results show that small synchronous oocyte populations were affected by eyestalk ablation while large oocytes were not affected; females with single-sized-oocyte ovaries tended to be more receptive to the treatment. Unilateral eyestalk ablation may present a solution for induction of spawning only in young females and perhaps in synchronized broodstock.