Eyestalk ablation in female crabs: Effects on egg characteristics

AbstractEyestalk ablation in Crustacea eliminates the inhibitory hormonal effects exerted by the eyestalk neuroendocrine center on ovarian growth. Planning to use crab eggs throughout the year as a model for physiological cell research, we performed a preliminary study to examine the characteristics of eggs that originated from eyestalk‐ablated females. Here we discuss the data that deal with the characteristics of eggs at fertilization and during the first 40 h of embryonic development. We found that eyestalk ablation in female crabs did not modify the resumption of egg meiosis that is stimulated by sea water, nor did it affect the electrical and cortical responses of eggs to fertilization. We also found that eyestalk ablation in females did not result in any changes in the nature of the two major ecdysteroids that are usually found in crabs' eggs (ponasterone A and 20‐hydroxyecdysone) or in their respective precursors (25‐deoxyecdysone and ecdysone) in eggs tested from 0 to 40 h post‐spawning. The respective variations in the concentrations of the four ecdysteroids were the same during this period as in control eggs. However, eyestalk ablation in females induced a striking decrease in the concentration of ponasterone A (60%) in eggs 30 to 40 h post‐spawning. Furthermore, eyestalk ablation in females promoted an increase in the titer of ponasterone A in the ovaries of about 2‐ and 20‐fold, at egg‐laying and 40 hours afterwards. This difference is discussed in terms of possible perturbations in either the synthesis of ponasterone A at the ovarian level, or its metabolism in spawned eggs.