Effect of Eyestalk-Ablation on Circulating Ecdysteroids in Hemolymph of Snow Crabs, Chionoecetes opilio: Physiological Evidence for a Terminal Molt

Jun 17, 2011Integrative and comparative biology

How Removing Eyestalks Changes Molting Hormones in Snow Crabs, Supporting a Final Molt

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Abstract

Circulating ecdysteroids were significantly higher in small-clawed male snow crabs compared to large-clawed males or terminally molted females.

Small-clawed male snow crabs exhibit higher levels of molting hormones than their large-clawed counterparts.
Eyestalk-ablation, which is known to influence hormone levels, increased ecdysteroid levels in small-clawed males.
No significant change in ecdysteroid levels was observed in large-clawed males or terminally molted females following eyestalk-ablation.
The study suggests that adult male snow crabs may not undergo a terminal molt based on hormonal regulation patterns.

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Bering Sea snow crabs (Chionoecetes opilio) are a commercially important crab harvested in the Bering Sea. Optimal management of this species requires an understanding of the biology of this crab that is currently incomplete. Fisheries managers apply a continuous growth model in their management of snow crab, which assumes that male crabs increase in size throughout their lifespan. Male snow crabs undergo a morphometric molt that leads to a disproportionate increase in chelae size and it is still debated whether this molt is associated with a terminal molt. This study was conducted to determine whether adult male C. opilio are anecdysic. Using current knowledge of the hormonal regulation of crustacean growth, snow crab physiology was manipulated to induce an increase in molting hormones (ecdysteroids). Since female snow crabs are known to undergo a terminal molt after attaining reproductive maturity, we compared ecdysteroid levels in eyestalk-ablated terminally molted females, small-clawed males and large-clawed males. Snow crabs were collected from the Bering Sea and maintained in circulating seawater at approximately 6°C. Animals were either eyestalk-ablated or left intact. Ecdysteroid levels in hemolymph were quantified using an enzyme-linked immunosorbant assay (ELISA). Circulating ecdysteroids were significantly higher in small-clawed male crabs when compared to large-clawed males or terminally molted females. Eyestalk-ablation increased circulating ecdysteroids in small-clawed males, but had no significant effect on circulating ecdysteroids in large-clawed males or in terminally molted females.

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