TAMONE, SL; GEHRINGER, DB: Effect of eyestalk-ablation on circulating ecdysteroids in the Tanner crab, Chionoecetes bairdi

Growth of decapod crustaceans is a periodic process that is under both environmental and hormonal regulation. The primary molt-promoting hormone is 20-hydroxyecdysone, a derivative of the hormone ecdysone, which is regulated by numerous factors. One important hormone, molt-inhibiting hormone (MIH) inhibits ecdysone (and growth) and is produced in crustacean eyestalks. It has long been recognized that removal of eyestalks from most crustaceans results in accelerated molt cycles. Certain crustaceans are capable of growing throughout their life while others are thought to undergo a final molt after which they no longer grow. We investigated the potential for growth in animals that are thought to undergo a terminal molt. We ablated eyestalks from the Tanner crab, Chionoecetes bairdi in order to look at the effects of this procedure on circulating ecdysteroids. Experimental animals were eyestalk-ablated after being held in the laboratory for three weeks. Daily hemolymph samples were taken for two weeks, after which hemolymph was sampled only once every week. Control animals were sampled at the same intervals. Sampling continued for 8 weeks. Ecdysteroids were measured using an enzyme-lined immunosorbant assay (ELISA) for ecdysteroids. Results indicate that ecdysteroid regulation in Tanner crab differs from that demonstrated for continually growing species. This work is supported by the Alaska Department of Fish and Game.