Meeting Abstract

P1.129  Monday, Jan. 4  Feedback Regulation of Ecdysteroid Analog on Y-organs of the Green Crab Carcinus maenas NIMITKUL, Sukkrit*; MYKLES, Donald L.; CHANG, Ernest S.; Bodega Marine Laboratory, University of California, Davis ; Colorado State University; Bodega Marine Laboratory, University of California, Davis snimitkul@ucdavis.edu

Crustaceans have a rigid exoskeleton that cannot be expanded when the animal needs to increase in size. To solve this problem, crustaceans shed their old exoskeleton and make a new one. This process is known as molting. The process of molting is highly regulated by hormones, especially ecdysteroids or molting hormones that are secreted by the thoracic Y-organs. The ecdysteroid level increases very rapidly during early premolt, reaches its peak, and then drops to a low level before molting (Chang and O’Connor, 1988). However, little is known about the regulation of ecdysteroid secretion. The incubation of green crab Y-organs in different concentrations of an ecdysteroid analog (Tebufenozide) was used in this experiment to elucidate the regulatory process. Tebufenozide was used instead of the authentic ecdysteroids ecdysone or 20-hydroxyecdysone due to their potentially confounding effects since presence in the incubation medium would crossreact with the ecdysteroid ELISA used for quantification of the hormone. Our results show that when incubated with high concentrations of analog (50 and 200 pg/µl), Y-organ secretion rate is significantly lower than the controls. In low concentrations of analog (1, 2.5, 5 and 10 pg/µl) the secretion rate is not significantly different from the controls. These results suggest that high levels of ecdysteroid analog have a negative feedback effect on the Y-organ and thus reduce the capability of the Y-organ to secrete more ecdysteroid. Further experiments will be conducted to determine the effects of Tebufenozide upon molting and ecdysteroid levels in vivo.