Crustecdysone mediated changes in crayfish

Abstract

Molting in crayfish, essential for growth is preceded by a decrease in total organic content during premolt. Mineral, as calcium, is conserved in gastroliths after mobilization from the exoskeleton. Crustecdysone treatment results in gastrolith formation by intact crayfish in intermolt, state C, but does not influence the rate of gastrolith formation in eyestalkless animals. Moreover, the rate of gastrolith formation is not increased at higher hormone doses; conversely, less dense, abnormal gastrohths result, while apolysis is evident by 48 to 60 hours after treatment. It appears that crustecdysone promotes reabsorption of the organic matrix since treatment with this hormone does not lead to a measureable decrease in calcium content of shell based on dry weight.Premolt crayfish normally have a higher amino acid pool in all tissues than do those in intermolt, and eyestalk removal from intermolt crayfish results in an increase in the free-amino acid level of all tissues by 24 hours; crustecdysone treatment results in a significant increase in muscle amino acids by 12 hours after a hormone dose of 5 μg/g body weight. In the context of integumentary growth and protein synthesis low doses of crustecdysone (1 μg/g) increase the in vivo incorporation of amino acid into hypodermis, but not hepatopancreas, by 24 hours, and the increase is significant by 36 hours; a higher dose (5 μg) does not change this rate of incorporation. Selective increase in hypodermis protein is not evident in acid phosphatase levels from 12 to 48 hours, but respiration of this tissue is significantly elevated within two hours after hormone injection. © 1972 by the American Society of Zoologists.