Changes in ecdysteroids in Astacus leptodactylus during the molting cycle

Abstract

1. 1. The changes in ecdysteroid titers were monitored in the hemolymph and integument of the crayfish Astacus leptodactylus at each stage of the molt cycle. Hemolymph titers rose slightly during the long C4 stage, and then considerably, between the late D1 and D2 stages. In integument extracts, steroid contents greatly increased first in D1 and then in D1-D2. 2. 2. 20-OH ecdysone and ecdysone were present in both compartments. Several other components were also detected in large amounts. One of them was slightly more polar than 20-OH ecdysone, and five or six others were apolar. Ponasterone A was only found at very low concentrations. 3. 3. Throughout the prolonged intermolt period, striking variations in the relative amounts of each steroid were observed in the hemolymph. 20-OH ecdysone decreased from the beginning until the middle of stage C4 and then rose again sometime before the molt. 4. 4. The total amount of low polar products (LPP) underwent exactly the opposite changes to those observed for 20-OH ecdysone. Ecdysone titers rose when the titer for 20-OH ecdysone was lowest. 5. 5. During the premolt stages, the amount of 20-OH ecdysone in the crayfish hemolymph increased a little in D1', and much more from D1 until the molt. Ecdysone decreased from DO to D1. Relative titers for LPP rose from DO to D1, fell dramatically and disappeared in Dl. In integument extracts, the level of 20-OH ecdysone dropped slightly from DO to D1 and then rose in D1 and D2. The amounts of ecdysone and high polarity products (HPP) were always very small. LPP titers increased until D1 and then fell in D1-D2-D3. 6. 6. The nature and role of the HPP and LPP found in intermolt and early premolt are discussed.