Ecdysteroid titers of larval lobsters

Ecdysteroid fluctuations during embryogenesis in the giant freshwater prawn, Macrobrachium rosenbergii

Ecdysteroid levels during the embryogenesis of the giant freshwater prawn, Macrobrachium rosenbergii, were determined by radioimmunoassay and high-performance liquid chromatography. Ecdysteroids consisting of significant amounts of 20-hydroxyecdysone and high-polarity products (HPP) and lesser amounts of ecdysone and low-polarity products (LPP) were detected in mature ovaries and newly laid eggs. All ecdysteroid groups decreased gradually during the nauplius phase. With the formation of the compound eye and the appearance of the carapace and other body-like structures, marking morphogenesis to the zoeal stage, embryos showed the beginning of a continuous and dramatic increase in ecdysteroid concentrations sustained until larval hatchout. Ecdysteroid levels at hatchout were above 20-fold greater than ecdysteroid levels in newly laid eggs. More specifically, HPP and 20-hydroxyecdysone increased concomitantly, with a decrease in 20-hydroxyecdysone only at the end of the embryogenic period, while ecdysone and LPP levels remained low or undetectable. It may be postulated that the presence of ecdysteroids in ovaries and eggs represents a reserve of maternal ecdysteroids which are necessary at the commencement of embryonic development; with the differentiation of embryonic tissue capable of ecdysteroid synthesis, ecdysteroids increase rapidly to play a role in later embryonic development.

Ecdysteroid levels during the larval development of the spider crab Hyas araneus

Ecdysteroid levels were determined by radioimmunoassay during the larval development of the spider crab Hyas araneus L. In each of the three larval instars (zoea I, zoea II, megalopa) a minimum in ecdysteroid levels was found during early postmoult and a maximum during premoult. The amounts of ecdysteroids increased during development and reached maxima of 93, 137, and 165 pg ecdysone equivalents per larva in zoea I, zoea II, and megalopa, respectively. Ecdysteroid concentrations per unit of body dry weight or carbon increased during each moulting cycle, but the average values showed decreasing tendency from the first to the last instar. The main ecdysteroid in all larval instars and during the moulting cycle was 20-OH-ecdysone, and practically no ecdysone could be detected by HPLC-RIA.