Ecdysteroid levels during embryogenesis in the shrimp, Palaemon serratus (Crustacea Decapoda): quantitative and qualitative changes.

During the embryogenesis of Palaemon serratus profound changes in ecdysteroid concentrations were found. Ecdysteroid concentrations increase at the appearance of the Y-organ and a slight decrease is observed just before hatching. Two peaks of ecdysteroid concentration occur between these two events if Palaemon is reared at 19 degrees, but only one broad maximum is observed after rearing at 11-12 degrees. The pattern of ecdysteroids changes during embryogenesis; the ecdysone level decreases, while the 20-OH-ecdysone concentration and the amount of high polarity products increase. During the embryonic stage C the ratio of 20-OH-ecdysone to ecdysone was shown by HPLC analysis to steadily increase. After enzymatic hydrolysis of high-polarity products the main RIA-positive material elutes from reversed-phase HPLC columns as 20-OH-ecdysone.