Ecdysteroids in the shrimp Palaemon serratus: relations with molt cycle

Ecdysteroids were studied during the molt cycle of the shrimp Palaemon serratus using radioimmunoassay and HPLC. Continuous presence of ecdysteroids was observed in whole extracts, with two hormonal peaks: a minor peak during stage B and a major one during stage D2. The ecdysteroid titers were generally higher in females than in males. The ecdysteroid peak at stage B was more pronounced in the integument (cuticle and epidermis) than in other tissues and, at this time, 20-hydroxyecdysone was the predominant form. The observed 20-hydroxyecdysone peaks in stages B and D2 are correlatable to the previously reported rise in integumental carbonic anhydrase activity.