Ecdysteroids in female shore crabs Carcinus maenas during the moulting cycle and oocyte development

The ecdysteroids ecdysone (E), 20-hydroxyecdysone (20E) and ponasterone A (PoA) were measured in the haemolymph, hepatopancreas and oocytes of female shore crabs Carcinus maenas during the moulting cycle and during oocyte maturation using HPLC-MS. In the haemolymph, ecdysteroid titres varied over the moulting cycle with high levels during premoult and low levels during postmoult and intermoult, however, no significant change in haemolymph ecdysteroid titres was observed in relation to oocyte development. In the hepatopancreas, PoA levels were high during premoult but low during postmoult and intermoult. This is in contrast to E and 20E where levels remained high from early intermoult (C(1)) until late premoult (D(3)) and only decreased during postmoult. In the oocytes, ecdysteroid levels were low during postmoult and for 20E and PoA also during late premoult D(2) and D(3). In contrast, all three ecdysteroids were observed to increase in the oocytes during oocyte development, in particular E and PoA. The present study demonstrates that changes in haemolymph ecdysteroid titres relate to changes in moulting status and not to changes in oocyte development. Also, the study indicates that the hepatopancreas is involved in the metabolism of ecdysteroids related to the moulting cycle but may also be involved in ecdysteroid metabolism during oocyte development. Furthermore, the pronounced increase in oocyte ecdysteroids during oocyte development during periods where haemolymph ecdysteroids titre is low, indicates that the oocytes are capable of de novo synthesis of the three ecdysteroids investigated.