Characterisation of moult-inhibiting activities of sinus glands of the spiny lobster, Jasus lalandii

We have characterised the major circulating ecdysteroid in the South Africa n spiny lobster, Jasus lalandii, as 20-hydroxyecdysone (20E) by means of ch romatographic separation and an enzyme immunoassay (EIA). The titre of ecdy steroids in the haemolymph, as quantified by EIA, varied greatly during the moult cycle: it was highest in premoult and lowest in postmoult stages. A significant decrease in ecdysteroid levels was measured shortly before ecdy sis. Since the major circulating ecdysteroid in J. lalandii is apparently 2 0E, which arises from peripheral 20-hydroxylation of ecdysone, we concluded that the Y-organs of this spiny lobster are synthesising ecdysone or/and 3 -dehydroecdysone. In order to establish an in vitro assay with which to cha racterise moult-inhibiting hormone (MIH) activity in the sinus gland, we ha ve incubated Y-organs from J. lalandii in vitro in the presence of crude ex tracts of homospecific sinus glands and measured the secreted ecdysteroid t itres by EIA. Our experiments show that only Y-organs from animals in the i nter- and premoult stages are negatively influenced by these extracts; Y-or gans from postmoult J. lalandii were not inhibited. The synthesis of ecdyst eroids in vitro from Y-organs of intermoult J. lalandii was inhibited by ex tracts of sinus glands in a dose-dependent manner: doses from 0.002 to 1 si nus gland equivalent were inhibitory; the highest inhibition (53%) was obta ined with the highest dose.