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

We have characterised the major circulating ecdysteroid in the South African spiny lobster, Jasus lalandii, as 20-hydroxyecdysone (20E) by means of chromatographic separation and an enzyme immunoassay (EIA). The titre of ecdysteroids 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 ecdysis. Since the major circulating ecdysteroid in J. lalandii is apparently 20E, 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 characterise moult-inhibiting hormone (MIH) activity in the sinus gland, we have incubated Y-organs from J. lalandii in vitro in the presence of crude extracts of homospecific sinus glands and measured the secreted ecdysteroid titres by EIA. Our experiments show that only Y-organs from animals in the inter- and premoult stages are negatively influenced by these extracts; Y-organs from postmoult J. lalandii were not inhibited. The synthesis of ecdysteroids in vitro from Y-organs of intermoult J. lalandii was inhibited by extracts of sinus glands in a dose-dependent manner: doses from 0.002 to 1 sinus gland equivalent were inhibitory; the highest inhibition (53%) was obtained with the highest dose. © 2001 Taylor & Francis Group, LLC.