Cardenolide storage inDanaus chrysippus(L.) with additional notes onD. plexippus(L.)

Abstract

Danaus chrysippuswas reared in the laboratory from stock obtained from Kampala (Uganda), Nairobi (Kenya), Dar-es-Salaam (Tanzania) and Freetown (Sierra Leone) and wild-caught samples from Nigeria, southwest Africa and Tanzania were also analysed.D. plexippuswas reared on the same plants for comparison. It was found that the adultD. chrysippusis a poor and inconsistent storer of cardiac glycosides compared withD. plexippus, and contained, chiefly, highly polar cardenolides. Populations in East Africa are, on the whole, more efficient storers than those from West Africa, a factor which may contribute to the dearth of mimics in West Africa. Furthermore there appears to be a genetic element in the storage capacity of these butterflies, not merely a ‘mirror’ effect, depending on the cardenolide content of their food plants. Differences in storage capacity were shown between morphsalcippusfrom both Sierra Leone and Dar-es-Salaam andaegyptiusfrom Tanzania and Dar-es-Salaam, reared side by side on the same tested food plants. In both casesaegyptiuswas the better storer but in other broods from Kenya, reared onAsclepiasrich in cardenolides, this morph was negative for these substances. During the investigation strains ofAsclepias curassavicawere found which contained calotropin, but lacked calactin.D. plexippusreared on these plants also lacked calactin, but sequestered and stored it when fed onGomphocarpus fruticosuswhich contained both substances. The methods for analysing cardenolides of this type are described. Maps are presented showing the distribution of the three principal morphs ofD. chrysippusand the formalbinusin Africa.