In vitro culture of hymenopterous larval endoparasitoids

Abstract

The solitary endoparasitoids Cotesia (= Apanteles) marginiventris and Microplitis croceipes, which attack noctuid larvae, were successfully cultured from post-germband stage eggs to fully grown first-instar larvae in completely artificial (but undefined) media. However, growth rates were slower than in vivo, and while some larvae of each species attained apparent competence to moult (based upon characteristic size and form), none did so. Up to 75% of pregermband M. croceipes eggs developed and hatched when co-cultured with fat body from non-parasitized larvae of the habitual host, Heliothis zea. Heat-treated haemolymph plasma from a non-permissive host, Manduca sexta, also fostered development by ca. 40% of newly laid M. croceipes eggs, but plasma from H. zea larvae was not beneficial. Growth rates of C. marginiventris and M. croceipes larvae were not improved by haemolymph plasma from their habitual hosts ( Spodoptera frugiperda and H. zea, respectively). Heat-treated foetal bovine serum was growth-promoting for post-germband eggs and larvae of both parasitoids. Treatment of foetal bovine serum by charcoal adsorption (to remove sterols and peptide hormones) diminished its value as a supplement. Two major proteins of the serum, foetuin and albumin, also promoted survival and growth for both parasitoid species. The potential relevance of these findings to in vitro rearing of endoparasitoids is discussed.