Effects of lipophorin and 20-hydroxyecdysone on in vitro development of the larval endoparasitoid Venturia canescens (Hymenoptera : Ichneumonidae)

We previously reported that development of the embryos of the larval endopa rasitoid Venturia canescens proceeded in the insect cell culture medium, MG M-450, and was promoted by the addition of a pupal extract from their host Galleria mellonella. The developmental promotion also was obtained by suppl ementing an equal amount of chicken egg yolk instead of the pupal extract t o the medium. In this case, approximately 30% of the embryos developed into the second instar, but the value increased to more than 90% by treatment w ith 20-hydroxyecdysone. The medium supplemented with a G. mellonella pupal extract obtained by using Carlson's solution displayed growth-promoting abi lity, and in the extract, apolipophorin I was electrophoretically detected in large amounts. Both lipophorin purified from G. mellonella pupae and low density Lipoprotein from chicken egg yolk acted as a growth-promoting subs tance for parasitoid development, although fetal bovine serum and 20-hydrox yecdysone were required as supplements to the medium for the expression of the ability. This indicated that lipophorin or lipophorin-transported lipid s could act as a substance closely related to the growth-promoting factor(s ) putatively involved in the host extract. (C) 1999 Elsevier Science Ltd. A ll rights reserved.