EXTRAEMBRYONIC MEMBRANES OF THE ENDOPARASITIC WASP COTESIA-CONGREGATA- PRESENCE OF A SEPARATE AMNION AND SEROSA

Little information is available describing the development of endopara sitic Hymenoptera prior to hatching of the first instar larva. The pre sent study reveals that in Cotesia congregata, and likely other bracon id wasp parasites, the serosa and amnion comprise separate layers enca sing the developing first instar larva. Examination of newly hatched f irst instar parasites in the hemocoel of Manduca sexta confirmed that the larvae were ensheathed in the remnants of an ''amnion'' at hatchin g, with patches of nucleated cells seen adhering in thin sheets to the larva. The amnion is delaminated from a cellular serosal membrane tha t lies directly beneath the chorion, which subsequently gives rise to teratocytes. Scanning electron micrographs indicate that remnants of t he amnion remained associated with the larvae for a longer period post hatch than did the teratocytes, which rapidly dispersed into the host hemolymph. The presence of an amnion-like layer in braconid endoparasi tic wasps may prove to be significant with respect to our understandin g of host-parasite immunological interactions occurring during the ini tiation of the relationship of the parasites with their host.