Growth patterns of Microplitis rufiventris (Hym., Braconidae) teratocytes in Spodoptera littoralis (Lep., Noctuidae) larvae treated with a chitin synthesis inhibitor

The influence of sublethal dietary levels (0.4 p.p.m.) of a chitin synthesis inhibitor lefenuron { N -2,5-dichloro-4-(1,1,2,3,3,3-hexafluoropropoxy)-phenylaminocarbonyl]-2,6-difluorobenzamide} on the development of Microplitis rufiventris teratocytes was investigated. Observations and data were taken on maturing teratocytes, i.e. at the end of parasitoid development. When embryogenesis of the parasitoid eggs was initiated in treated hosts, the dissociated cells of the embryonic membrane of some of the parasitoid larvae did not liberate in the haemolymph of the host, whereas in the other hosts, the released ones as individual cells scored the largest mean number per host larva. When young teratocytes were exposed to the treatment they were found in some cases clumping in masses or clustered around the parasitoid larvae. In treated hosts, different size classes of teratocytes co-existed. Larger and morphological abnormal cells were more common in hosts which contained older teratocytes at the time of treatments. Abnormal teratocytes were associated with developmental abnormalities of parasitoid larvae, possibly due to deterioration of the host environment. This observation was common in treated hosts and in few cases of untreated ones. A significant decrease in teratocyte size occurred 24 h after parasitoid emergence. Observations and results obtained in the present work suggested that: (1) teratocyte may function in controlling the growth and successful development of parasitoid larvae; (2) they might have a protective function through sequestering abnormal materials issuing in the haemolymph of the host either during the course of parasitoid development or due to external stress; and (3) number of teratocyte cells liberated from the embryonic membrane of parasitoid egg is not constant.