Free serosal cells originating from the embryo of the wasp Diadromus pulchellus in the pupal body of parasitized leek-moth, Acrolepiosis assectella. Are these cells teratocyte-like?

In braconid species, teratocytes are derived from a serosal cell membrane w hich envelops the developing parasitoid embryo. On hatching, this membrane dissociates into individual cells, the teratocytes, which then circulate in the haemolymph of the host. We describe herein such a membrane, surroundin g the embryo in eggs of the ichneumonid parasitoid wasp, Diadromus pulchell us. This membrane consisted of a single sheet of tightly packed cells with large 12+/-1.4 mu m nuclei. These cells were released after hatching in vit ro and cells of the same size were detected in vivo, in the vicinity of the D. pulchellus embryo. The number of nuclei detected suggests that the sero sal membrane consists of about 450+/-150 cells. These cells did not grow af ter hatching of the parasitoid egg in the parasitized host, Acrolepiosis as sectella, during the development of the parasitoid wasp larva. Southern blo t experiments, using D. pulchellus satellite DNA or the ribosomal genes as probes, showed that free-living floating cells of wasp origin were present in the body of the parasitized host. This is the first time that free-float ing teratocyte-like cells have been described in species of the Ichneumonid ae. (C) 1999 Elsevier Science Ltd. All rights reserved.