Development and morphology of teratocytes in Encarsia berlesei and Encarsia citrina: first record for Chalcidoidea.

In several species of parasitoids belonging to the superfamilies of Ichneumonoidea and Platygastroidea, the serosal membrane enveloping embryos dissociates at hatching in a number of cells, called teratocytes, which freely float in the haemolymph of the host, interfering with its physiology. In this work we report for Encarsia berlesei and Encarsia citrina (Hymenoptera: Chalcidoidea) the dissociation of serosa into cells, whose morphological and embryological features correspond to those of teratocytes. In E. berlesei the extraembryonic membrane dissociated, at larval eclosion, into 4-9 big cells (90 µm) associated with about ten smaller cells (60 µm), which scarcely doubled their size during maturation. In Encarsia citrina the membrane dissociated into five big cells (250 µm) which did not appreceably increased in size during larval development. Ultrastructural investigation of the dissociated serosal cells of E. berlesei revealed that their surface was covered by microvilli, whose density and length increase from the egg stage to the 12 h following hatching. During the same period, rough endoplasmic reticulum evolved from a parallel profile to a cysterne type, while abundant vesicles represented the dominant cytological feature. Their ploidy level ranged between 8c and 140c at hatching, but increased to 40c-350c at maturation. These evidences for the first time clearly point out to the presence of teratocytes for the superfamily Chalcidoidea.