A maternal gene mutation correlates with an ovary phenotype in a parthenogenetic wasp population

Endoparasitoid wasps rely on maternal protein secretions, including viruses and virus-like particles (VLPs), to overcome host defense reactions. In th e ichneumonid Venturia canescens, VLPs are assembled in the nuclei of ovari an calyx gland cells, secreted into the lumen of the gland, and eventually transmitted into the host caterpillar together with the parasitoid egg. One of the genes coding for VLP proteins, termed VLP1, exists in two alleles p roducing two structurally different proteins. Here we describe the establis hment and initial phenotypic characterisation of two parthenogenetic :Labor atory strains, which differ in VLP1 as well as in other genetic markers. A comparison of calyx tissues from the two strains revealed morphological dif ferences that seem to affect egg movement from the ovarioles into the ovidu ct. The observed histological changes are correlated with differences in eg g maturation and embryonic development causing a delay in larval hatching i n one of the strains. Under conditions that favour superparasitism, the two strains differ in the number of offspring produced. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.