Oogenesis in a thelytokous wasp, Nemeritis canescens (Grav.)

Abstract

Abstract In the fifty generations of reared Nemeritis, males have been totally lacking. Oogenesis is atypical in (1) the occurrence of a pronounced and lengthy prochromosome stage, (2) the partial fusion of the eleven tetrads at early first anaphase, (3) following first anaphase, a return of all dyads from both poles to form a common second metaphase plate consisting of twenty‐two separate dyads, (4) a second division which forms a single polar nucleus and an egg nucleus, each with twenty‐two chromosomes, (5) the parthenogenetic development of the egg nucleus with twenty‐two chromosomes. Oviposition, which occurs at first anaphase, is followed by a pronounced swelling of the egg through osmosis. Oogonia, follicle cells, cleavage nuclei and somatic cells in later embryogeny all show twenty‐two metaphase chromosomes, while pupai tissue shows also tetraploid and octoploid complexes.