Ultrastructural studies of egg envelopes in harvestmen (Chelicerata, Opiliones)

Abstract

Ultrastructural studies of egg envelopes in four species of harvestmen have shown that a spongy vitelline envelope secreted by the oocyte appears on the oocyte surface at the beginning of vitellogenesis. As the oocytes grow, characteristic changes in the thickness and structure of the vitelline envelope can be observed. The homogeneous vitelline envelopes of eggs located inside the uterus are coated with a layer of loose, foamy material. The vitelline envelopes of laid eggs are covered only with mucus which binds the eggs together. The involvement of follicle cells in metabolic exchanges with the oocyte is suggested.