Transmission electron microscopy of the eggshell in five damselflies (Zygoptera: Coenagrionidae, Megapodagrionidae, Calopterygidae)

The previously undescribed egghell ultrastructure of 5 spp. is discussed in relation to other known eggshells within the order. Whereas the vitelline envelope has the same structure in all species, the endo- and the exochorion are diverse. Endochorionic sublayers are present, being few and uniform in the smaller eggs but numerous and increasing in thickness from the inside in the larger eggs. The exochorion varies from a compact layer via a layer with pores to a fibrous layer acting as a jelly. It is proposed that endophytic eggs as a group are not so homogeneous as previously believed. Eggshell differences are possibly influenced by different egg-laying substrates, i.e. various living and decaying plants.