The eggs of Forficula auricularia L. (Dermaptera, Forficulidae): ultrastructure and resistance to low and high temperatures

Abstract

The morphology, ultrastructure, and resistance to low and high temperatures of the fertilized egg of Forficula auricularia were studied both before and after water absorption. The increase in volume resulting from water absorption did not modify the ultrastructure of the envelopes. The chorion was found to be made of five distinct layers and of a vitelline envelope under which a serosal cuticle was secreted by the embryo. Before hydration, the supercooling point of the egg was −27 °C; after hydration, it was −22 °C. Hydration did not alter the resistance of the egg to heat. It withstood a thermal rise to 36 °C without apparent damage. Morphological and physiological changes due to water absorption did not result in a modification of the viability of the eggs when they were exposed to temperature differences.

Maternal care provides antifungal protection to eggs in the European earwig

“…We showed that mothers transfer hydrocarbons to the egg surface, and it is well known that hydrocarbons on the cuticle of insects are key for water homeostasis (Blomquist and Bagnères 2010). Thus, the low quantities of hydrocarbons on the unattended eggs ( Figure 4B,C) might have facilitated passive water absorption by the embryos from the substrate and surrounding air leading to their heavier fresh weight at hatching (Chauvin et al 1991).…”

Hydropy and ultrastructure of egg envelopes in Aleochara bilineata (Coleoptera, Staphylinidae)

“…When no hydropyles are present, water is absorbed through the entire surface of the egg (Larink and Balinski 1989;Chauvin et al 1991). In contrast, in O. olens, there are about 4000 chorionic hydropyles (aeropyles) throughout the outer layer of the chorion in an equatorial band around the egg (Lincoln 1961).…”

“…Hydropic eggs require absorption of water from their environment to complete their development (Hinton 1981;Chauvin et al 1991). Such eggs are found in many aquatic and terrestrial insect species of Orthoptera, Hemiptera, Homoptera, Hymenoptera, Diptera and Coleoptera (Hinton 1981).…”

“…Water absorption is generally performed through specialised organs called hydropyles, although some species of Hymenoptera and Coleoptera have no apparent structure enabling the egg to absorb water. For these species, the absorption of water may occur through the egg surface (Hinton 1981;Chauvin et al 1991).…”