Micropores in the vitteline layer of the eggs of the dragonfly Oligoaeshna pryeri: A preliminary observation from the viewpoint of oxygen uptake

Abstract

In dragonfly eggs, oxygen diffusing in, and carbon dioxide diffusing out, encounter barriers in the shell.According to Tullett and Board, in avian eggs themost important of these barriers results from the geometry of the pores through the shells. As in birds, dragonfly egg shells consist of three layers: the exochorion, endochorion and the innermost vitellinemembrane.Trueman has described pores and fine anchorlike structures in the endochorion but the vitelline membrane does not seem to have been studied. In the present work we have used scanning electron microscopy to examine the vitelline membrane in hatching eggs of Oligoaeschna pryeri. We have assumed that the numerous openings seen on the micrographs are pores through the membrane. Results are expressed as means ± SD. The pore diameter, pore area and number per μm 2 of the vitelline membrane were 74.7 ± 61.3 nm, 4380 ± 3555 nm2 and 4.16 ±1.3 pores/μm2 (4.16 × 108 pores/cm2), respectively. The total pore area was calculated to be 18,222 nm2/μm2. In avian egg shells pore density depends on the weight of the egg. Results given by Tullett and Board suggest that an egg weighing 1 g may have a pore density of 300 pores/cm2, which is much lower than the present result for dragonflies. It seems likely that the difference reflects the fact that in Oligoaeshna pryeri the eggs are immersed in water. © 2011 Springer Science+Business Media, LLC.