Chorion Structure of Diapause and Subitaneous Eggs of Four Diaptomid Copepods (Calanoida, Diaptomidae): SEM Observations
Scanning electron microscopic examination of diapause eggs of freshwater Calanoida Hemidiaptomus amblyodon Marenzeller, Eudiaptomus vulgaris (Schmeil), E. graciloides (Lilljeborg) and subitaneous one s of E. gracilis (Sars) is described. The chorion surface ornamentation and number of coated layers are revealed. Diapause eggs have a thick (0.6-4.8 μ), at least two-layered chorion with patterned surface, whereas subitaneous eggs have a thin (0.13-0.25 μ), single-layered chorion with smooth surface. The mean number of eggs in egg sac, diameter of eggs and thickness of chorion were measured. The significance of the egg chorion thickness for diaptomid species inhabited temporary and/or permanent water-bodies is discussed.