P,p′-DDE-induced changes in the organic and inorganic structure of eggshells of the Mallard, Anas platyrhynchos

Abstract

Scanning electron microscopic examination of decalcified and inorganic preparations of Mallard ( Anas platyrhynchos) eggshells showed that dietary p,p′-DDE induced significant and consistent changes in both the organic and inorganic constituents of the eggshell. The numbers of mammillary cores, structures composed of organic knobs which serve as crystallization sites on the outer surface of eggshell membranes, as well as the numbers of basal caps, were reduced by dietary p,p′-DDE in eggshells which also showed a reduction in shell thickness. Polychlorinated biphenyls induced a lesser but significant reduction in the numbers of mammillary cores; a comparable decrease in numbers of basal caps was not found to be statistically significant with the sample sizes used. Effects of a diet containing both DDE and PCB were equivalent to those of DDE. Thickness of eggshells from mallards maintained on the PCB diet was equivalent to that of the controls. The reduction in the number of mammillary cores may therefore occur independently of the DDE-induced eggshell thinning. The density of mammillary cores on the eggshell membranes was found to be linearly related to the density of basal caps.