Experimental Manipulation of Egg Size and Hatchling Size in the Cobra, Naja Naja Atra (Elapidae)

Abstract

We experimentally manipulated eggs of Naja naja atra by partially removing yolk (approximately 15% of the total egg wet mass) from the freshly laid eggs to test the effect of such a manipulation on hatchling traits. Hatchlings from treated and control eggs took nearly the same time to complete embryonic development. Experimentally treated eggs produced size-reduced hatchlings. However, when shell excluded egg mass is statistically kept constant miniaturized hatchlings had slightly but significantly larger total dry body mass than did their control sibs. Relatively more yolk remained unutilized at the time of hatching in miniaturized hatchlings. Since no significant difference in body size or carcass size was found between miniaturized and control hatchlings when shell-excluded egg mass is kept constant, the difference in residual yolk dry mass explained much of their difference in dry body mass. The relative difference in residual yolk dry mass also explained much of the difference in lipid mass, energy contents and residual yolk ash mass between miniaturized and control hatchlings.