Nutritional Provision of the Yolk of Two Species of Viviparous Reptiles

Abstract

Recently ovulated eggs and newborn of two species of viviparous reptiles, Gerrhonotus coeruleus (Sauria: Anguidae) and Nerodia rhombifera (Serpentes: Colubridae), were analyzed for organic (nitrogen, lipid) and inorganic (total ash, sodium, potassium, calcium, magnesium) content. Eggs contain 41%–48% water, 46%–56% organic matter, and 3%–5% inorganic salts. Total protein (based on measurement of nitrogen) is higher in egg yolk than total lipid. Analysis of the composition of newborn indicates that eggs of both species gain water and lose dry mass during development. Most of the dry mass loss is a reduction in amount of lipid, presumably due to catabolism. There was no substantial change in total nitrogen in newborn compared to yolk. There was evidence of an extravitellogenic source of mineral ions in both species. Newborn G. coeruleus have a substantially higher ash content than recently ovulated eggs. Although total ash was not higher, newborn N. rhombifera contain more sodium and potassium than eggs. Transplacental transfer of inorganic material occurs in both species but to a greater degree in Gerrhonotus than Nerodia.