EGG components and reproductive characteristics of turtles: relationships to body size

Abstract

Components of eggs and the relationships of reproductive variables to body wet mass and plastron lengths of females were studied in 12 species of turtles. Individual egg size and clutch mass increased with body size among species, but the ratio of clutch wet mass/body wet mass decreased with body size. Within some species, clutch size, clutch mass, and individual egg mass increased with body size of females. No direct evidence was found for the egg size to clutch size tradeoff predicted in optimal egg size theories. The shell comprised 40.8% of total dry mass of eggs with brittle shells compared to 19.3% for eggs with parchment shells. Lipids averaged 31.1% of the dry mass of eggs (with shells removed) in species with hatchlings that overwinter on land and 24.3% in species that are known to have hatchlings that do not overwinter on land. Lipids make up 33% of the dry mass of the contents of brittle-shelled eggs and 26% of the dry mass of parchment-shelled eggs. No other distinct groupings of turtle eggs, based on their lipid fractions, were found. Provisioning of young with varying amounts of reserve yolk to meet different posthatching situations may explain some interspecific variation in lipid levels in turtle eggs.