Egg Comparisons and Volume Estimation Methods Between the Common Musk Turtle (Kinosternidae: Sternotherus odoratus) and the Texas Tortoise (Testudinidae: Gopherus berlandieri)




Nelan, Jane B.

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Egg volume, extensively studied in birds, has been largely overlooked in reptiles. This measurement is a valuable estimator of fresh egg weight, which could predict multiple physiological parameters. Morphological constraints of adult female turtles on egg size, shape and number result in production of a broad range of shapes and sizes. Eggs of Sternotherus odoratus and Gopherus berlandieri were used to determine the most accurate method of volume estimation alongside shape and size comparisons among species. Dimensional measurements of Kinosternon flavescens eggs were used for comparative purposes to Sternotherus. The most accurate method of volume estimation in Sternotherus was the ellipsoid formula (Iverson and Ewert, 1991), but the bicone method best approximated Gopherus egg volume (Preston, 1974). The elongation factor, a measure of increased cylindrical length, was 1.7 in Sternotherus compared to an index of 1.2 in Gopherus, thus quantifying the nearly round aspect of Gopherus eggs. When compared to Kinosternon, eggs of Sternotherus differed only in diameter; eggs of these species did not statistically differ in length or volume. Kinosternon produces eggs comparable in individual size and volume to eggs of Sternotherus, but is capable of producing more eggs per clutch resulting in a greater clutch volume.



turtles, kinosternidae, Texas tortoise


Nelan, J. B. (2001). Egg comparisons and volume estimation methods between the common musk turtle (Kinosternidae: Sternotherus odoratus) and the Texas tortoise (Testudinidae: Gopherus berlandieri) (Unpubilshed thesis). Southwest Texas State University, San Marcos, Texas.


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