Comparative morphology and allometry of select extant cryptodiran turtle kidneys

Abstract

Reptile, avian, and mammalian species all possess a metanephric kidney to maintain fluid homeostasis. The physiology of the kidney is intimately related to tissue organization and gross morphology, which is dependent upon organ size, animal habitat, and body plan. Reptiles have significant variations in body plan and as a result have differences in visceral organ placement and morphology. One organ that appears to show great morphological variation is the reptilian kidney found in Crocodylia, Testudines, and Squamata (Sauria and Ophidia). However, limited research has been conducted to evaluate and compare kidney morphology in reptiles and more specifically, in turtles. Here we have examined multiple cryptodiran turtle species from the families Chelydridae, Emydidae, Kinosternidae, and Trionychidae. Detailed descriptions of kidney morphology along with comparative allometry are provided. Significant differences in external renal morphology were found between and within turtle families as well as differences in scaling of kidney mass with body mass. Our study provides a foundation for understanding differences in organ development and tissue architecture as well as potential differences in physiology.