Mechanics of respiration in the snapping turtle, <i>Chelydra serpentina</i> (Linné)

Abstract

Abstract The mechanism of lung ventilation in chelonians has been much debated. Electromyographic studies show that the basic mechanism in the snapping turtle, Chelydra serpentina , is dependent on the activities of four major respiratory muscles that are capable of varying the volume of the visceral cavity. The precise mechanism utilized varies in response to environmental factors, especially the depth to which the animal is submerged. Chelydra tends to reduce muscular activity to a minimum, and hydrostatic pressure or gravity replaces muscular effort whenever possible. The response is subject to hysteresis. Both the mechanics and pattern of ventilation in Chelydra differ from those of Testudo . The differences appear to be attributable in part to Chelydra's markedly reduced plastron and more extensive respiratory musculature and in part to the different habitats occupied by the two species.