Image courtesy of: ThinkQuest

 

Pulmonary-function of the green sea turtle

The green sea turtle exhibits many cardio-pulmonary advantages for deep diving. These characteristics include: "large tidal volume relative to functional residual capacity which promotes fast exchange of the aleveolar gas when the turtle surfaces for breathing; and the concomitant rise of pulmonary blood flow and oxygen uptake with temperature assures efficient oxygen transport regardless of wide temperature variations encountered during migrations" (Gatz, 1987) Thus, pulmonary-function in sea turtles plays an integral role in respiratory regulation and the transport of oxygen. When considering oxygen uptake and ventilation, the green sea turtle seems to decrease pulmonary gas exchange due to breathholding, in turn increasing carbon dioxide retention, maximizing the green sea turtle's ability to tolerate anoxia. Furthermore, pulmonary blood flow and ventilations increase equally with body temperature. According to Gatz, "this accounts for a nearly constant pulmonary arteriovenous oxygen content difference (Gatz, 1987). This may lead to the conclusion that large tidal volumes in green sea turtles facilitate the turtle's ability to tolerate time elapsed without exhalation. Therefore, with low exhalation volume of the lungs, the green sea turtle is able to renew lung gas rapidly with a single breath. Due to this pulmonary shunting of blood in green sea turtle's, cardiac output may extend aerobic dive duration (Krosniunas, 2003). In turn, green sea turtles are more well adapted for swimming, revealing that swimming and deep diving arouse more cardiovascular response than any other activity.

How does oxygen uptake and oxygen-content affect heart rate in different activities?

Images courtesy of: Wikimedia Commons

Since the green sea turtle is able to combine blood oxygen properties, they are able to deplete oxygen from the lung, showing that cardiovascular responses are facilitated by cardiac shunts during swimming and diving. Yet, cardiovascular impact is dependent upon the activity of green sea turtles. That is, walking seems to have a greater impact on heart rate than swimmin, alluding to the conclusion that walking as opposed to swimming, requires more in aerobic demand. " In green sea turtles, the aerobic cost of walking has been found to be two to three times greater than the cost of swimming" (Prange, 1977). Thus, the affects of oxygen uptake and oxygen-content on heart rate, is dependent among th green sea turtles activity, whether it be swimming, diving, or walking.

 

When a green sea turtle is swimming, how do cardiovascular and respiratory mechanisms coalesce?

Image courtesy of: Wikimedia Commons

The cardiovascular and respiratory mechanisms coalesce in green sea turtles by creating a system in which there are checks and balnces. The circulatory system provides the cardiac, or vascular shunts in areas needing more oxygen, while the lungs transport and store this oxygen to maximize aerobic expenditure in turtle acitivity. In turn, the redistribution of blood either toward or away from the lungs, is in tandem with and reliant upon the breathing pattern of the turtle. In effect, a "blood-air barrier" exists in the green sea turtle, which perfectly displays the combining properties of both cardiovascular and respiratory mechanisms. The blood-air barrier is essential for gas exchange in the green turtle. " Each capillary projects markedly into the alveolar lumen, an arrangement which would allow a greater area of capillary wall to be exposed to the air and hence facilitate gaseous exchange" (Solomon, 1984). Thus, respiratory mechanisms and cardiovascular mechanisms converge in the green sea turtle, composing a complex system which help to facilitate gas exchange,the shunting of blood to various tissues to satisfy the aerobic demand of varied activities, and excessive breathhold.

 

This project was created as a part of a class project in the Animal Physiology class in the

Department of Biology at Davidson College

E-mail questions to: snreid@davidson.edu

 

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