Images courtesy of: Wikimedia Commons

How does the turtle lung compensate for buoyancy while storing oxygen?

 

It is interesting to find that the green sea turtle lung is able to function in its complexity while maintaining buoyancy control. The control of buoyancy is accomplished through lung volume regulation. "The turtle lung may serve a dual role as both an oxygen store and in buoyancy control" (Hays, 2004). Green sea turtles are able to submerge to extreme depthes while still maintaining a neutral buoyancy. "For turtles diving up to the maximum depth at which they can still use their lungs to attain neutral buoyancy, the total oxygen store will increase greatly with dive depth, and hence a corresponding increase in dive duration is predicted" (Hays, 2004). Yet, due to the fact that the green turtle is reptilian, it is possible that its surfacing to breathe may compromise its ability to achieve maximal oxygen storage for diving and the minimilization of the cost of swimming. Interestingly, to maximize oxygen store in anticipation of deep diving and obtaining neutral buoyancy, "a larger presubmergence inspiration is required, i.e. the oxygen stores will increase on deeper dives"(Hays, 2004). Moreover, the green turtle has developed a system in which the lung bears the weight of oxygen contol during descension. Essentially, the lungs are compressed as the green turtle dives deeper. As the green turtle descends, "they will lose buoyancy as the lunngs are compressed, until, at a certain depth, they become neutrally buoyant" (Hays, 2004). According to Hays, the maximum depth for bouyanncy (MDNB) is defined as "the depth at which a turtle attains neutral buoyancy after diving with fully inflated lungs".

 

How does lung regulation and buoyancy control vary during breathhold diving?

Once again, the green turtle's ability to tolerate time elapsed without exhalation is due to the regulation of the lungs at varying depths. According to (Lutz, 1985), the airway design of the sea turtle lung guarantees that only a single breath will suffice and is able to provide almost complete release and filling of air in the lung. Logically, lung regulation and buoyancy control vary during breathhold diving at different depths. Due to the green turtles ability to harvest a rapid flow rate, "ventilation and tidal volumes exceeding 50% of total lung capacity" (Tenney, 1974); the sea turtle is able to efficiently and rapidly renew lung oxygen storage, faciliting aerobic dives. Thus, green sea turtles are able to compensate and adjust buoyancy control at varying dive depths through its display of going "beyond full depletion of blood and lung oxygen stores" (Berkson, 1996). Essentially, buoyancy control is dependent upon lung regulation.

 

 

 

 

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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