Buccal oscillation in the aquatic turtle Platysternon megacephalum

DRUZISKY, K.*; BRAINERD, E.L.: Buccal oscillation in the aquatic turtle Platysternon megacephalum

Buccal oscillation has been demonstrated in all major groups of vertebrates except mammals (Brainerd, 1999). Using blowhole pneumotachography and video, we examined above-water buccal oscillations in an aquatic turtle, Platysternon megacephalum. In this study, we were able to distinguish between oscillation and ventilation based on tidal volume and sequence of exhalation and inhalation phases. The mean tidal volume for oscillations was found to be about 1/5 the tidal volume of lung ventilation. For ventilation, we recorded expiratory tidal volumes of 6.251 �0.85ml air, 5.645 �0.802 ml air, and 6.523 �0.829ml air for three individuals respectively. The oscillatory tidal volumes recorded were 1.315 �0.4931ml air, 1.208 �0.439 ml air, and 0.953 �0.569ml air. Oscillations also occur as inspiration/expiration sequences in contrast to the expiration/inspiration sequence of ventilation. Through simultaneous measurement of hyoid depression and airflow, we see a temporal correlation between hyoid movement and airflow during buccal oscillations and also a small hyoid depression at the start of respiratory exhalation. In examining the relationship between oscillatory and ventilatory events, preliminary data suggest that the two behaviors are independent with no fixed phase relationship. We have found that ventilation often interrupts the expiratory phase of oscillation thus overlapping the two behaviors. The data show ample variation in the pattern and individual volumes of oscillations with periods of large continuous oscillation interspersed with few breaths and periods of smaller oscillation more equally dispersed among breaths. Periods of ventilation only were recorded as well. The variation suggests the possibility of multiple functions of buccal oscillation.

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