Bimodal respiration and ventilatory behavior in two species of Central American turtles: effects of forced submergence

Respiratory gas exchange in both air and water was measured at rest and dur ing recovery from forced submergence in the giant Mexican musk turtle (Stau rotypus triporcatus) and the white-lipped mud turtle (Kinosternon leucostom um). Diving and ventilatory behavior were also measured in unrestrained ani mals of each species. Despite large differences in cutaneous surface area, both species exhibited an aquatic (V) over dot(o2) and (V) over dot(CO2) of approximate to 16 and 45%, respectively, with the remainder explained by a erial gas exchange. Aquatic (V) over dot(o2) and (V) over dot(CO2) did not significantly change during forced submergence or during the recovery perio d. Aerial (V) over dot(o2) and (V) over dot(Co2) however, profoundly increa sed after forced submergence in both species and were not significantly dif ferent from resting values until approximate to 60 min following the treatm ent. At rest, K. leucostomum took significantly more breaths per breathing bout than S. triporcatus. This inherent Ventilation pattern in each species remained unaltered following forced submergence. Cutaneous surface area, t herefore, remains a minor component for these two species which rely heavil y on pulmonary gas exchange to recover from forced submergence. (C) 2000 El sevier Science Inc. All rights reserved.