North American Freshwater Turtles Research Articles

The Comparative Physiology of Diving in North American Freshwater Turtles. II. Plasma Ion Balance during Prolonged Anoxia

Plasma ionic composition was measured during submergence in anoxic water ($P_{O_{2}} < 2 mmHg$) at 10 C of four species of North American freshwater turtles (Chrysemys picta, Chelydra serpentina, Sternotherus odoratus, and Trionyx spiniferus). As we reported in the previous paper, the species rank in the order listed in their capacity to survive prolonged anoxia at this temperature. The objectives of this study were to examine the changes in plasma ions in response to the anoxia and to relate these responses to the overall blood acid-base picture. The qualitatively similar pattern of ionic changes in each species included a primary increase in [lactate⁻] and decrease in [HCO₃⁻]. In addition, there were increases in [K⁺], total [Ca⁺⁺], and total [Mg⁺⁺] and decrease in [Cl⁻]. These latter strong ion changes are interpreted as compensatory changes that served to balance the lactate charge and that were associated with exchanges of weak ions that buffered the H⁺. The overall importance of these ionic changes ...

The Comparative Physiology of Diving in North American Freshwater Turtles. I. Submergence Tolerance, Gas Exchange, and Acid-Base Balance

The responses to prolonged diving in a representative of each of the four families of North American freshwater turtles (Chelydridae, Emydidae, Kinosternidae, Trionychidae) were investigated. For turtles submerged at 10 C in anoxic (N₂-equilibrated) and normoxic (aerated) water, we found: (1) Survival times in anoxia (days) were 2.6 (Trionyx), 5.2 (Sternotherus), 8.5 (Chelydra), and 17.0 (Chrysemys); the corresponding survival times in normoxia were >100, >100, 14.2, and 29.3. The differences between survival in anoxic and normoxic water were significant in all species except Chelydra. (2) The acid-base responses of Trionyx and Sternotherus were similar, apparently as a result of the efficient use of extrapulmonary gas exchange in these species. The lack of such efficient aquatic respiration was evident in both Chelydra and Chrysemys, whose acid-base responses were similar to each other but very different from those of the other species. (3) Buffer capacities ([HCO₃⁻]/pH) of the blood were -8.81 (Chelydra...

Digestive turnover rates in freshwater turtles: The influence of temperature and body size

1. 1. The digestive turnover times (ingestion to defecation) of five species of North American freshwater turtles were examined in the laboratory. 2. 2. Pond sliders ( Pseudemys s. scripta) and painted turtles ( Chrysemys picta) exhibited similar digestive turnover times (61 and 59 hr, respectively) at 25°C. 3. 3. Snapping turtles ( Chelydra serpentina) had a significantly faster turnover time (31 hr) at 25°C, which was considered to be an adaptation for living in a cool, benthic habitat. 4. 4. Single specimens of a loggerhead musk turtle ( Sternotherus minor) and stinkpot turtle ( Sternotherus odoratus) had turnover times of 57 and 49 hr, respectively. 5. 5. Digestive turnover times were inversely correlated with temperature in C. picta between 16 and 34°C ( Y = −3.33 X + 131.53, r 2 = 0.76). 6. 6. Body size and digestive turnover times in P. scripta were not correlated at 25°C.

Comparison of the fatty acid compositions of depot fats from fresh-water and marine turtles

1. 1. The fatty acids of depot fats of three species of Atlantic marine turtles and six species of North American fresh-water turtles have been determined. 2. 2. Dermochelys coriacea was exceptional in having 9·5% lauric acid, possibly replacing palmitic acid. 3. 3. Trans-6- hexadecenoic acid was found only in the marine species. 4. 4. Dermatemys mawi could be differentiated from the other fresh-water species by details of fatty acids indicative of a herbivorous diet.