Anoxia tolerance and recovery in freshwater and marine turtles

Anoxia tolerance and recovery in freshwater and marine turtles were investigated. This study quantified several factors thought to influence anoxia tolerance and recovery, including body size, feeding history, season, the turtle\u27s sex, and repetitive entrapment. In Chrysemys picta bellii, body size had little effect on anoxic metabolism, although small turtles regained normal behavior more rapidly and exhibited no lag in lactate clearance. Feeding history also had little effect on anoxia tolerance, but turtles that had recently fed recovered more slowly than fasted animals. There were no differences between the sexes in anoxia tolerance; however, females recovered faster behaviorally. The lack of influence of these factors suggests that, during anoxia, they are suppressed. In contrast, season had a profound effect on anoxia tolerance and recovery in freshwater turtles. Turtles that had recently emerged from hibernation were energetically compromised during anoxia and their recovery was significantly slower than for pre-hibernation turtles. Comparisons of liver tissue between fall Chrysemys picta picta and fall C. p. bellii reinforced the finding that fall animals are not energetically compromised and that the subspecies of C. picta are well adapted for hibernation. Simulated entrapment of sea turtles revealed that Chelonia mydas was unable to tolerate even 2 hr submergence, probably due to an inadequate energy supply during anoxia, perhaps exacerbated by stress. Body size had no measurable effect on the blood chemistry parameters examined, but anoxia had a significant impact on the behavior of small sea turtles. Repetitive entrapment did not affect anoxia tolerance because the five-day inter-capture period was likely too long to reinforce stress reactions. Behaviorally, both freshwater and sea turtles responded stereotypically during submergence and recovery, but because of their greater capacity to withstand anoxic conditions, it appears that freshwater turtles are a poor physiological model of anoxia tolerance for sea turtles. Observations of sea turtle behavior will provide a guide for recovering animals incidentally captured in fishing gear. Turtles should be held on deck and kept moist until they show coordinated flipper activity before being returned to the water. Animals put overboard before this point will probably not survive