Stabenau and Vietti: The physiological effects of multiple forced submergences of Caretta caretta 



897 



It must be noted that any discussion on lactate produc- 

 tion and recovery following submersion is applicable to 

 environmental conditions comparable to those reported 

 in this study. For example, lactate formation and recovery 

 rates of lactate build-up would be significantly influenced 

 by water temperature. Longer recovery rates may take 

 place in cold water, whereas warmer waters may lead to 

 additional lactate production thereby influencing the rate 

 of lactate elimination. In addition, the blood lactate con- 

 centrations measured in this study may underestimate the 

 true lactate burden. Lactate has been shown to partition 

 into other tissues, including the shell, following submer- 

 sion of freshwater turtles (Jackson et al., 1999). Finally, 

 sea turtle size could potentially alter lactate production 

 and elimination. Results from submersion experiments 

 conducted in our laboratory indicate that smaller animals 

 exhibit a significant acidosis and lactate build-up in com- 

 parison to larger sea turtles. Whether less acidosis and 

 lactate build-up is due to additional lactate buffering by 

 the larger sea turtles warrants further investigation. 



Ions, osmolality, and hematocrit 



There are three primary mechanisms for recovery of blood 

 pH following an acid-base disturbance: cellular buffer- 



ing, and respiratory and renal compensation. Cellular 

 responses occur immediately following the disturbance, 

 whereas respiratory and renal adjustments occur within 

 minutes to hours, respectively. Previously, Stabenau et al. 

 (1991) reported that Kemp's ridley sea turtles exhibited 

 a significant increase in plasma [K+] following trawl sub- 

 mergences. However, those authors reported that trawl 

 stress had no effect on plasma [Cli, [Na+], or hematocrit. 

 In the present study, a cellular response to the severe 

 acid-base disturbance caused by the multiple forced 

 submergences was suggested by alterations in plasma 

 ion concentrations, osmolality, and hematocrit during the 

 blood acidosis. As shown in Figure 3, decreases in blood 

 pH were correlated with increases in [K*], [Na*l, [CI"], 

 osmolality, and hematocrit. 



Hematocrit (percent packed red blood cells) changes may 

 result from washout of additional red blood cells into the 

 bloodstream, from areas such as the spleen, in order to pro- 

 vide more red blood cells during the hypoxic phases of the 

 forced submergence. This explanation, however, is unlikely 

 given that substantial fluctuations in hematocrit were ob- 

 served during the course of the submergence experiments 

 and that a normal hematocrit was measured in the final se- 

 rial blood sample. A more plausible explanation is that there 

 was an osmotically obliged influx of water into the red blood 



