VARIATIONS IN THE BLOOD CHEMISTRY OF 

 THE LOGGERHEAD SEA TURTLE, CARETTA CARETTA 



Peter L. Lutz and Ann Dunbar-Cooper^ 



ABSTRACT 



The natural blood chemistry profile of loggerhead sea turtles living in Cape Canaveral waters was deter- 

 mined over a 3-year period. Overall plasma osmotic pressure, potassium, and magnesium values were 

 similar to those reported for other reptiles, sodium and chloride was much less than for sea snakes. Plasma 

 calcium and glucose values were among the lowest of any reptile. Osmotic pressure, sodium, and potassium 

 values increased during the warmer months. Chloride and in particular magnesium, glucose, and 

 hematocrit levels were comparatively constant. Calcium and urea values showed wide variations but no 

 seasonal trend was apparent. Changes in urea concentrations closely tracked those of osmotic pressure. 

 Blood lactate values from trawl-captured sea turtles were 10-80 times higher than those from quiescent 

 sea turtles and calculations suggest that at least 20 hours is required for full recovery. The complex 

 changes in blood chemistry observed reflect changes in the sea turtle physiology and biochemistry; signifi- 

 cant changes from normal in plasma magnesium, potassium, and hematocrit could be useful indicators 

 of hibernation in sea turtles. 



For any animal a knowledge of the normal pattern 

 and changes in blood chemistry can be related to its 

 physiological state and can also be used to identify 

 chronic and pathological conditions. With the excep- 

 tion of sea turtles, there are many studies and 

 reviews on seasonal changes in the blood chemistry 

 of reptiles (Dessauer 1970; Duguy 1970; Gilles- 

 Baillien 1974; Minnich 1982). Since there is an 

 urgent need to understand the ecological physiology 

 of these endangered and threatened species, this 

 lack of information on sea turtles is undoubtedly due 

 to the logistical difficulties of long-term sampling 

 of a wild marine population. 



The year-round presence of large numbers of 

 loggerhead sea turtles, Caretta caretta, in and 

 around the Port Canaveral ship channel provided 

 a rare opportunity to study the monthly changes 

 that occur in the biology of this little understood 

 group of animals. Such a study was rendered all the 

 more urgent by finding, in the winter of 1978, num- 

 erous black stained and apparently torpid turtles 

 lodged in the mud of the ship channel (Carr et al. 

 1980). It was suggested that the loggerhead sea 

 turtle was able to survive prolonged exposure to cold 

 seawater temperatures (less than 15°C) by partial- 

 ly lodging in the mud at the bottom of the Port 

 Canaveral ship channel and by going into a state of 

 winter dormancy or apparent hibernation (Carr et 

 al. 1980; Ogren and McVea 1982). If this hypothe- 



^Rosenstiel School of Marine and Atmospheric Science, 4600 

 Rickenbacker Causeway, Miami, FL 33149. 



Manuscript accepted October 1986. 

 FISHERY BULLETIN: VOL. 85. NO. 1. 1987. 



sis were correct, it would mean that the Cape 

 Canaveral ship channel was serving as a hibernacu- 

 lum for this endangered species and the identifica- 

 tion of features that could confirm hibernation in 

 these loggerhead sea turtles was of some practical 

 importance. For this purpose, a study of blood chem- 

 istry is particularly apt. There is abundant evidence 

 of significant changes in certain blood constituents 

 in hibernating mammals (Fisher and Manery 1967; 

 Soivio and Kristoffersson 1974; Al-Badry and Taha 

 1983) and there are a few studies showing similar 

 changes in some reptiles (e.g., freshwater turtles, 

 Hutton and Goodnight 1957; lizards, Haggag et al. 

 1965). 



The purpose of this study was to establish the nor- 

 mal seasonal changes in blood chemistry that occur 

 throughout the year in the Cape Canaveral popula- 

 tion of loggerhead sea turtles and from this base of 

 data to identify, if found, those animals that are in 

 a state of hibernation. 



METHODS 



Selected National Marine Fisheries Service 

 (NMFS) shrimp trawl turtle surveys of the Port 

 Canaveral ship channel were accompanied by the 

 authors from December 1978 to August 1982. On 

 board ship the activity levels of newly caught logger- 

 head sea turtles were observed, and body tempera- 

 ture, weight, and sex recorded. Blood samples were 

 taken from freshly captured sea turtles, using a 

 heparinised syringe, from a venous sinus on the 



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