Changes in plasma levels of adrenaline, noradrenaline, glucose, lactate and CO₂ in the green turtle, Chelonia mydas, during peak period of nesting

Plasma concentrations of stress hormones [adrenaline (ADR), noradrenaline (NR)], lactate, glucose and CO₂ were monitored during peak nesting period (May-October) at different phases of nesting in the green turtle, Chelonia mydas. These include, emergence from sea, excavating body and nest chambers, oviposition, covering and camouflaging the nest and then returning to sea. Turtles that completed all phases of nesting including oviposition before returning to sea were considered "successful" turtles, while those that completed all phases but failed to lay their eggs were "unsuccessful". Blood samples were taken from the cervical sinus within 5 min of capture to avoid stress due to handling. The turtles were usually sampled for blood between 20:00 and 1:00 h of nesting time to ensure uniformity in the sampling. Plasma ADR and NR values were highly significant (P < 0.001) in successful turtles over emergence, excavating and unsuccessful turtles. Plasma glucose levels remained stable throughout the nesting phases while lactate levels were significantly higher in successful turtles over the other phases (P < 0.05) which signifies anaerobic metabolism during nesting. Plasma CO₂ values were negatively correlated with ADR and NR (r = -0.258, P = 0.03; r = -0.304, P = 0.010), respectively. Hematocrit was significantly higher in successful phase (P < 0.05) compared to other phases, and this may signify a higher degree of stress in successful turtles. Body temperature were significantly lower (P < 0.005) in the excavating phase compared to the other three phases. Overall, body temperatures were lower than sand temperatures around the nest, which may indicate a behavioral thermoregulation used by the turtles during nesting. This information will be of value to the ongoing conservation program at Ras Al-Hadd Reserve in the Sultanate of Oman.