Thermoregulation in the African side-necked Terrapin, Pelomedusa galeata.
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Date
2014
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Abstract
Ectotherm body temperature (Tb) is influenced by the thermal environment, thus maintaining stable Tb requires adjustments to physiological and behavioural thermoregulation. There is an abundance of literature on thermoregulation in reptiles, however, little is known about the thermoregulatory behaviour of the recently taxonomically resurrected semi-aquatic, African side-necked terrapin, Pelomedusa galeata. Adult (n = 17) and hatchling (n = 16) P. galeata were evaluated for preferred body temperature (Tpref), set point range temperature (Tset) and associated thermoregulatory behaviours. Wild adult terrapins were captured and implanted with temperature data loggers (Thermochron iButton®, Dallas Semiconductor, Texas, USA), and observed for basking behaviour in a semi-natural environment. Captive bred hatchlings (neonates and yearlings) were evaluated for Tpref, Tset and thermophilic responses to an aquatic thermal gradient. All experiments were carried out in the Animal House, at the University of KwaZulu-Natal, Pietermaritzburg, South Africa. Adult Tb was weakly correlated with mass and ambient air temperature (Ta) in winter and only Ta in summer. Adults basked most frequently in summer and basking behaviours differed between seasons. Basking at the water surface in full sun was observed most often during summer and out the water in full sun during winter. Hatchling Tb was highly correlated with aquatic thermal gradient temperature (Tag), and was higher than acclimation temperature. Neonate and yearling Tpref were not significantly different and mass affected relocation between Tag sites. Adult P. galeata displayed ‘cooling’ behaviours during hot periods in summer and ‘warming’ behaviours during cold periods in winter, and Ta and Tb were good predictors for P. galeata thermoregulatory behaviour. Hatchling P. galeata are highly sensitive to the thermal environment. They selected for high Tb although this may not be possible in natural environments, owing to increased predation risk while basking at exposed sites. In light of increasing global temperature, P. galeata will be relatively unaffected by higher temperatures by making adjustments to basking behaviour to maintain Tpref. General climate change, however, may change the landscape and water bodies P. galeata depend on, thus affecting distribution and survival. Empirical data from species-specific studies contribute to the knowledge required for implementing conservation measures.
Description
M.A. University of KwaZulu-Natal, Pietermaritzburg 2014.
Keywords
Animal heat., Turtles -- Physiology., Cold-blooded animals -- Physiology., Theses -- Ecology.