Temperature Compensation in Antarctic Pteropods: An Integrative Approach

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Life in polar waters requires physiological specialization to overcome thermal limits on reaction processes. The long-standing hypothesis of metabolic cold adaptation, which proposes upregulation of basal and active metabolic rates in polar taxa relative to temperate-zone counterparts, remains contentious and has been taxonomically limited in evaluation to fish and benthic invertebrates. Polar pteropods (Mollusca: Gastropoda) represent an abundant and metabolically active taxon with potentially substantial thermal compensation of the physiological processes underlying locomotion. This research will examine metabolic cold adaptation in two pteropod taxa, with particular reference to the thermal dependence of locomotor performance. Hypotheses of cold adaptation will be tested by comparing representative temperate zone and polar species and by evaluating possibly coordinated thermal compensation of metabolic, biomechanical and neural underpinnings to locomotor behavior. The proposed research comprises three parts: 1) comparison of basal and metabolic rates of sister pteropod species from polar and temperate zones, together with comparisons of mitochondrial energetics; 2) comparison of locomotor biomechanics for the same pteropod taxa, with particular reference to the differential effects of reduced temperature and concomitantly increased viscosity on locomotor performance and 3) comparison of the responses of swim system neurons to variable temperatures, with particular reference to resting potentials, firing thresholds, action potential durations and ion channel kinetics. The overall hypothesis of temperature compensation in polar pteropods will be tested by evaluating similarities and linkages in metabolic, biomechanical and neural responses to variable water temperature. This research will provide fundamental physiological and behavioral information for this taxon, will systematically evaluate the hypothesis of cold adaptation across organizational levels in pteropods, and more generally will evaluate the nature of thermal and locomotor constraints for the many invertebrate taxa living and moving within polar waters.