Physiology, pathophysiology and (mal)adaptations to chronic apnoeic training: a state-of-the-art review.

Breath-hold diving is an activity that humans have engaged in since antiquity to forage for resources, provide sustenance and to support military campaigns. In modern times, breath-hold diving continues to gain popularity and recognition as both a competitive and recreational sport. The continued progression of world records is somewhat remarkable, particularly given the extreme hypoxaemic and hypercapnic conditions, and hydrostatic pressures these athletes endure. However, there is abundant literature to suggest a large inter-individual variation in the apnoeic capabilities that is thus far not fully understood. In this review, we explore developments in apnoea physiology and delineate the traits and mechanisms that potentially underpin this variation. In addition, we sought to highlight the physiological (mal)adaptations associated with consistent breath-hold training. Breath-hold divers (BHDs) are evidenced to exhibit a more pronounced diving-response than non-divers, while elite BHDs (EBHDs) also display beneficial adaptations in both blood and skeletal muscle. Importantly, these physiological characteristics are documented to be primarily influenced by training-induced stimuli. BHDs are exposed to unique physiological and environmental stressors, and as such possess an ability to withstand acute cerebrovascular and neuronal strains. Whether these characteristics are also a result of training-induced adaptations or genetic predisposition is less certain. Although the long-term effects of regular breath-hold diving activity are yet to be holistically established, preliminary evidence has posed considerations for cognitive, neurological, renal and bone health in BHDs. These areas should be explored further in longitudinal studies to more confidently ascertain the long-term health implications of extreme breath-holding activity.

Baseline morphometric, haematological and plasma biochemical parameters in free-ranging eastern water dragons (Intellagama lesueurii lesueurii).

OBJECTIVE: The aim of this study was to determine baseline reference data for morphometric measurements and haematological and plasma biochemical parameters in clinically healthy eastern water dragons (Intellagama lesueurii lesueurii), accounting for the variables of season and sex. The clinical objective was to provide clinicians and researchers with baseline reference intervals (RIs) in order to assess accurately the health of a population or individual animals. METHODS: The study group comprised 39 free-ranging eastern water dragons. To monitor seasonal changes in data two study periods were assigned: September-October 2009 (spring) and January-March 2010 (summer). The 18 males and 21 females were captured in the grounds of Taronga Zoo, Mosman (33°50'45'' S, 151°15'20'' E) in Sydney, New South Wales, Australia. Basic morphometric, haematological and plasma biochemical parameters were measured. RIs were generated in accordance with the American Society of Veterinary Clinical Pathology guidelines. Data were analysed for the effects of sex, season and sex-season interactions using restricted maximal likelihood modelling. RESULTS: Reference values were established in eastern water dragons for morphometric data and RIs were generated for haematological and plasma biochemical levels. The study showed seasonal variation in uric acid. Weight, total length, snout-vent length and basophil % showed significant differences according to sex. Sex-season interactions were detected for calcium, monocyte % and total protein (refractometry). CONCLUSION: Multiple parameters exhibited normal physiological variation between season and sex and an interaction between the two factors. These variables need to be considered in the clinical context when interpreting results of haematological and biochemical analyses in eastern water dragons. The RIs established from this population will provide a basis for further studies in both free-living and captive eastern water dragons, and for comparison in clinical cases.

Conflicts between courtship and thermoregulation: the thermal ecology of amorous male garter snakes (Thamnophis sirtalis parietalis, colubridae).

Thermoregulatory behavior is an important component of daily activities for many reptiles, especially for small heliothermic (sun-basking) species that inhabit cold climates. However, the relative costs and benefits of thermoregulation depend on numerous factors, such that reptiles may sometimes accord a low priority to precise control of body temperatures. We observed and radio tracked garter snakes (Thamnophis sirtalis parietalis) in central Manitoba during the mating season (spring). Previous studies on this species have documented precise behavioral regulation of body temperatures during summer. In contrast, the courting snakes that we studied in springtime spent little time in overt thermoregulatory behavior. Body temperatures were extremely variable (both in outdoor enclosures and in the field) despite abundant opportunities for more precise thermal control. These small elongate reptiles cool so quickly (relative to the time periods needed for effective courtship) that any benefit to higher body temperatures would be transitory at best. Experiments show that hotter males are no better at obtaining matings or at detecting predators. Thus, male garter snakes concentrate on courtship rather than on basking. In the face of conflicting priorities, reptiles may often forgo precise thermoregulation because its benefits are too low, and its costs too high, compared with alternative behaviors.