Meeting Abstract
The tenrec, Tenrec ecaudatus, also known as the tailless tenrec, is a basal endothermic mammal resident in Madagascar. The animal’s basal status is emphasized by poor temperature regulation and anatomical plesiomorphisms including a cloaca. During the austral winter, they enter into a state akin to hibernation in 1-2m long burrows plugged with soil. We measured O2 consumption, CO2 production, respiratory exchange ratio, evaporative water loss, position and activity in the X and Y planes using a Promethion-C continuous metabolic phenotyping system, plus cutaneous temperature, at ambient temperatures ranging from 11-26°C at intervals of approximately 1 to 2° C for 24 hours in nominally hibernating tenrecs (body mass range 180-450 g, N = 7-8 at each temperature). The animals spontaneously aroused more frequently at higher temperatures, but the arousal duration was typically less than 20-40% of the 24 hour recording; thus we were able to obtain good hibernation data. The tenrecs were capable of basic ambulatory activity when their heart rate was < 30 BPM and their body temperature was practically indistinguishable from ambient temperature, even at 11° C. The temporal structure of the metabolic records during hibernation was anomalous and reminiscent of the insect DGC. Periods of apnea, or near-apnea, lasted approximately 15-30 minutes across the temperature range up to 20° C, interrupted by discontinuous gas exchange corresponding to a few breaths. Metabolic rates (Q10 of 3.0 across the temperature range) were exceedingly low. We hypothesize that this unusual ventilatory strategy may be adaptive in hypercapnic, hypoxic underground conditions (cf. the “chthonic hypothesis”).
