Standard and exercise metabolism and the dynamics of gas exchange in the giant red velvet mite, Dinothrombium magnificum

Abstract

Although many adult insects and adult, unfed ticks are known to exchange respiratory gases discontinuously, the respiratory physiology of other tracheate arthropods is almost unknown. In this paper we present data to test hypotheses on the gas exchange dynamics, standard metabolic rate (SMR, as a function of body mass and temperature) and activity metabolism of the giant red velvet mite Dinothrombium magnificum, which according to published accounts is a predator on termites and may forage for only a few hours every year. External gas exchange in D. magnificum is continuous, unlike the case in ticks, and its locomotion energetics are typical of other small arthropods in spite of its unsegmented, flexible exoskeleton. In its aboveground state D. magnificum has a conventional arthropod SMR, disproving our hypothesis that its SMR is low, as is the case with ticks. However, we show by modeling that D. magnificum must enter a tick-like low-SMR state if it is to survive year-long fasts and if our understanding of its ecology is correct.