Mass Scaling of Standard Metabolism in Ticks: A Valid Case of Low Metabolic Rates in Sit-and-Wait Strategists

Abstract

Ticks can survive for a year or more between blood meals, making them the ultimate sit-and-wait strategists. We accordingly hypothesize that their standard metabolic rates (SMRs) are unusually low. We test this hypothesis by measuring the SMRs of several tick species and comparing them with modern literature values for other arthropods (ants, beetles, and spiders). By ANCOVA ants, beetles, and spiders share a common mass scaling of SMR (SMR = 906 $BM^{0.825}$, where SMR is in microwatts at 25° C and BM is body mass in grams). Previous investigations suggesting low SMRs in spiders utilized a questionable yardstick equation relating SMR to BM in arthropods. Ticks, in contrast, are shown by ANCOVA to have genuinely low SMRs-12% of the predicted value for ants, beetles, or spiders of equivalent BM. We hypothesize that this low SMR is caused by an atjpically low ratio of actively respiring tissue (ART) to BM. We hypothesize further that this low ART/BM ratio results from maintaining metabolically near-iner...