The social transmission of disease between adult male and female reproductives of the dampwood termite Zootermopsis angusticollis

Abstract

The susceptibility of adult male and female dampwood termites (Zootermopsis angusticollis) to an infection carried by a mate was studied by exposing dealates to a 4 × 107 or a 6 × 104 spores/ml solution of the fungus Metarhizium anisopliae. Following exposure to spores, male and female dealates were paired randomly in four treatments: (1) male and female exposed to spores; (2) male exposed to spores/female exposed to a control solution lacking fungal spores; (3) male exposed to a control solution/female exposed to spores and (4) male and female exposed to a control solution. Males and females exposed to 4 × 107 spores/ml acquired and transmitted the infection to their unexposed mate, and had significantly lower survival relative to controls. When males and females were exposed to 6 × 104 spores/ml, however, there were no significant differences in survivorship among the four treatments. Therefore, at the lower pathogen load, dealates were able to control infection. To compare the susceptibility of exposed adults in the absence of social interactions, the survivorship of male and female dealates maintained in isolation following exposure to the lethal spore concentration (107 spores/ml) was recorded. Male and female adults maintained in isolation had 1.5 times the hazard ratio of death of paired adults, suggesting that mate allogrooming and other social exchanges decreased disease susceptibility.