Moisture requirements of a soil imperfect fungus,Scopulariopsis brevicaulisBainier, in relation to its tick host

We report heightened dehydration in ticks, Dermacentor variabilis (Say), parasitized by a ubiquitous fungus common in soil, Scopulariopsis brevicaulis. Ticks harboring this fungus had greatly accelerated net water loss rates (nearly twice as high compared to controls), and were unable to absorb water vapor from hydrating relative humidities. Parasitism did not alter tick water content and dehydration tolerance. Mortality was attributed to water losses that reached the dehydration tolerance limit of the tick. Because of the impact of S. brevicaulis on tick water balance, varying levels of infection of this fungus may alter the water balance profile, thereby restricting ticks to specific environments. Thus, this is the first study to propose that a naturally occurring fungus may influence the distribution of D. variabilis.