Water balance and nutrient procurement of Sarcoptes scabiei var. canis (Acari: Sarcoptidae).

Abstract

Sarcoptes scabiei var. canis were unable actively or passively to sorb sufficient water vapor from unsaturated air to compensate for water loss in spite of an active uptake mechanism. Maintenance of water balance in this mite is supported by its location at the dry stratum corneum–stratum lucidum and stratum granulosum interface by its ingestion of intercellular fluid that oozes into the burrow or around the mouth parts. Water loss rate constants for females were 20.6–23.8% h−1 (per hour) at 97% RH and ranged from 4.9 to 6.2% h−1 at 75 and 22% RH. Rate constants for uptake of tritiated water and approach of equilibrium tritiated body water content for males and females were independent of relative humidity and ranged from 8.55 to 12.4% h−1. Fast water loss and uptake rates, uptake rate constants independent of relative humidity, and the observation that isolated mites produce an external fluid secretion suggest that these mites actively gain water by ingesting a hygroscopic solution. However, this process is not adequate to fully compensate for water loss.