Differences in development time, mortality and water loss between eggs from laboratory and wild populations of Dermatophagoides pteronyssinus (Trouessart, 1897) (Acari: Pyroglyphidae)

A total of four microcultures of adults of Dermatophagoides pteronyssinus, two each from laboratory and wild populations, were fed on separate diets of house dust and yeast granules. A total of 35 eggs of known age from each of the four microcultures were harvested and incubated at 15°C, 60% RH for 16 h/day and 30°C, 75% RH for 8 h/day to simulate diurnal microclimatic fluctuations in a bed. Eggs from females fed on yeast were larger and underwent more rapid rates of water loss, estimated by measurements of reduction in visible surface area (VSA), than eggs from females fed on house dust. There were no significant differences in mean egg development time between the four microcultures (range 6.0-6.88 days). Mortality of the eggs was as follows: from laboratory females fed on yeast, 31.4%; laboratory females fed on house dust, 11.5%; wild females fed on yeast, 2.9%; wild females fed on house dust, 0%. Thus diet and egg size at oviposition had no effect on mortality. Since the microclimates at which eggs from both populations were oviposited and incubated were identical, it is hypothesized that mortality was higer in eggs from laboratory cultures because the mites had become acclimated to the optimal conditions at which they had been kept and were less able to withstand the diurnal fluctuations in microclimate, similar to those imposed upon wild mites in their natural habitats.