Desiccation tolerance of Muellerius cf. capillaris (Nematoda: Protostrongylidae) first-stage larvae.

Muellerius cf. capillaris is the most common lung worm of wild Nubian ibex (Capra ibex nubiana) in the northern Negev desert, Israel. The capacity of the free-living stages (L1) of the parasite to survive extreme desiccation was tested under 2 different dehydration regimes at 23 C: rapid dehydration through direct exposure to 0% relative humidity (RH), and a slow dehydration regime of preconditioning at 33% RH for 7 days prior to exposure to 0% RH for a further 21 days. In direct exposures to 0% and 33% RH, by day 11 survival rates of L1 were significantly higher than when stored in water and in 97% RH (P < 0.05). The slow dehydration regime enhanced the survival of L1 up to 10-fold by day 28 as compared with direct exposure to 0% RH. The same mean numbers of larvae were recovered from the land snail Theba pisana infected with L1 exposed for 21 days at 33% RH and from T. pisana infected with nondesiccated L1 (P > 0.1). L1 surviving after 21 days of desiccation at 0% RH were, on the other hand, less infective to T. pisana. The percentage of such postdesiccated L1 reaching infective stage (L3) was, however, the same as that of the control group. The ability of M. cf. capillaris L1 to survive anhydrobiosis and retain infectivity to land snails after extreme desiccation enables their coexistence with the Nubian ibex in desert habitat.