MIGRATORY BEHAVIOR AND DESICCATION TOLERANCE OF PROTOSTRONGYLID NEMATODE FIRST-STAGE LARVAE

Migration of first-stage larvae (L1) from faeces to soil is a crucial stage in the life-history of protostrongylids transmitted via land sna ils. Migration of Muellerius cf. capillaris and a Cystocaulus sp. L1 f rom fresh Nubian ibex (Capra ibex nubiana) faeces (48-50% water conten t, W.C.) to substrate soils (at 100% r.h., 26 degrees C) was measured experimentally using dry (3 +/- 1% W.C.), wet (31 +/- 0.43% W.C.) and flooded (48.4 +/- 2.45% W.C.) soils. The highest migration rates (90.4 +/- 1.6% migration) in both species occurred on flooded soils when th e faecal pellet W.C. reached 90%. The next highest migration rates (43 .2 +/- 3.6% migration, at 60% faecal W.C.) were on the wet soils and n o migration occurred on dry soil or dry-substrate papers. Migration ra tes did not differ significantly (P > 0.05) between species. Active Th eba pisana were not infected by M.cf. capillaris is L1 on dry infested soils, but were infected following rehydration of the same soils. By day 10, L1 of M. cf. capillaris demonstrated lower survival rates in w ater and in 97% and 76% r.h. (74.5%, 15.2% and 1.9%, respectively) tha n the Cystocaulus sp. (97.5%, 43.8%, 43.3%) and Protostrongylus sp. (9 7.9%, 43.2%, 23.8%, P < 0.05). All three nematodes had a remarkably hi gh survival rate (>99% overall survival, by day 10) when exposed direc tly to 0% r.h. at 23 degrees C. Results demonstrate the ability of L1 to survive extreme desiccation through anhydrobiosis. Migration of L1 from faeces to soil can take place only during rains which coincide wi th peak activity of land snails in desert habitat. (C) 1997 Australian Society for Parasitology. Published by Elsevier Science Ltd.