Trehalose: Its Role in the Anhydrobiotic Survival of Ditylenchus Myceliophagus

The anhydrobiotic potential of the free-living mycophagous nematode Ditylenchus myceliophagus was examined. Both individuals and small aggregates (mixed larvae and adults) were able to survive anhydrobiotically if dried slowly enough and exhibited those behavioural (swarming) and morphological (coiling) adaptations normally associated with dehydration stress. Comparison of biochemical profiles of nematode aggregates cultured on Agaricus bisporus or Rhizoctonia cerealis mycelia and exposed to 97% rh for three days (preconditioning) showed similar decreases in lipid and glycogen contents but trehalose contents increased to about 3.65% and 9.25% dry wt, respectively. Trehalose content had no effect on the abilities of the nematodes to survive exposure to reduced rh levels following preconditioning, with no nematodes surviving after 24 hr at 0% rh. Nematodes reared on R. cerealis and allowed to dehydrate naturally in culture for 6 weeks post-swarm showed an unexpected increase in lipid during swarming (28% to 42% dry wt), glycogen levels declined and trehalose levels increased from 2.0% to 4.0% dry wt. None of these changes were associated with dehydration stress. After 3 weeks nematodes began to coil and had lipid and trehalose contents of about 32% and 16.65% dry wt, respectively. At the end of the six week period lipid contents declined to 26% dry wt and trehalose contents remained stable. Naturally dehydrated nematodes showed an almost identical pattern of survival to preconditioned ones when exposed to reduced rh levels. The anhydrobiotic capabilities of D. myceliophagus are discussed in relation to other nematode anhydrobiotes and to the importance of trehalose as either a necessity for successful anhydrobiotic survival or a general adaptive response to environmental stress.