Achievement of Suspended Animation and the Assessment of Anyhydrobiotic Potential of Steinernema Carpocapsae (Kapow Str.)

Abstract

The effect of storage conditions, nematode aggregation (individuals vs. clumps), and different dehydration regimes on the survival of Steinernema carpocapsae (Kapow strain) was assessed, with a view to developing its potential as a biocontrol agent. Individuals were unable to survive direct exposure to 93% rh, whereas those dehydrated on a substrate of 0.5% agarose exhibited over 40% survival after five days at 93% rh. Small clumps of nematodes (c.a. 200) stored at 4°C for one week were able to survive sequential dehydration with a recorded survival of over 60% after direct exposure to 75% rh. Nematodes stored at 23°C for one week were unable to survive direct exposure to 85% rh and lower. After storage for three months at 4°C, sequentially dehydrated nematodes survived better with 80% survival at 75% rh and over 40% survival at 40% rh. A decrease in survival at 75% rh corresponded to a water content below 10%. Nematodes stored on attapulgite clay at 4°C for an extended period of time had a recorded survival of over 80% after 200 days, but this decreased to 13% over the next 25 days. A decrease in survival corresponded to a water content below 10%. No survival was recorded at 0% rh. These results indicate that S. carpocapsae (Kapow str.) can tolerate reduced rh levels and a high level of water loss at colder temperatures. However, survival is only ensured if water contents remain at or above 10%. This level of hydration corresponds with the tissue of model hydration interface between the restricted metabolic and ametabolic domains as proposed by Clegg (1978). These results are discussed in relation to the anhydrobiotic capabilities of S. carpocapsae (Kapow str.) and to its potential biocontrol agent of natural insect populations.