K. A. C. Madin

Abstract 1. Changes in the chemical composition of pellets of the nematode Aphelenchus avenae were studied as the worms experienced evaporative water loss during 72 hours at 97% RH. 2. Lipid content declines rapidly during the first 24 hours, and decreases to about 60% of the original by the end of 72 hours. 3. Glycogen content declines to about 50% of original by the end of 24 hours, and to 10% of original by 72 hours. 4. Glucose content remains constant. 5. Glycerol and trehalose contents both increase rapidly, reaching about 700% of the 24‐hour content by the end of 72 hours, in each case. 6. Strong correlations between survival in dry air and glycerol and trehalose contents were observed.

Abstract Nematodes, Aphelenchus avenae , can be induced to become anhydrobiotic by drying in aggregates (pellets) (>90 mg wet weight) at 97% relative humidity (RH). When the rate of weight loss exceeds 3% hr −1 survival is low. The number of animals in a pellet that survive exposure to dry air increases with time at 97% RH. The time required for recovery is shortened by rehydration at high humidities before the animals are placed in water and advances with the length of time they are in dry air. The proportion of animals recovering in water that will survive rapid dehydration decreases with the time they are in water. A hypothetical scheme for the events of the induction of anhydrobiosis and recovery is presented.

Abstract Changes in chemical composition, water content, respiration, and ability to survive rapid dehydration in dry air were studied in nematodes, Aphelenchus avenae , recovering from anhydrobiosis, in water. Water content rises rapidly, from about 0.02 mg H 2 O/mg dry weight to 2.0 mg/mg after five minutes and 2.9 mg/mg after four hours. Glycogen increases from 5 μg/mg to about 25 μg/mg after one hour. Glycerol and trehalose fall from 45 μg/mg and 125 μg/mg respectively to undetectable levels and 70 μg/mg after four hours. Oxygen uptake rises from about 25 nl/mg/min after ten minutes to 450 nl/mg/min after 1.5 hours and then falls to about 150 nl/mg min after four hours. Lipid content declines from 124 μg/mg to 51 μg/mg after 24 hours. Correlations were observed between survival in dry air and glycerol, trehalose, and water contents.

Abstract The pathway for the synthesis of trehalose in Aphelenchus avenae was demonstrated. As in other systems, the enzymes involved in the synthesis of trehalose of A. avenae were found to be trehalose phosphate synthetase (TPS) and trehalosephosphate phosphatase (TPP). Some of the characteristics of trehalose phosphate synthetase were studied. It was found that the rate limiting step in the reaction is catalyzed by TPS. Partially purified TPS was specific for UDPG as the glucosyl donor, and showed a pH optimum of 8.0. The partially purified enzyme has a Km of 0.6 mM and a V max of 2.2 × 10 −3 μmoles/mg protein min for glucose‐6‐phosphate, and a Km of 2.4 mM and V max of 2.5 × 10 −3 μmoles/mg protein minfor UDPG.