Desiccation of Panagrolaimus rigidus (Nematoda): survival, reproduction and the influence on the internal clock

Following the life-table experimental schedule, cohorts of a parthenogenetic strain of the free-living nematode Panagrolaimus rigidus were desiccated for six days at the ages of 4, 8, 12, and 19 d (age effect) and cohorts aged 8 d were dried for 15, 20, 40, and 60 days (time effect) to determine their ability to recover and to reproduce. Nematode age had poor effect on recovery after 6 days of desiccation until the mean longevity of the nematode (19 days in hydrated medium) is approached, while increasing times of desiccation (from 6 to 60 d) remarkably decreased capacity for recovery (from 80 to 8%). Anhydrobiosis experienced at different ages or for different durations modified the timing of the nematode life cycle events, but not the pattern of age-specific fecundity nor survival curves. The age-specific fecundity is largely retained following anhydrobiosis, but when matched to that of the nematodes kept hydrated (controls), it declines for increasing durations of desiccation. Anhydrobiosis appears to cause a reset of the animal's internal clock, that is dependent on the duration of desiccation.