SEASONAL-VARIATION IN THE COLD HARDINESS OF 3 SPECIES OF FREE-LIVING ANTARCTIC NEMATODES

Teratocephalus tilbrooki and Plectus antarcticus coexist within the relatively sheltered cushions and carpets of a moss, whilst Ditylenchus sp.B is found in the more exposed aerial thalli of a lichen. Ditylenchus sp.B shows consistent supercooling ability, low enough (c-28°C) to avoid any significant incidence of freezing during the study period. Both moss-dwelling species, which exhibit bimodal supercooling point distributions with a high group at -7°C and a low group at -22°C encounter field temperatures likely to result in freezing. Only T. tilbrooki exhibits any degree of freeze tolerance. P. antarcticus shows a marked pattern of seasonal change in cold hardiness. Juvenile nematodes show greater supercooling ability than adults. Increased body pigmentation, possibly related to recent feeding activity, increases the likelihood of P. antarcticus freezing at high temperatures (>-10°C), -from Author