Adaptations to the Arctic: low-temperature development and cold tolerance in the free-living stages of a parasitic nematode from Svalbard

Carlsson, A. M. and Irvine, R. J. and Wilson, K. and Coulson, S. J. (2013) Adaptations to the Arctic: low-temperature development and cold tolerance in the free-living stages of a parasitic nematode from Svalbard. Polar Biology, 36 (7). pp. 997-1005. ISSN 0722-4060

Abstract

For nematodes with a direct life cycle, transmission is highly dependent on temperature-related development and survival of the free-living stages. Therefore, in the Arctic, where the winter lasts from October to May, nematode transmission is expected to be focused in the short summer season, yet there is strong evidence that as well as focussing egg output during winter months, the nematode parasite, Marshallagia marshalli, infects Svalbard reindeer during the Arctic winter when temperatures are persistently below freezing. To investigate the potential for development and survival of eggs and infective third-stage larvae in winter and therefore the possibility of for winter transmission, we ran a series of low-temperature laboratory experiments. These provide five key insights into the transmission and survival of the free-living stages of M. marshalli: (1) eggs hatched at temperatures as low as 2 degrees C, but not below 0 degrees C, (2) eggs were viable and developed after being exposed to sub-zero temperatures for up to 28 months, (3) infective-stage larvae survived for up to 80 days at 5 degrees C, (4) infective-stage larvae could survive rapid exposure to temperatures below -30 degrees C, and (5) desiccation resistance may be important for long-term larval survival at low temperatures. Together, these results indicate that eggs deposited during the winter are highly tolerant of prevailing environmental conditions and have the potential for rapid development with the onset of spring. It is therefore likely that the parasite remains in the egg stage in the faeces during the winter of deposition, hatch and develop into the infective larval stage in the summer, remaining viable on the tundra until the reindeer host returns to the winter feeding grounds the following winter.