Effect of temperature on the Antarctic nematode Scottnema lindsayae

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Scottnema lindsayae is the most abundant land animal in Antarctica, and is critical to McMurdo Dry Valley ecosystem function. Assessments of S. lindsayae populations are a key indicator of ecological change and have been used in many previous studies. In the majority of dry soils S. lindsayae is the only animal present, and as such may possess unique physiological adaptations to extreme environmental conditions, knowledge of which may be useful to humans. However, attempts to maintain S. lindsayae in culture have been problematic, which limits our understanding of their basic biology and physiological capabilities, e.g. growth rates, life cycle, and survival, such as anhydrobiosis. We hypothesize that S. lindsayae will respond positively to variable cycling temperatures compared to constant temperatures, due to increased bacterial growth, its food source, in this resource limited system. Previous field studies have also suggested that increased freeze-thaw cycles limit growth in S. lindsayae by influencing the nematode’s growth and reproduction. Here we report the growth of Scottnema lindsayae populations grown on soil bacteria under different temperatures in laboratory experiments to better understand their response to environmental change and to provide information for laboratory culturing efforts.

Global climate change scenarios predict not only higher temperatures, but also increased climatic variability, e.g. freeze-thaw cycles, with unknown impacts on organisms and ecosystems. We will examine this by preliminary experiments exposing Dry Valley soils, and the S. lindsayae that they contain, to a range of different temperature treatments over several weeks. Temperatures are three constant (+10°C, 4°C, -4°C) and two fluctuating settings (0 to 10°C and -5 to 5°C; both cycling over 24 hours to simulate typical daily austral summer soil temperatures). The response will be measured in terms of changing S. lindsayae population size, demographics and individual size classes over time under each differing temperature. Dry Valley bacteria contained in soil samples will be the food source of S. lindsayae for this experiment. The different cycling temperature ranges will also enable a laboratory investigation of the impact of freeze-thaw cycles on S. lindsayae growth, which we hypothesize will yield similar results to response of this species to changes of temperature in the field.