Determination of the unique evolutionary patterns that prevail in the Antarctic springtail (Gomphiocephalus hodgsoni)

The energetic budgets (activity) of Antarctic springtails (Gomphiocephalus hodgsoni) was investigated at Cape Bird, Ross Island and the Garwood Valley, McMurdo Dry Valleys to determine the unique genetic, co-evolutionary and metabolic patterns/rates that evolved in polar invertebrates across sites in Antarctica. The activity of arthropods (mites and springtails) was measured with pitfall trapping which determines how activity varies through the day. 10 traps were sunk into the ground at two sites (5 at each site, ~1m apart), vegetated and non-vegetated, and checked twice daily for arthropods. Growth enclosures were used to determine the growth of springtails. Springtails were separated into two different size classes (first season: >250µm and <250µm, second season: >500µm and <500µm) and placed into the enclosures in groups (first season: 30 individiuals, second season: 50 individuals). Photographs were taken of individuals prior to addition to enclosure, at various times throughout the season and at the termination of time in the enclosure. The metabolic rate of individuals was measured with a fibre optic oxygen sensing system to measure drop in oxygen over time within a sealed chamber. Samples were conducted on field fresh samples at various stages throughout the seasons (i.e. between November to end of January to determine change in metabolic rate over time). Each metabolic run lasted for a set period of time (first season: 3 hour period, 12 hour period, second season: 2 hour period) during which percentage oxygen in the chamber was recorded continuously and the drop in oxygen over time calculated from the slope of the resulting graph. Temperature was held constant at 10°C. All individuals were photographed after metabolic rate measurements for later size determination. In addition to these experiments, a heating experiment to determine if an increase in temperature corresponded to an increase in metabolic activity was undertaken. The experiment followed one population of springtails through a temperature transition from 6, 12, 18 and 24°C and three populations that came straight from the field temperature to experimental temperatures. An acclimated experiment was also used where several individuals were incubated at 10°C for a five day period. Metabolic readings were then undertaken. Photographs in both additional experiments were taken before and after measurements. Molecular DNA markers (mtDNA and nuclear) were used to examine haplotypes of samples of multiple individuals.