Pressure effects on thermal preference behaviour in gammarid amphipods from 600–1000m in Lake Baikal

Temperature preference behaviour of gammarid crustaceans from depths between 600–2000 m in Lake Baikal was studied in a system which provided a stable temperature gradient at pressures ranging from 50–150 atm. At the pressure of their habitat, these animals show well-defined modal distributions of sojourn temperatures around mean values from 3.0–5.5°C, av. 3.9 ± 0.3°C; mean modal T_p is estimated at 3.5°C. Year-round habitat temperatures are 3.0–3.6°C. The effect of changing pressure upon sojourn temperatures was explored over the range 50–150 atm. The slope of the mean sojourn temperature/pressure curves was 2.1°C/100 atm, significantly greater than 0. Mean nodal temperature estimates indicate that the corresponding slope in the range of 50–100 atm is 3°C/100 atm, and in the range of 100–150 atm, is likely to exceed 5°C/100 atm.