The effects of temperature and oxygen partial pressure on the rate of oxygen consumption of the high-shore rock pool copepod Tigriopus brevicornis

Inhabitants of littoral rock pools such as the copepod Tigriopus brevicornis are subjected to highly variable physico-chemical conditions. The effect of temperature and PO₂ on the rate of oxygen consumption of T. brevicornis from a Scottish population was studied. As expected, VO₂ increased with increasing temperature over the range 5-30°C. However, at 0 and 35°C the rates of oxygen consumption were significantly lower than predicted. This was reflected in the very different values for Q₁₀ obtained over the temperature range 0-5°C (due to T. brevicornis entering a dormant state at 0°C) and 30-35°C (due to high mortality at 35°C), compared with the mean Q₁₀ of 2.9 for the temperature range 5-30°C. Spectrophotometric studies of the body fluids of T. brevicornis failed to detect the presence of a respiratory pigment. Nevertheless, T. brevicornis was able to maintain its rates of oxygen consumption independent of PO₂ under conditions of declining oxygen tension. However, the ability of T. brevicornis to maintain respiratory independence under hypoxia was affected by temperature since the P(c) was higher at 30°C than at lower temperatures. T. brevicornis appears to be able to withstand exposure to low temperature and to severe hypoxia by entering a quiescent or dormant state during which its metabolic rate is significantly reduced.