Rapid metabolic compensation in response to temperature change in the intertidal copepod, Tigriopus californicus

Animals living in the intertidal zone must adapt to thermal variability, including adjustments in metabolism. We examined metabolic responses to temperature in the copepod, Tigriopus californicus, which inhabits supratidal splash pools along the Pacific coast of North America. We maintained three populations of T. californicus at 20 °C, one from southern California (San Diego, "SD") and two from Oregon (Fogarty Creek, "FCN", Boiler Bay, "BOB") and examined possible geographic patterns in metabolism. We measured oxygen consumption rate (V̇o₂) at 20 °C and following 48 h (chronic) acclimation to 25, 27.5 and 30 °C. V̇o₂ was temperature-independent, with temperature quotients (Q₁₀) values ≤1 in all populations, indicative of metabolic compensation. We detected no variation in V̇o₂ or survival between populations. To explore the time course of metabolic compensation, we performed an acute acclimation experiment in which V̇o₂ was measured at 20 °C, following immediate exposure to 25 °C, and following 2 h, 4 h and 6 h exposure to 25 °C. This acute acclimation experiment revealed that V̇o₂ increased immediately in SD and FCN, but was no longer different than 20 °C levels by 2 h and 4 h at 25 °C, respectively. BOB showed no significant change in V̇o₂, which may indicate complete temperature-independent metabolism or different mechanisms of compensation between populations. This study demonstrates a time course of rapid metabolic compensation in response to temperature that occurs in a small intertidal animal, and suggests intertidal invertebrates can thermally acclimate within a few hours of a significant temperature change.