Respiration rates of the copepodPseudodiaptomus annandaleiin tropical waters: beyond the thermal optimum

We investigated the effects of temperature on weight-specific respiration rates (Rsp) of the euryhaline calanoid copepod Pseudodiaptomus annandalei collected from the Matang Mangrove Forest Reserve (Malaysia). We employed a simple experimental approach consisting of a short temperature exposure time from 24 to 368C. The relationship between temperature and Rsp of acclimated copepods under conditions of excess food fitted an exponential function and indicated a complete lack of acclimation at the higher temperature range. Both fine-scale temperature measurements and piecewise linear regression enabled the detection of a breakpoint produced by a significant increase in respiratory rates. It is argued that thermally stressed copepods can be detected by both a higher Q10 above 328C and monitoring this breakpoint in the metabolic response (Rsp). Similarly, the lower Q10 ( 2) indicates some degree of independence of their metabolic rates between 26 and 328C, which likely corresponds to their optimal thermal window. Results are discussed in relation to body mass, feeding status and gender.