Reproduction and respiration of a climate change indicator species: effect of temperature and variable food in the copepod Centropages chierchiae

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The abundance of the calanoid copepod Centropages chierchiae has increased at the northern limits of its distribution in recent decades, mainly due to oceanic climate forcing, suggesting this as a key species in monitoring climate change. Laboratory experiments were conducted to study the combined effect of temperature, food type and concentration on the egg production rate (EPR) and hatching success (HS) of C. chierchiae. Females were fed on two monoalgal diets (Gymnodinium sp. and Phaeodactylum tricornutum) at two food concentrations and at three different temperatures (13, 19, 24°C). Respiration rates of both genders were measured at four different temperatures (8, 13, 19, 24°C). EPR was significantly different between temperatures and food concentrations, the maximum EPR being attained when the copepods were exposed to high food levels and at 19°C. Prey type significantly influenced EPR; feeding on P. tricornutum resulted in higher egg production than Gymnodinium sp. HS was significantly lower at 13°C than at 19 and 24°C and higher with Gymnodinium sp. Respiration rates were sex independent and increased exponentially with temperature. To maintain basal metabolism, the minimum food intake of P. tricornutum ranged between 0.4 and 1.8 µg C and for Gymnodinium sp. between 0.03 and 0.13 µg C. Food intake was always higher than the metabolic demands, except for the highest temperature tested (24°C). The present results confirm the sensitivity of C. chierchiae to temperature variations and may help in understanding the successful expansion of its distribution towards northern latitudes.

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