The influence of fish-exuded chemical signals on the carbon budget of Daphnia

Abstract

Respiration and carbon assimilation rates were measured in juvenile instars of Daphnia magna cultivated either in fish-treated or in control medium without fish exudates. Respiration and carbon assimilation rates increase proportionally to Daphnia body size. This relationship did not differ between fish-influenced and control daphnids throughout juvenile development. The results imply that observed life-history shifts in Daphnia exposed to fish exudates are facultative changes and not the result of changes in the carbon budget induced by other predator-induced defense mechanisms or experimental setups.