Herbivory versus omnivory: Linking homeostasis and elemental imbalance in copepod development.

LASPOUMADERES, C.; MODENUTTI, B.E.; BALSEIRO, E.G.

JOURNAL OF PLANKTON RESEARCH

OXFORD UNIV PRESS

Año: 2010 vol. 32 p. 1573 - 1582

0142-7873

Organisms usually face and acquire food that is elementally imbalanced, andalthough they are affected by its quality, they do not reflect the elemental compositionof their resources. We analysed whether elemental homeostasis during theontogeny of freshwater calanoid copepods varied with herbivorous or omnivorousdiet. Boeckella gracilis and B. brevicaudata are herbivorous species, whereas Parabroteassarsi changes its feeding strategy throughout its ontogeny. We hypothesized thathomeostatic investment would decrease when food matches consumer requirementsin copepods that change their diet from herbivorous microphagy towards apredatory regime. Elemental analyses of each cohort and its food resourcerevealed a relation between trophic strategy and imbalance. A high level ofelemental imbalance was found in the herbivorous species, which were strictlyhomeostatic during their whole life cycle. The shift in P. sarsi trophic strategyresulted in changes in both imbalance and homeostasis. When nutrient conditionsare imbalanced, energy needs to be allocated to stoichiometric regulation in orderto maintain a relatively tight homeostasis. Our findings provide an example ofhow variable feeding strategies can counter the imbalance in C:nutrient ratios thatorganism typically face.