Effect of Prey Size on Growth of the Carnivorous Polychaete Halla okudai (Lysaretidae)

Abstract

The effect of prey size on growth of the carnivorous polychaete Halla okudai was evaluated in feeding experiments by combining three size classes of the prey, the clam Ruditapes philippinarum, with three size classes of the polychaete. Small polychaetes showed a significantly higher growth efficiency (growth increment / ingested portion of prey, measured as energy content) with small prey than with large ones. The reverse relation was observed in medium and large polychaetes. These results suggest that the optimal size of prey for this polychaete is 10 to 20% of its own body weight. The amount of jelly-like material secreted by the polychaete during handling increased with prey size; thus, handling was considered to be another large cost in the foraging behavior, in addition to the energy expended in searching.