Food Preference and Chemotaxis in the Sea Urchin Arbacia Punctulata (Lamarck) Philippi

Résumé du livre

When offered single species of seaweeds in excess amounts, the sea urchin Arbacia punctulata (Lamarck) Philippi consumed significantly more Gracilaria foliifera (Forsskal) Borgesen and Codium isthmocladium Vickers than Sargassum filipendula C. Agardh, Padina vickersiae Hoyt, or Dictyota dichotoma (Hudson) Lamouroux. When all five species were offered to urchins simultaneously, patterns of palatability remained the same but absolute consumption of favored species decreased significantly while consumption of less palatable species remained unchanged. During daytime hours, Arbacia is significantly more chemotactic toward Gracilaria (a rapidly eaten species) and Sargassum (a slowly eaten species) than toward Codium, Padina, or Dictyota. At night, Arbacia 's attraction for Gracilaria increases significantly and its attraction toward Sargassum declines significantly. We propose that the day-night changes in chemotaxis may minimize fish predation on Arbacia by tending to keep them hidden beneath Sargassum canopies during the day and allowing them to increase their foraging for favored foods at night when visual predators are less active.