Distance perception of food and the effect of food quantity on feeding behavior ofLytechinus variegatus(Lamarck) (Echinodermata: Echinoidea)

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Abstract
Lytechinus variegatus does not locate food items at a distance. Agar blocks containing 5% dry weight Thalassia testudinum or Gracilaria verrucosa were perceived only at 3–8 cm distance. Individuals exposed to 1% extracts of G. verrucosa changed neither their rate nor direction of movement, suggesting a lack of ortho‐ or klinokine‐tic resposes. Individuals exposed to extracts of T. testudinum moved less rapidly but did not exhibit search behavior. Unlike many carnivorous marine invertebrates, L. variegatus relies more upon random encounters than upon directed movement as a search strategy. This indicates an important difference between carnivore and herbivore feeding strategies. The frequency of feeding has no effect upon the feeding rate of large (114.5 ± 21.6 g wet weight; mean ±1 standard deviation) Lytechinus variegatus. Equivalent amounts of agarose blocks containing 5% dry weight Thalassia testudinum were consumed per feeding bout whether the echinoids were fed at daily, 3‐day, or 6‐day intervals. Small (37.7 ± 16.5 g wet weight) L. variegatus consumed less food when fed at intervals, an effect of starvation. This suggests that L. variegatus have a constant rate of ingestion, independent of hunger or of satiation, within the constraints of their well‐being. However, rates of movement in the laboratory were higher for individuals fed ad libitum than for starved individuals. This suggests that energy expenditure for movement is reduced when food is scarce and that movement is increased to exploit the available resources when food is abundant.