Echinoid larvae can express food-conditioned morphological plasticity at ecologically relevant culture densities
The feeding larvae of sea urchins and sand dollars use their ciliated arms to capture food. In a well-studied example of phenotypic plasticity, many of these larvae adjust their arm length in response to the feeding environment, developing long arms when food is scarce and short arms when it is abundant. However, this response has been observed almost exclusively in dense laboratory cultures, and recent work suggests that it may not occur at very low larval densities characteristic of the plankton. Nilsson and Pernet found that echinoid larvae can express phenotypic plasticity in arm length even at very low culture densities, suggesting that results of prior laboratory studies remain relevant for understanding the ecology of larvae in nature.
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