Echinoid larvae can express food-conditioned morphological plasticity at ecologically relevant culture densities

The feeding larvae of many echinoids develop long postoral arms relative to body length when food is sparse but relatively short abundant, a response thought adaptively adjust capability. However, in an important recent study, Dendraster excentricus exhibited this food-conditioned plasticity only reared at high density typical laboratory cultures; lower more representative larval densities nature, they did not exhibit plastic response. This finding suggests that results cannot be easily extended make inferences about phenotypic nature. We replicated study and it even culture second species, Lytechinus pictus . Larvae D. developed longer adjusted for fed the 2 rations all densities, though differences were marginally significant one experiment. L. tended rations, approached statistical significance highest For both contrasts between almost always showed inverse relationship arm stomach length, consistent with prior work demonstrating trade-offs investment these features characteristic plasticity. These suggest may low natural densities.