Relative Growth of Sea Urchin Jaws: An Example of Plastic Resource Allocation

The tropical sea urchin Diadema setosum was grown in Zanzibar from 1976 to 1977 in the field and in a large indoor tank. After 1 year, animals in the indoor tank had jaws (halfpyramids of Aristotle's lantern) that were relatively larger than the jaws of urchins in the field. The most obvious difference between the field and the tank was that there was less food in the tank. The hypothesis that available food led to an adaptive response in growth was partially tested by examining samples of the urchin Strongylocentrotus purpuratus from areas of Sunset Bay, Oregon, with documented food differences. The samples of S. purpuratus supported the hypothesis that low food availability leads to increased size of the food gathering apparatus in sea urchins.