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Resource allocation plasticity in sea urchins: rapid, diet induced, phenotypic changes in the green sea urchin, Strongylocentrotus droebachiensis (Müller)

1998; Elsevier BV; Volume: 220; Issue: 1 Linguagem: Inglês

10.1016/s0022-0981(97)00079-8

1879-1697

Michael P. Russell,

Echinoderm biology and ecology

The gonads of sea urchins have a dual function: reproduction and nutrient storage. In general, these animals are secondarily sessile and cannot easily migrate from areas of low resource availability to areas of high resource availability. Given these conditions, an experiment was performed to test the hypothesis that sea urchins (Strongylocentrotus droebachiensis Müller) from an area of low food quality could rapidly increase gonadal tissue in response to a sudden increase of high quality food. Sea urchins were collected from a site that lacked preferred algae on Swans Island, Maine. Initially, animals were dissected to determine the percentage of the various body components. The remaining animals were distributed among four groups of equal number and size distribution. Each group was assigned randomly to 1 of 4 feeding treatments: Alaria esculenta, Laminaria digitata, Laminaria longicruris, and Ascophyllum nodosum. Animals were fed ad libitum during the experiment. Half of the sea urchins from each treatment were dissected after 3 weeks and the rest after 6 weeks. Significant differences were found among the treatments at both the 3 and 6 weeks dissections with A. esculenta producing the greatest increase in gonad wet weight. For the 6 weeks dissections there appeared to be a compensatory loss of perivisceral fluid in sea urchins that increased gonadal tissue. No differences among treatments were found for the body wall, Aristotle's lantern, or gut body components. Synthesizing these results with studies of other closely related species reveals a dynamic picture of resource allocation and phenotypic plasticity in sea urchins. Environmental variation can induce morphological change in sea urchins and these modifications have been described as graded reaction norms. The results presented here show that the temporal responses of the reaction norms of the various body components are graded and different components vary in response time.