Plastic responses to limited food availability and spine damage in the sea urchin Strongylocentrotus purpuratus (Stimpson)

Abstract

The purple sea urchin Strongylocentrotus purpuratus (Stimpson) has been shown to exhibit phenotypic variation that is dependent on habitat. The interaction of two common conditions existing in the intertidal zone; viz., food limitation and wave action resulting in spine damage, were explored under laboratory conditions. Changes in overall size, test weight, and jaw length were determined as urchins were subjected to different food levels and spine damage. Results indicate that food availability influences overall growth to a greater degree than does spine damage. An increase in the length of the jaws begins almost immediately following a reduction in the amount of food. Animals that were subjected to spine damage, in addition to repairing spines, appeared to allocate a greater amount of material to the lanterns and tests, which suggests that spine repair may stimulate overall calcification. Reinforcement of the test clearly has survival value for sea urchins of exposed rocky shores.