BENTHIC ALGAL SPORES SURVIVING DIGESTION BY SEA-URCHINS
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1983
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Abstract
Present ideas on benthic algal adaptations to animal herbivory focus mainly on defensive and escape mechanisms of settled plants, and disregard the ability of algal reproductive bodies to escape from digestion by animals. To test this hypothesis, 150 individuals of the common Chilean sea urchin, T. niger Molina, were collected over a period of 7 mo., covering spring through fall. Fifty were examined for gut contents which revealed a total of 31 algal species, 62.9% of which could be categorized as opportunists and 37.1% as late successional forms. When the contents of fecal pellets were cultured the resulting algal species that had successfully resisted digestion by means of incomplete digestion or protective spore walls showed 84.6% as opportunists and 15.4% as late successional forms. There was no significant correlation between frequency of occurrence in the gut contents and in the fecal cultures, indicating that digestion survival depended on factors other than abundance. The capacity to survive digestion may play a role in the abundance of these species in overgrazed areas.