Meeting Abstract
59.3 Tuesday, Jan. 6 A coevolutionary arms-race between macroalgae and herbivores: are tropical herbivores more tolerant of lipophilic secondary metabolites than temperate herbivores? CRAFT, J.D.*; PAUL, V.J.; SOTKA, E.E.; The College of Charleston; Smithsonian Marine Station ; The College of Charleston craftjd@gmail.com
In contrast to temperate seaweeds, tropical macroalgae produce a greater diversity and higher concentrations of lipophilic secondary metabolites. This geographic variation in plant chemical defenses is likely due to a higher intensity of herbivory in tropical regions relative to temperate regions, a greater feeding tolerance by tropical herbivores relative to temperate herbivores, or both. However, few studies have tested the notion that tropical marine herbivores evolved greater feeding tolerance for tropical plant defenses. Here, we test this coevolutionary prediction by assessing feeding tolerance and biochemical detoxification activity for ecologically-important urchins from tropical versus temperate regions. Non-polar extracts were prepared from ten species of taxonomically diverse, chemically rich tropical macroalgae. In a series of pairwise feeding choice assays, extract-coated and control artificial foods were offered to two tropical (Diadema antillarum and Echinometra lucunter) and two temperate (Strongylocentrotus droebachiensis and Arbacia punctulata) echinoid species. If there is a coevolutionary arms-race between tropical algae and these urchins, then tropical urchins should feed on extract-coated algae more readily than temperate urchins. To elucidate the biochemical mechanisms that underlie echinoid herbivory, the activity of enzymes involved in xenobiotic metabolism (e.g., CYP450, GST) were assayed in both tropical and temperate urchins. This study represents one of a handful of tests of a diffuse coevolutionary arms-race among coral reef herbivores and their seaweed prey, and the first known examination into the biochemical adaptations urchins utilize to tolerate secondary metabolites of tropical seaweeds. Results will be presented.
