Research Areas and Sub-Specialties
Marine Chemical Ecology
Sponges are important
components of benthic marine communities, particularly coral reefs.
Organic extracts of their tissues have yielded a wealth of unusual
chemical compounds that are not involved in primary metabolism,
and have no known biological functions. The most commonly held theory
is that these compounds are distasteful to potential predators,
but they may also protect sponges from fouling or overgrowth. This
research program, funded by the National Science Foundation's Biological
Oceanography program, is designed to assess the defenses of Caribbean
demosponges, a group whose taxonomy and chemistry is fairly well
described. Because reef sponges are abundant, sessile, elaborate
putative structural and chemical defenses, and are subject to grazing
from generalist and specialist predators, they provide a useful
group for testing fundamental hypotheses proposed by terrestrial
In the first few years of this research program, the chemical, structural and nutritional antipredatory defenses of over 70 species of Caribbean sponges were surveyed using a laboratory feeding assay; the result is one of the most complete studies of the chemical and structural defenses of a group of organisms from one biogeographic region. Subsequent field feeding experiments using a natural population of reef fish have supported lab assay results, and led to the isolation and identification of the deterrent compounds from several sponge species. Both laboratory and field experiments have revealed that sponge structural elements, including glass spicules, do not appear to provide an antipredatory defense. A series of experiments in which sponges have been transplanted, caged, and exposed by overturning rubble, have clearly demonstrated that spongivorous fishes limit sponge distributions, and that parrotfish are major spongivores. These results have called into question conventional ideas about the effects of sponge-eating fishes on reef sponge communities. More information.
Faculty researching this area include:
 Joseph Pawlik |
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