Current research interests include marine biogeography and the conservation genetics of aquatic organisms. New data suggest that this traditional view needs to be re-examined. Generalist predatory fishes are deterred by chemistry, but not by structural elements, toughness, or nutritional quality of sponge tissue. Spongivorous fishes are not smorgasbord feeders, but instead choose to eat chemically undefended sponge species. Transplantation experiments reveal that the grazing activity of spongivorous fishes restricts certain sponge species to refugia, including cryptic habitats on the reef and mangrove and grassbed environments, where these fish are absent.
Chemical defenses play an important role in the ecology of sponges on Caribbean reefs.
We have examined 13 of the 15 known species of Antarctic icefishes to determine whether they express Mb. Eight species do express Mb in cardiac muscle only, while 5 other species completely lack the protein. Examining the pattern of Mb loss in context of the known phylogeny of this family indicates that loss of Mb expression has occurred at least 4 different times during the evolution of icefishes. Molecular genetic analyses further show that at least 3 discretely different mutations have led to loss of Mb expression. Despite this seemingly random pattern of Mb loss, we have developed data from physiological, biochemical and molecular genetic experiments that suggest that Mb does function in icefishes that express the protein, that its presence underwrites enhanced mechanical performance of the heart and, that the gene is under the influence of selective pressure.