DIGESTION OF PHLOROTANNIN-RICH ALGAE BY MARINE INVERTEBRATEHERBIVORES

Nancy M. Targett, Anne A. Boettcher, and Thomas Arnold
Graduate College of Marine Studies, University of Delaware, Lewes,DE 19958 U.S.A.

In an effort to better understand the mechanisms that affect the putativedefensive properties of marine phlorotannins, we studied (in vivo)the interactive effects of herbivore gut conditions and plant phlorotannincharacteristics on herbivore assimilation efficiencies. Although thereis considerable variability in gut characteristics for marine fishes, gutcharacteristics for marine invertebrates are more uniform, with pH valuesthat are generally neutral to slightly basic and redox conditions thatare slightly reducing. The marine invertebrates examined demonstrated highassimilation efficiencies when consuming phlorotannin rich diets. Comparisons of gut environments and assimilation efficiencies are madebetween marine and terrestrial invertebrate herbivores.