Species Description: Halichondria melanodocia is an amorphous, thickly encrusting or massive sponge (Wiedenmayer 1977). Specimens are often lobate, with digitate processes and oscular chimneys one to several centimeters thick. Live individuals are black with olive tinges externally, and usually greenish yellow internally. Living tissue is softly spongy, limp and easily torn. Dried specimens are black and somewhat shiny, hard and tough. The surface of all individuals is smooth to the touch, slightly tuberculate and rugose, with intermittent lobes of variable size. The oscules are flush with the surface, or raised on uneven conical projections with membranous collars 1-10 mm wide. The ectosome is a detachable skin stretched over wide vestibules, containing haphazardly placed spicules. The choanosome is fleshy and cavernous, containing foreign material such as algal fragments and detritus. The spicules are fusiform oxeas, slightly bent or curved, with long, conical, constricted points. Spicules range from 75 to 430 μm long by 0.5 to 0.8 μm wide.
Size: A single specimen of H. melanodocia can cover an area of at least 225 cm2 (Wiedenmayer 1977).
Abundance: The abundance of H. melanodocia in the IRL is undocumented, but studies of populations in Bimini, Bahamas have recorded densities of up to 8 specimens per 100 m2, with a total coverage of nearly one square meter (Wiedenmayer 1977).
Predators: Angelfishes, filefishes, parrotfishes, trunkfishes and cowfishes have been observed to feed on H. melanodocia, consuming over 50% of the total tissue in some cases (Pawlik 1998). Studies suggest that predation by reef fishes may significantly affect the distribution and abundance of this and other sponge species.
Associated Species: H. melanodocia has been documented to occur with several other sponge species (Wiedenmayer 1977, Engel & Pawlik 2005). In areas where competition occurs, H. melanodocia often lives alongside or overgrows other sponges, but is rarely overgrown by its neighbors (Engel & Pawlik 2005).
Economic Importance: Like many other species of marine sponges, H. melanodocia produces chemical metabolites that are isolated, identified and studied for potential pharmaceutical uses (e.g. Johnson & Bergman 2006).
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Wiedenmayer F. 1977. Shallow-water sponges of the western Bahamas. Birkhäuser Verlag. Basel, Switzerland. 287 pp.