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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Johnson A & J Bergman. 2006. Synthetic approaches towards an indole alkaloid isolated from the marine sponge Halichondria melanodocia. Tetrahedron 62: 10815-10820.
Nagelkerken I, Blaber SJM, Bouillon S and 8 others. 2008. The habitat function of mangroves for terrestrial and marine fauna: a review. Aquat. Botany 89: 155-185.
Pawlik J. 1998. Coral reef sponges: Do predatory fishes affect their distribution? Limnol. Oceanogr. 43: 1396-1399.
Wiedenmayer F. 1977. Shallow-water sponges of the western Bahamas. Birkhäuser Verlag. Basel, Switzerland. 287 pp.
Apopyle: Outlet from a flagellated chamber to an excurrent canal in leuconoid sponges.
Archaeocytes: Large cells with large nuclei; phagocytic and play a role in digestion; also known to be totipotent, capable of transforming into other cell types needed by the animal. Archaeocytes serve a variety of functions from engulfing large food particles to transporting nutrients, and in some sponges, they play a pivotal role in reproduction.
Asconoid: A simple and tubular body plan characteristic of small sponges, not usually solitary.
Choanocytes: Cells responsible for moving water through the sponge and for obtaining food; ovoid with one end adjacent to the mesohyl and the opposite end projecting into the spongocoel and bearing a flagellum surrounded by a collar of microvilli.
Collencytes: Fixed cell of sponges that is anchored by long cytoplasmic strands; secrete dispersed collagen fibers, not spongin.
Incurrent Canals: Tubular invagination of the sponge pinacoderm that leads into the flagellated chambers.
Leuconoid: Refers to a type of sponge organization built around flagellated chambers and an extensive system of canals that increases the efficiency of water movement. The largest species of sponge have this body type.
Megascleres: Larger spicules forming the chief supporting elements in the skeleton.
Mesenchyme: See Mesohyl.
Mesohyl: A gelatinous, proteinaceous matrix that lies beneath the pinacoderm, containing skeletal material and ameboid cells; equivalent to the connective tissue of other metazoans; sometimes referred to as the mesenchyme.
Microscleres: Spicules that are considerably smaller than the structural megascleres.
Oscula: Plural of Osculum.
Osculum: Large opening where water exits the sponge.
Ostia: Plural of Ostium.
Ostium: A small opening perforating the surface of asconoid sponges; also called a incurrent pore, from which the name Porifera is derived.
Pinacocytes: Epithelial-like flattened cells which cover the outer surface, making up the pinacoderm.
Porocyte: A ring-shaped cell that extends from the external surface to the spongocoel, making up each pore.
Prosopyle: Internal opening of a sponge through which water flows from the incurrent canal into a radial canal or flagellated chambers.
Sclerocytes: Cells involved in the secretion of spicules in calcareous sponges.
Spiicules: Can be siliceous or calcareous and of various morphologies or shapes, including simple rods (monaxons) to more complex forms with three (triaxons), four (tetraxons), or more (polyaxons) axes. Spicules, along with spongin, provide structural support, and are considered to be an anti-predator mechanism. They are also a helpful diagnostic tool for sponge identification.
Spongin: A collagenous, fibrous protein that, along with the spicules, forms the “skeleton” of most sponges.
Spongocoel: Interior cavity of the sponge, also known as the atrium, into which water flows.
Spongocytes: Cells that secrete the spongin skeleton.
Syconoid: Radially symmetrical sponges that have a body wall folded into radially-oriented canals.