Species Description: The sun sponge, Hymeniacidon heliophila, is amorphous-lobulate in shape (Wiedenmayer 1977). The base is 1-3 cm thick, with crowded, erect chimneys, fistules and uneven digitations that rise from a few millimeters to 4 cm high. Live specimens are generally yellow to yellow-orange, with a soft, limp, and fragile consistency. Specimens growing under high sunlight are lighter yellow to olive, while those in shady areas are often a more intense orange to reddish-orange (Ruppert & Fox 1988). Dried individuals are off-white and brittle (Wiedenmayer 1977). The underside and interstitial surfaces are smooth, and the sides and projections are finely conulose, denticulate or lacinulate. Fasiculate or denticulate ridges usually appear on the chimneys. Algae, sediment, shells and rock fragments often cover the surface. The oscules are inconspicuous, hidden in the interstices or on top of the chimneys. Tangentially placed spicules are found in the ectosome, with a few feathery tracts where spicules are less abundant. Echinating spicules are found in the longitudinal ridges and laciniulae. The choanosome is cavernous, with spicules haphazardly arranged in papyraceous sheets or in random tracts. The spicules are variable in size, straight or slightly curved, usually fusiform, from 150 to 440 μm long and 4 to 7 μm wide.
Potentially Misidentified Species: H. heliophila is similar to Lissodendoryx stigmata, although the two species do not commonly occur in the same area (Wiedenmayer 1977). L. stigmata is more brilliant orange-red externally, and usually displays a difference in color between the ectosome and the choanosome. The surface is rarely smooth, bearing more pronounced, coarser lacinules and tubercules. The choanosomal tracts are stouter than those in H. heliophila.
Habitat & Regional Occurrence: According to surveys of Bahamian populations, H. heliophila appears to prefer shallow, sheltered, euryhaline areas (Wiedenmayer 1977). This species has been found in deeper oceanic waters subject to tidal currents, although these specimens lacked the digitate processes characteristic of their shallow-water counterparts.
The sun sponge is uniquely tolerant of exposure to air and direct sunlight during low tides (Ruppert & Fox 1988). Individuals commonly occur intertidally, attached to exposed oyster clumps, anchored to buried shells on sand flats, on concrete pilings and rock jetties.
Size: Specimens occurring on partially shaded pilings and jetties appear to reach the greatest size, sometimes exceeding 40 cm in diameter (Ruppert & Fox 1988).
Associated Species: The loose, open organization of this sponge provides habitat for a variety of smaller animals, including the spiny brittle star, Ophiothrix angulata (Ruppert & Fox 1988) and the nematode, Leptosomatum acephalatum (Timm 1953).
Economic Importance: Like many other species of marine sponges, the sun sponge produces chemical metabolites that are isolated, identified and studied for potential pharmaceutical and antifouling uses (e.g. Henrikson & Pawlik 1995).
Henrikson AA & JR Pawlik. 1995. A new antifouling assay method: results from field experiments using extracts of four marine organisms. J. Exp. Mar. Biol. Ecol. 194: 157-165.
Ruppert EE & RD Barnes. 1994. Invertebrate zoology, 6th edition. Saunders College Publishing. Orlando, FL. USA. 1056 pp.
Ruppert, EE & RS Fox. 1988. Seashore animals of the Southeast: A guide to common shallow-water invertebrates of the southeastern Atlantic coast. University of SC Press. Columbia, SC. USA. 429 pp.
Timm RW. 1953. Observations on the morphology and histological anatomy of a marine nematode, Leptosomatum acephalatum Chitwood, 1936, new combination (Enoplidae : Leptosomatinae). Amer. Midland Natural. 49: 229-248.
Wiedenmayer F. 1977. Shallow-water sponges of the western Bahamas. Birkhäuser Verlag. Basel, Switzerland. 287 pp.