Lithophaga bisculata
Family: Mytilidae
Common names: Mahogany Date Mussel
Synonyms: Lithophaga bi-excavatus Reeve, 1857
Lithophaga bisculata image
Lithophaga bisculata  

Species Description: The fossil record dating back to the Paleozoic indicate that mussels in the genus Lithophaga have long been associated with reef building corals (Scott 1988b). L. bisculata is a member of the family Mytilidae. The mahogany date mussel attaches to the substratum and its congeners with byssal threads forming dense beds that can support rich epifaunal and infaunal invertebrate assemblages (Ruppert and Barnes 1994).

The shell of L. bisculata, a burrowing mussel, is elongated, cylindrical and inflated with umbones near the anterior end. It is thin-walled and whitish, with a yellow-brown periostracum and calcareous incrustation that projects bluntly beyond the posterior margin. It is smooth with a radial groove dividing the valve into two sections. The ventral half has periostracal pits that are more prominent in juveniles. The interior is yellow-brown with a purplish tint and a smooth margin (Ruppert and Barnes 1994).

Living specimens are found burrowed in soft rock or dead coral (Mikkelsen and Bieler 2008). L. bisculata is a common burrower that excavates chemically secreting a mucoprotein-chelating agent from glands in the middle fold of the mantle margin to soften the calcareous substratum. The softened substratum is then scraped away with the valves (Ruppert and Barnes 1994). L. bisculata glands also produce secretions that prevent corals from depositing calcium carbonate into the hole that has been burrowed, and inhibit the firing of coral nematocysts.

Regional Occurrence: Lithophaga bisulcata can be found in the temperate and tropical regions of North America, from North Carolina to Florida, Bermuda, Bahamas, West Indies, the Gulf of Mexico, and the Caribbean, and in Central and South America to Uruguay (Mikkelsen and Bieler 2008).

IRL Distribution: The mahogany date mussel is not common in the Indian River Lagoon. When they are encountered they are almost always living on live Crassostrea virginica (Boudreaux et al. 2006).

Age, Size, Lifespan: Lithophaga bisulcata grows to 45 mm (Mikkelsen and Bieler 2008) and becomes reproductive when the shell reaches 20 mm (Scott 1988a). In a Jamaican population, the sex ratio of male to female individuals was reported to be 1:1 (Scott 1988a).

Abundance: The mahogany date mussel is not reported to occur in high densities in Florida and Jamaica (Scott 1988b, Boudreaux et al. 2006).

Reproduction: Lithophaga bisulcata have separate sexes and reproduce annually. The reproductive season begins in August and spawning occurs between November and February (Scott 1988a).

Embryology: The embryology of the mahogany date mussel has been thoroughly studied in the laboratory. Within 3 hours of fertilization the embryo develops into the gastrula. The trochophore appears in 5 hours followed by the veliger in 12 hours. Pediveligers (competent larvae), possessing a foot and eyespots, develop within 8-21 days (Scott 1988a and b). Laboratory observations suggest that metamorphosis can be delayed if a suitable settlement site is not encountered. Pediveligers use their foot to explore potential settlement site. The competent larvae are immune to the nematocysts of their coral hosts Siderasterea siderea and Stephanocoenia michelini (Scott 1988b). Pediveligers enter the coral polyps with other plankton but appear to be immune to the digestive enzymes. Metamorphosis occurs once the pediveliger is in the host (Scott 1988a).

Temperature: There do not appear to be any studies addressing the temperature tolerance of Lithophaga bisulcata.

Salinity: There do not appear to be any studies addressing the salinity tolerance of Lithophaga bisulcata.

Trophic Mode: Lithophaga bisulcata are suspension feeders, filtering plankton and other small invertebrates from seawater (Ruppert and Barnes 1994).

The mahogany date mussel is often associated with sponges, corals, anemones, annelids (worms), crustaceans, other bivalves, bryozoans, sea stars and sea urchins (Ruppert and Barnes 1994). They are found in living and dead corals. The most common hosts for Lithophaga bisulcata are the corals Siderasterea siderea and Stephanocoenia michelini (Scott 1988b).

American Museum of Natural History, Bivalves- Research, Training, and Electronic Dissemination of Data.

Boudreax ML, Stiner JL, and LJ Walters. 2006. Biodiversity of sessile and motile macrofauna on intertidal oyster reefs in Mosquito Lagoon, Florida. Journal of Shellfish Research 25:1079-1089.

ITIS. Integrated Taxonomic Information System. Available online.

Mikkelsen PM and R Bieler. 2008. Seashells of Southern Florida. Princeton University Press, Princeton, NJ. pg. 90-91.

Ruppert EE and RD Barnes. 1994. Invertebrate Biology. Sixth Edition. Saunders College Publishing, Fort Worth, TX pg. 451

Scott PJB. 1988a. Initial settlement behavior and survivorship of Lithophaga bisculata (d'Orbigny) (Mytilidae:Lithophaginae). Journal of Molluscan Studies 54:97-108.

Scott PJB. 1988b. Distribution, habitat and morphaology of the Caribbean coral- and rock-boring bivalve, Lithophaga bisculata (d'Orbigny) (Mytilidae:Lithophaginae). Journal of Molluscan Studies 54:83-95.

ZipcodeZoo. Available online.