Brachidontes exustus is a member of the family Mytilidae. It has a
thin, fan shaped shell with fine divercating radial ribs. The ribbed
surface of the shell is most evident at the outer edges. Umbones are
present at the extreme anterior end. The shell can range from blue-gray to
yellow to dark brown. The interior has purple-brown blotches with one to
four small purplish dysodont hinge teeth (Abbott and Morris 2001, Mekkelsen
and Bieler 2008).
Species designations in the genus Brachidontes are currently under
revision (Berquist et al. 2006). A recent study of the Brachidontes
exustus species complex in Florida suggests that there are four
cryptic populations with distinct genetic profiles (Lee and O Foighil
HABITAT AND DISTRIBUTION
Brachidontes exustus occurs in the intertidal on rock surfaces. The scorched mussel has been recorded from New Jersey to Florida, Bermuda, Bahamas, West Indies, Gulf of Mexico, Caribbean Central America, South America to Argerntina, and St. Helena (Mekkelsen and Bieler 2008). It is commonly found washed ashore in clusters attached to other shells and seaweeds.
Brachidontes exustus is commonly associated with oyster reefs in the Indian River Lagoon.
LIFE HISTORY AND POPULATION BIOLOGY
Age, Size, Lifespan
The scorched mussel grows to 10 - 46 mm in length (Mekkelsen and Bieler 2008).
Brachidontes exustus is often the dominate mollusc in estuaries and mangrove roots (Barber et al. 2005).
The scorched mussel is gonochronistic, having separate sexes. In a study of populations from Tampa Bay, Florida, the ratio of males to females is reported to be nearly 1:1. Brachidontes exustus has two spawning periods in the spring, between March and April and, in the fall, between September and November (Barber et al. 2005).
The embryology of the scorched mussel has not been well studied. However,
other members in this family, such as Lithophaga bisulcata,
Mytilus edulis, and Perna perna, have been well studied. The
larvae of mytilid mussels appear to quickly develop into veligers followed
by pediveligers (competent larvae) within a few weeks (Siddall 1980, Scott
1988a and b). Metamorphosis of the pedivleiger occurs once an appropriate
area to settle is encountered (Siddall 1980, Scott 1988a).
Brachidontes exustus has a broad temperature tolerance. Its spawning periods correlate with changes in sea water temperatures. Spawning occurs in the spring when the sea water temperatures increase and in the fall when sea water temperatures decrease. Gametogenesis appears to decrease in the scorched mussel during the colder winter months (Barber et al. 2005).
Adult Brachidontes exustus appear to have a high tolerance for changes in salinity (Barber et al. 2005, Berquist et al. 2006).
Brachidontes exustus are filter feeders (RiisgŒrd 1988).
No information is available at this time
Abbott RT and PA Morris. 2001. A Field Guide to Shells: Atlantic and Gulf
Coasts and the West Indies pg. 17.
American Museum of Natural History, Bivalves- Research, Training, and
Electronic Dissemination of Data.
Barber BJ, Fajans JS, Baker SM and P Baker. 2005. Gametogenesis in the
non-native green mussel, Perna viridis, and the native scorched
mussel, Branchiodontes exustus, in Tampa Bay, Florida. Journal of
Shellfish Research 24:1087-1095.
Berquist DC, Hale JA, Baker P and SM Baker. 2006. Development of ecosystem
indicators for the Suwannee River estuary: oyster reef habitat quality
along a salinity gradient. Estuaries and Coasts 29: 353-360.
ITIS. Integrated Taxonomic Information System. Available online.
Lee T and D O Foighil. 2004. Hidden Floridian biodiversity: mitochondrial
and nuclear gene tree reveal four cryptic species within the scorched
mussel, Branchiodontes exustus, species complex. Marine Ecology
Mikkelsen PM and R Bieler. 2008. Seashells of Southern Florida. Princeton
University Press, Princeton, NJ. pgs. 84-85.
RiisgŒrd HU. 1988. Efficiency of particle retention and filtration rate in
6 species of Northeast American bivalves. Marine Ecology Progress Series
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.
Siddall SE. 1980. A classification of the genus Perna (Mytlidae).
Bulletin of Marine Science 30:858-870.