Two Invasive Mussels in the Genus Perna in the Gulf of Mexico

The bivalve genus, Perna (Bivalvia: Mytilacea), includes three extant species; P. perna (the brown mussel), P. viridis (the green mussel), and P. canaliculus (the green-lipped mussel) (Siddall 1980). The subtropical, marine, intertidal mussel, Perna perna, invaded Texas, Gulf of Mexico shores in 1990 and now ranges from Veracruz, Mexico, to Freeport, Texas (Hicks and Tunnel 1993, 1995). Records for P. perna include India, Sri Lanka, Madagascar, the Red Sea, the east coast of Africa from central Mozambique to False Bay, South Africa, and the African west coast from Lucero Bay north into the Mediterranean where it extends from Gibraltar to the Gulf of Tunis (Berry 1978). It also occurs in South America on the Atlantic coasts of Brazil, Uruguay, Venezuela, and in the West Indies (Berry 1978). Some authors recognize two other species; P. pica from the Mediterranean and northern Africa and P. indicia from southern India. These latter species have been synonymies with P. perna (Siddall 1980, Vainly 1989). In 1999, P. porno's tropical, estuarine congener, Perna viridis, was discovered in Tampa Bay, Florida and currently ranges from Venice to St. Petersburg, Florida (Ingrao peers. obis.). Prior to invasion of the Gulf of Mexico, P. viridis was first discovered outside of its endemic Indo-Pacific range at Point Lisa's, Trinidad in 1990 (Agar et al. 1992), Venezuela's Gulf of Praia coast in 1992, where it is sympatric with P. perna (Signing de Bravo et al. 1998), and Kingston Harbour, Jamaica in 1998 (D. Buddo and T. Bowes, per. comm.). The endemic, Indo-Pacific distribution of P. viridis ranges from the Persian Gulf to the southwestern Pacific Ocean and from southern Japan to Papua, New Guinea (Cheung 1993). International shipping is the likely vector for introduction of both species into the Gulf of Mexico, either as adults byssally attached to ship hulls or larvae in ballast seawater. Mitochondrial DNA sequence analyses have indicated that no indigenous Gulf of Mexico P. perna populations exhibited a clear genetic affinity with populations from Venezuela.