Texas Invasive Species InstitutePerna perna
Brown Mussel
Synonym(s): Chloromya perna, Mya perna, Mytilus afe
Class: Bivalvia
Order: Mytiloida
Family: Mytilidae
Photographer: USGS
Source: http://nas.er.usgs.gov/queries/factsheet.aspx?speciesid=109
Description
The Brown mussel (Perna perna) is also called the Mexilhao mussel. This smooth shelled mussel is brown in color and can vary in size from 90-120 mm. Larger maximum sizes are reached in sublittoral zones (depth approximately 660 feet). The brown mussel shell is thin at the edges and thickens toward the posterior end. A distinguishing feature of this mussel is the divided retractor mussel scar located internally on the posterior side.
Ecological Threat: The brown mussel is capable of becoming established rapidly in new areas due to its high genetic variability. This trait allows the mussel to adapt to new surroundings and is constantly capable of further adaptation. This mussel has become destructive to natural habitats resulting from this aggressive and highly adaptable behavior.
Further damage has occurred in water-cooling systems of power plants located near the gulf coast. As a colonistic mussel this species aggregates on navigation buoys, causing them to sink. Reports from Venezuela in 2004 indicated that this mussel is a vector for Paralytic Shellfish Poisoning (PSP) effecting individuals who consume contaminated mussels.
Biology: The brown mussel is capable of becoming established in new areas rapidly and maintain high populations even when preyed upon due to its rapid growth rate. Reports from Africa observed the mussel reaching 60-80 mm in less than seven months. This mussel reproduces via broadcast spawning involving a synchronized release of gametes from male and female mussels into the surrounding water. Fertilized larvae must attach to a hard surface before metamorphosis can occur into the adult form.
History: The brown mussel was introduced to the United States in 1990 by an oil ship from Venezuela. A significant population of mussels had been trapped in the ballast water allowing for establishment in the gulf coast region. Further dispersal of the mussel within the gulf coast region occurs via water current.
Habitat: The brown mussel is commonly located in marine habitats with warm water, but can also survive in estuarine habitats containing warm water that remains below 30C. The mussel attaches to hard surfaces such as navigation buoys, jetties, petroleum platforms, wrecks, and rocky shores.
Distribution
Native Origin: South America and Africa
U.S. Present: TX (gulf coast)
Texas: South and East Texas near the gulf coast (First found in Corpus Christi)
Resembles/Alternatives
The brown mussel is similar in appearance to the green mussel (Perna viridus). Each of these mussels can have different shell shape and color depending on environmental conditions allowing for similarities between the two species. The mussels can be differentiated genetically by identifying the number of chromosomes present. The green mussel has 30 chromosomes, while the brown mussel has 28.
Management
Preventative measures are important to prevent further establishment such as rinsing and draining boats before leaving an area. It is necessary to take the time to look over boats and trailers to ensure the brown mussel is not transferred unknowingly. Chemical management occurs in water cooling systems by using chlorine. The brown mussel has a very low tolerance for this chemical and is forced to close its shell preventing filter feeding and establishment of the area.
References
Holland, Brenden. 1997. Genetic aspects of a marine invasion. Quarterdeck 5(3).
Hicks, D. W., and J. W. Tunnell. 1993. Invasion of the south Texas coast by the edible brown mussel Perna perna (Linneaus 1758). The Veliger 36:92–94.
Internet Sources:
www.itis.gov
http://www.issg.org/
