Brown Mussel, Perna perna

The brown mussel, Perna perna, is an economically significant mussel, a bivalve mollusk belonging to the family Mytilidae. This particular mollusk is harvested as a food source but is known also to harbor toxins and cause damage to marine structures. It’s native to the waters of Africa, Europe, and South America and was introduced in the waters of North America.

This mussel is typically 90 millimeters long although it has the potential to reach sizes of up to 120 millimeters. It’s easily distinguished by its brown coloration but its identifying trait is the “divided posterior retractor mussel scar”. Its pitted resillial ridge differentiates it from other bivalves as well.

The brown mussel can be mistaken for the more renowned greenish-brown species Perna viridis, as their shell shape and color can change depending on the conditions of the environment.

The mussel is native to the tropical and subtropical regions of the Atlantic Ocean. It can be found in waters off of the west coast of Africa and the coast of South America up to the Caribbean. It’s accidentally introduced as an invasive species to the coast of Texas by means of the boat hulls and water ballasts of ships from Venezuela. Its distribution range includes Chile, South Africa, and Peru.

The brown mussel naturally colonizes rocky shores but can also attach to submerged man-made objects. An adult brown mussel can withstand temperature ranges of 10 to 30 degrees Celsius and a salinity range of about 15 to 50 ppt.

The mussel uses external fertilization during the spawning season which is between May and October although this is also reported to occur in December. The two sexes release eggs and sperm to the water during spawning to create veliger larvae. The larvae have well-developed hinge teeth just fifteen hours after fertilization. At about ten to twelve days after fertilization, the larvae undergo metamorphosis where byssal threads are secreted. The larvae then settle on rocky surfaces.

As a filter feeder, the brown mussel feeds on phytoplankton, zooplankton and suspended organic materials. It’s plagued by the parasite Proctoeces maculatus and an unidentified bucephalid spookiest which castrates both sexes. On the African coastline, it’s preyed upon by the whelk Nucella cingulata, lobsters, gulls, octopuses and the African Black Oystercatcher.

Image Caption: Brown Mussel, Perna perna. Credit: Veronidae/Wikipedia (CC BY-SA 3.0)