Asian Green Mussel, Perna Viridis

The Asian Green Mussel, Perna Viridis, is an economically noteworthy mussel, a bivalve in the family Mytilidae. It’s harvested for food but it is also known to harbor toxins and cause damage to submerged structures. It’s a native to the Asia-Pacific region but has been introduced in the Caribbean, and in the waters around Japan, North America, and South America.

This mussel ranges from 80 to 100 millimeters in length and might occasionally reach 165 millimeters. The shell ends in a downward-pointing beak. The smooth periostracum is a dark green, becoming increasingly brownish towards its point of attachment, where it’s lighter. The younger mussels are bright green and become darker as it ages. The interior of the shell has a pale-blue sheen. It has a large mobile foot which it utilizes in climbing vertically should it be covered in sediments. It produces byssus to aid in attaching to its substrate as well.

The mussel can be found in the coastal waters of the Indo-Pacific region. However, the mussels are introduced to other areas as invasive species by means of boat hulls and water ballasts. It inhabits estuarine habitats and is found in densities as high as 35,000 individuals per square meter in any submerged marine object. Although it is vivid green in appearance, the mussels are cloaked with overgrowth and are often difficult to find. They reside in waters that are 11-32 degrees Celsius with a wide-ranging salinity of about 18 to 33 ppt. This particular mussel grows fastest at 2 meters below the surface, in high salinity and high concentrations of phytoplankton although it can tolerate a range of salinity and turbid water.

The Asian green mussel has separate sexes and fertilizes externally. Spawning usually occurs twice a year between the early spring and late autumn; however, the mussels found in the Philippines and Thailand are known to spawn all year round. The zygote transforms to a larva seven to eight hours after fertilization. The larvae stay in the water column for ten to twelve days before undergoing metamorphosis into a juvenile and settling onto a surface. The young ones become sexually mature when they’re 15 to 30 millimeters in length, a size reached within two to three months. The growth is influenced by the availability of food, water movement, temperature, the mussel’s age, and caging.

Being a filter feeder, they feed on phytoplankton, zooplankton and suspended organic materials. They’re eaten by fishes, crustaceans, octopuses, humans, and seastars.

Image Caption: Perna viridis (Linnaeus, 1758) , the Asian green mussel, family Mytilidae; Philippines. Credit: Jan Delsing/Wikipedia