Ribbed Mussel

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Ribbed Mussel

Modiolus demissus

Range/Geographical Distribution: From the Gulf of St. Lawrence, Canada to Florida and the Gulf of Mexico.  Introduced in some places along the west coast of the United States.

Habitat: Tidal saltmarsh banks and flats.

Description: The thin, oblong shell is grooved and an olive/brown to brown/black color.

Size: Can reach four inches in length.

Food: Filter feeder; eats plankton and detritus.

Breeding: Separate sexes can be determined by color, females are brown whereas males are yellow/cream during breeding.  Mussels are broadcast spawners and release eggs and sperm into the water at synchronized times during the summer.  The fertilized eggs go through a planktonic stage before attaching to solid objects such as oysters or saltmarsh plants and transforming into a shelled form.

Predators: Crabs, whelks, and birds.

Conservation Status: No legal status.

Interesting Facts: Ribbed mussels can live for 15 years and you can determine their age by counting the ribs on the shell.  They can filter almost two gallons of water each hour.

On the Coast: In Georgia, ribbed mussels are often found in the saltmarsh attached to the stem of smooth cordgrass by their byssal threads.  This mutualistic relationship provides the mussel with an attachment site and the mussels’ fecal matter helps to feed the cordgrass.

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