Clams, oysters, scallops, and mussels are familiar marine invertebrates that all belong to the bivalve class of mollusks. Many species are commonly found in fish markets as seafood, or are picked up on the beach as seashells. These animals usually have two symmetrical shells that house the animal’s soft body. It might surprise you to learn that most of these animals do not have a head, and their brain consists only of a very small set of interconnected ganglia. That is not to say that these animals are not smart little creatures! They play an important role in the sea through their feeding technique known as filter feeding. To eat, these animals draw in water and filter out the suspended food particles as the water passes through the bivalve’s gills. By doing this, they also help to keep the water clean. Their gills allow the animal to breathe as well, which is pretty clever for an animal without much of a brain!


Bay Scallops

The water-filtering abilities of bivalves are legendary. The average adult oyster can filter 25 gallons of water each day. Zebra mussels (an introduced freshwater species, but nevertheless playing this important ecological role) can filter all of the water in Saginaw Bay (the large bay between the “thumb” and “mitten” of the U.S. state of Michigan) 1.3 times every day. But during their filtering activities, bivalves also are known to concentrate contaminants in their bodies without harm to themselves – this is called bioaccumulation. Perhaps the best known example of this concerns red tide (a toxic condition of the water caused by blooms of microscopic plankton that turns the seawater orange-red), which often results in local bivalve harvesting bans. This is because the bivalves have concentrated too much of the red tide toxin as a result of filtering. While the concentration doesn't hurt the bivalve, eating that bivalve would make us very sick.

There is a large diversity of bivalves living in the Gulf. According to a 2009 checklist[1], 528 species of bivalves can be found in the Gulf of Mexico. These animals live along the coastline, in the wetlands, in the coral reefs, and in deep-water habitats in the Gulf of Mexico. Here is a list of just a few of the common bivalves found in the Gulf with their common and scientific names, from “A Picture Guide to Shelf Invertebrates from the Northern Gulf of Mexico” website:

Note: All links below are in PDF format.

Resources on Bivalves

[1] “Gulf of Mexico: Origin, Waters, and Biota, Volume 1 – Biodiversity, edited by D. L. Felder and D. K. Camp, Texas A&M Press, 2009