Featured Creature: Scallops

Photo by David Moynahan

Which creature lives across the globe, has a unique escape mechanism, and a muscle like no other?


Photo by David Moynahan

Worldwide Wonder

Scallops live in every ocean and amount to over 300 living species! They live in between and on top of rocks, coral, rubble, sea grass, kelp, sand, and mud. They are one of the largest families of bivalves, which include freshwater and marine mollusks possessing a shell with two hinged valves connected by a ligament. Other bivalve families are clams, mussels, and oysters.

Scallops stand out from their shelled relatives due to their ability to swim. They swim by clapping their two valves together, creating what looks like a trail of smoke behind them. That’s one speedy mollusk!

Photo from Quora

Beneath the shell

The scallop family name, “Pectinidae,” comes from the Latin word pecten meaning comb, inspired by the shell’s comb-like structure. Inside the shell, the scallop’s organs are packed into a tight space.

The adductor muscle (the one that allows them to clap their values together and swim) is famous for being highly nutritious, and craved by many. Scallops are on the menu for a variety of predators, including starfish, crabs, gastropods, and humans.

Each type of predator has a different way of getting inside the scallop’s shell to get to the meat. Crabs break the shell with sheer force, while gastropods make holes in the shell and insert a substance that paralyzes the scallop. Starfish hold either side of the shell with their tube feet and apply pressure. After about ten minutes, the scallop’s adductor muscle begins to weaken and the shell starts to crack open, providing just enough space for the starfish to slip its stomach inside the opening and devour the meat. Needless to say, scallops have plenty of reasons to want to swim away.

Underneath the shell, scallops have about one hundred eyes. These eyes can see light and dark, but not shapes. Thankfully, detecting changes in light patterns and motion is enough to know when the shadow of a potential predator creeps closer or when particles of food are within reach.

Photo from Eastern Fisheries Buyers

Water cleanser

Scallops are filter feeders, meaning they eat small bits of food found in the water consisting mostly of plankton, algae, krill, and larvae. They trap their free-flowing food with mucus. Then, the hair-like structures along their shell, the cilia, move food particles into the mouth. 

As filter feeders, scallops increase water clarity by ingesting food particles at the water’s surface. This allows for sunlight to pass through and reach the depths, benefitting plants along the bottom of the ocean or lake floor. As these plants photosynthesize, they produce oxygen and help maintain the health of the ecosystem. Scallops help maintain water clarity, while they pave the way for underwater plants to maintain water quality. For this reason, scallops are a great bio-indicator, meaning their presence in a body of water is a positive sign of the ecosystem’s health.

Time for me to escape now, just like this King Scallop:

By Tania Roa