What Is a Byssal Thread?

Learning About Marine Biology

Mussels On Rock
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If you've been to the beach, you've probably noticed black, oblong shells on the beach. They are mussels, a type of mollusk, and are a popular seafood. In them, they have bysall or byssus threads. 

Byssal, or byssus, threads are strong, silky fibers that are made from proteins that are used by mussels and other bivalves to attach to rocks, pilings or other substrates. These animals produce their byssal threads using a byssus gland, located within the organism's foot. Mollusks can move slowly by extending a byssal thread, using it as an anchor and then shortening it.

The byssal threads from some animals, such as the pen shell, were once used to weave into a golden cloth.

To seafood enthusiasts, these threads are known as the animal's "beard," and are removed before cooking. Most of the time, they are gone by the time you find the shells washed up on the beach.

Fun Facts About Mussels

What exactly are mussels, and what role do they play in the marine ecosystem? Here, a few fun facts to know about these creatures:

  • Mussels form large colonies by attaching to each other using their byssal threads.
  • The word "mussel" refers to the edible bivalves of its family, Mytilidae. It is often found along the exposed shores of intertidal zones. They are called bivalves because of the two identical hinged shells, which are also called valves. 
  • Mussels are related to clams.
  • Some species of mussels live in the hydrothermal vents that are found in deep ocean ridges.
  • Their shells can be brown, dark blue or black; inside, they are silvery.
  • A mussel's byssal thread can be used as a defense mechanism to capture predatory mollusks that attack mussel beds. 
  • Mussels are found in both saltwater and freshwater ecosystems.
  • Both types of mussels in freshwater and saltwater feed on microscopic sea organisms including plankton. Their food floats freely in the water. 
  • They are available in male and female varieties.
  • The mussels that humans eat are broken up into 17 species; the most common types of mussels humans consume include M. galloprovincialis, Mytilus edulis, M. trossellus, and Perna canaliculus.
  • The byssal threads that help the animals attach to surfaces have been studied as "glue" substances for industrial and surgical arenas. They have offered insight into how artificial tendons can be created in the medical field. 
  • In addition to humans, the following creatures eat mussels: starfish, seabirds, ducks, raccoons, and otters. 
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Your Citation
Kennedy, Jennifer. "What Is a Byssal Thread?" ThoughtCo, Sep. 2, 2021, thoughtco.com/byssal-byssus-threads-2291697. Kennedy, Jennifer. (2021, September 2). What Is a Byssal Thread? Retrieved from https://www.thoughtco.com/byssal-byssus-threads-2291697 Kennedy, Jennifer. "What Is a Byssal Thread?" ThoughtCo. https://www.thoughtco.com/byssal-byssus-threads-2291697 (accessed June 2, 2023).