Solving a mystery about a common sight on local beaches.
Have you ever stumbled upon something strange-looking on Tybee Island’s beaches? What looks like meat or organs washed up along our shore is actually an oceanic creature called Sea Pork. This marine filter feeder, which is abundant in our waters and a common sight on local beaches, received its common name due to its resemblance to salted pork and fatback.
Aplidium stellatum, or Sea Pork, is a colonial tunicate. Tunicates are filter feeding organisms with a sack-like body structure. Tunicates can be either singular or colonial organisms. Other types of tunicates that can be found in South Carolina waters include sea squirts and sea grapes. These immobile creatures attach to hard substrates such as docks, pilings, boat bottoms, groins and jetties.
Sea pork is typically made up of hundreds and at times, millions of tiny zooids.
To create new colonies, these zooids, as larvae, can be free swimming creatures. They gather together and attach themselves to hard substrates.
Then they begin to metamorphose into sedentary creatures. They lose their tails and mobility, while their nervous system essentially disintegrates. These creatures then secrete digested cellulose that they acquire from filtering the sea water. This creates the outer covering of what will be the colonial sea pork.
Upon examining sea pork on the beach, you may notice tiny holes that are similar to human pores. Each of these pores houses its own zooid. The zooids have incurrent siphons that allow seawater in. The water is then filtered and passed through the ex-current siphon, once nutrients are taken from it. When you find sea pork washed up on the beaches, the entire colony has died. The zooids will then fall out of the larger cellulose body.
Sea pork appears as a tough globular colony that feels rubbery to the touch.
They can form colonies stretching up to 12 inches long. These sub-tidal creatures can be found from the low tide mark to about 30 feet deep. They are common along the Atlantic coast from Maine to Florida and also found throughout the Gulf of Mexico.
Once attached to a substrate these creatures become hermaphroditic. However, each zooid will release sperm into the water to cross fertilize its neighbors. Each zooid will filter in the sperm and continue to grow that individual colony.
Sea pork can come in a variety of colors including pink, green, red, lavender and black.
Once washed up on our beaches, they become bleached by the sun and may appear much duller in color.
These unusual creatures tend to show up on our beaches after storms, strong currents and powerful surf rip them from their hard substrate. Skates and bottom dwelling fish feed on the zooids that create the colonial sea pork.
Keep your eyes open when you walk the beaches on Tybee Island and you just may discover Sea Pork on your own.
Photo courtesy of http://www.dpr.ncparks.gov/photos/fromNRID.php?sciName=Aplidium%20stellatum&pid=6800&source=pub
By Kathleen McMenamin, Master Naturalist.