The terms fish, crustacean, mollusk, and even cephalopod are marine terms that most people are familiar with, as they are often the “centerpiece” of many dinner feasts.
The word echinoderm on the other hand, is one that is rarely discussed around the dinner table. Translated from the Greek language, the term echinoderm means “spiny skinned.” It is a phylum (group) containing roughly six thousand organisms that are only found living in marine environments.
Probably the best-known local echinoderm is the Forbes’ sea star. Growing to ten inches in diameter, they are brownish in color and typically have five arms. Each arm is equipped with hundreds of small, suction-cupped tube feet.
Found at the end of each of these legs is an eyespot. Until recently, researchers believed these eyes were primitive, only detecting light and dark shades. However, new research has shown that although their sight is nowhere near ours, they can see rough images that might be used for navigation and searching for a mate.
Located on the topside of their body is a small, bright orange spot known as a madreporite. This sieve-like structure allows seawater to enter the water vascular system of the sea star, enabling it to control its tube feet which are used for locomotion and more importantly predation.
Bivalves such as mussels and clams are the favorite prey of a sea star. Wrapping its legs around the prey’s shell, the sea star latches on to the shell with its suction-cupped tube feet and begins to pull them apart. As the prey becomes fatigued, the shell will open ever so slightly. Everting its stomach through its mouth, the sea star will pass it through the opening in the shell and will begin to secrete digestive enzymes. As the flesh is turned into a “soup,” it is absorbed by the sea star’s stomach until all that is left is the empty shell.
In addition to feeding on shellfish, I have witnessed sea stars also scavenging on dead organisms such as crabs, lobsters and fish.
Closely related to sea stars are a group of animals known as brittle stars. Unlike the stout body and arms of a sea star, brittle stars have a round central body with five wiry arms. These arms are extremely delicate and will easily break free if attacked by a hungry fish (hence the name brittle star). The loss of an arm will preoccupy the predator, giving the brittle star a chance to escape with its life. This causes no harm to the brittle star and it will regrow in a relatively short period of time.
Watching a brittle star move along the bottom, you will quickly notice that they move much faster than your typical sea star. Instead of using hundreds of tiny feet to walk slowly along the bottom, brittle stars quickly swing their long, flexible arms forward, dragging themselves along the bottom. This “slithering” motion is the reason behind a second common name, serpent star.
There are a couple species of brittle stars that can be found in the northeast. They are small and due to their cryptic nature spend most of their time hiding under rocks and sea shells. While many of the large tropical species are active predators that will hunt down small fish, our local brittle stars feed strictly on detritus (dead particulate organic material).
A common echinoderm found in deep waters with sandy bottoms is the sand dollar. A “flattened” echinoderm, they have a body that is covered in small spines and cilia that are used to burrow up and down through sand, while feeding on amphipods, plankton and detritus.
Go into any trinket store of your local seaside town and you will find sand dollars being sold as décor for ocean inspired rooms. These ornaments are the bleached skeletons of sand dollars. Alive sand dollars have a reddish-brown color and will be fuzzy to the touch.
Every year, I get a phone call, email, DM, etc. from someone who has been clamming the muddy bottoms of the back bay and they have found something they have never seen before. They describe it as a “turd” that is round in shape, brown/black in color, and is squishy to the touch. I inform them that although it looks like a turd, rest assured it is not. What they have found is a hairy sea cucumber. Growing to three inches in length, they bury in the substrate and extend their feeding tentacles into the water to capture plankton.
The echinoderm that is most deserving of its “spiny skin” name is the sea urchin. Covered in sharp spines, they graze on algae by scraping rocks with five teeth that are located in the center of their underside. Although the spines form a formidable defense, sea urchins are a favorite food of gulls, triggerfish, and wolfish. There are many species of sea urchins worldwide, but here on the North Fork you can find the purple sea urchin.
Although the word echinoderm might not be familiar around the dinner table, they are a well-represented phylum in our area and play an important part in local food webs.
With a degree in marine biology from LIU/Southampton, Chris Paparo is the manager of Stony Brook Southampton’s Marine Sciences Center. Additionally, he is a member of the Outdoor Writers Association of America and the NYS Outdoor Writers Association. You can follow Paparo on Facebook and Instagram @fishguyphotos