When you think of a worm, you might picture the lowly earthworm, which plays such a vital role in keeping surface soils aerated and healthy, or you might even think of a frightening parasite; something you work hard to prevent from taking over your pet’s intestinal tract. Marine worms are much different; while there are some species which are very simple, others are equipped with specialized tentacles that are used for feeding, respiration, and reproduction. Some of these species may surprise you with both their beauty and their biology; let’s take a peek into their strange and wonderful world.
Marine Worms: The Basics
Found in aquatic environments throughout the world, there are an estimated 8,000 different species of marine worms known to science, with new species being discovered as technology enables us to explore areas, such as deep ocean trenches, which were previously out of reach. One recently discovered species, the Rosy Acorn Worm, was found living 2,700 feet beneath the surface near the mid-Atlantic ridge. Another, the Giant Tube Worm, lives in waters around underwater volcanoes, and is known to be capable of withstanding temperatures of up to about 90 degrees Celsius – nearly 200 degrees Fahrenheit.
To obtain oxygen, marine worms absorb it from the environment around them. Many have extremely slow metabolism, which enables them to use this passive method of breathing. Eating is another matter; each different species of marine worm has a preferred food source. Some dine on vegetation and plankton, while others clean up after fish and other animals. Some species, such as the ribbon worms that live in tidal flats and which can be seen free swimming from time to time, are predatory.
Marine worms reproduce in a variety of ways. Some, like Planarians, are capable of reproducing asexually, by attaching themselves to substrate, stretching their bodies, and breaking in two. When this occurs, each half regenerates, forming a whole new worm. Planarians are also capable of reproducing sexually, and are hermaphroditic, as many other species are.
Commonly Encountered Marine Worms
While recreational divers and even technical divers are not likely to encounter massive marine worms, such as the Parborlasia corrugatus, which can grow to a length of about two meters and which has been found living at a depth of 4,000 meters beneath the Antarctic, there are some other marine worms which can be found easily, and which are just as fascinating as those newly discovered species.
Tube worms are found in a variety of environments. These worms secrete a tube which protects them from predators and provides them with shelter; many of the marine worms you will encounter in a recreational setting such as while exploring a reef or wreck are tube worms. Often found living in clumps or colonies, the tubeworm family includes Feather Duster worms, which are usually bright yellow or orange, blue, maroon, or purple, and which tend to be found among clumps of coral or beneath rocky overhangs. Some of the most colorful species are found in areas such as the Pacific Northwest of the United States, and up into Canadian and Alaskan waters. Giant feather duster worms with fans as wide as eighteen inches across have been found as far south as San Diego and the northern portions of the Mexican coast, while other species inhabit tropical and temperate waters around the world.
Christmas Tree Worms, another type of tubeworm species, are found in coral reef habitats around the world, normally in tropical environments. These warm water dwellers are usually yellow, orange, blue, or white. The species gets its name from the spiral of tentacles that runs down the length of its body, which gives it a shape much like a minuscule coniferous tree.
Sometimes mistaken for nudibranchs due to their brilliant colors and ruffled shape, marine flatworms can be found in every color of the rainbow, with some species exhibiting flamboyant stripes or delicate spotted patterns. While some marine flatworms are microscopic, inhabiting the spaces between grains of sand along the seabed, others are about the size of leaves, and are accomplished predators, feeding on little fish, bivalves, and crustaceans. To hunt, they wrap themselves around their prey, and inject the victim with digestive enzymes, absorbing nutrients through their skins.
Peanut worms, of which there are more than 300 species worldwide, are properly known as Sipuncula and live in shallow habitats, such as reefs, in tide pools, and beneath rocks. While some species are borers, tunneling into rocks, underwater structures, and wrecks to create shelters for themselves, some can be seen swimming freely, which is when you’ll be able to see how they got their common name. Shaped almost like a peanut or other tuber, they are a light tan color. They have a short cluster of tentacles attached to their heads, which gives them an interesting appearance. Usually just under 10 centimeters long, these worms feed on organic detritus from the water around them. In the town of Xiamen, located in China’s Fujian province, a jelly made from peanut worms is a local delicacy.
Spaghetti worms are reef dwellers which can be difficult to find, and when you see one, you’ll understand why the species is named as it is. With bodies that grow to be about six inches long, and a mass of thin, white tentacles that can grow to be about three feet long, these worms usually lie hidden in rocky crevices or wriggle into mucky substrate, leaving their tentacles waving free in the water, where tiny grooves channel nutrients into the worm’s mouth. Preferring warm water, and found in shallow habitats around the world, these hidden creatures are consummate scavengers, doing their part to help keep the ocean clean.
These are only a few of the worms you might very well encounter while diving. As most are small, you will need to move slowly and keep your eyes open, and avoid touching the worms or disturbing them, as they are easily frightened and will hide if bothered. Serving an important role as the ocean’s cleanup crew, and providing a good source of nutrition for fish and other creatures, these small creatures are often amazing to see; bring your camera with you; who knows – you might find a new marine worm species!