Annelids (annelida), also called ring worms or segmented worms, are an invertebrate species that lives in a wide variety of habitats. While some can be found in freshwater, others can even survive in the harsh depths close to hydrothermal vents. Some of the most special traits of these invertebrates are their symmetry and their use of parapodia (fleshy protrusions that allow the invertebrates to swim) for locomotion.
One of the most interesting things about annelids is that they can be found in a vast array of places, all over the world. They are primarily considered a marine invertebrate – many annelid species thriving in the ocean and known to survive anywhere from intertidal algal mats to the deepest hydrothermal vents and the bottom of the ocean. Highly adaptable, as well as very diverse, segmented worms are known to most people as leeches, but most of the roughly 12,000 species in existence are found in the ocean, with more than 10,000 species belonging solely to the Polychaeta class.
While some families of segmented worms have evolved jaws, and the wide range of feeding structures associated with them are quite diverse, there are also species – some even predators – that don’t have jaws, and are known to use palms to find food particles among the sediment from the bottom of the sea, wiping them against their mouths to feed. Many of these worms are highly resilient, however, because of their ability to use energy from both organic and inorganic matter. The gut is basically just a tube supported by vertical partitions known as mesenteries, and the invertebrates use a special type of symbiotic bacteria to convert inorganic matter from hydrothermal vents and other inhospitable habitats, into nourishing organic matter that provides vital sustenance to their hosts.
There are a very wide range of aquatic annelid species in the world, being generally divided up into two types of segmented worms: Polychaeta and Hirudinea (leeches). These classes branch out to the thousands of species in freshwater and, primarily, in various marine habitats. Species like Palpata, Aciculata, Scolecida and Psammodrilidae are among the most prevalent types of marine segmented worms, all belonging to the Polychaeta class. These species are extremely variable in shape and size, as well as versatile, when it comes to their ability to adapt well-developed sense organs, as well as specialized organs such as tentacles and specialized gills designed to facilitate feeding and respiration.
One of the most fascinating properties of segmented worms is that their bodies are essentially made up of segments, each featuring basically the same organs. There are, of course, a few exceptions to this rule, as some sections of the annelids’ bodies – generally the frontmost and earmost “segments” – differ greatly from the rest, as this is where the mouth, brain, sense organs or anus are located. The segments develop one at a time, and while some species of annelids have a limited number of segments they can grow, others never actually stop growing throughout their life spans.
Feather Duster Worm
The feather duster worm, also known as Sabellidae by its scientific name, is a common name for a family of sedentary tube worms that can easily be found in intertidal areas in most of the world’s seas and oceans. These worms are made unique by their multi-colored crown of tubes that contain their feeding appendages. Their name is derived from the shape of the crown, which faithfully resembles a feather duster. There are a total of 44 different species belonging to the Sabellidae family, some of the most well-known including Glomerula, Eudistylia and Sabella.
The species belonging to the family Sabellidae are marine polychaete tube worms that can vary greatly in size, shape and color, depending on the species. The genus Sabellastarte, for example, faithfully mimics most other species, and its feather duster-like appearance is clearly distinguished on the reef. Other species, like Glomerula, differ from all other Sabellidae and can only be found in specific areas. The worms can grow up to over 2.5 inches in length, and their fan-shaped clusters of radioles can be seen from afar. There are a total of eight thoracic body segments featuring hooked ventral chaetae and dorsal capillaries. The crown is made up of two distinct fan-shaped cluster that open up when the worm is under water.
One of the more curious particularities of feather duster worms is that they have been around since the early Jurassic period, their earliest fossils dating back almost 200 million years. Yet despite the long history of its evolution, the worm displays complex behavior and a level of resourcefulness that far surpasses many of its adjacent species. The feather duster can build tubes out of a wide variety of materials, including sand, broken shell pieces and even parchment. Also, the feather duster worm has a uniquely sensitive instinct of preservation, being able to quickly retract its entire crown when sensing the presence of a nearby threat.
While most species feed on small organisms brought by water currents, some can also extend down to the seabed to collect detrivores. Feather dusters sort trapped food particles and organisms through conducting grooves found on the radioles. Larger particles are subsequently rejected, while medium particles travel along the center of the grooves, and are sometimes stored to be used as a later time as construction materials. Some of the most common organisms on the menu for feather duster worm species include phytoplankton, fine detritus and other small microorganisms.
Christmas Tree Worm
Also known as Spirobranchus giganteus, the Christmas tree worm is an unusually shaped polychaeta that is a common sight for divers in tropical seas and oceans, close to most coral reef formations. These worms have gotten their names as a result of their Christmas tree-like shape, which develops as a result of its tendency to build highly derived structures for the purpose of easier feeding and breathing. Colorful, sedentary and capable of living in coral reefs for several decades, they are among the most closely studied sea creatures on the reef.
Their brightly colored crowns and repeating disc-like structures are the first elements of the Christmas tree worms’ anatomy you will notice. The worms feature tube-like bodies that only grow to an average of 1.5 inches in length, and their colorful crowns, resembling Christmas trees, are made from small radioles. These hair-like appendages radiate outward from the worm’s central spine, and are mainly used for catching microscopic organisms that are brought by the currents and represent a large part of the worms’ usual diet.
The Christmas tree worm is naturally found in many tropical areas in the Indian and Pacific Ocean. Many species can also be located in the waters of the Caribbean, and the most common place where you will find them is the coral reef. They are easily spotted due to their colorful crowns, and their bodies are usually anchored in the living coral itself. The worms bore a hole in the coral formation and can also secrete a calcareous substance that hardens around their bodies in the shape of a tube. This tube serves as protection against predators and strong ocean currents.
Unlike most reef creatures, Christmas tree worms are extremely sedentary. They tend to choose a single spot inside large coral heads where they will anchor their tube-like bodies and form their homes. Here they will remain, breathing and feeding on microscopic organisms for up to the next 40 years. When predators approach, the worms find it easy to retract into their burrows, and this is the only time when they use up any energy. The Christmas tree worm also prefers shallow waters, usually being found at a depth between 10 and 100 feet, and a particular trait of its biology is that it is capable of both sexual and asexual reproduction.