The Cirratulid is a name given to the family of marine worms known as the Cirratulidae. They are a group of polychaete worms (also known as bristle worms). This name is in reference to their bodies. Their bodies are made up of segments, on which there are two fleshy protrusions belonging to each segment.
These fleshy protrusions are also known as parapodia, and they are covered in tiny bristles. They have long filaments all over their bodies, some occurring in the form of an anterior cluster, and then of course, on the individual segments as already discussed.
There are many different types of bristles, also known as chaeta. The chaeta of the Cirratulid worm is typically in the form of tiny hooks. These are stout, curving bristles that often feature a translucent hood known as a hyaline hood. These bristles come directly out of their body. Identifying the chaeta is essential for helping experts correctly identify the species.
Cirratulid worms live under the sea. More specifically, they are marine animals and dwell on the bottom of the ocean floor in mud or crevices within rocks. The types of Cirratulidae that live in the mud can actually be found to burrow in the soft sediments. However, those in the rock crevices do not burrow.
Burrowing Cirratulids often remain buried for most of their lives with just some small antenna-like attachments visible above the mud. That being said, these are technically not antennae and are actually called writhing branchial filaments. These are used to help them feed. They also have the ability to make tubes from calcium carbonate.
The appearance of these Cirratulid worms varies. You may find them in the colors, red, orange, or yellow. Their bodies, tentacular filaments, and branchiae will all be this color. However, when they die off, they lose their color.
Talking of feeding, Cirratulids are typically deposit feeders. This means that they feast on the waste and detritus in their environments. Another name for this type of feeder is a detritivore. They are actually essential to the decomposition cycle as well as in the nutrient cycle within their environment.
That being said, not all Cirratulids are this type of feeder. Some of them are suspension feeds (also known as filter feeders) as they graze on food and other matter that is suspended in the water. Some of them even feed on algae in the water.
In terms of what we know about these Cirratulidae, the answer is: not very much. They are somewhat of a mystery to us, as are many dwellers of the ocean. It is known that the existence of the Cirratulid worms is spread worldwide.
An expert, James Blake, has worked on researching the genera to which Cirratulids belong since the 1990s and has been able to group them into three: the Multi-tentacular genera, the Bi-tentaculate soft-substrate genera, and the Bi-tentaculate hard substrate genera.