''Cirratulus cirratus'' is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of marine polychaete worm in the family

Cirratulidae Cirratulidae is a family of marine polychaete worms. Members of the family are found worldwide, mostly living in mud or rock crevices. Most are deposit feeders, but some graze on algae or are suspension feeders. Description Cirratulids vary in ...

. It occurs in the littoral and sub-littoral zones of the Atlantic Ocean. Polychaetes, or marine bristle worms, have elongated bodies divided into many segments. Each segment may bear

setae In biology, setae (singular seta ; from the Latin word for "bristle") are any of a number of different bristle- or hair-like structures on living organisms. Animal setae Protostomes Annelid setae are stiff bristles present on the body. Th ...

(bristles) and

parapodia In invertebrates, the term parapodium ( Gr. ''para'', beyond or beside + ''podia'', feet; plural: parapodia) refers to lateral outgrowths or protrusions from the body. Parapodia are predominantly found in annelids, where they are paired, unjointed ...

(paddle-like appendages). Some species live freely, either swimming, crawling or burrowing, and these are known as "errant". Others live permanently in tubes, either calcareous or parchment-like, and these are known as "sedentary".

Description

''Cirratulus cirratus'' grows to up to thirty centimetres long with up to 150 segments. It has a slender, orange, pinkish or brownish body. The

prostomium The prostomium (From Ancient Greek, meaning "before the mouth"; plural: prostomia; sometimes also called the "acron") is the cephalized first body segment in an annelid worm's body at the anterior end. It is in front of (but does not include) th ...

or head is a blunt cone with a row of 4 to 8 large black eyes on either side. The first segment bears two groups of up to eight feeding tentacles. At intervals along the body there are pairs of long slender

gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...

s which look like a mass of reddish threads. Short, blunt bristles are found on segments 10 to 12 and more on segments 20 to 23.

Distribution and habitat

''Cirratulus cirratus'' is found along the coasts of north west Europe and also in the south Atlantic Ocean. It mostly occurs living in burrows on the lower shore in mud or muddy sand, often underneath or between rocks.

Biology

''Cirratulus cirratus'' is a

filter feeder Filter feeders are a sub-group of suspension feeding animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animals that use this method of feedin ...

, catching particles floating past with its tentacles and conveying them to its mouth. The sexes are separate and the worms become sexually active spasmodically at intervals of one to two years. The males are white at this time and the females yellowish due to the

oocyte An oocyte (, ), oöcyte, or ovocyte is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum, or egg cell. An oocyte is produced in a female fetus in the ovary during female gametogenesis. The female ...

s in their

coelom The coelom (or celom) is the main body cavity in most animals and is positioned inside the body to surround and contain the digestive tract and other organs. In some animals, it is lined with mesothelium. In other animals, such as molluscs, it r ...

. Once the oocytes have been fertilised, they are stuck to rocks in a jelly-like mass. They hatch after six days into ciliated post-trochophore larvae. These live off the yolk sac for about twenty-four days before settling and starting filter feeding.

Asexual reproduction Asexual reproduction is a type of reproduction that does not involve the fusion of gametes or change in the number of chromosomes. The offspring that arise by asexual reproduction from either unicellular or multicellular organisms inherit the fu ...

by means of clones growing from the posterior of the worm have been recorded, but the taxonomic status of ''Cirratulus'' is under constant review and this report may refer to a different species.Petersen, M.E., (1999). Reproduction and development in Cirratulidae (Annelida: Polychaeta). Marine Biology, 8, 243-259.

References

{{Taxonbar, from=Q2195969 Terebellida