Scolecida
Encyclopedia
Scolecida is a subclass
of polychaete
worm. Scolecids are mostly unselective deposit feeders
on marine detritus.
with rami that are all alike.
The prostomium
is distinct. The head has no appendage
s or palps and is usually conical, though in the Scalibregmatidae, it has a "T"-shaped tip, and in Paraonidae, there is a single, central antenna. In some families there are sometimes some tiny eyespots. The oesophagus is evertable forming a sac-like proboscis which may have several finger-like lobes. The anterior segments and their appendages are all similar. The notopodia and neuropodia consist of unbranched capillary chaeta
e, sometimes with hooks. There is a single central gill in Cossuridae on an anterior segment and simple segmental gills are present in some other families.
is probably not a natural grouping and is likely to be revised in the future.
Class (biology)
In biological classification, class is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, order, family, genus, and species, with class fitting between phylum and order...
of polychaete
Polychaete
The Polychaeta or polychaetes are a class of annelid worms, generally marine. Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are made of chitin. Indeed, polychaetes are sometimes referred to as bristle worms. More than 10,000...
worm. Scolecids are mostly unselective deposit feeders
Detritivore
Detritivores, also known as detritophages or detritus feeders or detritus eaters or saprophages, are heterotrophs that obtain nutrients by consuming detritus . By doing so, they contribute to decomposition and the nutrient cycles...
on marine detritus.
Characteristics
Scolecids have parapodiaParapodium
Parapodia , singular parapodium, are paired, un-jointed lateral outgrowths from the bodies of two different invertebrate groups, which are primarily marine in habitat...
with rami that are all alike.
The prostomium
Prostomium
Prostomium is the first body segment in annelid worms. It is in front of the mouth, being usually a small shelf- or lip-like extension over the dorsal side of the mouth. It sometimes bears antennae and eyes. It often functions like a kind of overlip when the animal is feeding...
is distinct. The head has no appendage
Appendage
In invertebrate biology, an appendage is an external body part, or natural prolongation, that protrudes from an organism's body . It is a general term that covers any of the homologous body parts that may extend from a body segment...
s or palps and is usually conical, though in the Scalibregmatidae, it has a "T"-shaped tip, and in Paraonidae, there is a single, central antenna. In some families there are sometimes some tiny eyespots. The oesophagus is evertable forming a sac-like proboscis which may have several finger-like lobes. The anterior segments and their appendages are all similar. The notopodia and neuropodia consist of unbranched capillary chaeta
Chaeta
A chaeta or cheta is a chitinous bristle or seta found on an insect, arthropod or annelid worms such as the earthworm, although the term is also frequently used to describe similar structures in other invertebrates. The plural form is chaetae or chetae.In the Polychaeta, they are located on the...
e, sometimes with hooks. There is a single central gill in Cossuridae on an anterior segment and simple segmental gills are present in some other families.
Systematics
The families Arenicolidae, Capitellidae and Maldanidae were formerly part of the order Capitellida. They are now included in subclass Scolecida along with Cossuridae, Orbiniidae, Opheliidae, Paraonidae and Scalibregmatidae. This cladeClade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
is probably not a natural grouping and is likely to be revised in the future.
Subdivisions
-
- Family Aeolosomatidae
- Family ArenicolidaeArenicolidaeArenicolidae is a family of marine polychaete worms. They are commonly known as lugworms and the little coils of sand they produce are commonly seen on the beach. Arenicolids are found worldwide, mostly living in burrows in sandy substrates...
- Family Capitellidae
- Family Cossunidae
- Family Maldanidae
- Family OpheliidaeOpheliidaeOphelliidae is a family of small, annelid worms. It contains the following genera:*Ammotrypanella*Antiobactrum*Armandia*Dindymenides*Euzonus*Kesun*Lobochesis*Ophelia*Ophelina*Polyophthalmus*Pygophelia...
- Family OrbiniidaeOrbiniidaeOrbiniidae is a family of polychaete worms. Orbiniids are mostly unselective deposit feeders on marine detritus. They can be found from the neritic zone to abyssal depths....
- Family Paraonidae
- Family Parergodrilidae
- Family Potamodrilidae
- Family Psammodrilidae
- Family Questidae
- Family Scalibregmatidae