Nereididae

Nereididae (formerly spelled Nereidae) are a family of polychaete worms. It contains about 500 – mostly marine – species grouped into 42 genera. They may be commonly called ragworms or clam worms.
Characteristics
The prostomium of Nereididae bears a pair of palps that are differentiated into two units, the proximal unit is much larger than the distal unit. Parapodia are mostly biramous (only the first two pairs are uniramous). Peristomium fused with the first body segment, with usually two pairs of tentacular cirri. The first body segment with 1-2 pairs tentacular cirri without aciculae.
Compound setae present. Notopodia are distinct (rarely reduced), usually with more flattened lobes, notosetae compound falcigers and/or spinigers (rarely notosetae absent).
They have two prostomial antennae (absent in Micronereis). Their pharynx, when everted, clearly consists of two portions, with a pair of strong jaws on the distal portion and usually with conical teeth on one or more areas of both portions.
Most genera have no gills (if present, they are usually branched and arise on mid-anterior segments of body). The larval body consists of four segments.
Jaw material
Ragworms' teeth are made of a very tough, yet lightweight material. Unlike bone and tooth enamel, this is not mineralised with calcium, but is formed by a histidine rich protein, with bound zinc ions. Research on this material could lead to applications in engineering.
Systematics
Nereididae are currently considered a monophyletic taxon. Their closest neighbours in polychaete phylogenetic tree are Chrysopetalidae and Hesionidae (the superfamily Nereidoidea).
Nereididae are divided into 42 genera, but the relationships between them are as yet unclear. The family contains traditionally three subfamilies - Namanereidinae, Gymnonereinae and Nereidinae.
Genera
Subfamily Gymnonereidinae Banse, 1977
Australonereis Hartman, 1954
Ceratocephale Malmgren, 1867
Dendronereides Southern, 1921
Gymnonereis Horst, 1919
Kinberginereis Pettibone, 1971
Leptonereis Kinberg, 1865
Micronereides Day, 1963
Olganereis Hartmann-Schröder, 1977
Rullierinereis Pettibone, 1971
Sinonereis Wu & Sun, 1979
Stenoninereis Wesenberg-Lund, 1958
Tambalagamia Pillai, 1961
Tylonereis Fauvel, 1911
Tylorrhynchus Grube, 1866
Typhlonereis Hansen, 1879
Websterinereis Pettibone, 1971
Subfamily Namanereidinae Hartman, 1959
Namalycastis Hartman, 1959
Namanereis Chamberlin, 1919
Subfamily Nereidinae Blainville, 1818
Alitta Kinberg, 1865
Ceratonereis Kinberg, 1865
Cheilonereis Benham, 1916
Composetia Hartmann-Schröder, 1985
Eunereis Malmgren, 1865
Hediste Malmgren, 1867
Imajimainereis de León-González & Solís-Weiss, 2000
Laeonereis Hartman, 1945
Leonnates Kinberg, 1865
Micronereis Claparède, 1863
Neanthes Kinberg, 1865
Nectoneanthes Imajima, 1972
Nereis Linnaeus, 1758
Nicon Kinberg, 1865
Paraleonnates Chlebovitsch & Wu, 1962
Parasetia Villalobos-Guerrero, Conde-Vela & Sato, 2022
Perinereis Kinberg, 1865
Platynereis Kinberg, 1865
Potamonereis Villalobos-Guerrero, Conde-Vela & Sato, 2022
Pseudonereis Kinberg, 1865
Simplisetia Hartmann-Schröder, 1985
Solomononereis Gibbs, 1971
Unanereis Day, 1962
Wuinereis Khlebovich, 1996
Subfamily Nereididae incertae sedis:
Kainonereis Chamberlin, 1919
Lycastonereis Nageswara Rao, 1981
Ecology
Ragworms are predominantly marine organisms that may occasionally swim upstream to rivers and even climb to land (for example Lycastopsis catarractarum). They are commonly found in all water depths, foraging in seaweeds, hiding under rocks or burrowing in sand or mud. Ragworms are mainly omnivorous but many are active carnivores. Nereids only breed once before dying (semelparity) and most of them morph into a distinct form to breed (epitoky).
Ragworms are important food sources for a number of shore birds
Human use
Ragworms such as Hediste diversicolor are commonly used as bait in sea angling. They are a popular bait for all types of wrasse and pollock. They are also used as fish feed in aquaculture.
Ragworms, such as Tylorrhynchus heterochaetus, are considered a delicacy in Vietnam where they are used in the dish chả rươi.
In rice-growing areas of China, these worms are called 禾虫 (Mandarin: hé chóng, Cantonese: woh4 chuhng4). They are harvested from the rice fields and are often cooked with eggs.
References
Santos et al., 2006
A Key to Families of Polychaetes
The City University of Hong Kong page on Nereidae
More Information on Nereididae
Annelid families
Phyllodocida