Nereididae
Encyclopedia
Nereididae 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.
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 acicula
e.
Compound seta
e present. Notopodia are distinct (rarely reduced), usually with more flattened lobes, notosetae compound falcigers and/or spiniger
s (rarely notosetae absent).
They have two prostomial antennae
(absent in Micronereis). 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 larva
l body consists of four segments.
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.
are Chrysopetalidae and Hesionidae
(the superfamily Nereidoidea).
Nereidae are divided into 42 genera, but the relationships between them are as yet unclear. The family contains traditionally three subfamilies - Namanereidinae, Gymnonereinae and Nereidinae.
s. 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
in fishing
. They are a popular bait for all types of wrasse and pollock.
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
called ragworms or clam worms.
Characteristics
The prostomiumProstomium
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...
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
Cirrus
Cirrus may refer to:In science:*Cirrus cloud, a type of cloud*Cirrus , a German research rocket*Cirrus, a fleshy, downward extension of the upper lip in salamanders or fish*Cirrus, a thoracic limb of an adult barnacle...
. The first body segment with 1-2 pairs tentacular cirri without acicula
Acicula
This article is about a bristle-worm anatomical feature. For the snail of Aciculidae family, see Acicula Acicula are the chitinous support rods within parapodia found in the class Polychaeta....
e.
Compound seta
Seta
Seta is a biological term derived from the Latin word for "bristle". It refers to a number of different bristle- or hair-like structures on living organisms.-Animal setae:In zoology, most "setae" occur in invertebrates....
e present. Notopodia are distinct (rarely reduced), usually with more flattened lobes, notosetae compound falcigers and/or spiniger
Spiniger
Spiniger is a genus of fungi in the family Bondarzewiaceae. The widespread genus contains two species....
s (rarely notosetae absent).
They have two prostomial antennae
Antenna (biology)
Antennae in biology have historically been paired appendages used for sensing in arthropods. More recently, the term has also been applied to cilium structures present in most cell types of eukaryotes....
(absent in Micronereis). Pharynx
Pharynx
The human pharynx is the part of the throat situated immediately posterior to the mouth and nasal cavity, and anterior to the esophagus and larynx. The human pharynx is conventionally divided into three sections: the nasopharynx , the oropharynx , and the laryngopharynx...
, 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 larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
l body consists of four segments.
Jaw material
Ragworms' teeth are made of a very tough, yet lightweight material. Unlike boneBone
Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...
and tooth enamel
Tooth enamel
Tooth enamel, along with dentin, cementum, and dental pulp is one of the four major tissues that make up the tooth in vertebrates. It is the hardest and most highly mineralized substance in the human body. Tooth enamel is also found in the dermal denticles of sharks...
, this is not mineralised with calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
, but is formed by a histidine
Histidine
Histidine Histidine, an essential amino acid, has a positively charged imidazole functional group. It is one of the 22 proteinogenic amino acids. Its codons are CAU and CAC. Histidine was first isolated by German physician Albrecht Kossel in 1896. Histidine is an essential amino acid in humans...
rich protein, with bound zinc
Zinc
Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...
ions. Research on this material could lead to applications in engineering.
Systematics
Nereidae are currently considered a monophyletic taxon. Their closest neighbours in polychaete phylogenetic treePhylogenetic tree
A phylogenetic tree or evolutionary tree is a branching diagram or "tree" showing the inferred evolutionary relationships among various biological species or other entities based upon similarities and differences in their physical and/or genetic characteristics...
are Chrysopetalidae and Hesionidae
Hesionidae
Hesionidae are a family of phyllodocid "bristle worms" . They are marine organisms. Most are found on the continental shelf; Hesiocaeca methanicola is found on methane ice, where it feeds on bacterial biofilms.A characteristic apomorphy of the Hesionidae are the cirrophores of the anterior...
(the superfamily Nereidoidea).
Nereidae are divided into 42 genera, but the relationships between them are as yet unclear. The family contains traditionally three subfamilies - Namanereidinae, Gymnonereinae and Nereidinae.
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 carnivoreCarnivore
A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...
s. Nereids only breed once before dying (semelparity
Semelparity and iteroparity
Semelparity and Iteroparity refer to the reproductive strategy of an organism. A species is considered semelparous if it is characterized by a single reproductive episode before death, and iteroparous if it is characterized by multiple reproductive cycles over the course of its lifetime. Some...
) and most of them morph into a distinct form to breed (epitoky
Epitoky
Epitoky is a form of reproduction observed in polychaete marine worms. The worms undergo a partial or complete transformation into an epitoke, a pelagic morph capable of sexual reproduction....
).
Ragworms are important food sources for a number of shore birds
Human use
Ragworms are commonly used as baitFishing bait
Fishing bait is any substance used to attract and catch fish, e.g. on the end of a fishing hook, or inside a fish trap. Traditionally, nightcrawlers, insects, and smaller bait fish have been used for this purpose...
in fishing
Fishing
Fishing is the activity of trying to catch wild fish. Fish are normally caught in the wild. Techniques for catching fish include hand gathering, spearing, netting, angling and trapping....
. They are a popular bait for all types of wrasse and pollock.