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Nereididae

life science Maturity 11-13 Next article →

Nereididae is a large family of polychaete worms. These worms are often called ragworms or clamworms. This family contains about 500 different species. These species are organized into 42 distinct genera. Most of these worms live in marine environments. However, some can move into rivers or even climb onto land. They play a vital role in the ocean food web. Many shore-birds depend on them for food.

Cha ruoi
Cha ruoi

The physical structure of a ragworm is quite complex. Their head area, called the prostomium, has a pair of palps. These palps consist of two different units. The proximal unit is much larger than the distal unit. They also have two antennae on the prostomium. The exception to this is the genus Micronereis, which lacks them. Their body has segments with various parts like tentacular cirri. Most of their parapodia, which are limb-like structures, are biramous. This means they have two branches. Only the first two pairs of parapodia are uniramous, or single-branched.

A ragworm's feeding mechanism is truly remarkable. They possess a pharynx that can be everted, or pushed outward. This pharynx has two clear portions. The distal portion features a pair of strong jaws. Both portions often have conical teeth on one or more areas. These teeth are made from a very special material. Unlike human teeth, they are not mineralized with calcium. Instead, they are made of a histidine-rich protein. This protein has bound zinc ions within it. This makes the jaws both very tough and lightweight.

Cha ruoi
Cha ruoi

Scientists study these worms to understand their unique biology. The family Nereididae was named by Blainville in 1818. Researchers like Banse helped define the subfamily Gymnonereinae in 1977. In 2008, a study on the worm Nereis virens was published. This research appeared in the journal Biomacromolecules. The study focused on the structural protein in their jaws. Because the material is so strong and light, it is very interesting to engineers. Some believe it could help create new materials for the aerospace industry.

Cha ruoi
Cha ruoi

The family is divided into several taxonomic groups. Scientists currently view Nereididae as a monophyletic taxon. This means they all share a common ancestor. They are part of the superfamily Nereidoidea. Their closest relatives in the phylogenetic tree are Chrysopetalidae and Hesionidae. The family includes three traditional subfamilies. These are Namanereidinae, Gymnonereinae, and Nereidinae. While there are 42 genera, the exact relationships between them are still unclear.

Cha ruoi
Cha ruoi

Ragworms have unique life cycles and behaviors. Many species are omnivorous, meaning they eat many types of food. Some are active carnivores that hunt other creatures. Most ragworms practice semelparity. This means they breed only once in their lifetime before they die. Many also undergo epitoky. This is a process where they morph into a distinct form specifically to breed. They live in many habitats. They can be found in seaweed, under rocks, or burrowed in mud and sand.

Cha ruoi
Cha ruoi

Humans interact with Nereididae in several ways. In the fishing industry, worms like Hediste diversicolor are used as bait. They are popular for catching fish such as wrasse and pollock. They are also used as feed in aquaculture systems. In some cultures, these worms are a food source. In Vietnam, the worm Tylorrhynchus heterochetus is a delicacy. It is used to make a dish called chả rươi. In China, people harvest worms from rice-growing areas. They often cook these worms together with eggs.

Cha ruoi
Cha ruoi
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