Nereis
Encyclopedia
Nereis is a genus
of polychaete
worm
s in the family Nereidae
. It comprises many species, most of which are marine
, including the sandworm
(Nereis virens
) and the common clam worm (Nereis succinea). Nereis possess setae and parapodia for locomotion. They may have two types of setae, which are found on the parapodia. Acicular setae provide support. Locomotor chaetae are for crawling, and are the bristles that are visible on the exterior of the polchaeta.
Nereis are osmoconformer
s.
Nereids are dioecious and they release their haploid gametes into the water medium, a process called spawning. Moreover, upon fertilisation and mitotic divisions of the zygote
, Nereids form a larval stage which is similar to that of molluscs -- i.e. a Trocophore larva
.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
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
Worm
The term worm refers to an obsolete taxon used by Carolus Linnaeus and Jean-Baptiste Lamarck for all non-arthropod invertebrate animals, and stems from the Old English word wyrm. Currently it is used to describe many different distantly-related animals that typically have a long cylindrical...
s in the family Nereidae
Nereidae
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.-Characteristics:...
. It comprises many species, most of which are marine
Ocean
An ocean is a major body of saline water, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas.More than half of this area is over 3,000...
, including the sandworm
Sandworm
Sandworm may refer to:Living animals :* Arenicola marina , called "sandworm" in the UK* Nereis virens , called "sandworm" in the US...
(Nereis virens
Nereis virens
Alitta virens is an annelid worm that burrows in wet sand and mud. It is classified as a polychaete in the family Nereididae .Sandworms make up a large part of the live sea-bait industry...
) and the common clam worm (Nereis succinea). Nereis possess setae and parapodia for locomotion. They may have two types of setae, which are found on the parapodia. Acicular setae provide support. Locomotor chaetae are for crawling, and are the bristles that are visible on the exterior of the polchaeta.
Nereis are osmoconformer
Osmoconformer
An osmoconformer is a marine invertebrate that maintains the osmolarity of its body fluids such that it is always equal to the surrounding seawater. By maintaining their internal solute concentration the same as their environment, osmoconformers avoid water diffusing into their bodies.Marine...
s.
Nereids are dioecious and they release their haploid gametes into the water medium, a process called spawning. Moreover, upon fertilisation and mitotic divisions of the zygote
Zygote
A zygote , or zygocyte, is the initial cell formed when two gamete cells are joined by means of sexual reproduction. In multicellular organisms, it is the earliest developmental stage of the embryo...
, Nereids form a larval stage which is similar to that of molluscs -- i.e. a Trocophore 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...
.