Epitoky
Encyclopedia
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
.
Often an epitoke is the posterior part of the worm, which separates from the anterior part (called the atoke); gamete
s are produced inside the epitoke. The epitoke may also form by asexual budding
from the posterior.
There are two methods in which this can occur, epigamy and schizogamy. In epigamy, the whole worm transforms into a swarming epitoke. It rises and sheds its eggs and sperm. After reproduction, it dies. In schizogamy, the sexual forms are budded from the posterior or from the parapodia to swarm. This is effectively asexual reproduction of the epitoke.
In the third form (characteristic of Nereidae
, for example), the whole worm becomes an epitoke. This form may be accompanied by partial or full degeneracy of digestive
organs (causing the animal to die quickly) and enhancement of motor and sensory organs; in particular, whereas in its nonreproductive form the worm is a crawling animal, when it becomes an epitoke the worm develops swimming appendages, such as broad parapodia with paddle-shaped chaetae
.
Epitokes swim to the plankton
-rich surface region, where the gametes erupt from the body and the larva
e hatch. This action is often synchronized with moon cycles, and epitokes swim in swarms.
In the past it was thought that epitokes were separate species from polychaete
marine worms.
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...
marine worms. The worms undergo a partial or complete transformation into an epitoke, a pelagic morph capable of sexual reproduction
Sexual reproduction
Sexual reproduction is the creation of a new organism by combining the genetic material of two organisms. There are two main processes during sexual reproduction; they are: meiosis, involving the halving of the number of chromosomes; and fertilization, involving the fusion of two gametes and the...
.
Often an epitoke is the posterior part of the worm, which separates from the anterior part (called the atoke); gamete
Gamete
A gamete is a cell that fuses with another cell during fertilization in organisms that reproduce sexually...
s are produced inside the epitoke. The epitoke may also form by asexual budding
Budding
Budding is a form of asexual reproduction in which a new organism grows on another one. The new organism remains attached as it grows, separating from the parent organism only when it is mature. Since the reproduction is asexual, the newly created organism is a clone and is genetically identical...
from the posterior.
There are two methods in which this can occur, epigamy and schizogamy. In epigamy, the whole worm transforms into a swarming epitoke. It rises and sheds its eggs and sperm. After reproduction, it dies. In schizogamy, the sexual forms are budded from the posterior or from the parapodia to swarm. This is effectively asexual reproduction of the epitoke.
In the third form (characteristic of 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:...
, for example), the whole worm becomes an epitoke. This form may be accompanied by partial or full degeneracy of digestive
Digestive
Digestive may refer to:*Digestion, biological process of metabolism*Digestive biscuit, a British semi-sweet biscuit*Digestif, small beverage at the end of a meal...
organs (causing the animal to die quickly) and enhancement of motor and sensory organs; in particular, whereas in its nonreproductive form the worm is a crawling animal, when it becomes an epitoke the worm develops swimming appendages, such as broad parapodia with paddle-shaped chaetae
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...
.
Epitokes swim to the plankton
Plankton
Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...
-rich surface region, where the gametes erupt from the body and 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...
e hatch. This action is often synchronized with moon cycles, and epitokes swim in swarms.
In the past it was thought that epitokes were separate species from 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...
marine worms.