Epitoky

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Epitoky is a form of reproduction observed for polychaete marine worms.

The worms undergo a partial or complete transformaiton into an epitoke, a pelagic morph capable of sexual reproduction.

Often an epitoke is the posterior part of the worm, that separates from the anterior part (called atoke) and gametes are produced inside.

Epitoke may also form by asexual budding from the posterior.

In the third form, characteristic, e.g., to Nereidae, the whole worm becomes epitoke: sperm and ova form in its posterior. This form may be accompanied by partial or full degeneracy of digestive organs (causing the animal to die quickly) and enhancement of motoric and sensory organs; in particular, while normally crawling, the worm develops swimming appendages: broad parapodia with paddle-shaped chaetae.

Epitokes swim to the surface rich in plankton, where the gametes are released by eruption of the body, and the larvae are hatched to live swimming in plankton. 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.