Annelida: Polychaete Reproduction

Polychaete Reproduction

Most polychaetes reproduce sexually, and the sexes are separate. Sex cells develop from masses of tissue in the metameres and leave by way of tubules or by rupture of the body wall. In most cases fertilization of the eggs by sperm occurs externally in seawater and results in the formation of free-swimming larvae. Variations include internal fertilization, laying of egg masses that are attached to objects with mucus, and brooding of developing eggs in the worm's body. Some errant polychaetes, including the clamworm, undergo extreme changes in appearance and become active swimmers at the time of year that the sex cells mature; males and females swarm to the surface of the sea to spawn. In some of these species the portion of the body containing the sex cells breaks free and engages in swarming and spawning, leaving the asexual portion behind to regenerate its lost parts. Swarming generally occurs at night and is correlated with particular phases of the moon. Some species perform a kind of nuptial dance, swimming in circles as they spawn. In some species the worms liberate a luminous secretion, which produces circles of light on the ocean surface as they dance. The most famous swarming polychaete is the tropical palolo worm, a name sometimes applied to all swarming polychaetes.

Sections in this article:

The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2024, Columbia University Press. All rights reserved.

See more Encyclopedia articles on: Zoology: Invertebrates