Polychaetes are segmented worms, generally less than 10 cm (4 in) in length, although ranging at the extremes … See more

Polychaetes are predominantly marine, but many species also live in freshwater, and a few in terrestrial environments. They are extremely variable in both form and lifestyle, and include a few taxa that swim among the … See more

• One notable polychaete, the Pompeii worm (Alvinella pompejana), is endemic to the hydrothermal vents of the Pacific Ocean. Pompeii worms are among the most heat-tolerant complex animals known.
• A recently discovered … See more

Most polychaetes have separate sexes, rather than being hermaphroditic. The most primitive species have a pair of gonads in every segment, but most species exhibit some degree of specialisation. The gonads shed immat… See more

Stem-group polychaete fossils are known from the Sirius Passet Lagerstätte, a rich, sedimentary deposit in Greenland tentatively dated to the late Atdabanian (early Cambrian). The oldest found is Phragmoch… See more