Eeckhaut, Igor Laboratory of Marine Biology, University of Mons-Hainaut, Mons, Belgium.
Hartman, Olga Formerly, Allan Hancock Foundation, University of Southern California, Los Angeles, California.
- External morphology
- Internal morphology and physiology
- Life cycle and reproduction
- Geographic distribution
- Economic significance
- Links to Primary Literature
- Additional Readings
The largest class of the phylum Annelida (multisegmented worms) with about 13,000 described species. Polychaetes (Fig. 1) range from less than 1 mm (0.04 in.) to up to 3 m (10 ft) in length. Represented worldwide, they are predominantly marine organisms and occur from the intertidal zone to the greatest ocean depths at all latitudes. Some notable exceptions occupy nonmarine habitats such as supralittoral zones (beyond the high-tide mark) and freshwater lakes. The oldest known entire fossilized species dates back to the mid-Cambrian, but records on trace fossils suggest that the origin of the group predates this period. The only synapomorphy (a derived trait shared by two or more taxa that is believed to reflect their shared ancestry) that distinguishes them from other annelids is the pair of nuchal organs, chemosensory structures located on the prostomium (the portion of the head anterior to the mouth). See also: Annelida; Deep-sea fauna
The content above is only an excerpt.
for your institution. Subscribe
To learn more about subscribing to AccessScience, or to request a no-risk trial of this award-winning scientific reference for your institution, fill in your information and a member of our Sales Team will contact you as soon as possible.
to your librarian. Recommend
Let your librarian know about the award-winning gateway to the most trustworthy and accurate scientific information.
AccessScience provides the most accurate and trustworthy scientific information available.
Recognized as an award-winning gateway to scientific knowledge, AccessScience is an amazing online resource that contains high-quality reference material written specifically for students. Contributors include more than 9000 highly qualified scientists and 43 Nobel Prize winners.
MORE THAN 8500 articles and Research Reviews covering all major scientific disciplines and encompassing the McGraw-Hill Encyclopedia of Science & Technology and McGraw-Hill Yearbook of Science & Technology
115,000-PLUS definitions from the McGraw-Hill Dictionary of Scientific and Technical Terms
3000 biographies of notable scientific figures
MORE THAN 19,000 downloadable images and animations illustrating key topics
ENGAGING VIDEOS highlighting the life and work of award-winning scientists
SUGGESTIONS FOR FURTHER STUDY and additional readings to guide students to deeper understanding and research
LINKS TO CITABLE LITERATURE help students expand their knowledge using primary sources of information