Jump to ContentJump to Main Navigation
Animal EvolutionInterrelationships of the Living Phyla$
Users without a subscription are not able to see the full content.

Claus Nielsen

Print publication date: 2011

Print ISBN-13: 9780199606023

Published to Oxford Scholarship Online: December 2013

DOI: 10.1093/acprof:oso/9780199606023.001.0001

Show Summary Details
Page of

PRINTED FROM OXFORD SCHOLARSHIP ONLINE (oxford.universitypressscholarship.com). (c) Copyright Oxford University Press, 2021. All Rights Reserved. An individual user may print out a PDF of a single chapter of a monograph in OSO for personal use. date: 16 April 2021

Phylum Cnidaria

Phylum Cnidaria

(p.45) 13 Phylum Cnidaria
Animal Evolution

Claus Nielsen

Oxford University Press

The Cnidaria is a well-defined phylum consisting of approximately 10,000 living species that are aquatic and primarily marine in nature. The monophyly of the cnidarians is supported in all newer molecular studies. The freshwater polyp Hydra was for a long time commonly used as an experimental organism, but has since been supplanted by the marine starlet anemone Nematostella. Both morphological and molecular studies have established the radiation of the Cnidaria, which is a sister group of anthozoans and medusozoans. The phylum is characterised by highly complicated structures known as nematocysts (cnidae), which are formed inside special cells called cnidocytes (nematocytes). The epithelial cells are sometimes anchored to the mesogloea and to the perisarc by hemidesmosomes and tonofilaments, respectively. Eggs and sperm are often shed freely in the water and differentiate from ectodermal cells in hydrozoans, and from endodermal cells in anthozoans, scyphozoans, and cubozoans. The ancestral cnidarian could be a holopelagic, advanced gastrula, and therefore one of the very first metazoan carnivores.

Keywords:   cnidarians, Cnidaria, monophyly, Hydra, Nematostella, radiation, anthozoans, medusozoans, nematocysts, epithelial cells

Oxford Scholarship Online requires a subscription or purchase to access the full text of books within the service. Public users can however freely search the site and view the abstracts and keywords for each book and chapter.

Please, subscribe or login to access full text content.

If you think you should have access to this title, please contact your librarian.

To troubleshoot, please check our FAQs , and if you can't find the answer there, please contact us .