On this page Ctenophora characteristics - Ctenophora overview - Class tentaculata - Class Nuda - Cnidaria and Ctenophora comparison
|Spherical or oval body shape, usually with two long tentacles.|
|Body composed of 2 cell layers; the ectoderm and endoderm separated by the non-cellular mesoglea.|
|Eight ciliary comb plates.|
|Colloblasts (adhesive, lasso cells) on tentacles.|
|A gastrovascular cavity with mouth and anal pores.|
|Gas exchange by diffusion.|
|A nerve net.|
|All are hermaphrodites, reproduction is mainly sexual, with some asexual.|
|All are marine.|
The Ctenophora is a small phylum with fewer than 100 known species divided into two Classes. They are all marine and mainly found in warm waters. Most species are small, but some can grow up to 2 m long. Their common name, "comb jellies", comes from the eight comb rows of cilia that are used in locomotion.
Comb jellies are the largest animals to use cilia for locomotion. The threads in the colloblasts wrap around the prey entangling it. They have the ability to luminesce from chemical reactions in the gastrodermis. They have a statocyst containing a calcareous statolith which gives the animal information about its position and orientation.
All in the Tentaculata Class have two tentacles; a characteristic species is Hormimorpha plumosa seen below. Some in this class are flattened into a ribbon-like shape along the plane of the tentacles and have an undulatory motion, Cestium sp., above, is an example. It can grow to over 100 cm in length.
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The Nuda do not have tentacles at any stage in their lives; a characteristic species is Beroe punctatus, above. Another in the Beroe genus can be seen below, these can grow to 20 cm long and 5 cm wide. When found in cold waters they tend to have a pinkish tinge.
Beroe comb jellies have one of the biggest mouth to body size in the animal kingdom. When swimming the lips of the mouth are usually closed, but will spring open if they touch something. If the item they touch is edible, the Beroe simply engulfs it, and very quickly too. If the prey item is too big to be engulfed the Beroe "bites" off a piece using the thousands of tiny, sharp cilia that line its huge mouth. The lips then reseal around the prey and the bloated Beroe swims off to digest its meal at leisure.
|Both are radially symmetrical||All Cnidaria have nematocycsts; only 2 species of Ctenophore have|
|Both have their body parts arranged symmetrically around the mouth||Ctenophores have comb plates; Cnidaria do not|
|Both have a gelatinous body||Ctenophores are never colonial; many Cnidaria are|