Spherical or oval body shape, usually with two long tentacles.
Body composed of 2 cell layers; the ectoderm and endoderm separated by the non-cellualr 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.

On the right is Cestium sp., in the Tentaculata class

Class tentaculata - Class Nuda - Cnidaria and Ctenophora comparison Cestium sp., Ctenophora, Class tentaculata, comb jelly

Beroe punctatus This 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.

They 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.

Class Tentaculata

All in this class have two tentacles; a characteristic species is Hormimorpha plumosa seen on the right. 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.

Class Nuda

These do not have tentacles at any stage in their lives; a characteristic species is Beroe punctatus, above left. 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.

Hormimorpha plumosa

Cnidaria and Ctenophora Comparison

Similarities Differences
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

Beroe sp., Ctenophore, Class Nuda
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