Ctenophora
Eschscholtz 1829
Taxonomy
| Phylum | Ctephophora |
Size
- Vary in size from about 20 mm to 150 mm.
Description
- Gelatinous, mostly holoplanktonic animals commonly called sea gooseberries or comb jellies.
Distinguishing characteristics
- They swim by means of 8 rows of combs consisting of many fused cilia (hairlike extensions of cell membranes).
- These so-called combs or ctene plates are characteristic and give the phylum its name. Because of their structure they refract light, producing beautiful iridescent displays of colour as the animal swims.
- Body shape ranges from spherical to ribbon-like, and there is usually a pair of tentacles armed with sticky cells used to capture prey.
- Body has biradial symmetry. One central plane passes through both tentacle pouches, and another plane at a right angle to this, passes through the mouth slit.
- Body plan is similar to that of the Cnidarians. In fact they were included in the same phylum at one time, but they lack stinging cells, there is no alternation of generations in the life cycle and ctenophores are never colonial.
Distribution
- Worldwide.
- Most abundant in coastal areas.
- Up to depths of 4 km.
Ecology
- All ctenophores are carnivorous.
- Hermaphroditic.
- Spawning occurs in the water column.
- Unique early development characterized by blastomeres. Bisymmetry of adults is established in the early 4-cell stage (Larink and Westheide 2006).
Additional notes
- Comb-jellies can occasionally occur in concentrations dense enough to completely clog plankton nets.
- They are quite fragile and difficult to preserve intact.