Classification of Phylum Cnidaria

Phylum Cnidaria includes about 10,000 known species, classified into three main classes:

1. Class Hydrozoa:

1. Includes both marine and freshwater species.
2. Colonies often have zooids specialized for feeding, defense, and reproduction.
3. Medusa stage is present in some species and is equipped with a velum (a membrane).

 

2. Class Scyphozoa:

1. Primarily marine, with the medusa stage dominant.
2. Includes well-known jellyfish, with a cellular mesoglea and  gastrodermal  gonads.

 

3. Class Anthozoa:

1. Marine species, including corals and sea anemones.
2. Only the polyp stage is present, with no medusa phase.
3. The mouth is surrounded by tentacles, and the coelenteron is divided by mesenteries (radial compartments).