Ctenophora, also known as comb jellies, are a phylum of marine animals characterized by their gelatinous bodies, radial symmetry, and eight rows of cilia, called comb rows, used for locomotion. They capture prey with sticky cells called colloblasts.
General Characteristics of Phylum Ctenophora:
1) Habitat: All species are marine; either solitary or colonial.
2) Symmetry: They have biradial symmetry, oral-aboral axis.
3) Germ Layer: They diploblastic animals having outer epidermis and inner gastrodermis. At the middle jelly like Mesoglea with scattered cells, muscle fibres so they considered as ”Nearly Triploblastic”.
4) Organization: Tissue level of organization is present.
5) Comb plate: Comb like eight ciliary plates called comb plates present on help in body help in locomotion / swimming. Hence they are called “Comb Jellies”.
6) Colloblast cell: Special adhesive cells called colloblast cell present, help in food capture. Also known as “Lasso cell”.
7) Coelom: As they have no body cavity so they are acoelomate.
8) Appendages: Tentacles may or may not present. If present than two in number.
9) Digestion: Digestion is both extracellular & intracellular.
10) Reproduction: They are Monoecious (Hermaphrodite/bisexual). Fertilization is generally external. Paedogenesis is common.
11) Sense Organ: At the aboral end a sense organ present, called statocyst for equilibrium.
12) Organ System: Circulatory, Respiratory, Excretory system absent. The respiration & excretion take place through body surface.
Example: Beroe sp. ; Hormiphora sp. etc.