General Characters of Phylum Ctenophora

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The phylum Ctenophora takes its name from two Greek words, ktenos= comb and phora= bearing, as they possess eight comb like plates of locomotion. Ctenophora is a small phylum of marine animals, which are commonly known as comb jellies (sea walnuts) due to their jelly like consistncy and comb like locomotory organs. At night they are often bioluminescent. About 60 species of ctenophoran animals are known. The ctenophoran animals are closely allied to coelenterates.

Body is usually pear shaped (Example: Pleurobrachia) or ribbon like flat(Cestus).

Pleurobrachia species(Sea gooseberry ) Charleston Harbor Breakwater Beach Charleston, Oregon, USA
© 2013 Alan Holyoak

Cestrum (Ribbon like flat shaped body)
© David Wrobel

General Characters of Phylum Ctenophora

Marine, solitary, free swimming or pelagic.
No polymorphism and no attached stages.
Body transparent.
Cell tissue grade of body organization.

Ctenophora Digestive System

Digestive system with mouth, stomach, complex gastrovascular canals and two aboral anal pores

Symmetry biradial along an oral aboral axis.
Body acoelomate and triploblastic, with an outer epidermis, inner gastrodermis and middle jelly like mesogloea with scattered cells and muscle fibres.
External surface with eight vertical rows of comb plates of fused cilia of locomotion. Hence they are named comb jellies.
A pair of long, solid, rectractile tentacles present.

Unique Features of Ctenophora

Comb like ciliary plates for swimming.
Special adhesive cells, the colloblasts for capturing the prey
Two anal pores.
Mesogloea with amoebocytes and smooth muscle cells

Nematocysts absent. Instead, special adhesive and sensory cells, called colloblasts, present on tentacles, help in food capture. Skeletal,circulatory , respiratory and excretory organs absent.
nervous system diffuse. Aboral ends bears a sensory organ, the statocyst.
All monoecious(hermaphrodite). Gonads develop side by side on digestive canals and develop from endoderm.
Development of ctenophores usually includes a characteristic cydippid larva.
Alternation of generation and asexual reproduction absent.
Regeneration and Paedogenesis common.

Classification of Phylum Ctenophora

Class Tentaculata and Class Nuda
Phylum Ctenophora grouped into two classes: Class Tentaculata and Class Nuda

Sea Gooseberry (Pleurobrachia bachia) Feeding - Comb Jellyfish, Phylum Ctenophora

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