Phylum Ctenophora Characteristics with Examples | Animal Kingdom

The phylum Ctenophora takes its name from two Greek words, ktenos= comb and phora= bearing, as they possess eight combs 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 consistency 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).

🎯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, retractile 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 diffuses. 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
Phylum Ctenophora grouped into two classes: Class Tentaculata and Class Nuda

•      Class Tentaculata and Class Nuda
  
  

🎯Some of the Ctenophora common examples are 

• Pleurobrachia
• Ctenoplana
• Beroe
• Mnemiopsis 
• Bolinopsis

🎯Key Points Phylum Ctenophora: Ctenophores, commonly known as sea walnuts or comb jellies are exclusively marine, radially symmetrical, diploblastic organisms with tissue level of organisation. The body bears eight external rows of ciliated comb plates, which help in locomotion. Digestion is both extracellular and intracellular. Bioluminescence (the property of a living organism to emit light) is well-marked in ctenophores. Sexes are not separate. Hermaphrodites Reproduction takes place only by sexual means. Fertilisation is external with indirect development.