Phylum Ctenophora is a small group of marine organisms. They are also known as Comb Jellies or Sea Walnuts. Earlier the were included in the phylum Coelenterata. But they lack the characteristics of nematocytes of coelenterates, they were placed in a separate phylum called Ctenophora.
Feature of Ctenophora
- Exclusively marine, solitary, and pelagic in nature.
- The digestive system consists of a mouth, stomodaeum, gastro-vascular canals.
- Digestion is both extracellular and intracellular.
- No special organs are present for excretion, respiration, and circulation.
- The nervous system includes the sub-epidermal plexus.
- They are bisexual organisms.
- They possess External fertilization.
- They possess cell-tissue level of body organization.
- They have biradial symmetry.
- They have a diploblastic body.
- They are hermaphrodite.
- They have retractile tentacles.
- They have special adhesive and sensory cells that help in capturing food.
- Regeneration and paedogenesis are common in Ctenophoras.
- On the body, several com plates composed of long and fused cilia are arranged in the form of a comb, which helps in locomotion.
- No alteration of generation.
- Bioluminescence ( property of a living organism to emit light) is well marked.
- Development includes a characteristic cydippid larva.
- Example: Ctenoplana, Pleurobrachia, Beroe, Velamen, Mertensia, Nuda, Tentaculata, Ctenorhabdotus capulues, etc.
Phylum Ctenophora contains about 100 know species and grouped in 2 classes.