Classification of Cephalodiscus

• Phylum :- Hemichordata (Marine, enterocoelous coelomate. Notochord confined to head region)
• Class :- Pterobranchia (Small hemichordates with encased body. V-shaped intestine.)
• Order :- Cephalodiscida (Solitary or colonial, 2 gill slits, 2 gonads.)
• Genus :- Cephalodiscus

Geographical distribution of Rhabdopleura

• Cephalodiscus is found in antarctic and sub-antarctic region and restricted to archibenthal and sub-littoral zones. It has been reported from India, Japan, Sweden, Borneo, Malayasia, Archipelago and Pacific Ocean.

Habit and Habitat

It is a marine colonial animal, found at a depth of 50 to 60 meters. The animal was first discovered by Challanger (1876) at a depth of approximately 245 fathoms in Magellan Strait. Antarctic and Indian oceans have abundant number of this animal.

Characteristics of Rhabdopleura

• Colony of Cephalodiscus is composed of several unconnected animals, or zooids, which are enclosed in a common case known as coenoecium.
• Zooids have no organic connections with each other, but they can move freely in the chambers.
• Zooids are microscopic and differentiated into protosome or cephalic shield, mesosome or collar and trunk.
• Protosome or proboscis is flexible and contains heart, buccal diverticulum and the central sinus.
• Protosome is shield-shaped and continuous with collar, which bears two groups of bilaterally arranged arms which contain tentacles.
• Trunk is divided into anterior sacciform part, containing alimentation and genital organs, and posterior slender adhesive stalk.
• Anus is present ventrally.
• Digestive tube is V-shaped. Breeding seasonal, sexes are separate.
• A sexual reproduction takes place by the budding of the stolon.
• New individuals detach for free existence but maintaining colonial relationship.

Special features

Zooids or individuals separate but aggregated into a common housing

Identification

Since the specimen has coenoecium and all above features, hence it is Cephalodiscus