What is known as Sea-pen ?
APennatula
BHydra
CVellela
DActinia
Answer:
A. Pennatula
Read Explanation:
Phylum Cnidaria (Coelenterata):
- They are aquatic, mostly marine, sessile (attached) or free-swimming
- Radially symmetrical animals
- Cnidarians exhibit tissue level of organization
- They are diploblastic
- The name cnidaria is derived from the cnidoblasts or cnidocytes (which contain the stinging capsules or nematocytes) present on the tentacles and the body.
- Cnidarians exhibit two basic body forms called polyp and medusa.
- The Polyp is a sessile and cylindrical form like Hydra, Adamsia, etc. whereas, the Medusa is umbrella-shaped and free-swimming like Aurelia or jelly fish.
- Those cnidarians which exist in both forms exhibit alternation of generation (Metagenesis), i.e., polyps produce medusae asexually and medusae form the polyps sexually (e.g., Obelia).
Examples:
- Physalia (Portuguese man-of-war)
- Adamsia (Sea anemone)
- Pennatula (Sea-pen)
- Gorgonia (Sea-fan)
- Meandrina (Brain coral)