Sea Pen: Another master piece from Cnidaria
Sea pens are colonial marine cnidarians belonging to the order Pennatulacea. There are 14 families within the order; they are thought to have a cosmopolitan distribution in tropical and temperate waters worldwide. Sea pens are grouped with the octocorals (”soft corals”), together with sea whips and sea feathers.
sea pens are composed of physiologic structures called polyps (which look somewhat like miniature sea anemones), each with eight tentacles.sea pen’s polyps are specialized to specific functions: a single polyp develops into a rigid, erect stalk and loses its tentacles, forming a bulbous “root” or peduncle at its base. .
They position themselves favourably in the path of currents, ensuring a steady flow of plankton, the sea pens’ chief source of food. Their primary predators are nudibranchs and starfish, some of which feed exclusively on sea pens. When touched, sea pens emit a bright greenish light; this is known as bioluminescence.
Like other anthozoans, sea pens reproduce by co-ordinating a release of sperm and eggs into the water column; this may occur seasonally or throughout the year. Fertilized eggs develop into larvae called planulae which drift freely for about a week before settling on the substrate
Kingdom: Animalia
Phylum: Cnidaria
Class: Anthozoa
Subclass: Alcyonaria
Order: Pennatulacea
Source: Wikipedia
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