Sea Pens- Not The Underwater Writing Kind

ORIGINAL: AquaViews

BY NOREEN

MAY 26, 2010

A stunning creature of the seas, the sea pen a species of soft coral gets it’s name as it resembles a plump, old-fashioned quill pen.

Similar to anemone, sea pens are colonial marine cnidarians belonging to the order Pennatulacea, in other words they are a colony of polyps working together for the survival of the whole. The primary polyp loses its tentacles and becomes the stalk of the sea pen, with a bulb at its base—the bulb anchors the sea pen in the muddy or sandy bottom. The various secondary polyps form the sea pen’s “branches” and have specialized functions. The Sea Pen may grow up to 2 meters (6.6 ft) in some species, such as the tall sea pen (Funiculina quadrangularis) and are sometimes brightly colored. Rarely found above depths of 10 meters (33 ft), sea pens prefer deeper waters where turbulence is less likely to uproot them.

The Sea Pens primary source of nutrition and food is plankton. Though they don’t move around often, they are able relocate and re-anchor themselves if need be. They tend to position themselves favorably in the path of currents, ensuring a steady flow of plankton. Their primary predator and as unlikely predators as they seem are nudibranchs and sea stars some of which feed exclusively on sea pens.

Some sea pens when touched emit a bright greenish light, known as bioluminescence. They may also force water out of themselves as a defensive act, deflating and retreating into their peduncle. So the next time you’re diving keep a look out for these beautiful marine creatures in tropical and temperate waters worldwide.

*Photo Credits: photos by CW Ye, doug.deep, zlatkarp, Nick Hobgood on flickr