Of Sea Whips and Sea Pens
A patch of Sea Whips and Orange Sea Pens. Photo ©Jackie Hildering.
Awestruck yet again.
On yesterday’s exploratory dive, my buddies and I discovered a “garden” of Sea Whips and Orange Sea Pens at only 65′ (20 m).
These are the most surreal looking organisms.
They are octocorals – colonies of 8-tentacled polyp-like animals. The polyps filter feed on plankton.
The Sea Whips can reach a height of 2.5 meters (Halipteris willemoesi). Orange Sea Pens can be 48 cm tall (Ptilosarcus gurney).
This is another case where images speak louder than words.
Please enjoy the following photos and clips of Sea Whips and Orange Sea Pens and . . . the predators that stalk them.
Nudibranch fan alert !
Dive buddy Natasha Dickinson with Orange Sea Pen at full height (up to 48 cm) so that polyps can filter feed on plankton. Photo ©Jackie Hildering.
Orange Peel Nudibranch (Tochuina tetraquetra) feeding on a retracted Orange Sea Pen. Photo ©Jackie Hildering.
Diamondback Nudibranch feeding on a retracted Orange Sea Pen. ©2016 Jackie Hildering.
Striped Nudibranch (Armina californica) on the prowl for Orange Sea Pens. Photo ©Jackie Hildering.
Diamondback Nudibranch (10 cm) heading for a White Sea Pen. Photo ©Jackie Hildering.
2.5 minute clip below is of Sea Whips and Orange Sea Pens and the predators that stalk them.
The BBC video below is from SW Tasmania in Australia, NOT Northern Vancouver Island, British Columbia and shows a different species of sea pen. However, I have included it as it shows, with time lapse photography, how sea pens can slowly deflate and retract in response to predation attempts by nudibranchs.
Video: 1 minute of an Orange Sea Pen and Graceful Decorator Crab in the current in front of Port McNeill, BC.
For more information:
Orange Sea Pen that has retracted as a defence to being disturbed by a predator – a Diamondback Nudibranch! Additional nudibranch predators include Striped Nudibranchs and Orange Peel Nudibranchs and small aeolid species like Opalescent Nudibranchs when the octocorals are smaller. Nudibranch species not only benefit from the nutrients but may also incorporate the stinging cells of the sea pens for their defence. The nudibranchs are able to sense the presence of the sea pens from a distance by scent (using their rhinophores). Sea Stars also prey on Orange Sea Pens. Photo ©Jackie Hildering.