The sea pen, Ptilosarcus gurneyi, is a colonial cnidaria in the same class as the anemone, the anthozoa. One polyp has been modified to form the body while the fringes of the 'feather' contain numerous small feeding polyps.
This closeup shows the individual polyps lining the rows. A small majid crab has climbed aboard, and may be nipping at the polyps, though the crab's activity did not stimulate Ptilosarcus to close.
Buds seem to be growing off 3 of the laminae on the right side of the plume of this individual. Does Ptilosarcus do any budding for reproduction? Photo by Dave Cowles, July 2005
