I guess it's time to stop reminiscing about my wonderful experiences diving in Central America and get back to the reality of our southern California waters. It's important to remember that our waters have some pretty exotic critters living in them as well. One is the sea pansy, a species I haven't seen in decades... but haven't been looking for either. So this week I'll discuss an unusual local marine organism that many of you will never see... unless you are snorkeling over shallow sandy bottoms.
Sea pansies are related to the wonderful hard and soft corals of Belize and Utila in that they too are cnidarians (coelenterates). Specifically they are a type of soft coral known as pennatulaceans which includes the sea pansies and sea pens. Our sea pansies are flat, heart-shaped and purple in color with white polyps on their upper surface. Each polyp has the eight feeding tentacles typical of the soft corals. Like gorgonian soft corals, each feeding polyp sends its food to a common digestive system so all prosper (or starve) together. A fleshy structure known as a peduncle extends from the bottom of the main colony and is used to anchor them in the sand. The end of the peduncle expands into a bulb under the sand to better serve as an anchor.
Found from Santa Barbara south into Mexican waters, our sea pansies rest on the sandy bottom with their upper surface partially covered by sand. The feeding polyps extend above the sand and capture small animal (zoo) plankton and organic matter. They cannot ingest larger plankton including many invertebrate larvae. In turn, sea pansies are eaten by a type of nudibranch (the striped armina) and the sand starfish. Sea pansies can detect the presence of these predators through chemicals they release into the water, and withdraw their polyps and contract when they approach. In addition to the feeding polyps, sea pansies have specialized polyps that pump water into and out of the colony allowing this contraction.
Sea pansies begin life as planktonic larvae. They initially settle into offshore waters, then move in towards shallower sand flats. Adults in colonies move around on the sandy bottom quite a bit. They creep along the surface using muscular contractions of the entire colony. More like the turtle than the hare, but speed is not essential to their lifestyle and they conserve energy that way.
Although I have observed sea pansies in Catalina waters, it has been rare. Since my research focus is on kelp forest ecology, I spend most of my time over rocky bottom substrate. Back in 1972 when I took a group of students from the old Toyon school to Bahia de Kino, Mexico, we encountered many of them. We were down there at the same time as a marine biology class from Prescott College in Arizona. Their professor asked me if I'd seen any sea pansies there, and I said "many." She was surprised since they were trying to collect them and had found none. I asked where she was looking, and her response was in the local mudflats. I knew the sediments in mudflats are too fine and would tend to "clog" sea pansy polyps and colonies. The next day I went out with a few of my students and collected two dozen for her in no time from their preferred habitat on sandy bottoms.
One phenomenon that was of great interest to my students was the bioluminescence observed in these colonies. When touched (or attacked by a predator), waves of greenish light pulse outward from the point of contact. This "cold light" is produced by the reaction of two chemicals similar to those found in the fireflies of my Midwestern youth, or the dinoflagellates in our salt water toilets on the island. Luciferin and luciferase react to create energy which is transferred to a protein known as GFP (green fluorescent protein) that releases this energy as cold light. The pulses of light may serve to distract the potential predator. Unfortunately my students tended to touch them repeatedly until they expended too much energy to luminesce. Guess they rarely encounter human curiosity underwater.
© 2004 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 49, 10:00 AM and 5:00 PM weekdays.
Upper surface of a sea pansy colony with polyps
extended; colony showing peduncle that anchors
it into sand; a closer view of the feeding polyps; the sand starfish which feeds on them.
This document maintained by
Dr. Bill Bushing.
Material © 2004 Star Thrower Educational Multimedia