Dive Dry with Dr. Bill

#271: A Valentine's Pansy?

This column is appearing on Valentine's Day, normally a mildly depressing day for solo divers like myself. However, this year is different... although I'll keep my secret hidden for the time being! Gentlemen like myself may kiss, but they don't tell. I did want a species that might remind my readers of Cupid's favorite day. Arrow worms didn't seem quite appropriate, bow head whales spend their lives in the Arctic and aren't found in our waters, and I covered heart urchins a while back. I finally decided to resurrect a species I covered several years ago which has a vague resemblance to a heart.

Last summer the King Neptune stopped on the inside of the dive site referred to as Hen Rock. In other words, we were actually close to the rock given that name thanks to someone's wild imagination (or foggy glasses), and were within easy striking distance of the mooring area there. Rather than spend my time over the rocky reef, where I'd most likely see just "the usual suspects," I elected to spend my time out over the sandy bottom between the moorings.

Now sandy bottom habitats often appear very barren like their similar terrestrial habitat, the desert. But if you look closely, this really isn't true. And despite not wearing a prescription dive mask, I can see clearly... if I look just below the surface. Life abounds over sandy bottoms. It just doesn't spend much of its energy budget advertising its presence. If it did, predators could easily spot... and eat them in these habitats with little protective cover other than the sand itself. Most sand-dwelling critters are known as "infauna," that is they live beneath the surface of the sand to hide from hungry halibut or other perambulating predators.

As I filmed the many burrows, piles of feces and trails in the sand that were the clues to the presence of these "infauna," I saw a purple heart-shaped critter partially buried at the surface of the sand. No, I don't think one of our brave soldiers lost their Purple Heart. Although the color and timing just wasn't right for Valentine's Day at the time, it is close enough to qualify today!

This purple colony was none other than the sea pansy, a relative of the soft corals known as gorgonians or sea fans found on rocky bottoms. However, the sea pansy lives on the sandy bottom just like another close relative, the sea pen. These critters have small feeding polyps with eight tentacles that capture food and pass it on to a common stomach in the heart-shaped "body." All polyps, and the rest of the purple pansy, share in the food resources captured. Somehow that seems a lot more appropriate than the "slash and bite" mentality some mistakenly attribute to Darwin's "survival of the fittest." The whole organism survives, so each polyp prospers. I think human social orders could use a bit more of this compassion and graciousness towards "others," but then I'm a child of the... er, 60's. Actually Darwin later said it is not necessary the strongest or the most intelligent that are most fit, but the individuals and species most adaptable to change.

Sea pansies only eat the smaller animal or zooplankton, and drifting organic matter. Their polyps are too small to engulf a large steak... er, I mean a large invertebrate. Since this is the "mutual eating society," in turn they fall prey to large invertebrates like the sand starfish or striped armina nudibranch. After all, food webs and ecological systems are all about capturing and passing on energy, as well as recycling matter, in the form of the billions of different species on Earth... as long as the "matter" isn't mine! If you're inclined towards time travel, next time you take a bite of broccoli or local swordfish, consider that at one time many millions of years ago, the atoms in it may have been part of a Tyranosaurus rex! Go back billions of years, and the carbon in that meal may have been created in the deep interior of a star. Isn't that a tasty thought.

Recently I've also seen a number of sea pansies in the sandy shallows and eelgrass beds off Salta Verde Point. I'm reminded of a collecting trip I took with my Catalina Island School (Toyon Bay) students to Bahia de Kino Mexico in the early 1970's. A group of university students was there and saw a bucket of sea pansies I had collected for the Los Angeles County Museum. The professor was astounded since she had been searching for them on the mudflats, which one field guide suggested was their favorite habitat. I guess it was written by one of those armchair naturalists who study biology from the comfort of high rises and libraries, since the sediments on mudflats are very fine and might clog the polyps. The next day my students and I gathered about two dozen sea pansies from the coarser sandy bottom habitats for her class.

Sea pansies live at the surface of the sandy substrate. They use a long, fleshy peduncle that extends into the sand as an anchor to keep the colony stable in the surf and surge. However, when the water is still, or they are dislodged, the colonies are able to slowly "crawl" along the surface of the sand. They do so by muscular contractions of the colony, not unlike that of an inchworm on your garden's tomato plants. This makes them "epifauna," animals which live on top of the substrate.

So how do these potentially vulnerable, soft bodied critters survive? There are no obvious spines, claws or biting mouthparts to use for defending their lives. If there were, they would belong to a different phylum. Members of the phylum Cnidaria usually possess stinging cells known as nematocysts. When triggered, these shoot barbs into a potential predator and inject a toxin. I've never felt nematocysts while handling these critters in the lab, but did a little research and found they do indeed possess them. They also have a secondary defense mechanism. When approached by a predator, or a curious student, sea pansies may emit pulses of bioluminescence just as the diatoms in your salt water toilet do late at night! This cold green light is produced by a process similar to that in fireflies... the combination of the chemicals luciferin and luciferase which transfer energy to GFP (green fluorescent protein). Unfortunately my students tended to continually prod the poor critters... I guess in hopes they could write a "glowing report" for my class.

So, Happy Valentine's Day to all my readers. I'm taking Darwin's advice, and adapting well to what may be a change in my romantic status!

© 2008 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 and on Charter Communications Cable channel 33 at 7:30 PM on Tuesdays in the Riverside/Norco area. Please help me climb out of self-imposed poverty... buy my "Munching and Mating in the Macrocystis," "Great White Sharks of Guadalupe," "Calimari Concupiscence: Mating Squid, " "Playful Pinnipeds: California Sea Lions," "Belize It or Not: Western Caribbean Invertebrates, Fish and Turtles," "Gentle Giants: Giant Sea Bass," "Common Fish and Invertebrates of the Sea of Cortez" or the upcoming "Sharks and Rays of Southern California" DVD's. Yes, take Dr. Bill home with you... we'll both be glad you did!

Sea pansy seen out of its element in my lab, overturned sea pansy showing
the peduncle used to anchor it in the sand, feeding polyps of the colony.

This document maintained by Dr. Bill Bushing.
Material and images © 2008 Star Thrower Educational Multimedia