DIVE DRY WITH DR. BILL #455: THE COLORFUL CORYNACTID CORALLIMORPHS!
Many divers, especially the WWWs (Warm Water Wussies), think one has to spend lots of hard earned dough and travel to the tropics to see really colorful underwater habitats. Poppycock! Balderdash! Bison DooDoo! You don't have to dive warm, clear coral reefs to see brilliant colors (although conditions there are really nice and the bikini-to-neoprene ratio is much higher). I wrote recently about my trip to the oil rigs Ellen and Eureka off the Long beach coast. I tantalized you with talk about the colorful critters I would write about in future columns. Well, this week it is time for me to put up... and I know I won't have to shut up!
After descending beneath platform Ellen and switching on my LED video lights, the rather drab "landscape" exploded with bright and varied hues of pink, purple, red, yellow, lavender and others my partially color-blind eyes could not detect. Fortunately my high definition video gear can capture them so I can share them with you! Much of this blaze of beauty came from a single species, the club-tipped or strawberry "anemone" (Corynactis californica). These critters are relatives of the coral and jellyfish and are placed in the phylum Cnidaria (formerly Coelenterata) which means they have stinging cells or nematocysts. Individual corynactids are small, up to one inch in diameter and three inches tall, but they may form large masses on suitable substrate.
Corynactids are found from Nootka Sound in British Columbia south to San Martin Island off Baja. They attach to hard substrate such as rock (or oil rigs!) especially in areas bathed in current. Although I didn't dive to sufficient depth to check this on the rigs, they are said to live as deep as 150 ft. We don't see them often on Catalina's protected leeward side, but they are more frequent on the exposed windward coast.
Like many cnidarians, the corynactids reproduce in a rather boring way. The adults simply divide in half longitudinally using asexual reproduction. Now what fun would that be? Of course it does make it much easier to start a "family" (or a colony) since they don't have to waste time looking for a mate in places like the Marlin Club (the one beneath the sea of course). This mode of reproduction means that all the individuals in a colony are genetically the same. We refer to them as clones. This includes their color, which is controlled by at least six genes rather than food or environmental conditions. No room for individuality in a colony of Corynactis. Because of this, each colony may take on a different color depending on what the genes of the original anemone were. Herein lies the source for the vivid colors on the oil rigs. I was surprised to see the Wikipedia entry for this species refers to only the red color variant (as is suggested by the common name strawberry anemone). To make it even more interesting, corynactids are able to fluoresce in several colors... if you have the eye pigments necessary to see those wavelengths!
Technically, corynactids are not true anemones. They are placed in a group known as corallimorphs, sometimes called mushroom corals. I find these cnidarians most frequently when I dive tropical waters. An obvious difference between them and the true anemones is found in their other common name, club-tipped. Tentacles on these species are generally not capable of being fully retracted. There are no other cnidarians in our waters with these club-like tentacles. Corallimorphs are also similar to stony corals... except they lack the hard calcium carbonate "skeleton."
While the clubs are not used as instruments of mass destruction, corynactids will aggressively attack and damage relatives like anemones when they come in contact with them. They extend certain tissues into the adjacent species. Corals tend to withdraw their tentacles when they come in contact with corynactids since they can't move away from their stony cups. Anemones may actually detach from the bottom and move away from the attacker. Cnidarians attacked by the corallimorph may die. When different clonal colonies of corynactids come into close contact (how's that for consonance?), there is no such hostility. Apparently the different color morphs can exist in harmony with one another... something we humans need to learn. So the aggressive behavior is only "interspecific" (between different species) rather than "intraspecific" (between members of the same species).
Corynactids feed on small crustaceans and other bottom dwelling organisms, as well as scavenge on dead critters including fish. With larger prey, the same mesentery filaments used to combat their distant relatives may come into play in feeding. Such prey may be partially digested outside the body using these tissues. You think baby humans are sloppy when they use their fingers to eat? Imagine what would happen if they could extend digestive tissue out their mouths to "lick" their food! Yes, I know... sometimes it seems like they do. Smaller prey can be transported into the corynactid's oral opening and digested internally. Most parents greatly prefer this method.
Unfortunately for those readers who get my columns through the newspaper, the black-and-white images will reveal nothing of the brilliant colors of these corynactids. For the full color version of this column, and all the rest of them please visit the archived versions on my web site (http://www.starthrower.org/products/DDDB/column.htm). You'll be glad you did (and I won't try to sell you anything... but you're free to "stimulate" my economy if you so desire!).
Image caption: The strawberry color variant and club tips of the corallimorph Corynactis californica; and incredible colors of their colonies on the oil rigs Ellen and Eureka off Long Beach.