Ocean Watch
By Susan Scott
Cleaner shrimp play
medical role for fishRecently, I went diving with my husband, and as usual, I lost track of him. This happens often because Craig thinks scuba diving is a distance event that tests how far a person can go on one tank of air. I, however, can use up an entire tank poking around one coral head. We try to compromise, but still, we get separated.
This time, a patch of garden eels slowed my progress, and when I looked up, Craig had vanished. I followed the distant bubbles down a slope and came upon an astonishing sight. There he was, lying on his stomach next to a coral head, holding his regulator in his hand and his mouth wide open. And out of his gaping mouth poked the long white antennae of a scarlet cleaner shrimp. Craig was getting his teeth cleaned.
When he could hold his breath no longer, he slowly exhaled. The shrimp gently whooshed out of his mouth and disappeared under coral.
I had to try it. I positioned myself near the shrimp's hideout, and before I even removed my regulator, that industrious little creature headed for my mouth. In a moment, I, too, got my teeth cleaned by the shrimp. And it tickled.
This bold behavior, I later learned, is not unusual for these cleaner shrimp. If a diver extends a hand, the shrimp will usually pick the human's fingernails. One picture I found shows two red cleaner shrimp (another species) walking over a person's hand, grazing on bits of dead skin.
Hawaii's scarlet cleaner shrimp grow to about 2.5 inches long, but their two pairs of long, whiplike antennae make them seem larger. Researchers believe the brandishing of these distinct feelers is a location signal. When a fish spots these white whips waving from a hole, it swims over for a cleaning.
A common picture in books and on calendars shows one of these colorful shrimp working busily inside the wide-open mouth of a large moray eel.
This cleaning looks like a dangerous occupation, but it isn't. Fish allow cleaner shrimp to crawl over their bodies and inside their mouths and gills because of parasites. Small crustaceans called isopods and copepods, and certain worms, attach themselves to fish wherever they can. These parasites live off their hosts and can cause considerable damage, including infections.
This relationship between cleaner shrimp and fish is a good example of symbiosis, also called mutualism, in which different species benefit from their interaction with one another. In this case the fish get rid of parasites and dead tissue, and the shrimp get meals.
Other shrimps on Hawaii's reefs also offer cleaning services. The red-and-white banded coral shrimp (also called barber pole shrimp) provides the same assistance as its scarlet cousin, only at night. An equally beautiful but less common cleaner is the flameback coral shrimp. All these shrimp bear red markings, which may also act as a signal to fish.
Craig didn't invent the practice of letting a cleaner shrimp roam in his mouth. Our dive master, I later learned, showed him the location of the shrimp and the way to attract it.
I am reminded by my speedy spouse that by being poky, I nearly missed the whole thing. But he missed playing with the garden eels.
NEXT MONTH: Puffins, selkies and the Loch Ness monster. Aye, I'm off to Scotland. Byan achk leht (goodbye). Back Sept. 6.
Marine science writer Susan Scott's Ocean Watch column
appears weekly in the Star-Bulletin. Contact her at http://www.susanscott.net.
