| The Magazine of the CALIFORNIA ACADEMY OF SCIENCES |
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Wild Lives Weedy Scorpionfish"Scuba-diving on a coral reef is like going on a three-dimensional Easter egg hunt," my dripping wife tells me with a bemused gleam as we surface from searching the nooks and cranies for elusive species. Last April, Pam and I were diving with a group of friends from the California Academy of Sciences off northern Papua New Guinea, perhaps the most beautiful and biologically diverse reef habitat on the planet. At the top of our search list of ichthyological eggs was Rhinopias aphanes, the weedy scorpionfish. Although it is known from New Guinea, northern Australia, New Caledonia, and Japan, in my 35 years of underwater exploration I had never seen a living R. aphanes. To be precise, I may have seen it several times, but it is so well camouflaged that I didn't know. This tall, flat-sided scorpionfish is festooned with tentacles, lappets, and fleshy growths, and dressed with a marbled livery in a variety of zebra-striped hues, ranging from yellow to brown to orange to plain black and white. Although it reaches a length of nearly ten inches, its flanks are no wider than an inch. Included with the venomous scorpionfishes, lionfishes, and stonefishes of the family Scorpaenidae, Rhinopias is probably painfully poisonous. But camouflage is its main defense; only if attacked would its venomous dorsal spines come into play. Like the warty frogfish or wide-mouth stargazer, it is a lie-in-wait predator resting motionless about 30 feet down, awaiting an incautious cardinalfish or damselfish seeking refuge on the bottom. To further the ruse, Rhinopias settles on reefs that are washed by plankton-laden currents and harbor numerous hand-sized crinoids. Such filter-feeding echinoderms pose no threat to the small plankton-feeding fishes upon which Rhinopias preys. Some scientists suggest that the scorpionfish might mimic the surrounding crinoids; after seeing them together, I'm convinced that it does. The weedy scorpionfish received its scientific appellation from Academy ichthyologist William N. Eschmeyer in 1973, on the basis of a specimen collected alive off Noumea, New Caledonia. (Lacking an internal gas bladder, the fish came up alive and didn't suffer from embolism as do so many other reef fishes that are rapidly brought up from depth. The gas bladder has either atrophied or been severely reduced in the evolution of most lie-in-wait predators that choose to remain on the bottom.) Eschmeyer named the new species aphanes, a Greek word meaning "that which is unapparent or inconspicuous," alluding to the camouflage provided by its remarkable coloration and skin flaps. It is closely related to other scorpionfishes of the genus Rhinopias, whose generic name was created by the American ichthyologist Theodore Gill in 1905, an allusion to its prominent, upturned nose. But back to the hunt. I had advised our two dozen diving cohorts to look carefully for Rhinopias along the reefs, realizing that it might be mimicking black-and-white crinoids, and to search carefully for its eyes, the only part of any fish's anatomy that is difficult to hide. After several days the Easter egg hunt was renamed the "aquatic snipe hunt," but finally one morning on a remote reef in the D' Entrecasteaux Islands my wife persevered, hooted "yahoo" underwater through her regulator, and pointed proudly to a fist-sized weedy scorpionfish. As I pondered this incredible beast, lying and waiting calmly on the reef, I was made aware of two biological maxims. First, without a search image in place, a predator, particularly Homo sapiens, is likely to overlook the obvious. And secondly, many widely distributed species, although described as "rare" in field guides, are often common somewhere. This is not to suggest that our species hasn't made many others (particularly in freshwater habitats) rare, endangered, or even extinct, but rather that the patterns of nature are often right before our eyes if only we are patient enough to search for them. John E. McCosker is Senior Scientist and Curator of Aquatic Biology at the California Academy of Sciences. |
Fall 1998
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