Finding the right costume and "dressing up" for Halloween is all in good fun for us humans. But for
ocean inhabitants, the right disguise, or "costume," can mean the difference between life and death. Survival in the underwater world depends on whatever combination of color, texture, shape and pattern enables a particular animal to feed successfully, attract a mate and avoid being eaten. "Costumes" sometimes border on the weird or fantastical, while others are plain and simple. Either way, it's all part of nature's evolutionary design.
Brilliantly colored animals may be advertising toxicity - whether real or imagined - to would-be predators. The reproductive processes of many marine animals likewise require colorful displays, usually by males, to attract mates. Dominant, or "supermales," among parrotfishes and wrasses typically are far more lavishly colored than the drab females they attract. If not properly "attired" to draw feminine attention, these potential suitors might well be ignored.
The Hawaiian lionfish, a type of scorpionfish, is a master of disguise, blending into rocks and coral, even growing algae on its body, to fool its unsuspecting prey. When alarmed, it flashes the undersides of its pectoral fins, revealing cautionary colors of bright yellow, red and black to discourage any would-be predators. This crafty animal is endemic, found only in Hawaiian waters.
Maui Ocean Center photo
Decorative accessories such as bars, stripes, spots, dots, shadings and countershadings serve to enable a particular species to stand out from, blend in with or even be indistinguishable from its surroundings. Sometimes, a pattern simply creates confusion. Judiciously placed black "ocular bars" concealing the eyes of many butterflyfishes, and false black "eye spots" located on the tail ends of some fishes are good examples of patterns that may confuse and deter predators.
Predators often are peerless masters of disguise. By resembling something as harmless as a floating leaf or pile of rubble, they can lure unsuspecting prey into venturing close enough for capture. Without the ability to affect a disguise, creatures such as sedentary frogfishes could starve. These slow-moving creatures can stalk prey but generally prefer to remain still, resembling the habitat. They attract prey to come to them by wiggling the "esca," or lure, above their mouths.
Most scorpionfishes fall into the category of "lie-and-wait predators" that "disappear" into their surroundings. The humpbacked devil scorpionfish blends with rocks or coral and may even grow algae on its body. When alarmed, it flashes the undersides of its pectoral fins, revealing cautionary colors of bright yellow, red and black that serve to discourage any creature thinking about preying on it. In this case, color patterning serves the dual purpose of both disguise and warning.
Cephalopods excel at successful "costuming." Almost instantaneously, octopuses and cuttlefishes can change color, shape and texture to match the adjacent scenery. The rippling, iridescent mating displays of some squid species are renowned for their magnificence.
Disguise coloration can be subtle, too. Countershaded animals such as the great white shark are dark on top and light on the underside. Seen from above, the shark blends in with the seafloor. Seen from below, it blends in with the sunlit surface of the ocean. Some sharks, such as the voracious little cookie cutter, resort to bioluminescence to attract prey. The cookie cutter may produce a green glow to attract predators far larger than its self. It then turns on the unsuspecting fish or mammal and carves out a golf-ball sized plug of flesh for a meal.
So extensive is the use of "costuming" in the underwater world that many creatures appear lifeless. They may be masquerading as a waving sea frond or simply as a rock. Visitors to Hawaii often are surprised to learn that coral is made up of individual living polyps and pretty seashells actually house animals, some highly endangered. The season of Halloween reminds us all to see past the "costumes" and disguises, and consider how we might best cherish and protect the amazing inhabitants of our local waters.
* Pam Daoust is an author and marine educator at the Maui Ocean Center. "Ka Mo'olelo Moana," or "the Ocean Story," is a monthly column submitted by the Maui Ocean Center. It is open from 9 a.m. to 5 p.m. daily in Maalaea. For more information, call 270-7000.