National Geographic : 1995 Sep
A MUTUAL admiration society exists between divers and the giant cuttlefish. Shy and solitary by nature, Sepia apama are often attracted to bright col ors; they sidle right up to divers wearing today's fashionable hot pink and green wet suits. Maybe it is because of the yellow tank I sometimes carry, or maybe it is simple curiosity, but giant cut tlefish have come so close that I can pet them on the back. Just as cuttlefish will follow meforupto15minutesata time, I can't help ogling them back. They change colors as flu idly as a neon sign, showing reactions like aggression, fear, or sexual excitement. Divers encounter S. apama only in southern Australia's coastal waters. Reaching four feet in length, they are the larg est of the hundred or so species of cuttlefish, all characterized by the thick, chalky internal shell called a cuttlebone. Cuttlefish belong to a class of mollusks called Cephalopoda, which includes octopuses and squid. Like their kin, cuttlefish have highly developed brains for invertebrates; I sense their intelligence whenever I meet the stare of their large eyes. Some one is obviously home. Like the octopus and the squid, the cuttlefish has sucker lined appendages growing from its head; the cuttlefish has ten in all, including two hidden tenta cles. When it goes for speed, it shoots its eight arms out to streamline its form. When it hovers, using skirtlike fins to stabilize itself, the arms droop down and sway like kelp fronds. A cuttlefish communicates as vividly with its arms as with its skin colors. Brushing past a div er 30 feet down in Jervis Bay, south of Sydney, a large adult, probably a male, showcases its long outer arms (right), flattened and angled downward like bent swords-a posture assumed when confronting other males. In the same area, near a bright patch of ascidians, or sea tulips, I startled a smaller adult rounding a corner. Its skin flashing the colors of its surroundings, the animal threw up its arms (below), in what I took to be a back-off gesture. Cuttlefish will bite pushy divers, snipping through wet suits with sharp, parrot-like beaks. Heeding the message, I gave way.