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The Australian giant cuttlefish (Sepia apama) is the world’s largest cuttlefish. Specimens can measure up to 50 centimeters in length and weigh up to 10 kilograms (23 pounds). Like other cuttlefish, the giant cuttlefish are masters of color transformation and can use the chromatophores (special transformative muscle cells) in their skin to instantly change the hue, reflectivity, polarization, and even the shape of their skin. They use this ability for hunting, hiding from predators, and for spectacular mating displays. Indeed, the giant cuttlefish is a remarkable animal in many ways, but, above all, it is notable for its operatic sex life!
Sepia apama ranges in all coastal habitats from Brisbane on the Pacific to Shark Bay on the Indian Ocean (effectively the entire southern coast of the continent). Thanks to jet propelled speed, color-transforming ability, sharp eyesight, high intelligence, and lightning fast grab jaws (which are located on two extendable arms), these cuttlefish are terrifyingly effective hunters of fish and crustaceans. Australian giant cuttlefish from different regions of the coast do not interbreed, even though they are genetically the same species. Like humans, the giant cuttlefish seem to form different sorts of societies with different mating customs: for example the giant cuttlefish of the Spenser Gulf region are unique (apparently among all cuttlefish) in that they join together for a spawning aggregation in the waters immediately around Point Lowly.
Unlike humans, there are eleven male cuttlefish for every single female giant cuttlefish! Large dominant male cuttlefish carve out territories with aggressive posturing and insanely bright flashing color displays. Smaller males (who do not wish to be ripped apart), distract the alpha male cuttlefish by adapting the color schemes of female cuttlefish and courting him. They then abruptly change color and pay (rapid) court to the polyandrous females. The female stores sperm packets from several males and she chooses the paternity of her offspring only after she lays her eggs. Cuttlefish are semelparous—they mate only once, and then they immediately die. The whole beautiful horrifying op-art orgy in the waters around Point Lowly is of paramount importance—and is also reckoned to be one of the unrivaled diving spectacles of the world.
Unfortunately all of the Spenser Gulf cuttlefish tend to be in one place at once. Since they only reproduce one time, they are very vulnerable to fisherman, who, up until the mid nineties, descended upon the area, captured most of the cuttlefish, and chopped them into bate for snappers. When one cohort was removed, the next was seriously attenuated!
Fortunately the spawning waters of Spenser Gulf are now a protected refuge, yet hydrological changes, agricultural run-off, and industrial development could still threaten the entire population. Perhaps the other Australian Giant Cuttlefish (who conduct their romantic affairs in a more disparate manner) are on to something.
When I was a child, my family went to the invertebrate house in Washington, DC. Upon entering the building, there was a very beautiful aquarium which contained the most alien creature I have ever encountered. It was a beautiful glistening red…and then it instantly changed color to bright white with pale dun spots. Next the strange being sank through the water column and changed color and texture. Its smooth skin knotted up into ropey bumps. The speckled white tuned to wavy deep brown lines. Intelligent eyes with W-shaped pupils regarded me from what suddenly seemed to be a hunk of rock. I had encountered my first live cuttlefish. In fact there were two in the tank, as I discovered when a patch of unremarkable sand changed shape and color and jetted to the surface while flashing rainbow colors. They were worked up because they were about to be fed and, when eating their suppers, the cuttlefish put on a particularly good show. They changed color like digital screens and waved their eight arms about and then ZAP! elongated feeding tentacles shot out from under their mantles to grab the anchovies from across the length of the tank. Then they rocketed around with uncanny torpedo speed.
Cuttlefish are cephalopods like octopuses, argonauts, squid, and nautiluses. Across the long ages they have descended from those magnificent nautiloids and othocones who ruled the world during the Ordovician era. Cuttlefish are one of the most intelligent invertebrates: their brains make up a substantial portion of their body mass, and their behavior when hunting, hiding, and courting is complex. The unusually shaped eyes of the cuttlefish are among the finest in the animal kingdom. Their blood makes use of copper rather than iron to fix oxygen so it runs green. All cuttlefish possess poisons in their saliva. In fact the Pfeffer’s Flamboyant Cuttlefish is as toxic as the Blue-ringed octopus.
But why am I talking about these extraordinary mollusks during a week devoted to blogging about color? First of all cuttlefish are “the chameleons of the sea.” As I observed at the zoo, they can change color with a speed and facility unrivaled by any other creature. They use their mastery of color to camouflage themselves, to hunt, and to communicate with each other. The animal’s existence literally hinges around the color-changing chromatophores in their skin. But the association of cuttlefish and color doesn’t stop there. Cuttlefish produce a dense ink which they squirt into the ocean to disguise their movements when frightened. This sepia ink, collected from the ink-sacks of common cuttlefish destined for the table, was prized for writing and for drawing during the classical era. Many of the great histories and literary masterpieces of Greco-Roman thought were first penned in sepia ink. Although other inks took the place of sepia for writing, it maintained its place in the artist’s studio up until the late nineteenth century when it was supplanted by synthetic pigments.
This means that many of the masterpieces of draftsmanship were also created with sepia ink. A particularly effective and pleasing style was to sketch something in watered down sepia washes and finish the details with black india ink. Like chartreuse, magenta, and vermilion, the name sepia itself has become synonymous with a color. This reddish brown is famous in old masters pen-and-ink drawings, antique photos, and memory-hazed movie flashbacks. Not only has this ink provided some of the most beautiful drawings in history, recent studies have shown that cephalopod ink is toxic to certain cells—particularly tumor cells, so we may not have written the last concerning sepia ink.