Not quite an octopus, and not quite a squid either, cuttlefish are cephalopods and are so closely related to these animals that they are sometimes misidentified. Like their close cousin, the nautilus, they are capable of making very deep dives; some species have been recorded at depths around 600 meters beneath the surface. These amazing creatures prefer shallow water, however; meaning that if you know when and where to look, you could find yourself swimming among them, awestruck by their pulsating, colorful bodies. Let’s take a closer look.
What is a Cuttlefish? The Basics
Members of the order Sepiida, and actually mollusks rather than fish, Cuttlefish are highly intelligent invertebrates. Although they lack a spine, their bodies do contain an internal shell called a cuttlebone. This little structure has gas filled chambers and is used for buoyancy control, allowing the cuttlefish more mobility than some of its relatives. They have three hearts, eight arms equipped with suckers, and highly developed eyes with distinctive “W” shaped pupils. Unlike most other creatures that hatch from eggs, they are capable of seeing before they emerge.
While most cuttlefish range in size from just under 6 inches to about 10 inches, the Australian Giant Cuttlefish is much larger, reaching about 20 inches long and weighing in at around 23 pounds. Like many other cephalopods, cuttlefish can release a cloud of inky looking pigment when alarmed, creating a smokescreen effect that allows them to escape would-be predators.
Feeding mostly on sea worms, shrimp, crabs, smaller mollusks, and even octopus and other cuttlefish, these animals live for an average of one to two years. Besides other cuttlefish, their predators include seabirds, fish, seals, sharks, dolphins, and humans.
Nicknamed the Chameleon of the Sea, cuttlefish are capable of changing their skin color for both communication and camouflage purposes. Their highly specialized skins contain up to 200 individual pigment cells per square millimeter, which are controlled by minuscule muscle cells that are used to effect changes in color and pattern. Their skins are amazing, containing a veritable rainbow of chromatophores, with yellow colors closest to the skin’s surface, shades of orange and red beneath those, and darker colors ranging from blue to black beneath those. Under all these layers lie another layer of cells called iridophores, which are plates of chitin that are capable of reflecting the environment around the cuttlefish and producing metallic green, blue, silver and gold tones that look much like flashing lights. Not only are they capable of color change, they can change reflected light’s polarization in order to create special signaling sequences. This means that cuttlefish can sometimes be very hard to find, blending in perfectly with their surroundings; sometimes, however, they can be seen from a distance, particularly when communicating.
While cuttlefish use their incredible color changing capacity to hide from predators, they also camouflage themselves to hunt, sneaking up on unsuspecting prey, grabbing it, and consuming it quickly.
Commonly Encountered Cuttlefish Species
There are more than 120 distinct cuttlefish species, with some being more spectacular than others. Here are just a few of the many intriguing types of cuttlefish you might encounter while diving.
Pfeffer's Flamboyant Cuttlefish
Pfeffer's Flamboyant Cuttlefish occurs in tropical Indo-Pacific waters around southern New Guinea, northern Australia, the Philippines, Malaysia, and Indonesia. The only species of cuttlefish known to walk on the ocean floor, it has a very small cuttlebone and can only float for short periods of time. It is a small cuttlefish, with its mantle only growing to an average length of about three inches; even so, it is easy to spot, thanks to its brilliant displays that flash bright yellow and red. One of only three cephalopods to have been shown to be toxic, its flesh contains a potent neurotoxin which can be lethal, and which is comparable to that released by its cousin, the Blue Ringed Octopus. Usually found in shallow water and never recorded at a depth greater than 86 meters, it is a favorite subject for photographers.
The Broadclub Cuttlefish
The Broadclub Cuttlefish has a mantle nearly 20 inches long and is the second largest known cuttlefish species. Capable of displaying a wide range of colors and textures, it often appears to be yellowish to light tan with mottled white markings while at rest. The arms have white bands that expand to large white blotches when extended, and some have been recorded with brown bands as well. Often displaying vibrant shades of pink and sometimes taking on a pearlescent look, they commonly prey on shrimp and prawns, which they seem to mesmerize by rhythmically pulsating their color bands. Widely distributed throughout northern Australia, New Guinea, Fiji, and the Andaman Sea, these reef-dwellers never seem to stray to depths beyond 30 meters.
European Cuttlefish
European Cuttlefish range throughout the European Union, particularly around the UK, as well as in the Mediterranean, North and Baltic Seas. Sometimes found in South Africa as well, this species is extremely adaptable and often takes on the characteristics of ocean substrate, enabling it to hide and hunt effectively. Often very difficult to spot until you know exactly what you’re looking for, these cuttlefish can be found at depths from just below the low tide line all the way down to 200 meters. Like many other cuttlefish species they mate year-round, with spikes between March and June. Averaging a bit more than 15 inches long, this large species is fished, both for culinary use and for its cuttlebone, which is commonly used as a calcium and mineral supplement for pet birds, chinchillas, hermit crabs, and reptiles like tortoises.
Stumpy-Spined Cuttlefish
Stumpy-Spined Cuttlefish can be found throughout the Indo-Pacific region, with thriving populations around northern Australia and the Marshall Islands. Shallow coral reef dwellers that are most active at night, these cuttlefish display a walking behavior and put on flamboyant shows in territorial disputes and mating dances. Ambush predators that tend to take on the substrate pattern of whatever is behind them, they have lightning fast reflexes. Sadly, this species lives for only about a year before it dies, often being consumed by crabs while still alive. Researchers have noted that this species becomes listless and loses its eyesight before finally succumbing to a slow death.
Whyalla Cuttlefish
Whyalla Cuttlefish, also known as Giant Australian Cuttlefish, are a migratory species found mostly around Australia. Each year, between May and August, they congregate by the thousands along the coastline between Fitzgerald Bay near Whyalla, and False Bay, where they spawn. Incredible to observe, these fish bring in droves of divers who enjoy watching their unique and colorful displays.
These are only a few of the most spectacular cuttlefish you might find as you enjoy diving at sites around the world. While most are completely non-poisonous, some are toxic; remember never to try to handle them and you’ll get the privilege of watching them in action.