>Newsletters>September 2006>Diving with Cuttlefish

Scuba Your Guide to Diving in Myanmar Newsletter

Cuttlefish

It's normally love at first sight with the fascinating cuttlefish. On your first encounter you're likely to be struck by its overt curiousity in you, the rhythmic wafting of its frills, its pulsating skin and its seemingly intelligent eyes.

Common throughout the Indo-Pacific, Europe, Africa and beyond, the cuttlefish is not a fish, but a mollusc from the class of cephalopods, and a cousin of the octopus. It can swim at great speeds over short distances, camouflage itself instantly, confuse its predators with a blast of foul ink and capture its prey with an incredible display of visual hypnotism.

Cephalopods are widely believed to be the most intelligent of the world's invertebrates, which make up 95% of all creatures in the animal kingdom. Experiments show that cuttlefish learn swiftly, and many scientists are of the opinion that they can learn by observation.

Cuttlefish Fact Sheet

Family name: Sepiidae
Order name: Sepiida
Common name: Common or European cuttle-fish
Scientific name: Sepia officinalis

Distinguishing Features

The cuttlefish is so called because they have a bone in the middle of their bodies, known as a Cuttlebone. This bone is filled with gas which is used for buoyancy control. Averaging 30cm in length (giant cuttlefish can grow up to 100cm), they have 8 arms and 2 prehensile (capable of grasping) tentacles around their parrot-like beak, which they use for feeding.

Like octopus, cuttlefish have chromatophores on their skin which they can change instantaneously both in colour and texture, making them among the best camouflage experts in the animal kingdom.

Their eyes are remarkably similar in construction to human eyes and there is an unmistakable feeling that you are dealing with an intelligent creature when you find yourself in a staring at a cuttlefish.

Habits of Feeding

The cuttlefish is a bottom-dweller which often lies in ambush for smaller animals such as crabs, shrimp, fish and small molluscs. Stealthily a cuttlefish will sneak up on its prey. Often this gradual movement is accompanied by a light show over its skin where bands of colour pulsate along its body causing its prey to freeze, seemingly entranced. Then it splays its 8 arms wide and fires out 2 long white feeding tentacles that grab the prey and pull it back into the crushing beak. It's such a dramatic attack that divers are often endlessly fascinated after their dive.

Reproduction

Mating cuttle-fish align their bodies head to head so the male can transfer a sealed package of sperm into a pouch beneath the female's mouth. The female then scurries off to a quiet place where she draws eggs from her cavity and passes them over the sperm, thereby fertilising them. In the event of there being multiple sperm deposits, unlike humans, it is the one at the back of the queue, i.e. the last to deposit, who wins the day.

The eggs are often then distributed in clutches coated with sepia both to act as an adhesive force and also to camouflage them. Cuttlefish can lay around 200 eggs in clutches often nearby eggs of other females. After between 2 and 4 months the young hatch with a supply of yolk that nourishes them until their first kill.

Life-cycle

Unlike their squid and octopus cousins, baby cuttlefish are highly developed and independent straight after hatching. They immediately begin tracking down small crustaceans and instinctively employ all their natural predatory armoury.

Despite their incredible range of defence and attack mechanisms and their obvious intelligence, cuttle-fish do not live very long. Life expectancy is between 1½ - 2 years and females die shortly after spawning.

Predation

The first form of defence that cuttlefish employ is try to avoid being spotted in the first place by using their remarkable and instantaneous camouflage which can make them look like coral, rock or sea bed in the blink of an eye. Similar to squid, a cuttlefish can squirt ink into the water, enveloping its would-be predator in a disorientating cloud of foul tasting blackness. The main predators of cuttlefish are sharks, fish and other cuttlefish. Dolphins also attack cuttlefish but oddly eat only their heads.

Distribution

European common cuttlefish are found all along the eastern Atlantic from Scandinavia to South Africa and the Mediterranean. Most other species, such as the flamboyant cuttlefish, are found in Asian waters and in Australasia. They are not present in the Americas.

Ecological Considerations

Cuttlefish are not high on endangered species lists and there is not a lot of data on their population numbers. However, fishermen in South Australia catch up to 71 tonnes during their mating season. Because of their short life span and their spawning only once in a lifetime, the threats of over-fishing are obvious. Currently there are no restrictions to limit the number of cuttle-fish that can be caught but there is pressure to add Giant Cuttlefish to the endangered species list.

Destinations

Dive the World has many great destinations for diving with of these fascinating creatures. Cuttlefish are common in the dive destinations of Myanmar, Thailand, Malaysia and Indonesia.