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Home › Ocean Wildlife Facts › Marine Species › Invertebrate › Mollusks › Cuttlefish

Fun and Interesting Facts about Cuttlefishes

[Cuttlefish Phylum: Mollusca] [Class: Cephalopoda] [Order: Sepiida] [Family: Sepiidae]

Even though cuttlefishes are cephalopods with quite a broad distribution around the world, they are mostly absent from the Atlantic and Pacific coastlines of Central America.

This section contains some fascinating facts about cuttlefish (order Sepiida) including where they thrive best, what they eat, and how these decapodiformes reproduce.

Cuttlefish Global Distribution and Habitats

The greatest diversity of cuttlefishes is found in the Indian and Pacific Oceans, and especially:

• East Africa
• Japan
• Northern Australia
• Southeast Asia

Some species of cuttlefish also exist in the Red Sea, the Mediterranean, and the Eastern Atlantic, including the British Isles and even Norway.

The typical habitats that these soft-bodied marine molluscs prefer are shallow neritic zones and coastal waters less than two hundred metres deep.

Unlike some squids and octopuses, cuttlefish are not a pelagic species. Instead, they like to bury themselves in the sand or muddy bottoms of the seabed for maximum camouflage. Hence, they are commonly found hiding near the coral reefs and seagrass beds of healthy ecosystems.

Cuttlefish Characteristics and Behaviour

The molluscan class Cephalopoda contains several cephalopods with remarkable body structures and behavioural traits, such as the chambered nautiluses (family Nautilidae).

Cuttlefishes (sometimes called cuttles) are not actually fish, but they rank among the most intelligent of all aquatic invertebrates.

Along with their close relatives, squids and octopus, cuttlefish are marine invertebrate mollusks that also exhibit a number of idiosyncrasies that often defy belief.

For example:

They display observational mimicry (a form of dynamic camouflage) and they are also capable of solving problems.

They communicate through changes in body colour, patterns, and postures. Research also shows that cuttlefishes remember past experiences and specific prey locations.

Body Structure and Tentacles

The body shape of cuttlefish is mainly flattened and oval with wide fins running down each side. With help from the cuttlefish bone (a rigid internal chambered, calcareous shell), they can hover motionless and carry out maneuvers with near perfect precision and buoyancy control.

Cuttlefish have two (2) tentacles that are like spring-loaded harpoons and tipped with toothed clubs (denticulated) used to grab their favourite prey - small slippery fish.

However, apart from the 2 tentacles, they also have eight (8) legs, making a total of ten (10) appendages.

They usually keep their retractable tentacles hidden in special pockets beneath their eyes - curiously with "W" shaped pupils for binocular vision.

Using a two-step feeding system of tentacles for capture, and arms for retrieval back to the beak, cuttlefishes have become extremely efficient ambush predators.

Cuttlefish Size and Weight

One of the smallest of all cuttlefishes is the dwarf cuttlefish, measuring about nine (9) centimetres long (4 inches overall body length) and weighing around 45 grams.

However, the giant cuttlefish is one of the biggest. Full grown adults can be fifty centimetres long (around 20 inches) and weigh more than ten (10) kilograms (23 pounds).

Interesting Fact: Most cephalopods possess an ink sac that contains an "inky" substance made of melanin and mucus. They can squirt ink through a funnel to confuse their predators and as a form of deception.

What Do Cuttlefish Eat?

Using a deadly combination of speed and camouflage, they shoot out their extendable tentacles to snag a victim and immobilise it with a toxic bite from their beak-like mouth.

Cuttlefish are typical invertebrate carnivores that consume marine crustaceans (e.g., crabs, shrimps), mollusks (e.g., clams, snails), polychaete worms, and fish.

Different Types of Cuttlefish Species

How Do Cuttlefish Reproduce?

To say cuttlefish reproduction is intriguing, dramatic, strategic, and sometimes deceptive would actually be a bit of an understatement.

Not only do cuttlefish have a short lifespan, generally between one and two years, most die soon after reproducing due to a life strategy known as 'semelparity'.

In more detail...

The males try to attract females with a dazzling display of colour pattern changes and arm gesturing postures. This dynamic ritual also serves as a warning to any potential rivals that want to mate with their chosen female.

Some of the larger males have enough confidence to guard their females. Whereas, smaller species often resort to using 'sneakier' tactics.

They disguise themselves with body patterns that resemble a female's to try and slip past their rivals and perform the courtship without being noticed.

Male Mating Process and Fertilisation

Using a specialised reproductive arm (called the hectocotylus), the male transfers his sperm packet that contains spermatophores into the pouch located near the mouth of a female.

Following that, internal fertilisation occurs when she decides to fertilise her eggs using the stored spermatophores.

Females need to attach the dark coloured, ink-coated eggs (sometimes several hundred in each clutch) onto some solid substrate, such as coral, rock, or some other kind of artificial structure.

Depending on the water temperature, it can take a few months for the eggs to develop enough for the hatchlings to emerge as miniature versions of the adults. Nonetheless, they will be fully formed with suitable camouflage and effective hunting abilities.

Fun Fact: It is quite common for cuttlefish males to compete fiercely for access the ripest females. Furthermore, some of these "male on male" battles involve physical grappling and intense colour displays.

Cuttlefish Predators and Threats

The incredible camouflage skills and clever defences of cuttlefishes are the main reasons why their populations are not particularly vulnerable.

However, all marine cephalopods face a multitude of natural predators in the wild, along with a few human-related activities that are causing some habitat loss and degradation.

Apart from large squid and other cuttlefishes in the order Sepiida, the top predators of cuttlefish species include:

• Large fish families (barracudas, groupers, and tuna)
• Marine mammals (dolphins, seals, whales)
• Rays
• Seabirds
• Sharks

Human-Related Threats to Cuttlefish

It's fair to say overfishing and bycatch have an effect on a significant amount of sea wildlife and vulnerable marine species in the seas and oceans.

Cuttlefish are also targeted as seafood in many countries, especially in Asia and around the Mediterranean. Besides being caught "accidentally" in trawls and nets, other issues environmental include:

• Climate change (rising sea temperatures and ocean acidification may affect cuttlebone formation)
• Ocean pollution (especially plastics and heavy metals)
• Noise pollution (cuttlefish rely on subtle cues and vision for hunting and communication)
• Loss of natural habitats (e.g., coral reef decline, seagrass destruction, and coastal developments)

Pro Tip: In 2009, the IUCN Red List of Threatened Species logged the conservation status of the Giant Australian Cuttlefish (Sepia apama) as "Near Threatened" (NT).

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