Cuttlefish are molluscs (related to snails and clams) and along with squid, nautilus and octopus make up the group called cephalopods, meaning ‘head foot’. All species in this group have tentacles attached to their head.
The brain of a cuttlefish is enormous compared to other invertebrates (animals without a backbone) enabling cuttlefish to learn and remember. Despite being colour blind, they have very good eyesight and can vary their colour, shape and movement rapidly to communicate or camouflage.
Male cuttlefish will display vibrant colour variations during courtship. In reproduction the male passes the female a packet of sperm using a specially adapted tentacle. The male will then guard the female until she lays a cluster of fertilised, black grape-like eggs which are attached and anchored to seaweed or other structures.
There are three species of true cuttlefish found in British waters, with several other species of small or bobtail cuttlefish. In recent years, the MBA has undertaken research into cuttlefish in the English Channel through the CRESH project.
- Cuttlefish produce clouds of ink when they feel threatened. This ink was once used by artists and writers (sepia).
- Cuttlefish are skillful colour-changers. From birth, young cuttlefish can already display at least thirteen types of body pattern.
- The buoyancy organ of the cuttlefish (the ‘cuttlebone’), can be found washed up on beaches once the animal has died and flesh is decomposed or eaten.
“How do they move?”
Cuttlefish (Sepia officinalis) propelling itself through the water with ‘jet propulsion’
Cuttlefish have a fin fringe running along their sides. By undulating these fins cuttlefish are able to hover, crawl and swim. They can also move by ‘jet propulsion’, which can be an effective escape mechanism. This is achieved by assuming a streamline body shape and quickly squeezing water from a cavity in their body, through a funnel-like siphon which thrusts them backwards.
“What do they eat?”
Cuttlefish are impressive predators. They are able to catch large, fast moving prey such as fish and crustaceans like crabs, shrimps and prawns.
“How do they feed”
Cuttlefish feed by using their extendable tentacles to catch prey as it moves past. They also have a razor sharp beak (similar to a parrot’s beak) hidden behind its tentacles which enables cuttlefish to feed on hard shelled animals such as crabs. The bite introduces a toxin, to quickly immobilise any troublesome prey.
“What is the biggest and smallest?”
The largest species of cuttlefish in the world is the Australian giant cuttlefish (Sepia apama) which can grow up to one metre in length and weigh over 10kg. The smallest is Spirula spirula which rarely exceeds 45 mm in length. The largest british species is the common cuttlefish (Sepia officinalis) which can grow to around 45cm in length.
“Where do they live?”
Cuttlefish are exclusively marine species and can be found in most marine habitats from shallow seas to deep depths and in cold to tropical seas. Cuttlefish typically spend the winter in deep water and move into shallow coastal waters to breed in the spring and summer. There are around one hundred species of cuttlefish around the world.
“How long do they live?”
Cuttlefish have short life cycles and rapid growth patterns. Most cuttlefish are expected to have a 2 year life span and female cuttlefish will die shortly after laying eggs.
Some species commonly found around the British Isles
Common cuttlefish (Sepia officinalis) – is locally common off the coasts of South and South West England and Wales. The common cuttlefish can be seen in shallow water during the spawning period in late spring and summer.
Elegant cuttlefish – (Sepia elegans) – Found offshore in southern British waters. The cuttlebones are slimmer that those of the common cuttlefish, often with a pink tinge and a small tooth at one end.
Pink cuttlefish – (Sepia orbigniana) - A rare cuttlefish in British waters, similar in appearance to the elegant cuttlefish, but found occasionally in the south of Britain.
Little cuttlefish (Sepiola atlantica) – Has the appearance of a miniature Sepia cuttlefish, but is in fact a type of ‘bobtail’. It is most common off the South and South West coasts of England.