Marine Life - Common Cuttlefish (Sepia officinalis)
Ever been on a dive and seen something you didn’t recognise? The Marine Life pages might help you to recognise the wonderful organisms you have explored in the underwater realm. Read on to find information on such aspects as the feeding, breeding and physiology of some of your favourite marine flora and fauna.
The closest most people get to cuttlefish is coming across cuttlebones washed up on beaches. The cuttlebone is the animal’s buoyancy organ, and can be filled with liquid or gas in order to give precise control over its degree of lift. Cuttlefish cannot live in very deep water or the cuttlebone would implode under high pressure. They inhabit relatively deep water in winter and move into shallow coastal waters to breed in the spring and summer. This is the time when divers in South West waters can see these remarkable animals. The body is broad and slightly flattened, can be up to 30 cm long, and is fringed by a fin on each side which runs from just behind the head right back to the rear. The mouth is surrounded by eight arms and two longer, extensible tentacles. Cuttlefish are impressive predators, able to catch fast moving prey such as fish and prawns. The tentacles are quickly shot out to capture prey, and the arms are used to hold and manoeuvre it. They have a parrot-like beak and a radula to tear and rasp their food.
A cuttlefish spends much of the time on the sea bed and usually only swims to catch prey or when interacting with other cuttlefish (when mating for example). If startled, a powerful burst of jet propulsion moves it rapidly through the water while a cloud of black ink can be released to briefly distract a pursuer while the cuttlefish escapes. When not employing this escape mechanism the cuttlefish may well move slowly away from an inquisitive diver, using a little gentle jet propulsion aided by the rippling motion of its fringing fins. It is then that their most impressive skill, the ability to rapidly change the colour and pattern of their skin to match their surroundings, can be appreciated. If a cuttlefish swims off over a varying seabed its shade can change instantly, going dark over kelp-covered rocks and almost white over sand. The secret of this rapid change is due to the presence of special cells, chromatophores, within the cuttlefish skin. These are effectively little flexible bags of pigment which, when expanded by muscular action, make the area of skin dark. When the bags are allowed to contract under the power of their own elasticity, the skin appears pale. To further improve camouflage, projections on the skin’s surface will change its texture to replicate that of the surroundings.
In addition to avoiding predators, pattern control is also used in courtship. Male cuttlefish display brilliant zebra stripes in order to impress females and warn off other males. After mating, the male will often defend the female while she lays her eggs. Clumps of eggs, dyed black with ink and known as ‘sea grapes’, can be seen attached to seaweed in the summer months. The eggs hatch after 2-3 months and miniature cuttlefish emerge. Females breed once and die soon after laying their eggs.
See More ..
Ballan Wrasse - Common Lobster - Conger Eel - Cuckoo Wrasse - Dogfish - Jewel Anemone - Red Sea Fish
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