Lobsters and crayfish

Homarus vulgaris, European lobster

Homarus vulgaris, European lobster

The European lobster, above, is also known as Homarus gammarus. It can grow up to 60 cm long and weigh 6 kg. It is found in the north east Atlantic, Baltic, and the Mediterranean, from 0 to 150 m deep, usually on hard substrates. Its natural colour is blue/black which changes to red on cooking. It is a highly prized food caught in lobster pots around the U. K. coast. It is considered to have a better flavour than the American lobster.

It lives in holes and crevices during the day, emerging to feed at night. Prey items include crabs, molluscs, urchins, and polychaete worms. The larger of the two front claws is used for crushing prey, and the other - which usually has sharp ridges and teeth - is used for cutting and tearing prey apart. Females are mature when they reach 80 - 85 mm long. Mating occurs in summer, soon after the female has moulted when her exoskeleton is still soft, and when the male is between moults and has a fully hardened exoskeleton. The female can carry her eggs for up to one year before they hatch. Moulting occurs several times a year for small and medium sized individuals, but only once or twice a year for larger specimens.

Rock lobster, Panulirus ornatus

Rock lobster, Panulirus ornatus

The Rock lobster, above, is also known as the Tropical rock lobster, and the Ornate spiny lobster. It is widespread and abundant around the coast in Indo-Pacific waters, and is edible. It is usually found down to 8 m deep, but has been caught as deep as 50 m. It is usually nocturnal.

As you can see from the photograph above, it does not have huge front claws, and it has spines growing all over its body. Its antennae are very long, and can reach 60 cm, and are used to search for prey. The antennae can also be used to warn off other lobsters by being rubbed against the head to produce a sound.

They are very social and gather together in groups. Juveniles travel in single file, but when threatened form themselves into a circle with their protective spines outermost. They eat small crustaceans, molluscs, worms, and algae.

Slipper lobster, Parribacus antarcticus

Slipper lobster, Parribacus antarcticus

The Slipper lobster, also known as the Mitten lobster, below, is found in the Indo-Pacific and the Caribbean. It is a bottom dweller found at depths down to 20 metres. Its preferred habitat is coral or stony reefs with a sandy or muddy bottom.

As with other Malacostraca it has two pairs of antennae, but in the Slipper lobster one pair is flattened into a pair of large, projecting plates. Also unlike other Malocostracans it has no claws. It can grow up to 20 cm long, but most are 12 - 15 cm long.

Slipper lobsters are nocturnal, and hide during the day. They eat molluscs, shrimps, crabs and urchins.

Slipper lobsters are edible.

Mud lobster, Thalassina anomala

Mud lobster, Thalassina anomala

The mud lobster, above, is found in mangrove swamps from the Indian Ocean down to N. W. Australia. It digs into the mud feeding off organic matter. In the process it raises a large mound, sometimes three metres in height. These mounds are used as habitats by many species. It is considered a keystone species in mangrove swamps because its digging aerates the mud and brings deeper mud to the surface, as well as creating new habitats. The lobster is nocturnal spending its days inside its blocked up U-shaped burrow under the mound.

The mud lobster is considered a pest by fish and prawn farmers because of its habit of digging and burrowing, and so weakening the bunds constructed by the farmers.

Mud lobsters are edible, but are not considered very tasty.

Although their common name implies they are lobsters, in fact they are more closely related to ghost shrimps.

Signal crayfish, Pacifastracus leniusculus

Pacifastracus leniusculus, Signal crayfish

Pacifastracus leniusculus, the Signal crayfish, above, is found in still and slow-flowing freshwater. This crayfish is native to North America where it is fished commercially, but is now found in Scottish and other rivers where it eats trout and salmon eggs as well as frogs, fish and even other signal crayfish, and also carries an infection which kills the native Scottish crayfish. It was deliberately introduced into Europe in the 1960s, but is now considered an invasive species in both Europe and Japan. The average length is 6 - 9 cm, but individuals can reach up to 18 cm long. Its colour ranges from blue/brown to red/brown.

In Europe the native crayfish had been dying off from an infectious disease called crayfish plague, and the Signal crayfish was introduced to be fished commercially. It is nocturnal and spends its days hiding under rocks and in cavities. In the winter it digs a tunnel to shelter in, and enter a torpid state. It is highly aggressive and has strong claws. In the U. K. it is preyed upon by otters, and mink, salmon and eels will prey on small individuals.

After mating in autumn 200 - 400 eggs are laid, and are carried around by the female under her tail, until spring when they hatch. The young moult three times before dispersing from their mother. They are sexually mature when they are two or three years old, and can live until they are twenty.

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