British Squat Lobster
Sometimes, on approaching a pile of boulders, you can see tiny squatties scattering in all directions as they sense danger looming, and they have good reason to be nervous. As we know, crustaceans are meaty and nutritious, and squatties are small enough to be snapped up whole by larger fish. Lacking the armoury of their larger relatives, squatties rely on retreating quickly into their holes to escape predators. Their big eyes give them good vision, and flapping the muscular tail propels them backwards at great speed. Their closest relatives are actually hermit crabs, rather than lobsters, but instead of using a second-hand snail shell for protection, they retreat into rock crevices, from which they are then impossible to extract.
Shining a torch into a rock crevice often reveals several of these little crustaceans, but you might see more squatties on a night dive, as they are largely nocturnal, foraging under cover of darkness for food. They are unfussy eaters, holding and defending the food with their claws, and cutting and processing it with their various mouthparts. The brown squat lobster also feeds by filtering suspended material from the water.
Squatties also spend much time grooming, with a special leg that can reach just about anywhere, removing unwanted larvae and spores that otherwise might settle on them. In order to grow, squatties must moult regularly, their whole body pulling out from a split at the base of the carapace. A newly-moulted squattie must hide while its soft, larger shell hardens. Female squatties carry fertilised eggs in the colder months, eventually releasing tiny larvae into the water. After four or five moults, they settle on the sea bed as miniature adults.
Squat lobsters are also common in deep water worldwide, out of the range of divers. However, visitors to Lanzarote don’t even need to enter the water to have a privileged view of deep-water squat lobsters. An unusual colony of pure white squatties lives in Jameos de Agua, a volcanic cave with a deep pool of sea water. These squatties (Munidopsis polymorpha), known locally as ‘blind cave crabs’, are thought to have been swept up from the deep by volcanic eruptions, and are now trapped in the cave pool. Inside the huge cave, the environment, dark and still, mimics conditions in the deep sea, with the added benefit of no predators!
Beast at a glance
SPINY SQUAT LOBSTER Galathea strigosa BROWN OR SCALY SQUAT LOBSTER Galathea squamifera HAIRY-CLAWED SQUAT LOBSTER Galathea nexa, Galathea intermedia LONG-CLAWED SQUAT LOBSTER Munida rugosa BLIND CAVE CRABS Munidopsis polymorpha
KNOWN HAUNTS Rock crevices, beneath stones and boulders, excavations in sand and mud. The brown squat lobster is found mainly in seashore pools and in very shallow water.
BEST PLACE TO SEE Squat lobsters are common all around Britain, the long-clawed squat lobster being particularly common off west Scotland. The hairy-clawed squat lobster occurs only in the south and west of the UK.
LIKELY TO APPEAR Present all year, but may be more obvious in winter when breeding.
DISTINGUISHING FEATURES Squat lobsters are small crustaceans with a lobster-like front end, and tail curled round under the body. There are six squatties common in British coastal waters. Munida rugosa is orange with very long claws and a distinctive long spike between its eyes, with a smaller one on each side. Galathea strigosa has a red carapace with blue stripes, while Galathea squamifera is dark brown. Other Galathea species are mostly red to orange, small, and difficult to distinguish from each other. Galathea nexa has very hairy claws, while Galathea intermedia is tiny with fine, pointed pincers, and often has a pale stripe down its back.
SIZE Munida rugosa has a body length of up to 6cm. Galathea strigosa to 10cm; Galathea squamifera to 6.5cm; Galathea nexa to 4cm and Galathea intermedia to 2cm.