CRUSTACEANS

Phylum Crustacea

This large phylum has over 30,000 members worldwide and crustaceans can be found in every marine habitat. In general they have segmented bodies with a head, thorax and abdomen and are heavily protected by calcareous outer body armour. Most divers see the obvious decapod species, which have ten legs, which, depending on the species, are adapted for walking, feeding, swimming, defence, food capture, respiration and even the carrying of eggs.

SEA SPIDER

SEA SPIDER

Nymphon gracile

This sea spider is regarded as very rare, principally due to it being quite small and difficult to find at only 10–15mm (ca. ½in) long. The body is smooth and pale cream to light brown in colour, and is rigidly segmented. The legs are of equal length and may well have bits of detritus attached to them. Widely distributed, it is commonly found at the base of sea fans and around hydroids and various calcareous algae, where it is able to hide its vulnerable body should danger threaten.

BARNACLES

STAR BARNACLE

Chthalamus stellatus

Newly developed barnacles, whilst in the plankton, display their feeding arm. It looks like a catching mitt, which is what it is. A distant relation of the crabs, barnacles settle onto a suitable habitat in the shallow water surf zone where they develop a protective shell of calcified rigid overlapping plates. Only a few millimetres across, they are packed closely together. They are able to seal themselves off in bad conditions or exceptionally low tides and are able to live for a short while out of the water.

GOOSE BARNACLE

Lepas anserifera

The Goose Barnacle adopts a similar procedure in catching prey to that of the Star Barnacle, but although this species is also sedentary in nature, it attaches itself onto floating bits of debris, ships’ keels and piers. Tolerant of poor water conditions, the Goose Barnacle is around 4cm (1½in) long and has a long, leathery foot and a strong, calcified, protective head where the catching mitt is kept.

SHRIMPS

OPOSSUM SHRIMP

Paramysis helleri

Found throughout the Mediterranean and Black Sea, the Opossum Shrimp occurs in large numbers and is an important food source for small fish. Growing to only 1.1cm (ca. ½in) in length, it lives close to the sea floor or rocky crevices where it can quickly hide from predators. Vast numbers of Opossum Shrimps can be found in the cave systems along the coast of northern Spain, the Balearics, Corsica and Sardinia during the summer months. Deep inside the caves, they are preyed upon by slipper lobsters, Unicorn Shrimps, Common Shrimps and even Anthias, which will venture away from the light of day after this veritable feast.

ELEGANT SHRIMP

Palaemon elegans

This is one of the more common shrimps found around the coastline and is normally associated with a rocky subsurface. Quite a stout prawn, growing to around 6cm (2½in), it has strong, dark reddish-brown stripes on a fairly transparent body. Generally found in association with Dead Men’s Fingers and preferring low light conditions, this shrimp is an active forager by dusk and at night time. It is an important food source and is harvested commercially in a number of Mediterranean countries that have vast sand banks and shallow sheltered bays, such as the north African coast.

COMMON SHRIMP

Palaemon serratus

Unlike the Elegant Shrimp, this species prefers low light and even pitch black conditions and is more commonly found deep inside caves. The species is also much larger at 11cm (4½in). Although this species of shrimp enjoys a communal lifestyle with large numbers of its own species or alongside Unicorn Shrimps, more often than not it is found on its own, wandering around deeper caverns in search of Opossum Shrimps or edible detritus.

AMETHYST SHRIMP

Periclimenes amethysteus

One of the most colourful of all the Mediterranean shrimps, the Amethyst Shrimp has a symbiotic relationship with a few anemones, but principally Cribinopsis crassa. Stout of body, up to 2.5cm (1in) long and nearly transparent, it has pinkish, well-defined markings with long, beige pincers and blue-striped legs. Seemingly rather docile when near its anemone protection, it is able to dodge very rapidly out of the way should danger threaten. The species can also be found around Posidonia seagrass beds, where its bright colours are a very rare delight for divers.

UNICORN SHRIMP

Plesionica narval

More common in the central and western Mediterranean, the Unicorn Shrimp is found deep in caverns and at night. It has a distinctive clear body with red and gold lateral lines and quite often blue eggs attached to the underside, and can grow to 10cm (4in). Like many other shrimp species, it starts life as a male and changes to female with maturity.

CLEANER SHRIMP

Stenopus spinosus

The Mediterranean Cleaner Shrimp is very timid and only rarely seen, and then only at dusk or during the night. It is a golden orange or rust brown in colour with long, white feelers with which it communicates with the various fish species that it cleans of parasites. Performing an important role in the health of the reef, this small shrimp is closely related to the Banded Coral Shrimp of more tropical waters. It is 10cm (4in) long.

LOBSTERS

STRIDENT SQUAT LOBSTER

Galathea strigosa

There are a few species of squat lobster in these waters and they are migrants from the Atlantic. Principally found in the western Mediterranean, they have become quite adaptable to warmer waters. The most colourful of all is the Strident Squat Lobster with its brilliant orange-red body armour and vibrant, iridescent blue stripes across its head and around the eyes. It grows up to a maximum length of around 10cm (4in) and prefers low-light shaded conditions.

LONG-CLAWED SQUAT LOBSTER

Munida rugosa

Often referred to as ‘Langoustine’ by the French, the Long-clawed Squat Lobster enjoys a deep-water habitat where it lives under stones and rocks. Often associated with brittle starfish beds and ascidians. Instantly recognized by its bright orange, fairly slim body, which is around 30cm (12in) long and its chelipeds or pincer arms at twice the body length.

SMALL LOCUST LOBSTER

Scyllaris arctus

Extremely light sensitive, this very shy, small slipper lobster lives in deep caves with very little light. Growing to only 12cm (4¾in) in length, it has plate-like antennae, which have rounded, lobed edges. It is a mottled brown in colour with splashes of red in the joints of the abdomen and a red ring around the slightly stalked eye. It has a very broad tail to allow for rapid movement and its eight obvious striped legs are used to grip onto the undersides of cavern ceilings and walls. When approached, it literally hops in reverse very quickly out of danger. It lives in fairly large colonies and is a sociable lobster.

COMMON LOBSTER

Homarus gammarus

This lobster is more associated with Atlantic and North Sea waters, but it is surprising to note that it is quite common in the Mediterranean. Preferring to live under large boulders or in deep rocky crevices, the Common Lobster is a nocturnal feeder and divers are more likely to see it at night. It is a large, robust animal, bluish in colour with stout pincers, one of which is modified for gripping, the other modified for cutting. Highly sought after for the commercial food market, these animals rarely get to a ripe old age. They can live over 25 years and reach 1m (3ft 3in) in length.

SPINY LOBSTER

Palinurus elephas

This is a large spiny lobster in shades of orange and red with a sharp spiny carapace and abdomen. Growing over 50cm (1ft 8in) in length, it lives in caverns and rocky crevices. It is more active at night. It guards its lair, standing at the entrance on stout, long, striped legs with its huge, long, sensory antenna protruding into open water. Very timid in character, it is commercially fished by traditional lobster pot. Breeding occurs in September and like all lobsters, the female carries the eggs under her abdomen with specially adapted feet.

CRABS

HERMIT CRABS

RED HERMIT CRAB

Dardanus calidus

One of the larger hermit crabs to be found, at over 2.5cm (1in), it is instantly recognized by its bright red coloration, green eyes set out on long stalks and orange antennae. It is often associated with the parasitic anemone Calliactis parasitica, which it lugs around on the back of its heavy shell home.

SEDENTARY HERMIT CRAB

Calcinus tubularis

Curiously, it is only the female of this species that is sedentary in nature, preferring to live in old worm snail holes. The male is much more errant. Slim in body, it is more commonly found inhabiting empty cowrie shells. It grows up to 10mm (½in), has long stalked eyes, is reddish-brown in colour with pale striped legs and has pincer arms with red spots.

STRIPED HERMIT CRAB

Pagarus anachoretus

This species is fairly recognizable by its overall brownish coloration and white to bluish stripes and bands over all of its legs and pincer arms. It also has relatively few hairs on its legs, but they are long. Its antenna are also long and banded with white. Its body length is 2.5cm (1in).

HAIRY HERMIT CRAB

Pagarus cuanensis

This is quite a small and distinct species, growing to 1.5cm (½in) and is characterized by its extremely hairy lower legs and pincers, which always appear to be clogged up with bits of detritus. Overall brown in colour, it has long, stalked, pale blue eyes and brown-and-white striped antennae.

PRIDEAUX’S HERMIT CRAB

Pagarus prideux

This species is mainly associated with the commensal anemone Adamsia carciniapados, which completely envelops its carrier shell. The crab is speckled with white and tinged with mauve and is overall a light tan in colour with pinkish striped legs and striped eye stalks. It grows up to 3cm (1¼in) long. The females lay eggs throughout the summer season. They are bright gold and are kept in the shelly home until the larvae are freed by the crab, climbing out of the anemone-covered shell, endangering its softer body parts.

OTHER CRABS

MASKED CRAB

Corystes cassivelaunus

This soft sand- and mud-living crab grows to around 7.5cm (3in) in length and has two long antennae, which form a breathing tube when the crab is hidden under the surface. Coloured a uniform light tan or pale cream, the carapace is roughly triangular in shape. The pincer arms or chelipeds are very long in the male and short and stout in the female.

SPONGE CRAB

Dromia personata

A muddy brown in colour and covered in fine hairs, the Sponge Crab lives in low light areas generally in caverns or caves, where it sometimes places a sponge on its back for additional camouflage. Growing over 7cm (2¾in), it is quite a stout crab with strong limbs and pincers, which have pinkish tips.

ANEMONE SPIDER CRAB

Inachus phalangium

Commonly associated with the Snakelocks Anemone Anemonia sulcata, this spider crab enjoys the protection of the anemone, being seemingly immune to its stinging tentacles. It is only the female of the species that lives in the anemone. Brownish in colour, it is often covered in fine hairs and bits of algae and sponge to help in camouflage. It only leaves the anemone at night to feed but stays close by. It grows to 5cm (2in) in length.

SPINY SPIDER CRAB

Herbstia condyliata

This small species grows to only 3cm (1¼in) and is widely distributed. An active scavenger, it only comes out at night and prefers under-hanging rock faces dotted with small holes. The legs are striped and it is of an overall reddish-brown colour.

RED SPIDER CRAB

Lissa chiragra

Rarely seen, and then only at night, the Red Spider Crab grows to only 5cm (2in) and is quite happy on rocky substrates or amidst Posidonia. Brilliant red in colour, it is also characterized by the nodular outgrowths on its carapace and at each of the joints on its legs.

COMMON SPIDER CRAB

Maja crispata

A master of camouflage, this crab lives in most habitats and fastens bits of algae and sometimes sponge all over its carapace, legs and pincers. Owing to its fairly sedentary nature and not moving when it senses danger, it is very rarely seen as it is often so overgrown that it resembles a lump of seaweed-covered rock. It can grow to over 7cm (2¾in) and is sold commercially for the meat contained within its carapace.