Like shrimps and lobsters, crabs belong to the order decapoda, meaning ten-legged. Crabs can be classified into two infraorders, anomuran crabs and brachyuran crabs or true crabs. Most brachyura can easily be seperated from the so-called "false crabs" belonging to the infraorder Anomura by having four pairs of well-developed walking legs. Anomuran crabs always have only two or three pairs of walking legs clearly visible, while the fifth is very small, normally tucked under the body and hardly noticeable. However, this is only a general rule rather than a distinct character for seperation as there are a number of true crabs which have their fourth pair of legs greatly reduced as well or even completely reduced. The current number of anomuran crabs in the world ranges from 1500 to 2000 species. Width: 2,5 cm. Distribution: from the Indian Ocean towards the W- Pacific Ocean. This white with brown zebra crab can be found on several sea urchin species. The commensal way of living has advantages for one of both, the crab cleans the urchin from organic materials and feeds on the left-overs from the sea urchin. Length: 2 cm. Distribution: Red Sea & S-E Africa to Japan, Philippines, Australia and New Caledonia. Smooth and shiny body with a few large spikes and pale band on back and head. Same colour like the hosting coral. Cylindrical snout, feeds on plankton and detritus. Mostly found on long Cirripathes spiralis ‘’black’’coral. Width: 3 cm. Distribution: the whole Indo-Pacific region. Cream to pink, covered with around 200 red dots on body and legs. On and between branches of Stylophora and Pocillopora corals. Feeds on mucus and detritus(organic material). Often living together with other coral crabs. Length: 2 cm. Distribution: E- Africa to Philippines, Indonesia, French Polynesia and New Caledonia. A very common Trapezia, round carapace and large claws. Orange to red colour. During daytime always in pairs, on and between branches of Stylophora and Pocillopora corals. Lives together with other coral crab species. Width: 1,5 cm. Distribution: from E- Africa to S- Japan, New Guinea and tropical Australia. Round Carapace(body). Variable in colour, from pink to dark brown. Red dotted line from the sides towards the centre of the back . Between branches of Stylophora or Pocillopora corals. Width: 1,2 cm. Distribution: R. Sea to Indonesia, Japan, Micronesia, Polynesia and Australia. From pale brown to greyish-white, reddish edge between eyes, leg joints with dark blotches. On and between branching Acropora corals, where they feed on fallen detritus, particles trapped by the coral polyp’s and the coral’s mucus. Lives in harmony with other porcelain crab species. Length: 10 cm. Distribution: from the Red Sea to Fiji and Japan. First pair of legs have big claws, body and legs often overgrown with pieces of sponge, soft coral, algae and other organisms(see right photograph). Nocturnal, on coral reefs from -5 to -15 m. Length: 15 cm. Distribution: SE- Africa to Japan, Philippines, Indonesia and Hawaii and Fr. Polynesia. Reddish-brown carapace (body) which is it’s widest at the front. Around ten pale spots on back, red margin on cheeks. Males larger than females Nocturnal, mostly buried in sand during the day. Width: 20 cm. Distribution: from the Red Sea and E- Africa throughout the entire Indo-Pacific. Lives solitary and is very active. Can be very aggressive towards everything that crosses their path. Prefers sandy and muddy substrates, can be found from shallow waters down to - 65 m. Is able to dig itself completely into the substrate. The photograph right below shows a mating couple. Width: 2 cm. Distribution: from the Indian Ocean to Indonesia, Japan, Micronesia, ?. Small red-brown to pink crab with several pale saddles on chelipeds (larger arms), often dark-margined. Pale spork(spoon-fork) design on top of carapace (body). Solitary or in pairs, lives in a sea pen of the genus Pteroeides or Veretillum. Feeds on plankton and detritus which they catch with their bristle-like claws. Female bigger than male. Width: 10 cm. Distribution: from E- Africa throughout the entire Indo-Pacific area. Thin brownish carapace(body), little bit longer than broad. White or pale blue line from between eyes to back, 3 to 4 pale blue lines on each side of middle line. First two short legs with small chelipeds(pliers), used to pick algae. Long walking legs, often with pale patches. Lives solitary between rocks of intertidal area, shy. Width: 12 cm. Distribution: from E- Africa troughout the whole Pacific Ocean. Swimming crabs live solitary, they only meet during maiting season. They feed on fish corpses, other crabs, worms and other small marine life. Can be found on different substrates, sometimes migrate to estuaries. They are quite aggressive and attack everything that stands in their way. Width: 2,5 cm. Distribution: China Sea, SW- Japan, Indonesia, Coral Sea and New Caledonia. Pale body with numerous very small reddish dots, uneven carapace(body), with elevated triangular-shaped area. Long antenna. As all others of the family, found on larger anemones. Width: 2,5 cm. Distribution: Indo-west Pacific. Mostly found in pairs on anemones like Entacmaea, Gyrostoma, Stichodactyla, Crypto-dendrum and Heteractis. White to creamy coloured body with dark red spots. Similar to Neopetrolisthes maculatus which has smaller spots. Length: 3 cm. Distribution: from the Red Sea to the Philippines, Indonesia and Australia. Very similar to Neopetrolisthes oshima, this species has more but smaller red spots on the body. Strong broad chelipeds with large claws. Can be found on, or underneath large anemones. The male species are smaller than the females. Width: 1,5 cm. Distribution: E- Africa to SW- Japan, Indonesia, Marshall Is. and Cook Is. A brightly marked carapace (body), slender striped legs with very fine white spots. In each claw they hold an anemone of the species Bundeopsis sp. or Triactis producta, which it uses as both defense and capturing food. Feeds mainly on detritus. Length: 4 cm. Distribution: from the Red Sea to the Philippines, Indonesia and Hawaii. Dark creamy coloured body with brown spotted pattern. Banded legs, commensal on tube anemones and sea cucumbers. Length: 4 cm. Distribution: from the Red Sea to the Philippines, Indonesia and Hawaii. Brown-red with big white patches, pattern is mostly the same. If available, they like to house in big cylinder anemones like the Cerianthus sp. Is able to dig it’s whole body into sand. Length: 2 cm. Distribution: Indonesia. Brown triangular-shaped body, mostly covered with some algae. First pair of legs with bristles. On sandy areas. No more information found on this species. Length: 2 cm. Distribution: S.E- Africa to Japan, Palau, Australia and Kermadek Is. Green elongate triangular-shaped carapace(body) and legs, mostly with some small white lines or patches. Attaches leaves from the Halimeda algae to it’s rostrum and body to camouflage itself. Mostly found between or around Halimeda algae. Coastal areas, from -3 to -20 m. Length: 1,5 cm. Distribution: from the Red Sea to Japan and Fiji. Pale body with some coral growth, often with reddish or yellow stripes or bands, depending the colour of the host. Large spines on top of body and legs. First pair of legs with very small claws. Lives on soft coral which it mimics for camouflage. Feeds on soft coral polyps and floating particles which fall down on the coral. Length: 20 cm. Distribution: from the Red Sea to Hawaii. Body and legs completely red with strong black spoon-tipped claws. Nocturnal, feeds on shelled molluscs. Width: 1 cm. Distribution: probably the entire Indo-Pacific region. This very small pointy nosed crab can be variable in colour, it mostly has the same colours as it’s host. It inhabits the anal pore of the sea urchins Echinothrix calamaris and Diadema savignyi as shown on the photographs below. Length: 20 cm. Distribution: from the Red Sea to S-and E-Africa, Japan and Hawaii. The largest of all sponge crabs, it has a high-domed carapace (body) and large white-tipped claws. This crab has a very fine furry layer on top of the body and arms. Has mostly a piece of sponge on top of the body to camouflage themselves. The sponge is hold by their last two legs. Length: 5 cm. Distribution: from S- Africa to Vanuatu, Korea and Society Islands. Probably the most common hermit crab in tropical waters. The coloration can be very different. Spiny legs, red and white striped eye stalks and green eyes. The shells they use for protection are mostly covered with small anemones. When disturbed, the anemones expel long stinging threads called acontia. Down to -40 m. Length: 15 cm. Distribution: Red Sea & E- Africa to Japan, Hawaii, Society Islands and Fr. Polynesia. One of the largest of the species. Very easy to identify because of the red-orange colour, fine white ocellus and very spiny chelipeds. Scavenger, feeds on molluscs and death marine life which they find on their path. Is able to open shells. Length: 5 cm. Distribution: from Malaysia to S- Japan, Philippines and Indonesia. Top of the body densely packed with tubercles, which helps them to attach anemones and tunicates. First pair of legs white to creamy colour, sometimes with a pattern. All the other legs are white and black banded. Nocturnal. Width: 6 cm. Distribution: probably the entire Indo-Pacific area. Top carapace(body) dark olive-green with some dark blotches, white underside. Large spiny claws and six similar sized sharp frontal teeth. Red area around the eyes. Last pair of legs have a fin, which turned them into a swimming crab On sand, rock or coral, coastal reefs, from -10 to -30 m. Width: 6 cm. Distribution: From Malaysia to Indonesia and Japan. Lives on rocky areas and coral reefs, from -10 down to -30 m. Carapace (upper-side body) olive green with dark red blotches on the sides. Pereiopods (side-legs) pink to purple with orange. Length: 3 cm. Distribution: from the Red Sea to Japan and Philippines. The body and legs completely covered with different marine organisms like algea and detritus (dead organic material). Moves very slow and is active during night, among coral reefs. Can be found on a depth of -7 to -15 m. Width: 9 cm. Distribution: Red Sea to Japan, Philippines, P.N.G., Australia and New Caledonia. Spiny carapace(body), from light- to reddish-brown, mostly with six dark blotches on chelipeds (arms) and behind the eyes. The eyes have vertical lines and a white-greyish round plate on top, right photograph. Digs itself into sand and feeds on molluscs. Width: 6 cm. Distribution: R. Sea & E- Africa to Maldives, Philippines, Indonesia, Fr. Polynesia, G.B.R, N. Caledonia. Warty carapace(body), arms and claws. From ivory to pale- or red-brown. Is able to bury itself very fast into the substrate when threatened. Feeds on mollusc, crushes the shell between chest and claws. Night-active. On sand and rubble areas of coastal reefs. Length: 4 cm. Distribution: from the Red Sea to the West Pacific. The first pair of legs are short with small claws, the other legs are much longer. Two pointed spines between the eyes, light body and red eyes. Nocturnal, mostly seen on soft corals and gorgonia(sea fans). Short bristles on the body and legs helps them to attach organic materials to camouflage themselves. Feeds on organic particles. Length: 1,2 cm. Distribution: from Indonesia to Japan and Fiji. Body with long pink to dark red hairs, these help the crab to attach particles to the body for camouflage. Bright red eyes. Mostly found on mushroom -or bubble coral and in some places on tunicates.