Decapod crustaceans are ten-footed (five pairs of legs) scavenging marine animals which include many familiar groups, such as crabs, hermit crabs, lobsters, and shrimp.
Even though decapods are ten-footed animals, they can actually have as many as 38 appendages, arranged in one pair per body segment, though only 10 are considered 'legs'.
The macrurous (shrimplike) species, which can be as small as 1 cm, have elongated bodies with long abdomens, well-developed fan tails, and often long, slender legs.
The brachyurous (crablike) types, which in the case of spider crabs can have spans of almost 4 metres between their outstretched claws, have bodies that are flattened and laterally expanded, frequently with stout, short legs and reduced tail fans.
Porcelain crabs are small decapod crustaceans which resemble true crabs, but are in fact closer to squat lobsters in their structure. Reaching a maximum 15 - 20 mm across, their compact and flattened bodies allow them to live and hide in rock crevices for protection.
The family Diogenidae comprises the 'left-handed hermit crabs' as the left claw is enlarged, rather than the right claw which is the case for the majority of hermit crabs. There are 429 species of left-handed hermit crabs, however these are not actually 'true crabs' as they do not have an external shell on their soft abdomen.
Achelata contains the spiny lobsters (Palinuridae), the slipper lobsters (Scyllaridae) and the furry lobsters (Synaxidae), and whilst similar in appearance to true lobsters, are not in fact true lobsters.
Smashing Mantis Shrimp
Mantis shrimp are neither shrimp, nor mantis, they are a separate group of 450 species called stomapod. Sporting a thick shell that covers the back of the head and the first four segments of the main body, mantis shrimp are among the most efficient crustacean predators. Typically growing to around 10 - 15 cm in length, this group of animals have some of the most complex eyes in the world, including the ability to see polarised light.
Spearing Mantis Shrimp
Unlike the smashing mantis shrimp, spearing mantis shrimp have barbed â€˜spring-loadedâ€™ front limbs used to stab and capture soft-bodied prey, such as fish and worms. Building their burrows in soft sediments close to the reef edge, spearing mantis shrimp are usually found at the dive sites around Koh Lanta in their 4 - 6 cm diameter burrow holes.
Palaemonid Shrimp are small to moderate-sized shrimps, rarely reaching more than 5 cm, however a few species are large enough to be of commercial value. This family of shrimp have a long toothed beak and the front two legs have claws. The second pair of legs are larger and longer than the first pair.
Hinge-beak Shrimps, also known as Dancing Shrimps due to the way they move, are a family of small red, orange and white coloured shrimp with large greenish-bluish eyes. These shrimp are defined by their beak which is hinged and can open upward.
The Anemone Shrimp, also called Broken-back Shrimp, are a large family of over 330 species, including several species of cleaner shrimp. A small number of these species can be found at the dive sites around Koh Lanta.