Mantis Shrimp

Mantis shrimp or stomatopods are marine crustaceans the members of the order Stomatopoda. They may reach 30 centimetres (12 in) in length, in exceptional cases up to 38 cm (15 in) has been recorded. The carapace of mantis shrimp covers only the rear part of the head and the first four segments of the thorax. Mantis shrimp appear in a variety of colours, from shades of browns to bright neon colours.

 

Although they are common animals and among the most important predators in many shallow, tropical and sub-tropical marine habitats, they are poorly understood as many species spend most of their life tucked away in burrows and holes. Called "sea locusts" by ancient Assyrians, "prawn killers" in Australia and now sometimes referred to as "thumb splitters".

 

Because of the animal's ability to inflict painful gashes if handled incautiously mantis shrimp sport powerful claws that they use to attack and kill prey by spearing, stunning, or dismemberment. Although it only happens rarely, some larger species of mantis shrimp are capable of breaking through aquarium glass with a single strike from this weapon. These aggressive and typically solitary sea creatures spend most of their time hiding in rock formations or burrowing intricate passageways in the sea bed.

 

They either wait for prey to chance upon them or, unlike most crustaceans, at times they hunt, chase, and kill prey. They rarely exit their homes except to feed and relocate, and can be diurnal, nocturnal, or crepuscular, depending on the species. Most species live in tropical and subtropical seas (Indian and Pacific Oceans between eastern Africa and Hawaii), although some live in temperate seas.

Around 400 species of mantis shrimp have currently been described worldwide; all living species are in the suborder Unipeltata. They are commonly separated into two distinct groups determined by the manner of claws they possess. Smashers use this ability to attack snails, crabs, molluscs and rock oysters, their blunt clubs enabling them to crack the shells of their prey into pieces. Spearers, on the other hand, prefer the meat of softer animals, like fish, which their barbed claws can more easily slice and snag.

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Crab

Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (abdomen) usually entirely hidden under the thorax. They live in all the world's oceans, in fresh water, and on land, are generally covered with a thick exoskeleton and have a single pair of claws. Many other animals with similar names such as hermit crabs, king crabs, porcelain crabs, horseshoe crabs and crab lice are not true crabs.

Crabs are generally covered with a thick exoskeleton, composed primarily of calcium carbonate, and armed with a single pair of chelae (claws). Crabs are found in all of the world's oceans, while many crabs live in fresh water and on land, particularly in tropical regions. Crabs vary in size from the pea crab, a few millimetres wide, to the Japanese spider crab, with a leg span of up to 4 metres (13 ft).

 

About 850 species of crab are freshwater, terrestrial or semi-terrestrial species; they are found throughout the world's tropical and semi-tropical regions. They were previously thought to be a monophyletic group, but are now believed to represent at least two distinct lineages, one in the Old World and one in the New World. The earliest unambiguous crab fossils date from the Jurassic, although Carboniferous Imocaris, known only from its carapace, may be a primitive crab.

The radiation of crabs in the Cretaceous and afterward may be linked either to the break-up of Gondwana or to the concurrent radiation of bony fish, crabs' main predators. Crabs often show marked sexual dimorphism. Males often have larger claws, a tendency which is particularly pronounced in the fiddler crabs of the genus Uca (Ocypodidae). In fiddler crabs, males have one claw which is greatly enlarged and which is used for communication, particularly for attracting a mate.

Another conspicuous difference is the form of the pleon (abdomen); in most male crabs, this is narrow and triangular in form, while females have a broader, rounded abdomen. This is due to the fact that female crabs brood fertilised eggs on their pleopods. Crabs attract a mate through chemical (pheromones), visual, acoustic or vibratory means.

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