''Mithraculus sculptus'', the green clinging crab or emerald crab, is a species of crab in the

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Majidae Majidae is a family of crabs, comprising around 200 marine species inside 52 genera, with a carapace that is longer than it is broad, and which forms a point at the front. The legs can be very long in some species, leading to the name "spider c ...

. It is a dark green colour and is found in tropical waters in the

Caribbean Sea The Caribbean Sea ( es, Mar Caribe; french: Mer des Caraïbes; ht, Lanmè Karayib; jam, Kiaribiyan Sii; nl, Caraïbische Zee; pap, Laman Karibe) is a sea of the Atlantic Ocean in the tropics of the Western Hemisphere. It is bounded by Mexico ...

. It is sometimes kept in reef aquaria.

Description

''Mithraculus sculptus'' is a small crab with a

carapace A carapace is a dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tortoises, the und ...

longer than it is wide and large

chelae A chela ()also called a claw, nipper, or pinceris a pincer-like organ at the end of certain limbs of some arthropods. The name comes from Ancient Greek , through New Latin '. The plural form is chelae. Legs bearing a chela are called chelipeds. ...

(claws). The carapace is flat, shiny and green, finely sculpted, with whitish material adhering to the projections. The chelae are also green and are spoon-shaped and tipped with white. The walking legs are rather paler in colour and are hairy and often covered with encrustations. This crab grows to a length of about .

Distribution and habitat

''Mithraculus sculptus'' is native to the

and

Gulf of Mexico The Gulf of Mexico ( es, Golfo de México) is an ocean basin and a marginal sea of the Atlantic Ocean, largely surrounded by the North American continent. It is bounded on the northeast, north and northwest by the Gulf Coast of the United S ...

. Its range extends from the Bahamas and southern Florida to the northern part of Brazil at depths down to about . It is found in a number of varied habitats but may be most abundant in back reef environments.

Behaviour

''Mithraculus sculptus'' is largely

nocturnal Nocturnality is an ethology, animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnality, diurnal meaning the opposite. Nocturnal creatures generally have ...

, hiding in caves, crevices and under rocks during the day. It is principally a

scavenger Scavengers are animals that consume dead organisms that have died from causes other than predation or have been killed by other predators. While scavenging generally refers to carnivores feeding on carrion, it is also a herbivorous feeding b ...

but it also feeds on

algae Algae ( , ; : alga ) are any of a large and diverse group of photosynthetic, eukaryotic organisms. The name is an informal term for a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from ...

. It is tolerant of both high and low temperatures and is capable of withstanding strong currents as it can use its legs to cling on to the

substrate Substrate may refer to: Physical layers *Substrate (biology), the natural environment in which an organism lives, or the surface or medium on which an organism grows or is attached ** Substrate (locomotion), the surface over which an organism lo ...

. It is often to be seen among the branches of corals such as the ''

Porites furcata ''Porites furcata'', commonly known as hump coral, thin finger coral or branched finger coral, is a species of stony coral in the genus ''Porites''. It is found in the Caribbean Sea and western Atlantic Ocean. Description ''Porites furcata'' is ...

''. It also feeds on organisms encrusting the leaf blades of

turtle grass ''Thalassia testudinum'', commonly known as turtlegrass, is a species of marine seagrass. It forms meadows in shallow sandy or muddy locations in the Caribbean Sea and the Gulf of Mexico. Turtle grass and other seagrasses form meadows which are ...

(''Thalassia testudinum''). When threatened it often hides beneath the extended

tentacle In zoology, a tentacle is a flexible, mobile, and elongated organ present in some species of animals, most of them invertebrates. In animal anatomy, tentacles usually occur in one or more pairs. Anatomically, the tentacles of animals work main ...

s of the sun anemone (''Stichodactyla helianthus'').

Use in aquaria

''Mithraculus sculptus'' is sometimes kept in

reef aquaria A reef aquarium or reef tank is a marine aquarium that prominently displays live corals and other marine invertebrates as well as fish that play a role in maintaining the tropical coral reef environment. A reef aquarium requires appropriately ...

where it is said to be compatible with other reef species. It will feed on algae including bubble algae (''Valonia ventricosa'') and eat any left-over meaty foods but, if it is underfed, may consume coral polyps or small fish. Research has shown that it can be used to control excessive growth of bubble algae in aquaria, but best results are found when its diet is supplemented with

mysid Mysida is an order of small, shrimp-like crustaceans in the malacostracan superorder Peracarida. Their common name opossum shrimps stems from the presence of a brood pouch or "marsupium" in females. The fact that the larvae are reared in this ...

s but not with pelleted food.

References

{{Taxonbar, from=Q5221500 Majoidea Crustaceans of the Atlantic Ocean Crustaceans described in 1818