Calappa (crab)

Calappa is a genus of crabs known commonly as box crabs or shame-faced crabs. The name box crab comes from their distinctly bulky carapace, and the name shame-faced is from anthropomorphising the way the crab's chelae (claws) fold up and cover its face, as if it were hiding its face in shame.

Distribution

Calappa are benthic and found on sandy, shelly, and muddy seabeds. They are found from the shore to depths of around Template:Convert, with some species being found deeper at around Template:Convert. They commonly inhabit reef areas, seagrass beds, and sandy flats where they can easily burrow and camouflage with the surrounding environment. They are typically found in warm marine environments, favoring tropical and subtropical climates. Many species, like Calappa calappa and Calappa hepatica, are common in the Indo-Pacific region and can be found in areas such as the Red Sea, Hawaii, French Polynesia, Cocos Island, and northern Australia. They can be found in other parts of the world, such as Calappa granulata, which has been found in the Mediterranean Sea and off the coast of Venezuela. Other species have also been found in Central America.

Description

Calappa generally range in carapace width from about Template:Convert. Most Calappa have a broad, rounded, and convex carapace. This in conjunction with its broad, flat, shield-like claws give the crab a box-like appearance. The claws' shielding posture gives rise to the other common name, "shame-faced crabs". Calappa are often difficult to distinguish based on morphology alone, and thus molecular phylogenetics are sometimes used alongside morphometrics to identify specimens with unique color patterns, size ranges, and textures.

Behavior

Calappa are known to burrow in the seabed.Template:Sfn They push their chelae forward against the substratum which in turn pushes their carapace down and backward into the sediment.Template:Sfn Through this process, Calappa either submerges itself completely or leaves just its eyes exposed.Template:Sfn This burial process disturbs the substratum and has been observed to inadvertently aid fish in hunting invertebrates and small fish hiding in the seabed.

CalappaTemplate:'s chelae are specialized for feeding on marine gastropods and bivalves.Template:Sfn A study of the feeding behavior of C. ocellata found that the chelae are of about equal size but differ noticeably in function and internal morphology.Template:Sfn The right chela has a thick, calcified apodeme, broad teeth, and greater mechanical advantage than the left.Template:Sfn It is used to crush or shear shells, but it is not robust for this task.Template:Sfn Likely to compensate for this, the outside face of the right chela additionally features a "peg and cusp" structure which is used like a can opener to break the lip of gastropod shells.Template:Sfn The left chela is slim, pointed in a beak-like fashion, lined with small, pointed teeth along the propodus, and fringed with setae which may be used for sensing.Template:Sfn It is used for faster or more delicate tasks such as holding a shell in place during crushing, picking flesh from crushed prey, and possibly capturing agile prey.Template:Sfn

Species

Calappa contains the following extant species:

• Calappa calappa
  Calappa calappa
• Calappa flammea
  Calappa flammea
• Calappa gallus
  Calappa gallus
• Calappa granulata
  Calappa granulata
• Calappa hepatica
  Calappa hepatica
• Calappa japonica
  Calappa japonica
• Calappa lophos
  Calappa lophos
• Calappa philargius
  Calappa philargius
• Calappa sulcata
  Calappa sulcata

Extinct species

Calappa contains the following extinct species:

File:Calappidae - Calappa species.JPG

Fossil of Calappa species

Fossils of species within this genus can be found in sediment of Europe, United States, Mexico, Central America, Australia and Japan from Paleogene to recent (age range: 33.9 to 0.0 Ma).