| Emerita | |
|---|---|
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| Female Emerita analoga | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Malacostraca |
| Order: | Decapoda |
| Suborder: | Pleocyemata |
| Infraorder: | Anomura |
| Family: | Hippidae |
| Genus: | Emerita Scopoli, 1777 [1] |
| Type species | |
| Cancer emeritus | |
Emerita is a small genus of decapod crustaceans, [3] known as mole crabs, sand fiddlers, or sand crabs. These small animals burrow in the sand in the swash zone and use their antennae for filter feeding. [4] [5]
Emerita has a barrel-shaped body. It has a tough exoskeleton and can hold its appendages close to the body, allowing it to roll in the tidal currents and waves. [6] It has feathery antennae, which are used to filter plankton and detritus from the swash. [6]
Males are typically smaller than females, and in some species, such as Emerita rathbunae , the minute males live attached to the legs of the female. [7] Females are around 8–37 mm (0.31–1.46 in) in carapace length, depending on the species, while males vary from a similar size to females in E. austroafricana , down to 2.5 mm (0.098 in) carapace length in E. rathbunae and E. talpoida . [8]
The genus as a whole has a broad distribution in tropical and subtropical regions. Most individual species, however, are restricted to smaller areas, and their ranges rarely overlap. [9] The genus is common on both coasts of the United States and along the Atlantic coast of Africa; the related genus Hippa is found across the Indo-Pacific, including Australia. [10]
Twelve species are recognised: [3] [Note 1]
The Old World species had been widely thought to form a monophyletic group, as did the New World species. The use of molecular phylogenetics has shown, however, that E. analoga, a species living along the Pacific coast of North America, is more closely related to African species than it is to other New World species. [9]
The genus Emerita was erected by Giovanni Antonio Scopoli in his 1777 work Introductio ad Historiam Naturalem. [11] The type species is Cancer emeritus (now E. emeritus), because at one time, it was the only species in the genus. [2] Other genera with the same name have been rejected for nomenclatural purposes; these were published by Laurens Theodorus Gronovius (1764) and Friedrich Christian Meuschen (1778 and 1781). [1]
Emerita is adept at burrowing, and is capable of burying itself completely in 1.5 seconds. [6] Unlike mud shrimp, Emerita burrows tail-first into the sand, using the pereiopods to scrape the sand from underneath its body. [12] During this action, the carapace is pressed into the sand as anchorage for the digging limbs. [12] The digging requires the sand to be fluidised by wave action, and Emerita must bury itself in the correct orientation before the wave has passed to be safe from predators. [12]
As the tide changes, Emerita changes its position on the beach; [6] most individuals stay in the zone of breaking waves. [7] This may be detected by the physical characteristics of the sand. As the tide falls, the sand is allowed to settle; when Emerita detects this, it uses the temporary liquefaction from a breaking wave to emerge from its burrow, and is carried down the beach by the wave action. [7] Longshore drift may also drag Emerita laterally along a beach. [7]
The main predators of Emerita are fish; in the eastern Pacific Ocean, the barred surfperch (Amphistichus argenteus) is particularly important. [7] Seabirds also eat Emerita, but do not appear to target the aggregations of mole crabs. [7] Carcasses of Emerita provide an important food source for the closely related scavenger Blepharipoda . [7]
Due to the Emerita being the predominant diet of the barred surfperch, surf fishermen use sand crabs as bait. Soft-shelled Emerita are kept also as bait by commercial fisheries.
In some cultures, sand crabs are eaten as a popular snack, such as in Thailand. They are often prepared via shallow frying in a pan or deep frying in batter. The taste is often described as falling somewhere between that of shrimp and crab. Eating sand crabs presents a risk of paralytic shellfish poisoning and/or infection with Profilicollis parasites. [13] In Malaysia, the sand crab locally known as yat yat, ibu remis, kutu laut or udang pasir can be found along the beaches in Kelantan during the monsoon season. The crab is a local delicacy that is usually fried with eggs or roasted on a skewer like satay. [14]
Emerita has a short lifespan, perhaps no more than two to three years, and can reproduce in its first year of life. [7] The eggs are bright orange, and hatch into larvae, which may live as plankton for more than four months and can be carried long distances by ocean currents. [7] The number of zoeal stages varies between species from six to eleven. [2] Somatic growth and sexual differentiation in Emerita are restricted to discrete events (molts) and both processes compete for energy reserve. In some conditions of high food availability, overlapping reproductive and molting processes would enable females to reach an optimum size and sexual maturity with fewer molts. [15]
The sanderling is a small wading bird. The name derives from Old English sand-yrðling, "sand-ploughman". The genus name is from Ancient Greek kalidris or skalidris, a term used by Aristotle for some grey-coloured waterside birds. The specific, alba, is Latin for "white".
Ghost crabs are semiterrestrial crabs of the subfamily Ocypodinae. They are common shore crabs in tropical and subtropical regions throughout the world, inhabiting deep burrows in the intertidal zone. They are generalist scavengers and predators of small animals. The name "ghost crab" derives from their nocturnality and their generally pale coloration. They are also sometimes called sand crabs, though the name refers to various other crabs that do not belong to the subfamily.
Giovanni Antonio Scopoli was an Italian physician and naturalist. His biographer Otto Guglia named him the "first anational European" and the "Linnaeus of the Austrian Empire".
Mary Jane Rathbun was an American zoologist who specialized in crustaceans. She worked at the Smithsonian Institution from 1884 until her death. She described more than a thousand new species and subspecies and many higher taxa.
The bird genus Apus comprise some of the Old World members of the family Apodidae, commonly known as swifts.
Sand bubbler crabs are crabs of the genera Scopimera and Dotilla in the family Dotillidae. They are small crabs that live on sandy beaches in the tropical Indo-Pacific. They feed by filtering sand through their mouthparts, leaving behind balls of sand that are broken up by the incoming high tide.
The Puerto Rican sand crab, Emerita portoricensis, is a species of "sand crab" belonging to the genus Emerita, which is native to the main island of Puerto Rico and its archipelago. This species has also been found on beaches off the coast of Venezuela. The most detailed study conducted on the species was done by Miguel P. Sastre between 1988 and 1992. This investigation determined that the species has diotic traits and that there are size and survival differences between sexes. Both sexes reach sexual maturity three months after birth.
Cardisoma guanhumi, also known as the blue land crab or great land crab, is a species of land crab found in tropical and subtropical estuaries and other maritime areas of land along the Atlantic coast of the Americas from Brazil and Colombia, through the Caribbean and Gulf of Mexico, to the Bahamas, and north to Ponce Inlet, Florida Princess Place Preserve on the Palm Coast, and Bermuda. The species varies in colour from dark blue to brown or pale grey, and may grow to 15 centimetres (6 in) in carapace width and weigh over 500 grams (18 oz).
Hippoidea is a superfamily of decapod crustaceans known as mole crabs or sand crabs.
Profilicollis is a genus of acanthocephalan parasites of crustaceans. The status of the genus Profilicollis has been debated, and species placed in this genus were formerly included in the genus Polymorphus. However, research on the morphology of the group and their use of hosts has concluded that Profilicollis and Polymorphus should be regarded as distinct genera, and species previously described as Polymorphus altmani are now referred to as Profilicollis altmani in taxonomic and biological literature. Profilicollis parasites infect decapod crustaceans, usually shore crabs, as intermediate hosts, and use many species of shorebirds as definitive (final) hosts.
The Atlantic ghost crab, Ocypode quadrata, is a species of ghost crab. It is a common species along the Atlantic coast of the United States, where it is the only species of ghost crab; its range of distribution extends from its northernmost reach on beaches in Westport, Massachusetts, south along the coasts of the tropical Western Atlantic Ocean to the beach of Barra do Chui, in Rio Grande do Sul in southern Brazil.
Mictyris longicarpus, the light-blue soldier crab, is a species of crab that lives on sandy beaches from the Bay of Bengal to Australia; with other members of the genus Mictyris, it is "one of the most loved crabs in Australia". Adults are 25 mm (1 in) across, white, with blue on their backs, and hold their claws vertically. They feed on detritus in the sand, leaving rounded pellets of discarded sand behind them. The males may form into large "armies" which traverse the beach at low tide, before the crabs dig into the sand to wait for the next low tide.
Ocypode gaudichaudii, also known as the painted ghost crab or cart driver crab, is a species of crab found on Pacific beaches from El Salvador to Chile as well as on the Galápagos Islands. The species was first described by Henri Milne-Edwards and Hippolyte Lucas in 1843.
Emerita analoga, the Pacific sand crab, Pacific mole crab or coldwater mole crab, is a species of small, sand-burrowing decapod crustacean found living in the sand along the temperate western coasts of North and South America. It is found on exposed sandy beaches in the swash region of the intertidal zone.
Emerita rathbunae is a species of "mole crabs" or "sand crabs" in the genus Emerita that lives along the tropical Pacific coasts of the Americas.
Albunea carabus is a rare species of "sand crab" or "mole crab" in the family Albuneidae. It lives in shallow, turbulent waters in sandy areas of the tropical eastern Atlantic Ocean and the Mediterranean Sea.
The gulf ghost crab, Hoplocypode occidentalis, is a species of ghost crabs native to the Pacific coast of the Americas, from the Gulf of California to Colombia. It is the only species in the genus Hoplocypode. Gulf ghost crabs are medium-sized, reaching a maximum overall body diameter of 6 in (15 cm). They are one of only two ghost crab species found in the eastern Pacific. However, gulf ghost crabs can easily be distinguished from painted ghost crabs by the absence of "horns" on their eyes.
Ocypode africana, commonly known as the African ghost crab, is a species of ghost crabs native to the eastern Atlantic coast of western Africa, from Mauritania to Namibia. They are medium-sized ghost crabs reaching carapace width of 3.4 cm (1.3 in). They can vary in coloration from pinkish to dark grey. They are one of only two ghost crab species found in the eastern Atlantic. However, African ghost crabs can easily be distinguished from tufted ghost crabs by the absence of long tufts of hair on the tip of their eyestalks.
Hippa adactyla is a species of small, sand-burrowing decapod crustacean found living along the coasts of Indo-West Pacific waters. It is found on exposed sandy beaches in the swash region of the intertidal zone.
Emerita talpoida, known generally as the Atlantic mole crab or Atlantic sand crab, is a species of mole crab in the family Hippidae. It is found in the western Atlantic Ocean and Mexico along the shoreline.
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