Emerita analoga

Last updated

Emerita analoga
Female-sand-crab-back.jpg
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Malacostraca
Order: Decapoda
Suborder: Pleocyemata
Infraorder: Anomura
Family: Hippidae
Genus: Emerita
Species:
E. analoga
Binomial name
Emerita analoga
(Stimpson, 1857)
Synonyms   [1]
  • Hippa analogaStimpson, 1857
  • Hippa chilensisPhilippi, 1860 – nomen nudum

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.

Contents

Description

The Pacific sand crab is a small crustacean growing up to 35 mm (1.4 in) long and 25 mm (1.0 in) wide. The female is nearly twice as large as the male and can often be identified by the orange egg mass carried under the telson. The adult is sand-coloured and well camouflaged, and has no claws or spines. It has five pairs of legs and three pairs of pleopods. Sand crabs moult periodically, so their exoskeletons may be found washed up on the beach. [2]

The sand crab is well adapted to life in the sand, which presents an unstable substrate, and its shape is an elongated dome shape designed for fast burrowing. The eyes are on long stalks and the antennules are also elongated so as to project above the surface of the sand. These form a tube which channels water downwards through the gills. The much longer antennae are retractable. When water is overhead, they also project above the sand surface to collect food particles. The legs and uropods have hairy margins to assist in digging and for use in collecting food and transferring it to the mouth. [3]

Distribution

The sand crab occurs in North America from Alaska to Baja California and in South America, where it is found from Salaverry, Peru, southwards to around Cape Horn and into southern Argentina. [4] The species is common on the beaches of California, but greater changes in population levels occur further north, probably as a result of variations in the coastal currents which in some years passively disperse the planktonic larval stages northwards. In Oregon, the populations seem not to be self-sustaining and recruitment is largely from larvae originating in California. [5] There is an established population of sand crabs on the Twin Harbors Peninsula of Washington state.

On any particular beach, the distribution of sand crabs from one part to another can vary greatly for reasons not fully understood. Females tend to be found far down the beach, whereas males and immature crabs are found at higher levels. [2]

Biology

Underside of female sand crab with eggs Emerita analoga.jpg
Underside of female sand crab with eggs

The sand crab always moves backwards when burrowing or crawling. It can also swim (backwards) and tread water using its back legs. [6] It is a suspension feeder. It burrows backwards into the sand and faces the sea. As each wave retreats, it extends its antennae and catches floating organisms. It then retracts the antennae and scrapes the particles into its mouth. It can do this several times per wave. [6] When it becomes uncovered by water, it coils its antennae and burrows backwards deeper into the sand. [3] The diet is plankton, mostly consisting of dinoflagellates. [2]

The sand crab mates in spring and summer. The female lays batches of up to 45,000 eggs each month and carries them about beneath her abdomen tucked under her telson. The eggs hatch in about four weeks. [6] The larvae have five planktonic zoeal stages and a final megalopal stage. The zoeal stages last up to 130 days. [4] The megalopae settle out onto sandy beaches where they moult and develop into juveniles, which mature into adults within a few weeks. [7] The long planktonic stage means that the larvae can become widely dispersed and colonize new areas. The adults reproduce in both their first and second summers and most die in the autumn of their second year. [8]

Ecology

Sand crab burrowing back into the sand Emeritaanaloga.jpg
Sand crab burrowing back into the sand

The sand crab lives under the surface of the sand, moving up and down the beach according to the state of the tide. As each wave advances and retreats, the crab comes to the surface and extends its antennae to feed. This makes it vulnerable to predatory birds such as the sanderling. These birds actively patrol the part of the beach washed by incoming waves, probing the softened sand with their bills. The sand crab retreats under the sand surface as each wave goes out, maximizing its chance of being out of reach of the bird's beak. The bird maximizes its chance of feeding on sand crabs by scurrying at the edge of the surf. [9]

Other birds that eat sand crabs include willets, godwits, surf scoters, blackbellied plovers, and curlews. The crabs are hosts to the intermediate stages of various parasitic worms, like acanthocephalans. These are passed on to predators when the predators eat the crabs, and if enough worms are ingested, they have been known to kill the predator. [2]

The barred surfperch (Amphistichus argenteus), found off the coast of California, consumes a large number of sand crabs. [6] Surf fishermen use the crabs for bait and commercial bait fisheries extract them from the beach. The sand crabs with soft shells that have just moulted are kept for bait, while the hard-shelled crabs are thrown back into the sea. [6]

The sand crab has been evaluated as an indicator species for monitoring the level of domoic acid-synthesizing diatoms ( Pseudo-nitzschia spp.) which sometimes cause toxic blooms off the coast of California. [10]

Related Research Articles

<span class="mw-page-title-main">Sanderling</span> Species of bird

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".

<i>Emerita</i> (crustacean) Genus of crustaceans

Emerita is a small genus of decapod crustaceans, known as mole crabs, or sand crabs. These small animals burrow in the sand in the swash zone and use their antennae for filter feeding.

<span class="mw-page-title-main">Japanese spider crab</span> Species of crab

The Japanese spider crab is a species of marine crab and is the biggest one that lives in the waters around Japan. It has the largest known leg-span of any arthropod around 3.7 meters. The Japanese name for this species is taka-ashi-gani,, literally translating to “tall legs crab”. It goes through three main larval stages along with a prezoeal stage to grow to its great size.

<span class="mw-page-title-main">Sand bubbler crab</span> Genus of crabs

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.

<span class="mw-page-title-main">Pea crab</span> Species of crab

The pea crab, Pinnotheres pisum, is a small crab in the family Pinnotheridae that lives as a parasite in oysters, clams, mussels, and other species of bivalves.

<span class="mw-page-title-main">Surf zone</span> Nearshore zone where wave water comes onto the shore

As ocean surface waves approach shore, they get taller and break, forming the foamy, bubbly surface called surf. The region of breaking waves defines the surf zone, or breaker zone. After breaking in the surf zone, the waves continue to move in, and they run up onto the sloping front of the beach, forming an uprush of water called swash. The water then runs back again as backwash. The nearshore zone where wave water comes onto the beach is the surf zone. The water in the surf zone is shallow, usually between 5 and 10 m deep; this causes the waves to be unstable.

<span class="mw-page-title-main">Puerto Rican sand crab</span> Species of crustacean

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.

<i>Gilvossius tyrrhenus</i> Species of crustacean

Gilvossius tyrrhenus is a species of thalassinidean crustacean which grows to a length of 70 mm (2.8 in). It lives in burrows in shallow sandy parts of the sea-bed in the Mediterranean Sea and northern Atlantic Ocean. It is the most common thalassinidean in the Mediterranean, and has been used as bait by fishermen for at least 200 years.

<span class="mw-page-title-main">Hippoidea</span> Superfamily of crustaceans

Hippoidea is a superfamily of decapod crustaceans known as mole crabs or sand crabs.

<i>Profilicollis</i> Genus of thorny-headed worms

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.

<i>Dendraster excentricus</i> Species of sea urchin

Dendraster excentricus, also known as the eccentric sand dollar, sea-cake, biscuit-urchin, western sand dollar, or Pacific sand dollar, is a species of sand dollar in the family Dendrasteridae. It is a flattened, burrowing sea urchin found in the north-eastern Pacific Ocean from Alaska to Baja California.

<span class="mw-page-title-main">Hippidae</span> Family of crustaceans

Hippidae is a family of decapod crustaceans, currently known by the English name as either mole crab or sand crab, and by an earlier English name as sand bug. They are closely related to the family Albuneidae, with which they are usually joined in the superfamily Hippoidea. The family Hippidae comprises the three genera Emerita, Hippa and Mastigochirus. They burrow into sand, and are found throughout the world, except the Arctic and Antarctic.

Pinnixa chaetopterana, the tube pea crab, is a small decapod crustacean that lives harmlessly within the tube of the polychaete worm, Chaetopterus variopedatus.

<i>Petrolisthes eriomerus</i> Species of crustacean

Petrolisthes eriomerus is a species of marine porcelain crab found in the eastern Pacific Ocean. It is commonly known as the flattop crab. It is a flattened, rounded animal, with a carapace up to 20 mm (0.8 in) across. It is a filter feeder, and also sweeps food from rocks.

<i>Pyromaia tuberculata</i> Species of crab

Pyromaia tuberculata is a species of crab in the family Inachoididae.

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.

<i>Albunea carabus</i> Species of crustacean

Albunea carabus is a rare species of "sand crab" or "mole crab" in the genus Albunea. It lives in shallow, turbulent waters in sandy areas of the tropical eastern Atlantic Ocean and the Mediterranean Sea.

<span class="mw-page-title-main">Gulf ghost crab</span> Species of crab

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.

<i>Emerita talpoida</i> Species of crab

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.

<i>Urechis caupo</i> Species of annelid worm

Urechis caupo is a species of spoon worm in the family Urechidae, commonly known as the innkeeper echiuran, the fat innkeeper worm, the innkeeper worm, or the penis fish. It is found in shallow water on the west coast of North America, between southern Oregon and Baja California, where it forms a U-shaped burrow in the sediment and feeds on plankton using a mucus net.

References

  1. ↑ DecaNet (2023). "Emerita analoga (Stimpson, 1857)". WoRMS. World Register of Marine Species . Retrieved 1 June 2023.
  2. 1 2 3 4 "The Pacific Mole Crab" (PDF). LiMPETS. Retrieved July 21, 2011.
  3. 1 2 Peter J. Bryant. "Pacific Sand Crab (Mole Crab), Emerita analoga". Natural History of Orange County, California. University of California, Irvine . Retrieved July 21, 2011.
  4. 1 2 Efford, Ian E. (1970). "Recruitment To Sedentary Marine Populations as Exemplified By the Sand Crab, Emerita Analoga (Decapoda, Hippidae)". Crustaceana. 18 (3): 293–308. doi:10.1163/156854070x00248. JSTOR   20101692.
  5. ↑ Sorte, C. J. (September 2001). "Larval dynamics of the sand crab, Emerita analoga, off the central Oregon coast during a strong El Nino period". Journal of Plankton Research. 23 (9): 939–944. doi: 10.1093/plankt/23.9.939 .
  6. 1 2 3 4 5 "Sand crab". Monterey Bay Aquarium . Retrieved July 21, 2011.
  7. ↑ Johnson, Martin W.; Lewis, Weldon M. (1942). "Pelagic Larval Stages of the Sand Crabs Emerita analoga (Stimpson), Blepharipoda occidentalis Randall, and Lepidopa myops Stimpson". Biological Bulletin. 83 (1): 67–87. doi:10.2307/1538014. JSTOR   1538014.
  8. ↑ Tam, Y. K.; Kornfield, I.; Ojeda, F. P. (May 1996). "Divergence and zoogeography of mole crabs, Emerita spp. (Decapoda: Hippidae), in the Americas". Marine Biology. 125 (3): 489–497. Bibcode:1996MarBi.125..489T. doi:10.1007/BF00353262.
  9. ↑ Schultz, Stewart T. (1990). The Northwest Coast: A Natural History. Portland, Oregon: Timber Press. pp. 129–130. ISBN   978-0-88192-418-3.[ page needed ]
  10. ↑ Ferdin, M.E; Kvitek, R.G; Bretz, C.K; Powell, C.L; Doucette, G.J; Lefebvre, K.A; Coale, S; Silver, M.W (September 2002). "Emerita analoga (Stimpson)—possible new indicator species for the phycotoxin domoic acid in California coastal waters". Toxicon. 40 (9): 1259–1265. doi:10.1016/S0041-0101(02)00129-0. PMID   12220710.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.