Atlantic ghost crab

File:Ocypode quadrata.png

Adults are grayish or the color of straw, and around {{convert|5|cm|in|abbr=on}} wide at maturity.{{cite web |title=Atlantic Ghost Crab, Ocypode quadrata |author=David Knott |publisher=South Carolina Department of Natural Resources |access-date=January 2, 2009 |url=http://www.dnr.sc.gov/cwcs/pdf/Ghostcrab.pdf |archive-date=October 31, 2020 |archive-url=https://web.archive.org/web/20201031163714/https://www.dnr.sc.gov/cwcs/pdf/Ghostcrab.pdf |url-status=dead }} They must return to water periodically to moisten their gills, and when larvae must be released into the sea, but are otherwise terrestrial. Their stalked compound eyes can swivel to give them 360° vision. Young crabs are cryptically colored to blend in with their sandy habitats.

Atlantic ghost crabs are found from Santa Catarina north to Massachusetts, USA. They have been recorded in Block Island, Rhode Island, Nantucket, Massachusetts, Martha's Vineyard, Massachusetts, Delaware beaches, northern Virginia beaches, the Outer Banks of North Carolina to Santa Catarina, Brazil, on Fernando de Noronha, and Bermuda. Its planktonic larvae have been documented in Woods Hole, Massachusetts, although the adults have not been recorded at this location.

Fossil specimens of O. quadrata have been found in rocks dating from the Pleistocene.{{cite journal |journal=Journal of Crustacean Biology |volume=23 |issue=3 |pages=712–722 |year=2003 |doi=10.1651/C-2340 |title=Occurrence of the Atlantic ghost crab Ocypode quadrata from the Upper Pleistocene to Holocene Anastasia Formation of Florida |author=Roger W. Portell, Richard L. Turner & John L. Beerensson |doi-access=free |bibcode=2003JCBio..23..712T }}

File:Atlantic ghost crab of Rehoboth Beach 2020c.jpg near Rehoboth Beach, Delaware in 2020]]

The Atlantic ghost crab lives in burrows in sand above the strandline. Older individuals dig their burrows farther from the sea, some starting as much as {{convert|400|m|ft|abbr=on}} inland. Burrows can be up to {{convert|1.3|m|abbr=on}} deep, and can be closed off with sand during hot periods.

This crab can produce a variety of sounds by striking the ground with the claw, by stridulation with the legs, and an incompletely explained "bubbling sound".{{cite web |url=http://www.vims.edu/~jeff/ghost.htm |title=The ghost crab, Ocypode quadrata |author=Jeffrey Shields |year=1998 |publisher=Virginia Institute of Marine Science |access-date=January 2, 2010 |archive-url=https://web.archive.org/web/20100104115041/http://www.vims.edu/~jeff/ghost.htm |archive-date=January 4, 2010 |url-status=dead }} Males compete in a heavily ritualised manner which prevents the need for physical contact.{{Explain|date=March 2022}}

Ghost crabs are arguably the fastest terrestrial invertebrates, capable of running at more than a meter per second.• Whittemore, S. B., Hoglin, B., Green, M. A., & Medler, S. (2015). Stride frequency in relation to allometric growth in ghost crabs. Journal of Zoology, 296(4), 286–294. https://doi.org/10.1111/jzo.12244

Studies on O. quadrata and its gonadal regions has revealed that, while the species can breed year-round, they have a tendency to be more active in their reproductive efforts during the summer months of the year.{{cite journal |last1=Antunes |first1=G. F. |last2=Wiilland |first2=E. F. |last3=Zancan |first3=D. M. |last4=Vinagre |first4=A. S. |title=Reproductive cycle of the ghost crab Ocypode quadrata at Rondinha beach (Rio Grande do Sul State, Brazil) |journal=Comparative Biochemistry and Physiology |date=2007 |volume=148 |issue=1 |pages=S88–S89 |doi=10.1016/j.cbpa.2007.06.230 }}

O. quadrata is more active at night than in the day, and is an omnivore, eating clams (such as coquina clams and Donax spp.),{{Cite web|url=https://animaldiversity.org/accounts/Ocypode_quadrata/|title=Ocypode quadrata (Atlantic ghost crab)|first1=Lisa|last1=Izzo|first2=Nikhita|last2=Kothari|website=Animaldiversity.org|access-date=16 March 2022}} mole crabs (including Emerita talpoida),{{cite web|url=https://sta.uwi.edu/fst/lifesciences/sites/default/files/lifesciences/documents/ogatt/Ocypode_quadrata%20-%20Atlantic%20Ghost%20Crab.pdf|title=Ocypode quadrata (Atlantic Ghost Crab)|website=Sta.uwi.edu|access-date=16 March 2022}} insects, plant material, detritus, and even other crabs. They also feed on the eggs and hatchlings of sea turtles, such as the loggerhead sea turtle.

Sandy beaches, a habitat frequented by ghost crabs, have had a decrease in the abundance of ghost crabs due to human behavior.{{cite journal |author=Thomas A. Schlacher, Luke Thompson & Sam Price |year=2007 |title=Vehicle versus conservation of invertebrates on sandy beaches: mortalities inflicted by offroad vehicles on ghost crabs |journal=Marine Ecology |volume=28 |issue=3 |pages=354–367 |doi=10.1111/j.1439-0485.2007.00156.x|bibcode=2007MarEc..28..354S }} Ghost crabs are negatively impacted by human and vehicle trampling, which results in direct crushing of crabs, as well as indirect damage such as compression of sediment which reduces habitat suitability, interference with reproductive behaviors, reduction in food supply, and light pollution.{{cite journal |author1=Graziani de Freitas Antunes, Ana Paula Nunes do Amaral |author2=Fabiana Pinto Ribarcki, Elenir de Fátima Wiilland |author3=Denise Maria Zancan, Anapaula Sommer Vinagre |year=2010 |title=Seasonal variations in the biochemical composition and reproductive cycle of the ghost crab Ocypode quadrata (Fabricius, 1787) in Southern Brazil |journal=Journal of Experimental Zoology |pmid=20127661 |volume=313A |issue=5 |pages=280–291 |doi=10.1002/jez.593|doi-access=free |bibcode=2010JEZA..313..280A }} Consequently, they may be less common on beaches frequented by people.

A 2023 study using the well known mirror test found that these crabs seem to be capable of recognizing themselves in a mirror. The study's author concluded that the data indicate that the crabs have "a rudimentary form of self-awareness".{{cite journal |last1=Robinson |first1=T. |title=Mirror self-recognition in ghost crab (Ocypode quadrata) |journal=Animal Cognition |date=14 June 2023 |volume=26 |issue=5 |pages=1539–1549 |doi=10.1007/s10071-023-01800-2 |pmid=37314594 |url=https://link.springer.com/article/10.1007/s10071-023-01800-2 |access-date=25 November 2023|url-access=subscription }}

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• {{Commons category-inline|Ocypode quadrata|Ocypode quadrata}}

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Category:Ocypodoidea

Category:Crabs of the Atlantic Ocean

Category:Fauna of Bermuda

Category:Crustaceans of the United States

Category:Crustaceans of the Dominican Republic

Category:Crustaceans described in 1787