Encope emarginata

Encope emarginata has a thick test, or shell, that often remains intact and preserved.{{Cite journal |last1=Coppard |first1=Simon E. |last2=Lessios |first2=H. A. |date=2017-09-14 |title=Phylogeography of the sand dollar genus Encope: implications regarding the Central American Isthmus and rates of molecular evolution |journal=Scientific Reports |language=en |volume=7 |issue=1 |pages=11520 |doi=10.1038/s41598-017-11875-w |pmid=28912431 |pmc=5599539 |bibcode=2017NatSR...711520C |issn=2045-2322}} Tests are oval-shaped, centrally domed, typically greenish-brown colored, and have 6 lunules, or notches, as well as large bowed petaloids {{Cite web |title=Encope emarginata - Plazi TreatmentBank |url=http://treatment.plazi.org/id/C4255B094E14FFC4FF551ECAFCADFC86 |access-date=2023-03-23 |website=treatment.plazi.org |language=en}} Young E. emarginata can be mistaken for its sibling, E. michelini, because of the presence of open lunules as juveniles, although closed as adults.{{Cite journal |last1=Francisco |first1=V. |last2=Pauls |first2=S. M. |date=2008 |title=Especies del Orden Clypeasteroida (Echinodermata: Echinoidea) de las costas de Venezuela |url=https://www.redalyc.org/articulo.oa?id=44920273011 |journal=Revista de Biología Tropical |volume=56 |issue=3 |pages=215–228 |issn=0034-7744}}

File:Anatomy_of_Encope_emarginata.pngFile:Encope emarginata (Leske, 1778) derivate 2013.jpg published in 1904.|center]]

File:E._emarginata_Brazil.jpg by @fernandas via iNaturalist]]

Mostly found in subtropical and tropical waters of the Caribbean Sea, Gulf of Mexico, and southwestern Atlantic Ocean, E. emarginata ranges from Belize to Argentina.{{Citation |last1=Ventura |first1=C |title=Morphological dimensional differences in two geographically separated populations of Encope emarginata (Leske) from the coast of Brazil |date=2004-12-15 |url=http://dx.doi.org/10.1201/9780203970881.ch45 |work=Echinoderms: Munchen |pages=261–265 |access-date=2023-02-20 |publisher=Taylor & Francis |last2=Hopkins |first2=T |last3=Kuhajda |first3=B|doi=10.1201/9780203970881.ch45 |doi-broken-date=2024-11-11 |isbn=978-0-415-36481-2 |url-access=subscription }} Common on the South America Atlantic coastline, they are one of the only extant echinoids found on the coast of Rio Grande do Sul (the other being Mellita quinquiesperforata) and the only one south of the La Plata river.{{Cite journal |last=Lopes |first=Renato Pereira |date=2011-12-30 |title=Fossil sand dollars (Echinoidea: Clypeasteroida) from the Southern Brazilian coast |journal=Revista Brasileira de Paleontologia |volume=14 |issue=3 |pages=201–214 |doi=10.4072/rbp.2011.3.01 |issn=1519-7530|doi-access=free }} Area inhibited by Encope emarginata is below the action of the normal wave regime, thus the fossils of this species is only truly disturbed during extreme coastal weather.

Encope emarginata inhabits sandy, muddy sediments of coastal waters. Although a marine species,{{Cite web |title=WoRMS - World Register of Marine Species - Encope emarginata (Leske, 1778) |url=https://www.marinespecies.org/aphia.php?p=taxdetails&id=513255 |access-date=2023-02-20 |website=www.marinespecies.org |language=en}} they have also been found in estuaries and river mouths.{{Cite journal |last1=Brustolin |first1=Marco C. |last2=Thomas |first2=Micheli C. |last3=Mafra |first3=Luiz L. |last4=da Cunha Lana |first4=Paulo |date=2016-05-20 |title=Bioturbation by the sand dollar Encope emarginata (Echinoidea, Mellitidae) changes the composition and size structure of microphytobenthic assemblages |url=http://dx.doi.org/10.1007/s10750-016-2815-6 |journal=Hydrobiologia |volume=779 |issue=1 |pages=183–192 |doi=10.1007/s10750-016-2815-6 |s2cid=254554493 |issn=0018-8158|url-access=subscription }} The waters they live in are typically shallow, as deep as 20 meters.{{Cite journal |last=Biología Tropical |first=Revista de |title=Indice y Creditos |date=2015-06-01 |journal=Revista de Biología Tropical |volume=63 |issue=2 |pages=1 |doi=10.15517/rbt.v63i2.18577 |issn=2215-2075|doi-access=free }}

These sand dollars were originally named Echinodiscus emarginatus,{{Cite book |url=https://gdz.sub.uni-goettingen.de/id/PPN573613834 |title=Jacobi Theodorie Klein naturalis dispositio Echinodermatum |publisher=Gleditsch}} but have since been transferred to the Encope genus within the Mellitidae family. Encope is thought to be the most diverse genus among sand dollars, containing 7 extant species. Fossils can be dated back to the Pliocene or Pleistocene, up to 5 million years ago.

There is ongoing research suggesting that two populations of E. emarginata may emerge as separate species as a result of a barrier created by upwelling, a process known as allopatric speciation.

Encope emarginata is well-known for its bioturbation within the sediment, especially its effect on the spatial distributions of phytoplankton and other small benthic organisms. Moving at a maximum rate of 15 cm per hour, these sand dollars typically work through surface-layer sediments. E. emarginata has shown to have significant impacts on the concentrations of Chlorophyll-a within the sediment, as well as causing a greater variance in microphytobenthic and meiofaunal populations due to the sand dollars' foraging behaviors. The bioturbation of this echinoid is thought to create top-down effects, enhancing sediment heterogeneity and maintaining benthic biodiversity.{{Cite journal |last1=Brustolin |first1=Marco C. |last2=Thomas |first2=Micheli C. |last3=Mafra |first3=Luiz L. |last4=Lana |first4=Paulo da Cunha |date=2014-08-01 |title=Does Encope emarginata (Echinodermata: Echinoidea) affect spatial variation patterns of estuarine subtidal meiofauna and microphytobenthos? |url=https://www.sciencedirect.com/science/article/pii/S1385110114000677 |journal=Journal of Sea Research |language=en |volume=91 |pages=70–78 |doi=10.1016/j.seares.2014.03.006 |bibcode=2014JSR....91...70B |issn=1385-1101|url-access=subscription }}

File:Tu - Encope emarginata - 1.jpg

Genus Dissodactylus are commensal or parasitic crabs found to live on the bodies of irregular echinoids, such as E. emarginata. There is ongoing debate whether the size of E.emarginata influences the number of crabs found on it, where one study found a positive correlation{{Cite journal |last1=Martinelli Filho |first1=José Eduardo |last2=dos Santos |first2=Ronan Brito |last3=Ribeiro |first3=Caio Cesar |date=2014-07-01 |title=Host selection, host-use pattern and competition in Dissodactylus crinitichelis and Clypeasterophilus stebbingi (Brachyura: Pinnotheridae) |url=https://doi.org/10.1007/s13199-014-0292-0 |journal=Symbiosis |language=en |volume=63 |issue=3 |pages=99–110 |doi=10.1007/s13199-014-0292-0 |bibcode=2014Symbi..63...99M |s2cid=256075356 |issn=1878-7665|url-access=subscription }} and another found no relationship.{{Cite journal |last1=Guilherme |first1=Pablo D. B. |last2=Brustolin |first2=Marco C. |last3=Bueno |first3=Maristela de L. |last4=Guilherme |first4=Pablo D. B. |last5=Brustolin |first5=Marco C. |last6=Bueno |first6=Maristela de L. |date=June 2015 |title=Distribution patterns of ectosymbiont crabs and their sand dollar hosts in a subtropical estuarine sandflat |url=http://www.scielo.sa.cr/scielo.php?script=sci_abstract&pid=S0034-77442015000600209&lng=en&nrm=iso&tlng=en |journal=Revista de Biología Tropical |language=en |volume=63 |pages=209–220 |doi=10.15517/rbt.v63i2.23155 |doi-broken-date=1 November 2024 |issn=0034-7744}} The crabs are thought to consume the spines of the sand dollar, but additional research is necessary to determine if the Dissodactylus are truly parasitic.

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Category:Mellitidae

Category:Animals described in 1778

Category:Echinoderms of Brazil