Nurse shark

{{Short description|Elasmobranch fish in the family Ginglymostomatidae}} {{Distinguish|grey nurse shark|tawny nurse shark}} {{Speciesbox | name = Nurse shark | fossil_range = {{Fossil range|112|0}} [[Albian]] to Present<ref>{{cite journal |last=Sepkoski |first=J. |title=A compendium of fossil marine animal genera (Chondrichthyes entry) |journal=Bulletins of American Paleontology |volume=364 |page=560 |year=2002 |url=http://strata.geology.wisc.edu/jack/showgenera.php?taxon=575&rank=class}}</ref> | image = nurse shark.jpg | image_caption = At [[Gray's Reef National Marine Sanctuary]], [[Sapelo Island]], [[Georgia (U.S. state)|Georgia]] | status = VU | status_system = IUCN3.1 | status_ref =<ref name="iucn status 18 November 2021">{{cite iucn |last=Carlson |first=J. |last2=Charvet |first2=P. |last3=Blanco-Parra |first3=MP |last4=Briones Bell-lloch |first4=A. |last5=Cardenosa |first5=D. |last6=Derrick |first6=D. |last7=Espinoza |first7=E. |last8=Herman |first8=K. |last9=Morales-Saldaña |first9=J.M. |last10=Naranjo-Elizondo |first10=B. |last11=Pérez Jiménez |first11=J.C. |last12=Schneider |first12=E.V.C. |last13=Simpson |first13=N.J. |last14=Talwar |first14=B.S. |last15=Pollom |first15=R. |last16=Pacoureau |first16=N. |last17=Dulvy |first17=N.K. |date=2021 |title=''Ginglymostoma cirratum'' |volume=2021 |article-number=e.T144141186A3095153 |doi=10.2305/IUCN.UK.2021-1.RLTS.T144141186A3095153.en |access-date=18 November 2021}}</ref> | genus = Ginglymostoma | species = cirratum | authority = ([[Pierre Joseph Bonnaterre|Bonnaterre]], 1788) | range_map = Ginglymostoma cirratum distmap.png | range_map_caption = Range in blue }} [[File:Nurse Shark, Davis Reef, Florida Keys.jpg|thumb|A nurse shark at the Davis Reef Sanctuary Preservation area, Florida Keys National Marine Sanctuary]] The '''nurse shark''' ('''''Ginglymostoma cirratum''''') is an [[Elasmobranchii|elasmobranch fish]] in the family [[Ginglymostomatidae]]. The [[conservation status]] of the nurse shark is globally assessed as [[Vulnerable species|vulnerable]] in the [[IUCN Red List|IUCN List of Threatened Species]].<ref name="iucn status 18 November 2021" /> They are considered to be a species of least concern in the United States and in [[The Bahamas]], but considered to be near threatened in the western Atlantic Ocean because of their vulnerable status in South America and reported threats throughout many areas of Central America and the Caribbean.<ref name="iucn status 18 November 2021" /> They are directly targeted in some fisheries and considered by-catch in others.

Nurse sharks are an important species for shark research.<ref name="Osgood">{{cite journal |author=Osgood, G. J and J. K. Baum. |year=2015 |title=Reef sharks: recent advances in ecological understanding to inform conservation |journal=Journal of Fisheries Biology |volume=87 |issue=6 |pages=1489–1523 |doi=10.1111/jfb.12839|pmid=26709218 |bibcode=2015JFBio..87.1489O }}</ref> They are robust and able to tolerate capture, handling, and tagging extremely well.<ref name="Aucoin">{{Cite journal |last1=Aucoin |first1=S. |last2=Weege |first2=S. |last3=Toebee |first3=M. |last4=Guertin |first4=J. |last5=Gorham |first5=J. |last6=Bresette |first6=M. |year=2017 |title=A new underwater shark capture method used by divers to catch and release nurse sharks (Ginglymostoma cirratum) |journal=Fishery Bulletin |volume=115 |issue=4 |pages=484–495 |doi=10.7755/FB.115.4.5 |doi-access=free}}</ref>

==Taxonomy and name== The nurse shark genus ''Ginglymostoma'' is derived from [[Greek language]] meaning hinged mouth, whereas the species ''cirratum'' is derived from [[Latin]] meaning having curled ringlets. Based on [[morphology (biology)|morphological]] similarities, ''Ginglymostoma'' is believed to be the sister genus of ''[[Nebrius]]'', with both being placed in a [[clade]] that also include species ''[[Pseudoginglymostoma brevicaudatum]]'', ''[[Rhincodon typus]]'', and ''[[Stegostoma fasciatum]]''.<ref name="goto">{{cite journal |author=Goto, T. |title=Comparative Anatomy, Phylogeny and Cladistic Classification of the Order Orectolobiformes (Chondrichthyes, Elasmobranchii) |journal=Memoirs of the Graduate School of Fisheries Science, Hokkaido University |volume=48 |url=http://eprints.lib.hokudai.ac.jp/dspace/handle/2115/22014 |issue=1 |year=2001 |pages=1–101}}</ref>

The name "nurse" may have originated from antiquated spelling conventions. The ''[[Oxford English Dictionary]]'' notes that in [[medieval]] times, the "n" of the word "an" was frequently [[Rebracketing|transferred to a following word that began with a vowel]]. Huss, husse, and hurse were antiquated names for [[Squalidae|dogfish]] and other sharks.

Another possibility is noted by Lineaweaver and Backus in ''The Natural History of Sharks'', which posits instead that the name comes from the fact that the nurse shark is [[ovoviviparous]].

<blockquote>"Possibly, some bygone observer watched a shark giving birth to live young and thought the shark was giving nurse."<ref>{{cite web | url=http://www.elasmo-research.org/education/topics/ng_nurse_name.htm | title=Where did "Nurse" shark come from? }}</ref> </blockquote>

==Description== The nurse shark has two rounded dorsal fins, rounded pectoral fins, an elongated caudal fin, and a broad head.<ref name="McEachran Fechhelm 1998">{{cite book |last1=McEachran |first1=J. |last2=Fechhelm |first2=J.D. |title=Fishes of the Gulf of Mexico, Vol. 1: Myxiniformes to Gasterosteiformes |publisher=University of Texas Press |publication-place=Austin |year=1998 |isbn=978-0-292-75206-1 |oclc=38468784 |url=https://books.google.com/books?id=lAgyDQAAQBAJ |access-date=13 July 2021 |page=45}}</ref> Maximum adult length is currently documented as {{convert|3.08|m|ftin|frac=2|abbr=on}}, whereas past reports of {{convert|4.5|m|abbr=on}} and corresponding weights of up to {{convert|330|kg|abbr=on}} are likely to have been exaggerated.<ref name="iucn status 18 November 2021" /> Adult nurse sharks are brownish in color. Newborn nurse sharks have a spotted coloration, which fades with age, and are about 30 cm in length when nascent.

==Distribution and habitat== The nurse shark has a wide but patchy geographical distribution along tropical and subtropical coastal waters of the Eastern Atlantic, Western Atlantic, and Eastern Pacific.<ref>{{cite book |author=Compagno, L.J.V. |title=Bullhead, mackerel and carpet sharks (Heterodontiformes, Lamniformes and Orectolobiformes). Family Ginglymostomatidae. In: Sharks of the World: An Annotated and Illustrated Catalogue of Shark Species Known to Date, vol. 2 |publisher=Food and Agriculture Organization of the United Nations |year=2002 |pages=188–195 |url=http://www.fao.org/docrep/009/x9293e/x9293e00.HTM}}</ref> In the Eastern Atlantic, it ranges from [[Cape Verde]] to [[Gabon]] (accidental north to France).<ref name="iucn status 18 November 2021" /> In the Western Atlantic, including the Caribbean, it ranges from [[Rhode Island]] to southern [[Brazil]],<ref name="FAO">{{cite book |author=Compagno, L.J.V. |title=Sharks of the World: An Annotated and Illustrated Catalogue of Shark Species Known to Date |publisher=Food and Agriculture Organization of the United Nations |year=1984 |pages=205–207, 555–561, 588 |url=http://www.fao.org/docrep/009/x9293e/x9293e00.htm}}</ref> and in the Eastern Pacific from [[Baja California]] to [[Peru]].<ref name="iucn status 18 November 2021" />

Nurse sharks are a typically inshore, bottom-dwelling species. Juveniles are mostly found on the bottom of shallow coral reefs, seagrass flats, and around mangrove islands, whereas older individuals typically reside in and around deeper reefs and rocky areas, where they tend to seek shelter in crevices and under ledges during the day and leave their shelter at night to feed on the seabed in shallower areas.<ref name="Castro">{{cite journal |author=Castro, J. I. |year=2000 |title=The biology of the nurse shark, Ginglymostoma cirratum, off the Florida east coast and the Bahama Islands) |journal=Environmental Biology of Fishes |volume=58 |issue=1 |pages=1–22 |doi=10.1023/A:1007698017645|bibcode=2000EnvBF..58....1C |s2cid=32772305 }}</ref>

Nurse sharks are also subject to [[piebaldism]], a genetic condition that results in a partial lack of body pigmentation and a speckled body.<ref>{{Cite web |title=Piebald nurse shark with incredible speckled skin may be first on record {{!}} Sharks {{!}} Earth Touch News |url=https://www.earthtouchnews.com/oceans/sharks/piebald-nurse-shark-with-incredible-speckled-skin-may-be-first-on-record |access-date=2023-03-16 |website=Earth Touch News Network |language=en}}</ref>

==Biology and ecology== Nurse sharks are opportunistic predators that feed primarily on small fish (e.g. [[stingray]]s, [[teleost]]s) and some invertebrates (e.g. [[crustaceans]], [[molluscs]], [[sea urchin]]s, [[tunicates]], and [[anthozoa]]ns), as well as [[alga]]e.<ref name="Castro" /><ref name="animaldiversity.org">{{cite web | url=https://animaldiversity.org/accounts/Ginglymostoma_cirratum/ | title=ADW: Ginglymostoma cirratum: INFORMATION | website=[[Animal Diversity Web]] }}</ref> They are typically solitary [[nocturnal]] animals, rifling through bottom sediments in search of food at night, but are often gregarious during the day forming large sedentary groups. Nurse sharks are [[suction feeder|obligate suction feeders]] capable of generating [[suction|suction forces]] that are among the highest recorded for any aquatic vertebrate to date.<ref name="Tanaka">{{cite journal |author=Tanaka, S. K. |year=1973 |title=Suction feeding by the nurse shark |journal=Copeia |volume=1973 |issue=3 |pages=606–608 |doi=10.2307/1443135 |jstor=1443135}}</ref><ref name="Motta1">{{cite journal |author=Motta, P. J., Hueter, R. E., Tricas, T. C., Summers, A. P., Huber, D. R., Lowry, D., Mara, K. R., Matott, M. P., Whitenack, L. B., Wintzer, A.P. |year=2008 |title=Functional morphology of the feeding apparatus, feeding constraints, and suction performance in the nurse shark Ginglymostoma cirratum |journal=Journal of Morphology |volume=269 |issue=9 |pages=1041–1055 |doi=10.1002/jmor.10626|pmid=18473370 |s2cid=15066259 |doi-access=free }}</ref> Although their small mouths may limit the size of prey, they can exhibit a suck-and-spit behavior and/or shake their head violently to reduce the size of food items.<ref name="Motta">{{cite book |author=Motta, P. J. |title=Prey capture behavior and feeding mechanics of elasmobranchs. In Biology of sharks and their relatives. |publisher=CRC Press, Taylor & Francis Group |year=2004 |pages=165–202}}</ref>

Nurse sharks are exceptionally [[sedentary]], unlike most other shark species.<ref name="Heithaus">{{cite book |author=Heithaus, M.R., Burkholder, D., Hueter, R. E., Heithaus, L. I., Prat Jr. H. L., Carrier, J. C. |title=Reproductive biology of elasmobranchs. In: Biology of sharks and their relatives. |publisher=CRC Press, Taylor & Francis Group |year=2004 |pages=269–286}}</ref> Nurse sharks show strong [[site fidelity]] (typical of reef sharks) and are one of the few shark species known to exhibit [[Fidelity#Scientific modelling and simulation|mating-site fidelity]],<ref name="Carrier">{{cite journal |author=Carrier, J. C., Pratt, H. L., Castro, J. I. |year=2004 |title=Spatial and temporal variation in shark communities of the lower Florida Keys and evidence for historical population declines |journal=Canadian Journal of Fisheries and Aquatic Sciences |volume=64 |issue=10 |pages=1302–1313 |doi=10.1139/f07-098}}</ref> as they will return to the same breeding grounds time and time again.

[[American alligator]]s (''Alligator mississippiensis'') and [[American crocodile]]s (''Crocodylus acutus'') may occasionally prey on nurse sharks in some coastal habitats. Photographic evidence and historical accounts suggest that encounters between species are commonplace in their shared habitats.<ref>{{cite news |url=http://news.nationalgeographic.com/2017/09/american-alligator-sharks-predators-stingrays/ |archive-url=https://web.archive.org/web/20170920232103/http://news.nationalgeographic.com/2017/09/american-alligator-sharks-predators-stingrays/ |archive-date=September 20, 2017 |title=Alligators Attack and Eat Sharks, Study Confirms |author=Jason Bittel |date=20 September 2017 |newspaper=National Geographic}}</ref><ref>{{cite journal |title=Reciprocal Intraguild Predation between ''Alligator mississippiensis'' (American Alligator) and Elasmobranchii in the Southeastern United States |journal=Southeastern Naturalist |volume=16 |issue=3 |year=2017 |pages=383–396 |first1=James C. |last1=Nifong |first2=Russell H. |last2=Lowers |doi=10.1656/058.016.0306|s2cid=90288005 }}</ref>

==Reproduction== Nurse sharks are [[Ovoviviparity|ovoviviparous]], with fertilized eggs hatching inside the female. The mating cycle of nurse sharks is biennial, with females taking up to 18 months to produce a new batch of eggs. The mating season runs from late June to the end of July, with a [[gestation]] period of six months and a typical litter of 21–29 pups.<ref name="FAO" /> The young are born fully developed at about 30 cm long.

Nurse sharks engage in multiple paternity during mating season. A study conducted over a 10-year span found that a brood of nurse sharks had more genotypes than broods with one father. Fourteen separate genotypes were found in the brood examined, which suggests that more than one father fertilized the mother's eggs. Engagement in multiple paternity promotes genetic variation.<ref>{{Cite journal |last1=Saville |first1=Kenneth J. |last2=Lindley |first2=Andrea M. |last3=Maries |first3=Eleanora G. |last4=Carrier |first4=Jeffrey C. |last5=Pratt |first5=Harold L. |date=2002-03-01 |title=Multiple Paternity in the Nurse Shark, Ginglymostoma Cirratum |journal=Environmental Biology of Fishes |language=en |volume=63 |issue=3 |pages=347–351 |doi=10.1023/A:1014369011709 |bibcode=2002EnvBF..63..347S |s2cid=22777142 |issn=1573-5133}}</ref>

==See also== {{Portal|Sharks}} * [[List of sharks]] * [[List of prehistoric cartilaginous fish]] * [[Great white shark]]

==References== {{Reflist}}

==External links== {{Commons category}} * {{SealifePhotos|105846|Ginglymostoma cirratum}}

[[Category:Fish described in 1788|Nurse shark]] [[Category:Fish of Cuba]] [[Category:Fish of the Atlantic Ocean]] [[Category:Fish of the Caribbean]] [[Category:Fish of the Dominican Republic]] [[Category:Ginglymostomatidae|Nurse shark]] [[Category:Ovoviviparous fish]]