Nurse shark

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Nurse shark
Temporal range: 112–0 Ma Albian to Present[1]
Nurse shark.jpg
Scientific classification edit
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Order: Orectolobiformes
Family: Ginglymostomatidae
Genus: Ginglymostoma
Species:
G. cirratum
Binomial name
Ginglymostoma cirratum
(Bonnaterre, 1788)
Ginglymostoma cirratum distmap.png
Range in blue

The nurse shark (Ginglymostoma cirratum) is an elasmobranch fish in the family Ginglymostomatidae. The conservation status of the nurse shark is globally assessed as Vulnerable in the IUCN List of Threatened Species.[2] 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.[2] They are directly targeted in some fisheries and considered by-catch in others.

Nurse sharks are an important species for shark research (predominantly in physiology).[3] They are robust and able to tolerate capture, handling, and tagging extremely well.[4] As inoffensive as nurse sharks may appear, they are ranked fourth in documented shark bites on humans,[5] likely due to incautious behavior by divers on account of the nurse shark's slow, sedentary nature.

Taxonomy[edit]

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 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.[6]

Description[edit]

The nurse shark has two rounded dorsal fins, rounded pectoral fins, an elongated caudal fin, and a broad head.[7] Maximum adult length is currently documented as 3.08 m (10.1 ft), whereas past reports of 4.5 m (15 ft) and corresponding weights of up to 330 kg (730 lb) are likely to have been exaggerated.[2] Adult nurse sharks are brownish in color. Newly born nurse sharks have a spotted coloration which fades with age and are about 30 cm in length when nascent.

Nurse shark swimming
Nurse shark turning
Nurse shark swims near boat

Distribution and habitat[edit]

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.[8] In the Eastern Atlantic it ranges from Cape Verde to Gabon (accidental north to France).[2] In the Western Atlantic, including the Caribbean, it ranges from Rhode Island to southern Brazil,[9] and in the East Pacific from Baja California to Peru.[2]

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.[10]

Biology and ecology[edit]

Nurse sharks are opportunistic predators that feed primarily on small fish (e.g. stingrays) and some invertebrates (e.g. crustaceans, molluscs, tunicates).[10] They are typically solitary nocturnal animals, rifling through bottom sediments in search of food at night, but often gregarious during the day forming large sedentary groups. Nurse sharks are obligate suction feeders capable of generating suction forces that are among the highest recorded for any aquatic vertebrate to date.[11][12] 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.[13]

Nurse sharks are exceptionally sedentary unlike most other shark species.[14] Nurse sharks show strong site fidelity (typical of reef sharks), and it is one of the few shark species known to exhibit mating site fidelity,[15] as they will return to the same breeding grounds time and time again.

American alligators (Alligator mississippiensis) 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.[16][17]

Reproduction[edit]

Nurse sharks are 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.[9] The young nurse sharks are born fully developed at about 30 cm long.

See also[edit]

References[edit]

  1. ^ Sepkoski, J. (2002). "A compendium of fossil marine animal genera (Chondrichthyes entry)". Bulletins of American Paleontology. 364: 560. Archived from the original on 2012-05-10.
  2. ^ a b c d e f Carlson, J., Charvet, P., Blanco-Parra, MP, Briones Bell-lloch, A., Cardenosa, D., Derrick, D., Espinoza, E., Herman, K., Morales-Saldaña, J.M., Naranjo-Elizondo, B., Pérez Jiménez, J.C., Schneider, E.V.C., Simpson, N.J., Talwar, B.S., Pollom, R., Pacoureau, N. & Dulvy, N.K. 2021. Ginglymostoma cirratum. The IUCN Red List of Threatened Species 2021: e.T144141186A3095153. https://dx.doi.org/10.2305/IUCN.UK.2021-1.RLTS.T144141186A3095153.en. Downloaded on 23 April 2021.
  3. ^ Osgood, G. J and J. K. Baum. (2015). "Reef sharks: recent advances in ecological understanding to inform conservation". Journal of Fisheries Biology. 87 (6): 1489–1523. doi:10.1111/jfb.12839.
  4. ^ Aucoin, S., Weege, S., Toebe, M., Guertin, J., Gorham, J., Bresette, M. (2017). "A new underwater shark capture method used by divers to catch and release nurse sharks (Ginglymostoma cirratum)". Fishery Bulletin. 115 (4): 484–495. doi:10.7755/FB.115.4.5.CS1 maint: multiple names: authors list (link)
  5. ^ Ricci, J. A., Vargas, C. R., Singhal, D. and B. T. Lee. (2016). "Shark attack-related injuries: epidemiology and implications for plastic surgeons". Journal of Plastic, Reconstructive and Aesthetic Surgery. 69: 108–114. doi:10.1016/j.bjps.2015.08.029.CS1 maint: multiple names: authors list (link)
  6. ^ Goto, T. (2001). "Comparative Anatomy, Phylogeny and Cladistic Classification of the Order Orectolobiformes (Chondrichthyes, Elasmobranchii)". Memoirs of the Graduate School of Fisheries Science, Hokkaido University. 48 (1): 1–101.
  7. ^ McEachran, J.; Fechhelm, J.D. (1998). Fishes of the Gulf of Mexico, Vol. 1: Myxiniformes to Gasterosteiformes. Fishes of the Gulf of Mexico. Austin: University of Texas Press. p. 45. ISBN 978-0-292-75206-1. OCLC 38468784. Retrieved 13 July 2021.
  8. ^ Compagno, L.J.V. (2002). 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. Food and Agriculture Organization of the United Nations. pp. 188–195.
  9. ^ a b Compagno, L.J.V. (1984). Sharks of the World: An Annotated and Illustrated Catalogue of Shark Species Known to Date. Food and Agriculture Organization of the United Nations. pp. 205–207, 555–561, 588.
  10. ^ a b Castro, J. I. (2000). "The biology of the nurse shark, Ginglymostoma cirratum, off the Florida east coast and the Bahama Islands)". Environmental Biology of Fishes. 58: 1–22. doi:10.1023/A:1007698017645.
  11. ^ Tanaka, S. K. (1973). "Suction feeding by the nurse shark". Copeia. 1973 (3): 606–608. doi:10.2307/1443135. JSTOR 1443135.
  12. ^ 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. (2008). "Functional morphology of the feeding apparatus, feeding constraints, and suction performance in the nurse shark Ginglymostoma cirratum". Journal of Morphology. 269 (9): 1041–1055. doi:10.1002/jmor.10626.CS1 maint: multiple names: authors list (link)
  13. ^ Motta, P. J. (2004). Prey capture behavior and feeding mechanics of elasmobranchs. In Biology of sharks and their relatives. CRC Press, Taylor & Francis Group. pp. 165–202.
  14. ^ Heithaus, M.R., Burkholder, D., Hueter, R. E., Heithaus, L. I., Prat Jr. H. L., Carrier, J. C. (2004). Reproductive biology of elasmobranchs. In: Biology of sharks and their relatives. CRC Press, Taylor & Francis Group. pp. 269–286.CS1 maint: multiple names: authors list (link)
  15. ^ Carrier, J. C., Pratt, H. L., Castro, J. I. (2004). "Spatial and temporal variation in shark communities of the lower Florida Keys and evidence for historical population declines". Canadian Journal of Fisheries and Aquatic Sciences. 64 (10): 1302–1313. doi:10.1139/f07-098.CS1 maint: multiple names: authors list (link)
  16. ^ Jason Bittel (20 September 2017). "Alligators Attack and Eat Sharks, Study Confirms". National Geographic.
  17. ^ Nifong, James C.; Lowers, Russell H. (2017). "Reciprocal Intraguild Predation between Alligator mississippiensis (American Alligator) and Elasmobranchii in the Southeastern United States". Southeastern Naturalist. 16 (3): 383–396. doi:10.1656/058.016.0306.

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