Bonnethead
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Bonnethead shark | |
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Chondrichthyes |
Subclass: | Elasmobranchii |
Subdivision: | Selachimorpha |
Order: | Carcharhiniformes |
Family: | Sphyrnidae |
Genus: | Sphyrna |
Species: | S. tiburo
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Binomial name | |
Sphyrna tiburo | |
Range of the bonnethead shark |
The bonnethead (Sphyrna tiburo), also called a bonnet shark or shovelhead,
Description
The shark is characterized by a broad, smooth, spade-like head: it has the smallest cephalofoil (hammerhead) of all Sphyrna species. The body is grey-brown above and lighter on the underside. Typically, bonnethead sharks are about 80–90 cm (2.6–3.0 ft) long, with a maximum size of about 150 cm (4.9 ft).[4] The generic name Sphyrna derives from the Greek word for "hammer", referring to the shape of this shark's head; the specific name tiburo derives from the Spanish word tiburón, meaning "shark".[citation needed]
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Head, underside
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Head, upper side
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Upper teeth
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Upper teeth, posterior
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Lower teeth
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Lower teeth, posterior
Morphology
Sexual dimorphism
Bonnethead sharks are the only sharks known to exhibit sexual dimorphism in the morphology of the head. Adult females have a broadly rounded head, whereas males possess a distinct bulge along the anterior margin of the cephalofoil. This bulge is formed by the elongation of the rostral cartilages of the males at the onset of sexual maturity and corresponds temporally with the elongation of the clasper cartilages.[5]
Pectoral fins and swimming
The
Evolution
Using data from mtDNA analysis, a scientist has found that the evolution of hammerhead sharks probably began with a taxon that had a highly pronounced cephalofoil (most likely that similar to the winghead shark, Eusphyra blochii), and was later modified through selective pressures. Thus, judging by their smaller cephalofoil, bonnethead sharks are the more recent developments of a 25-million-year evolutionary process.[6]
Distribution and habitat
This species occurs on both sides of the American coast, in regions where the water is usually warmer than 70 °F (21 °C). In the
It frequents shallow estuaries and bays over seagrass, mud, and sandy bottoms.[1]
Ecology
Behavior
The bonnethead shark is an active
Diet
The shark feeds primarily on
Bonnetheads also ingest large amounts of seagrass, which has been found to make up around 62.1% of gut content mass. The species appear to be omnivorous, the only known case of plant feeding in sharks.[7] The shark may perform this activity to protect its stomach against the spiny carapaces of the blue crab which it feeds on.[8] A 2018 study with a carbon isotope-labelled seagrass diet found that they could digest seagrass with at least moderate efficiency, with 50±2% digestibility of seagrass organic matter, and had cellulose-component-degrading enzyme activity in their hindgut.[9][10]
Reproduction
The bonnethead shark is
Bonnetheads have one of the shortest gestation periods among sharks, lasting only 4.5–5.0 months.[1]
A bonnethead female produced a pup by
Conservation
The bonnethead was formerly classified as a
Since October 2021, S. tiburo has been classified as Largely Depleted by the IUCN.[12]
References
- ^ . Retrieved 20 May 2023.
- ^ "Appendices | CITES". cites.org. Retrieved 14 January 2022.
- ^ "Definition of BONNETHEAD". www.merriam-webster.com. Merriam-Webster, Incorporated. Retrieved 8 February 2021.
- ^ Froese, Rainer; Pauly, Daniel (eds.) (2021). "Sphyrna tiburo" in FishBase. 11 2021 version.
- S2CID 357244.
- ^ "Hammerhead shark study shows cascade of evolution affected size, head shape". ScienceDaily. Retrieved 24 November 2020.
- ^ Hannah Lang (29 June 2017). "This Shark Eats Grass, and No One Knows Why". National Geographic. Archived from the original on 30 June 2017.
- ^ Michael, Scott (2001). Aquarium Sharks & Rays. Neptune City, NJ: T.F.H Publications, Inc.
- PMID 30185641.
- ^ Ian Sample (5 September 2018). "First known omnivorous shark species identified". The Guardian. Retrieved 5 September 2018.
- ^ "Captive shark had 'virgin birth'". BBC News. 23 May 2007.
- ^ Pérez-Jiménez, J.C. (2021). "Sphyrna tiburo (Green Status assessment)". The IUCN Red List. Retrieved 20 February 2022.
External links
- "Sphyrna tiburo". Integrated Taxonomic Information System. Retrieved 23 January 2006.
- Species Description of Sphyrna tiburo at www.shark-references.com
- Photos of Bonnethead on Sealife Collection