Horn shark
Horn shark | |
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Chondrichthyes |
Subclass: | Elasmobranchii |
Subdivision: | Selachimorpha |
Order: | Heterodontiformes |
Family: | Heterodontidae |
Genus: | Heterodontus |
Species: | H. francisci
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Binomial name | |
Heterodontus francisci (Girard, 1855)
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Range of the horn shark | |
Synonyms | |
Cestracion francisci Girard, 1855 |
The horn shark (Heterodontus francisci) is a species of bullhead shark, in the family Heterodontidae. It is endemic to the coastal waters off the western coast of North America, from California to the Gulf of California. Young sharks are segregated spatially from the adults, with the former preferring deeper sandy flats and the latter preferring shallower rocky reefs or algal beds. A small species typically measuring 1 m (3.3 ft) in length, the horn shark can be recognized by a short, blunt head with ridges over its eyes, two high dorsal fins with large spines, and a brown or gray coloration with many small dark spots.
Slow-moving, generally solitary
Horn sharks are harmless unless harassed, and are readily maintained in captivity. They are not targeted by either
Taxonomy
The French biologist
Description
Like other bullhead sharks, the horn shark has a short, wide head with a blunt snout and prominent
The body is cylindrical, with two high, somewhat falcate (sickle-shaped)
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The horn shark has a distinctively shaped head with prominent ridges above its eyes.
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Jaws
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Lower teeth
Distribution and habitat
The horn shark inhabits the continental shelf of the eastern Pacific Ocean, occurring off the coasts of California and Baja California from Monterey Bay southward, and in the Gulf of California. Uncommon influxes of warm water northward may bring it as far as San Francisco Bay.[2] There are unconfirmed reports of this species off Ecuador and Peru, which may be misidentifications of other species.[1]
For most of the year, horn sharks are most common at a depth of 2–11 m (6.6–36.1 ft). At the onset of winter, they migrate to water deeper than 30 m (98 ft).
The relative abundances of the horn shark and the
Biology and ecology
The horn shark is a sporadic swimmer that prefers to use its flexible, muscular pectoral fins to push itself along the bottom. It is usually solitary, though small groups have been recorded.[2] During the day, horn sharks rest motionless, hidden inside caves or crevices, or within thick mats of algae, though they remain relatively alert and will swim away quickly if disturbed. After dusk, they roam actively above the reef in search of food.[5] Horn sharks maintain small home ranges of around 1,000 m2 (11,000 sq ft), which they may remain faithful to for over a decade, returning to the same shelter every day. The shelter is usually located at the edge of the resident shark's foraging area.[3] The longest documented movement for an individual horn shark is 16 km (9.9 mi).[4]
The daily activity pattern of the horn shark is under
The horn shark is preyed upon by larger fishes and the
Feeding
95% of the adult horn shark's diet consists of hard-shelled mollusks (e.g.
Other prey items of adults include
The horn shark captures prey via suction, created by expanding its
Life history
Mating in the horn shark occurs in December or January, on a possibly annual reproductive cycle.[15] The male chases the female to indicate interest; once she is ready both sharks settle on the bottom, where the male grips the female's pectoral fin in his teeth and inserts one of his claspers into her cloaca. After 30–40 minutes of copulation, the pair disengages and the female spins with her snout in the sand for another 30 minutes.[6] From February to April, the females lay a maximum of 24 eggs two at a time once every 11–14 days, in water 2–13 m (6.6–42.7 ft) deep.[1] The egg case has two flanges spiraling around it, and thus may take the female several hours to deposit.[16] At first the case is soft and light brown, and over a few days it hardens and darkens in color. Not including the flanges, the case measures 10–12 cm (3.9–4.7 in) long and 3–4 cm (1.2–1.6 in) wide; sharks from the Channel Islands produce longer egg cases than those from mainland California, suggesting that they are separate populations.[2][3]
One of the few sharks to exhibit parental care, female horn sharks in the wild pick up their eggs in their mouths and wedge them into crevices.[3] However, in captivity the eggs are simply dropped on the bottom and may later be cannibalized.[2] The eggs hatch in 6–10 months; at emergence the young measure 15–17 cm (5.9–6.7 in) long.[1] Newly hatched sharks are provisioned with an internal yolk sac and do not have to feed until they are a month old, though they are capable of feeding and will accept food during this period. Horn sharks grow slowly and at a highly variable rate that does not correspond to their size; this has frustrated attempts to determine their aging process.[3] Males mature at a length of 56–61 cm (22–24 in) and females at a length of at least 58 cm (23 in).[1] Individual sharks have lived to over 12 years old in captivity, and there exists an unconfirmed report of a shark reaching 25 years of age.[3]
Human interactions
Under normal circumstances, horn sharks are harmless to humans and can readily be approached underwater.[3] However, they can be provoked into biting, and some pugnacious individuals have been known to chase and bite divers after being harassed.[6] These sharks should be handled with care as their fin spines can inflict a painful wound.[3] The horn shark adapts well to captivity and has been maintained and bred in many public aquariums across the United States.[2] In July 2018, three people were arrested after stealing a juvenile horn shark from the San Antonio Aquarium. The shark was smuggled out of the aquarium in a stroller under a blanket. It was returned unharmed two days later.[17]
The horn shark has no commercial value in California, where it is captured unintentionally in traps and trawls and by
References
- ^ . Retrieved 19 November 2021.
- ^ ISBN 978-92-5-104543-5.
- ^ ISBN 978-0-520-23484-0.
- ^ a b c d Buch, R. Biological Profiles: Horn Shark. Florida Museum of Natural History Ichthyology Department. Retrieved on June 18, 2009.
- ^ JSTOR 1442315.
- ^ a b c d Martin, R.A. Kelp Forests: Horn Shark. ReefQuest Centre for Shark Research. Retrieved on June 19, 2009.
- JSTOR 3278414.
- S2CID 24843398.
- S2CID 45745111.
- ISBN 978-0-85199-421-5.
- ^ PMID 16155227.)
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: CS1 maint: multiple names: authors list (link - ISBN 978-0-387-23192-1.)
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: CS1 maint: multiple names: authors list (link - S2CID 44239227.
- S2CID 21860117.)
{{cite journal}}
: CS1 maint: multiple names: authors list (link - ^ ISBN 978-2-8317-0700-6.)
{{cite book}}
: CS1 maint: multiple names: authors list (link - ^ Martin, R.A. Heterodontiformes: Bullhead Sharks. ReefQuest Centre for Shark Research. Retrieved on June 19, 2009.
- ^ "Shark returned to San Antonio aquarium after being stolen in baby stroller". ABC News.