Epaulette shark

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Epaulette shark

Least Concern (IUCN 3.1)[1]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Subdivision: Selachimorpha
Order: Orectolobiformes
Family: Hemiscylliidae
Genus: Hemiscyllium
Species:
H. ocellatum
Binomial name
Hemiscyllium ocellatum
(Bonnaterre, 1788)
Range of the epaulette shark
Synonyms

Squalus ocellatus Bonnaterre, 1788
Squalus oculatus Banks & Solander, 1827

The epaulette shark (

tail fin
is attached) comprises over half the shark's length. Adults are light brown above, with scattered darker spots and indistinct saddles.

Epaulette sharks have

Least Concern, as outside of the small aquarium trade it is of little interest to fisheries
.

Taxonomy and phylogeny

The epaulette shark was originally described as Squalus ocellatus by the French

phylogenetic relationships between the epaulette shark and its sister species could not be resolved.[4]

Distribution and habitat

The range of the epaulette shark extends from the southern coast of

Description

Epaulette sharks are named for the prominent black spot behind their pectoral fins.

The epaulette shark has an elongated body, over half of which is comprised by the slender caudal peduncle. The snout is short and rounded, with the

nares placed almost at the tip along with a pair of tiny barbels; there are grooves running from the nares to the mouth. There are 26–35 tooth rows in the upper jaw and 21–32 tooth rows in the lower jaw. The teeth are small, with broad bases and triangular cusps. The eyes are oval in shape and elevated, with a large spiracle below each. The five pairs of gill slits are small, with the fourth and fifth very close together.[2]

The pectoral and

caudal fin. The caudal fin has only an upper lobe, which contains a prominent ventral notch near the tip and is angled almost horizontally relative to the body. Adult epaulette sharks are beige to brownish above with many widely spaced brown spots and subtle darker bands. There is a very large black spot ringed in white located behind each pectoral fin; this pair of spots are the origin of this shark's common name. Juveniles have alternating light and dark bands over their body and fins, which break up as they mature.[5][6] Epaulette sharks are typically 70–90 cm (27.5–35.5 in) long; the maximum reported length is 107 cm (42 in).[3][6]

Biology and ecology

As an

nocturnal and are most active in low water. They often hide inside or below coral heads, though it is enough for the head to be covered even if the rest of the body is exposed.[2] Sometimes they perch in the open on sandy flats or atop reefs facing into the current, a form of orientation known as rheotaxis that may improve respiration or predator awareness.[10]

Epaulette sharks are preyed upon by larger fishes such as other sharks.

protozoan Haemogregarina hemiscyllii, which infects the blood,[13] the ostracod Sheina orri, which attaches to the gills,[14] and the nematode Proleptus australis, which infests the stomach.[15]

Hypoxia tolerance

Epaulette sharks can survive for hours with little oxygen, and can clamber over land to reach the nearest suitable area of water.

At night, the shallow reef platforms inhabited by the epaulette shark often become isolated from the ocean by the receding tide. The amount of

dissolved oxygen in the pool can drop 80% or more overnight from the combined respiration of all the organisms within the pool. The epaulette shark has evolved to cope with these hypoxic conditions, being able to survive for over three hours in 5% of the atmospheric O2 level without losing behavioral responsiveness. In the laboratory, epaulette sharks have survived for an hour without any oxygen at 30 °C (86 °F), which is also unusual in that most animals capable of tolerating oxygen deprivation do so at low temperatures.[16]

The physiological responses of the epaulette shark to low oxygen are mediated by the nucleoside adenosine. In hypoxic conditions, the heart and ventilation rates drop sharply.[17] The shark's blood pressure falls by half as the blood vessels dilate to deliver more blood to the brain and heart. Unlike in bony fishes and tetrapods, the blood flow rate remains constant and there is no elevation of blood glucose levels.[18] The brains of sharks only consume a third as much ATP as those of teleosts.[16] The epaulette shark is able to lower this energy demand further by reducing the metabolism of certain areas of its brain, e.g. keeping the sensory nuclei functional while deactivating the motor nuclei. This allows the shark to supply enough ATP to prevent neuron death, while still remaining alert to its environment.[19]

Temperature susceptibility

Epaulette shark development rate and fitness are strongly affected by temperature during development.[20] Temperature rises due to climate change are sufficient to weaken the sharks, which risks damage to ecosystems.[20]

Feeding

The epaulette shark is an opportunistic predator of

chew its food for up to 5–10 minutes.[9] Its teeth can be depressed to form a flat surface for crushing hard-shelled prey.[5]

Life history

Epaulette shark eggs.

mature sexually at a length of 54–64 cm (21.5–25 in), corresponding to an age of at least seven years.[1][9]

Human interactions

An epaulette shark on display in a public aquarium.

Epaulette sharks are harmless to humans, though if handled they may nip their captors. They are easily observed and handled by beachgoers as they move slowly whilst out of water, and show little fear of humans; the shark is often injured by these encounters.

public aquariums in the United States, Canada, and Australia.[2] In an article for Aquarium Fish Magazine, Scott W. Michael referred to the epaulette shark as "the best shark for the home aquarium." They will breed in captivity, even in tanks as small as 510 L (135 gal), though full-grown sharks are best housed in tanks of 680 L (180 gal) or more. They are not compatible with community tanks as they will eat other fish.[25]

The

In 2015, the behaviour of an epaulette shark was filmed in detail by the

BBC for the first episode of a new documentary series named Shark, released around the 40th anniversary of Jaws.[26]
The documentary shows an epaulette shark's ability to walk over land, and its hunting behaviours in the ebbing tide.

References

  1. ^ . Retrieved 12 November 2021.
  2. ^ .
  3. ^ a b c Froese, Rainer; Pauly, Daniel (eds.) (2009). "Hemiscyllium ocellatum" in FishBase. May 2009 version.
  4. ^ 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.
  5. ^ a b c d Bester, C. Biological Profiles: Epaulette Shark Archived 2016-01-04 at the Wayback Machine. Florida Museum of Natural History Ichthyology Department. Retrieved on May 14, 2009.
  6. ^ .
  7. .
  8. ^ Martin, R.A. Why Do Sharks Expose Their Dorsal Fins? Archived 2009-10-03 at the Wayback Machine ReefQuest Centre for Shark Research. Retrieved on October 4, 2009.
  9. ^ a b c d e Martin, R.A. Intertidal Zone: Epaulette Shark Archived 2008-10-06 at the Wayback Machine. ReefQuest Centre for Shark Research. Retrieved on May 14, 2009.
  10. .
  11. .
  12. .
  13. .
  14. .
  15. .
  16. ^ .
  17. .
  18. ^ Wise, G.; Mulvey, J.M. & Renshaw, G.M.C. "Hypoxia tolerance in the epaulette shark (Hemiscyllium ocellatum)". Journal of Experimental Zoology Part A: Comparative Experimental Biology. 281 (1): 1–5.
  19. S2CID 21800654
    .
  20. ^ a b Readfearn, Graham (2021-01-12). "Baby sharks emerge from egg cases earlier and weaker in oceans warmed by climate crisis". the Guardian. Archived from the original on 2021-01-12. Retrieved 2021-01-12. In normal temperatures, the sharks emerged from the egg cases after 125 days. But in 31C waters, they emerged after 100 days. The researchers also measured the fitness of the baby sharks, and found that it peaked at 29C but then fell sharply at 31C... Weaker sharks were less efficient hunters ... which could then have a knock-on effect across the coral reefs where they live, upsetting the balance of the ecosystem.
  21. PMID 10469996
    .
  22. ^ West, J.G.; Carter, S. (1990). "Observations on the development and growth of the epaulette shark Hemiscyllium ocellatum (Bonnaterre) in captivity". Journal of Aquariculture and Aquatic Science. 5: 111–117.
  23. ^ "Aquarium Fish: The Epaulette Sharks ( Hemiscyllium SPP.) - the Perfect Aquarium Sharks — Advanced Aquarist | Aquarist Magazine and Blog". Archived from the original on 2015-05-07. Retrieved 2015-05-08.
  24. ^ "Epaulette shark".
  25. ^ Michael, S. W. (2004). "Sharks at Home". Aquarium Fish Magazine. Vol. March 2004. pp. 20–29.
  26. ^ "BBC One - Shark". Archived from the original on 2016-12-01. Retrieved 2015-05-08.

External links