Squalidae

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Dogfish sharks
Temporal range: Upper Cretaceous–Recent [1]
Squalus acanthias.jpg
Spiny dogfish, Squalus acanthias
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Superorder: Selachimorpha
Order: Squaliformes
Family: Squalidae
Bonaparte, 1834
Genera

Squalidae, more commonly known as dogfish, dog sharks, or spiny dogfish,[2] are one of several families of sharks categorized under Squaliformes, making it the second largest order of sharks, numbering 119 species across 7 families.[3] Having earned their name after a group of fishermen reportedly observed the species chasing down smaller fish in dog-like packs,[4] dogfish have slender, streamlined bodies, usually more compact in comparison to other species, and a pointed snout. Dogfish likewise have two dorsal fins, each with smooth spines, but no anal fin, and their skin is generally rough to the touch.[1] As the species reaches adulthood, males usually measure a maximum of 39 inches (990 mm), while females typically measure 49 inches (1,200 mm) long. The species therefore exhibits female-dominant sexual dimorphism.

Dogfish sharks have slate-gray or gray-brown skin with white dots that becomes paler (almost white) around the belly region. These sharks are characterized by teeth in upper and lower jaws similar in size; a caudal peduncle with lateral keels; the upper precaudal pit usually is present; and the caudal fin is without a subterminal notch.

They are carnivorous, principally preying upon organisms smaller than themselves. Some of their prey include herring, mackerel, and capelin. In special cases, they may consume jellyfish and squid. Even at a young age, spiny dogfish pups may hunt fish two or three times their size.[citation needed] Unlike virtually all other shark species, dogfish sharks possess venom which coats their dorsal spines; this venom is mildly toxic to humans and would be harmful if the shark were to be mishandled. The livers and stomachs of the Squalidae contain the compound squalamine, which possesses the property of reduction of small blood vessel growth in humans.[5] Dogfish sharks use their strong jaw and sharp teeth to consume their prey.

The spiny dogfish has broken several records in the areas of migration and gestation. This shark tends to be a highly migratory species: one shark was recorded as traveling 5,000 miles (8,000 km) after being tagged in Washington state, United States, and found again later in Japan. In addition to its long distance migration, the spiny shark holds the record for longest gestation period of any other vertebrate at 22-24 months. Females produce eggs and give birth to live young that measure to be 7.9–13.0 inches (20–33 cm).

Taxonomy[edit]

Dogfish are scientifically classified as the Squalidae family, categorized under the Squaliform order, which encompasses seven families in total, including Squalidae. The Squalidae family itself contains two separate genera: Cirrhigaleus and Squalus, numbering 37 species between the two.

Squalidae Classification
Order: Squaliformes

Family: Within Squaliforme order, there are 7 families

Genus: Within the Squalidae dogshark family, are two known genera

  • Squalus: The Squalus genus encompasses 34 different species of dogfish, or spurdogs, home to waters all around the world. With the exception of one - Squalus margaretsmithae, or Smith's dogfish shark, known to be a maximum of 21.3 inches (54.3 cm) in length [6] - species classified under the genus are known to range from 22 inches (58 cm) to 63 inches (160 cm) in length.[7] While the majority of the species are characterized by their slate or blue-grey body coloration and white underbelly, only 2 - Squalus acanthias and Squalus suckleyi - are more easily recognizable by the notable, evenly-spaced array of small white dots decorating their darker dorsal sides. [8]
  • Cirrhigaleus: In contrast to its counterpart genus, Cirrhigaleus currently includes only 3 species, the most recent of which, Cirrhigaleus australis, was discovered and classified in 2007.[9] Cirrhigaleus species are typically the larger of the two Squalidae genera, ranging from 47 inches (120 cm) to 49.5 inches (126 cm) in length (although the largest species of 63 inches, Squalus acanthias, is classified under the Squalus genus, the vast majority of the species within the same genus remain under or around 39 inches (100 cm) in length, whereas only 3 of 34 total species exceed 47 inches (120 cm)).[10] The genus likewise shares many phenotypic similarities with its Squalus counterpart, namely the blue-grey body coloration, white underbelly, and basic morphology, however with some variation; common body coloration may also be a grey-brown hue, and most notably, Cirrhigaleus differs from Squalus in having extremely long nasal barbels, and small black instead of white spots in a similar pattern.[11]
for a full list of species in each genera: list of sharks
Squalus acanthias, or the Spiny dogfish (adult), with grey-brown body coloration, decorated by evenly-spaced, small, white dots, and lighter underbelly.
Cirrhigaleus barbifer, or the Mandarin dogfish (adult), pictured with gray-brown body coloration, decorated in an array of speckled black dots, with a lighter underbelly, and elongated nasal barbels.







References[edit]

  1. ^ a b Froese, Rainer, and Daniel Pauly, eds. (2009). "Squalidae" in FishBase. January 2009 version.
  2. ^ "Squalidae". Integrated Taxonomic Information System. Retrieved 16 November 2013.
  3. ^ Straube, N.; Li, C.; Claes, J.M. (2015). "Molecular phylogeny of Squaliformes and first occurrence of bioluminescence in sharks". BMC Evolutionary Biology. 15 (162). doi:10.1186/s12862-015-0446-6.
  4. ^ "Spiny Dogfish". Oceana. Retrieved 2019-04-12.
  5. ^ National Geographic June 1998
  6. ^ S.T. de F. L. Viana, M. W. Lisher, & M.R. de Carvalho. (2018). "Two new species of short-snouted dogfish sharks of the genus Squalus Linnaeus, 1758, from southern Africa (Chondrichthyes: Squaliformes: Squalidae)". Marine Biodiversity. 48: 1787-1814. doi:10.1007/s12526-017-0673-8.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  7. ^ Froese,R. & Pauly, D. "Genus: Squalus". fishbase.org. FishBase.{{cite web}}: CS1 maint: multiple names: authors list (link)
  8. ^ Ebert, D.A. (2010). "Resurrection and redescription of Squalus suckleyi (Girard, 1854) from the North Pacific, with comments on the Squalus acanthias subgroup (Squaliformes: Squalidae)". Zootaxa. 2612 (1): 22-40.
  9. ^ W.T. White, P.R. Last, & J.D. Stevens. (2007). "Cirrhigaleus australis n. sp., a new Mandarin dogfish (Squaliformes: Squalidae) from the south-west Pacific". Zootaxa. 1560 (1): 19-30. doi:10.11646/ZOOTAXA.1560.1.2.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  10. ^ Froese, R. & Pauly, D. "Genus: Cirrhigaleus". fishbase.org. FishBase.{{cite web}}: CS1 maint: multiple names: authors list (link)
  11. ^ Tanaka, Shigeho (1917). "Three new species from Japan". Zoology. 29: 225-226.

Further reading[edit]