Smalleye pygmy shark

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Smalleye pygmy 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: Squaliformes
Family: Dalatiidae
Genus: Squaliolus
Species:
S. aliae
Binomial name
Squaliolus aliae
Teng
, 1959
Range of smalleye pygmy shark

The smalleye pygmy shark (Squaliolus aliae) is a little-known

fisheries
.

Taxonomy

The first known specimen of the smalleye pygmy shark was a female 18 cm (7.1 in) long, caught off

Teng Huo-Tu, who gave it the specific epithet alii after a woman.[2] The name subsequently came to be rendered as aliae in scientific literature. Some authors questioned the validity of the species, and in 1977 Jeffrey Alan Seigel and colleagues synonymized S. aliae with S. laticaudus.[3] In 1987, Kunio Sasaki and Teruya Uyeno performed morphological comparisons and reaffirmed the distinctiveness of S. aliae.[4]

Distribution and habitat

The smalleye pygmy shark appears to be widely distributed, but in patches, in the western Pacific Ocean, having been reported from off southern Japan, the Philippines, and northern and eastern Australia. It inhabits the upper and middle layers of the water column near land, at depths of 150–2,000 m (490–6,560 ft). It conducts a diel vertical migration, spending the day in deeper water and rising to shallower waters at night.[5]

Description

Among the smallest of extant sharks, the smalleye pygmy shark attains a maximum recorded length of 22 cm (8.7 in). It is shaped like a

chevron-shaped rather than nearly straight. The nostrils lack substantially expanded skin flaps in front. The mouth is nearly transverse and bears thin lips; a pair of papillae (nipple-like structures) is on the upper lip that is absent in S. laticaudus.[4][5] There are 20–27 upper tooth rows and 18–23 lower tooth rows.[6] The upper teeth are slender and upright. The larger, broader lower teeth have angled and knife-like cusps, and interlock to form a continuous cutting surface. The five pairs of gill slits are tiny and uniform.[5][7]

The two Squaliolus species are the only sharks that have a spine on the first

dermal denticles are flattened and not toothed or elevated on stalks. This species is dark brown to black in color, becoming light towards the fin margins. Its underside is covered by light-producing photophores.[5][7]

Biology and ecology

Little is known of the natural history of the smalleye pygmy shark.

aplacental viviparous as in other members of its family, with the young being born under 10 cm (3.9 in) long. Males attain sexual maturity around 15 cm (5.9 in) long.[5]

Human interactions

The smalleye pygmy shark is infrequently caught by

Least Concern.[1]

References

  1. ^
    doi:10.2305/IUCN.UK.2015-4.RLTS.T41858A68643995.en
    . Retrieved 13 November 2021.
  2. ^ Teng H.T. (1959). "Studeis [sic] on the elasmobranch fishes from Formosa. Pt. 4. Squaliolus alii, a new species of deep sea squaloid shark from Tung-Kang, Formosa". Report – Laboratory of Fishery Biology, Taiwan Fisheries Research Institute. 8: 1–6.
  3. ^
    JSTOR 1443196
    .
  4. ^ a b Sasaki K. & Uyeno T. (1987). "Squaliolus aliae, a dalatiid shark distinct from S. laticaudus". Japanese Journal of Ichthyology. 34 (3): 373–376.
  5. ^
    ISBN 978-0-674-03411-2
    .
  6. ^ a b Tanakamaru H.; Shibuya T. & Kubota T. (1999). "Some Biological Aspects of the Spined Pygmy Shark, Squaliolus aliae, from Suruga Bay, Japan". Journal of the Faculty of Marine Science and Technology, Tokai University (48): 51–67.
  7. ^
    ISBN 92-5-101384-5
    .
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