smalleye pygmy shark

Taxonomy:

Phylum– Chordata

Class– Chondrichthyles

Subclass– Elasmobranchii

Order– Squaliformes

Common Name– Dogfish Sharks

Family– Dalatiidae

Common Name– Kitefin Sharks

Genus– Squaliolus

Species– aliae

Status: IUCN Red List LEAST CONCERN

Average Size and Length: The Smalleye Pygmy shark is known to reach only 22 cm or 8.7 inches long. Mature males are typically 15 cm or 5.9 inches long.

Teeth and Jaw: The mouth of the Smalleye Pygmy shark is nearly transverse and has thin lips; a pair of papillae is on the upper lip that partially covers the teeth. There are 20–27 upper tooth rows and 18–23 lower tooth rows. 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.

Head: The Smalleye Pygmy shark has a bulbous, conical, pointed snout. The eyes are relatively small, with their diameters measuring 43–66% as long as the snout. The upper rim of the eye socket is chevron-shaped rather than nearly straight; the upper eyelid is angular. The nostrils lack significantly expanded skin flaps in front.

Denticles: The dermal denticles are flattened and not toothed or elevated on stalks.

Tail: The caudal peduncle of the Smalleye Pygmy shark is thin and bears slight lateral keels. Males have longer caudal peduncles than females. The caudal fin is broad and triangular, with nearly symmetrical upper and lower lobes and a prominent notch in the trailing margin of the upper lobe.

Demographic, Distribution, Habitat, Environment and Range: The Smalleye Pygmy shark is found in water 490–6,560 feet deep in the Western Pacific, near Japan, the Philippines, and northern and eastern Australia. It is epipelagic or mesopelagic and inhabits the upper and middle layers of the water column near land. It performs a diel vertical migration, spending the day in deep water and the night in shallower water.

Diet: The Smalleye Pygmy shark feeds primarily on midwater squid, krill, shrimps, and small bony fishes such as lanternfish.

Aesthetic Identification: The Smalleye Pygmy shark has a dark-brown to blackish, spindle-shaped or cigar shaped body, which becomes lighter towards the fin margins. The five pairs of gill slits are tiny and uniform. There is a spine on the first dorsal fin but not on the second (which is usually only exposed in males, the spine on females is covered by skin). The tiny first dorsal fin originates about over the rear tip of the pectoral fin. The second dorsal fin is long and low and originates over the front half of the pelvic fin bases. The pectoral fins are short with rounded margins, and the pelvic fins are long and low. The anal fin is absent. Males have shorter abdomens than females. Its underside or ventral surface is covered by light-producing, bioluminescent photophores that are more than likely used for counter illumination.

Biology and Reproduction: The Smalleye Pygmy shark is ovoviviparous. The young are under 3.9 inches long. Males attain sexual maturity at 5.9 inches long.

Behavioral Traits, Sensing and Intelligence: The bioluminescent photophores are used for counter illumination.

Smalleye Pygmy Shark Future and Conservation: The Smalleye Pygmy shark is infrequently caught by fisheries because of its small size and has no economic value and therefore is listed as least concern.

Smalleye Pygmy Shark Recorded Attacks on Humans: Not a threat to humans.