spined pygmy shark
Another minuscule bioluminescent deep-water shark!
The Spined Pygmy shark (Squaliolus laticaudus) is in the order of Dogfish shark in the family Dalatiidae (Kitefin sharks) found widely in all oceans. Growing no larger than 28 cm or 11 inches (maximum female), it is one of the smallest sharks alive. Males are typically 15 cm or 5.9 inches, and females are typically between 17-20 cm or 6.7 and 8 inches. The maximum recorded male was 22 cm or 8.7 inches. It has a slender, cigar-shaped body with a conical snout, a long but low second dorsal fin, and an almost symmetrical caudal fin. Spined Pygmy sharks are dark brown to black, with abundant bioluminescent organs called photophores on their ventral surface. It is believed that they use them for counter illumination. They typically can be found over upper continental and insular slopes. It conducts a diel vertical migration, spending the day at close to 1,600 feet deep and moving towards a depth of 660 feet at night. It feeds on squid and small bony fished that also migrate in the same way within the 24-hour cycle. Spined Pygmy sharks are thought to be ovoviviparous, with a maximum of 4 pups per litter. The Spined Pygmy shark ranked 8 in our PSD ranked top 10 of the world’s smallest sharks. Read the full list and story in our articles section.
Family: Dalatiidae – Kitefin sharks
Common Name– Dogfish Sharks
Common Name– Kitefin Sharks
Status: IUCN Red List LEAST CONCERN
Average Size and Length: Growing no larger than 28 cm or 11 inches (maximum female), the Spined Pygmy shark is one of the smallest sharks alive. Males are typically 15 cm or 5.9 inches, and females are typically between 17-20 cm or 6.7 and 8 inches. The maximum recorded male was 22 cm or 8.7 inches.
Teeth and Jaw: The mouth of the Spined Pygmy shark has thin, smooth lips and contains 22–31 tooth rows in the upper jaw and 16–21 tooth rows in the lower jaw. The upper teeth are narrow and smooth-edged with single upright cusps. The bases of the lower teeth are broad and interlocked to form a continuous cutting surface, with each tooth bearing a single upright, smooth-edged, knife-like cusp.
Head: The Spined Pygmy shark has a bulbous, conical snout, somewhat pointed. The photophores extend to the snout and around the eyes and nostrils. The eyes are large, with the upper rim of the orbit almost straight; a broadly arched upper eyelid. Each nostril is preceded by a short flap of skin.
Denticles: The dermal denticles are flat and blocky, not elevated on stalks or with marginal teeth.
Tail: The caudal peduncle of the Spined Pygmy sark is slender and laterally expanded into weak keels. The caudal fin is broad and paddle-like, almost symmetrical, with the upper and lower lobes of similar size and shape, and a deep notch in the trailing margin of the upper lobe.
Demographic, Distribution, Habitat, Environment and Range: The Spined Pygmy shark can be found widely around the world, almost circumtropical. They are tropical epipelagic. In the Atlantic Ocean, it can be found off Bermuda, the United States, Suriname, southern Brazil, and northern Argentina in the west, and off northern France, Madeira, Cape Verde, and the Azores in the east. In the Indian Ocean, it has only been recorded off Somalia. In the Pacific Ocean, it is found off southern Japan, Taiwan, and the Philippines. The Spined Pygmy shark is found at depths of 660–1,640 feet and does conduct a diel vertical migration, however it is seldom caught at the surface, suggesting it spends less time there than its relatives. It prefers areas of high biological productivity over upper continental and insular slopes and island land masses. It may also be found over outer shelves but avoids central ocean basins.
Diet: It feeds on squid and small bony fished that also migrate in the same way within the 24-hour cycle.
Aesthetic Identification: The Spined Pygmy shark has an elongated, slender, cigar or spindle-shaped body. The openings of the five pairs of gill slits are minute and uniform in size. Spined Pygmy sharks are dark brown to black, with light fin margins, and with abundant bioluminescent organs called photophores on their ventral surface. It is believed that they use them for counter illumination. The photophores extend to the snout, around the eyes and nose. They have a spine on the first dorsal fin, but not on the second. The spine is only exposed for males and covered by skin for females. The first dorsal fin is tiny and originates over the trailing margin of the pectoral fins. The second dorsal fin is low, with a base twice as long as that of the first and originates over the anterior half of the pelvic fin bases. The pectoral fins are short and triangular, with the rear margin slightly curved. The pelvic fins are long and low, and there is no anal fin.
Biology and Reproduction: Spined Pygmy sharks are thought to be ovoviviparous, with a maximum of 4 pups per litter. The young are born at 3.5–3.9 inches long. Males mature sexually at a length of 5.9 inches, and females at a length of 6.7–7.9 inches.
The Spined Pygmy shark has on average only 60 vertebrae, the fewest of any shark.
Behavioral Traits, Sensing and Intelligence: Unknown.
Spined Pygmy Shark Future and Conservation: Spined Pygmy sharks have no commercial value. They sometimes appear in the bycatch of trawl fisheries but are generally too small to be captured.
Spined Pygmy Shark Recorded Attacks on Humans: Not a threat to humans.