A normally hermaphroditic shark
The Longhead catshark or sometimes called the Smoothbelly catshark (Apristurus longicephalus) is a species of shark belonging to the family Scyliorhinidae. It has a patchy distribution in the Indo-Pacific. It is found in water between 1,640-4,724 feet. It is characterized by its extremely long and narrow snout, short abdomen, and long anal and caudal fins. The Longhead catshark is a hermaphrodite, but not much is known about this shark.
Family: Scyliorhinidae – Catsharks
Common Name– Ground Sharks
Common Name– Catsharks
Average Size and Length: Mature males have been measured greater than 41 cm/13 feet. The maximum is at least 50 cm/1.6 feet. New records reach 59 cm/1.9 feet.
Current Rare Mythical Sightings: The first known specimen of the longhead catshark was captured in Tosa Bay, Kōchi Prefecture, Japan, on May 12, 1972. The 38-cm-long specimen was initially thought to be an immature male, but has since been identified as a functionally female hermaphrodite. (Iglésias, S. P.; Sellos, D. Y.; Nakaya, K. (2005). “Discovery of a normal hermaphroditic chondrichthyan species: Apristurus longicephalus“. Journal of Fish Biology. 66 (2): 417.). The species was described by Kazuhiro Nakaya in a 1975 volume of the scientific journal Memoirs of the Faculty of Fisheries, Hokkaido University.
Teeth and Jaw: The mouth is short and arched. The teeth are very small and wide-spaced, sharp and almost burr-like. The teeth number 36–44 rows in the upper jaw and over 45 rows in either jaw. Each tooth has three or five cusps, with the central cusp much longer than the others. The labial furrows are very long. The uppers reach the upper symphysis and the lowers are shorter.
Head: The head is broad and flattened with a very long snout. The preoral length is about 12% of the total length of the shark. The nostrils are broad. They are oblique in shape and are divided into large, oval incurrent and excurrent openings by triangular flaps of skin on their anterior rims. The mouth extends to the anterior ends of the eyes. The eyes are cat-like in appearance being horizontally oval. They are quite small and somewhat upward-facing, and equipped with nictitating membranes. Behind each eye is a spiracle.
Denticles: A large area of the anterior ventral portion of its body lacks dermal denticles. Denticles are also absent near the fin margins. The dermal denticles are small and spaced, each having a median ridge and three posterior points. This is where it gets its soft surface.
Tail: The caudal fin is long and narrow. It comprises about one-third of the total length and has a distinct lower lobe and a ventral notch near the tip of the upper lobe.
Demographic, Distribution, Habitat, Environment and Range: The Longhead catshark can be found in the west Pacific in Japan, China, Taiwan, Philippines and northern Australia. In the west Indian Ocean, they can be found in Seychelles. They can be found in deep water more than likely on or near the bottom between 1,640-4,724 feet. They are considered bathydemersal.
Aesthetic Identification: The Longhead catshark is grey-black to dark brown without any conspicuous markings. The naked patches of skin and the interior of the mouth are black. The body is soft and thin. The gill slits are quite small. They are smaller than the adult eye length. The fourth and fifth pairs are over the base of the pectoral fins. The first dorsal fin is above the pelvic fin base, close to the second dorsal fin and slightly smaller. The first dorsal fin has a rounded apex. The second dorsal fin is similar in shape but larger than the first, and located over the latter half of the anal fin base. The pectoral fins are moderately large and broad and the pelvic fins are medium sized and round. The pelvic, pectoral and anal fins are all close together. The anal fin is large, elongated and angular. It is separated from the caudal fin by a small notch.
Biology and Reproduction: The Longhead catshark is oviparous. The Longhead catshark is rudimentary hermaphroditic, with the majority of individuals (85%) having both the functional reproductive organs of one sex and the undeveloped reproductive organs of the opposite sex (Iglésias, 2005).
A single partial egg case has been found, which had tendrils on the posterior corners (Flammang, B.; Ebert, D.; Cailliet, G. (2007). “Egg cases of the genus Apristurus (Chondrichthyes: Scyliorhinidae): phylogenetic and ecological implications“. Zoology (Jena, Germany). 110 (4): 308–317).
The Longhead catshark is unique among its genus in that the duodenum is not short, but almost as long as the spiral valve intestine. The function of this trait is unknown, as the feeding habits of this shark have not been documented (Nakaya, K. (December 13, 1991). “A Review of the Long-Snouted Species of Apristurus (Chondrichthyes, Scyliorhinidae)“. Copeia. 1991 (4): 992–1002.).
Behavioral Traits, Sensing and Intelligence: Unknown, but possibly nocturnal.
Longhead Catshark Recorded Attacks on Humans: Not a threat to humans.