The blotchy swellshark, or Japanese swellshark, (Cephaloscyllium umbratile) is a common species of catshark, belonging to the family Scyliorhinidae. The Blotchy swellshark is found at depths of in the northwestern Pacific Ocean, from Japan to Taiwan. It is benthic in nature and favors rocky reefs. Reaching in length, this thick-bodied shark has a broad head, large mouth, and two unequally-sized dorsal fins positioned far back past the pelvic fins. It can be identified by its dorsal coloration, consisting of seven brown "saddles" and extensive darker mottling on a light tan background. This species has often been confounded with the draughtsboard shark (C. isabellum) and the Sarawak pygmy swellshark (C. sarawakensis) in scientific literature.
Voracious and opportunistic in feeding habits, the blotchy swellshark is known to consume numerous types of fishes and invertebrates, including an unusually high diversity of cartilaginous fishes. Like other Cephaloscyllium species, it is capable of rapidly inflating its body as a defense against predators. This species is oviparous, with females laying encapsulated eggs two at a time. There is no well-defined breeding season and reproduction occurs year-round. The eggs hatch after approximately one year. The blotchy swellshark is harmless and fares well in captivity. It is caught as bycatch in commercial bottom trawls, though its population does not seem to have suffered from fishing activity.
Taxonomy
American ichthyologists David Starr Jordan and Henry Weed Fowler described the blotchy swellshark in a 1903 volume of Proceedings of the United States National Museum, based on a long stuffed dry skin originally obtained from Nagasaki, Japan. They gave it the specific epithet umbratile (from the Latin umbratilis, meaning "shaded") and assigned it to the genus Cephaloscyllium.
The taxonomy of the blotchy swellshark has a history of confusion. The holotype dried skin could not be located when shark expert Stewart Springer prepared his 1979 review of the catsharks, and in its absence he synonymized C. umbratile with C. isabellum on the basis of "inconclusive morphometric differences". Some authors followed Springer's judgment while others, particularly in Japan, preferred to keep referring to C. umbratile. The taxonomy of this species was further muddled by the application of the name C. umbratile to a similar but smaller species sharing part of its range. This second species, once referred to as "pseudo-umbratile" by Leonard Compagno, has since been identified as C. sarawakensis. Recently, the holotype was found again, and in 2008 Cephaloscyllium umbratile was re-described as distinct from C. isabellum by Jayna Schaaf-Da Silva and David Ebert.
Distribution and habitat
The blotchy swellshark is known to inhabit the northwestern Pacific Ocean from Hokkaido, Japan southward to Taiwan, including the Yellow Sea. Its range may extend as far as New Guinea. This abundant species is a bottom-dweller that inhabits rocky reefs on the continental shelf, at depths of .
Description
The maximum reported length of the blotchy swellshark is . It has a firm, stout body with a soft, distensible abdomen, and a short, broad, flattened head. The snout is proportionately long and rounded, with large nostrils divided by short, triangular flaps of skin in front. The small, horizontally oval eyes are placed high on the head and equipped with rudimentary nictitating membranes (protective third eyelids). A tiny spiracle lies closely behind each eye. Behind the spiracle are five pairs of gill slits, which are short and become progressively smaller posteriorly. The capacious mouth forms a broad arch, and lacks furrows at the corners. The small teeth have a central cusp flanked by a smaller cusplet on both sides. There are around 59 tooth rows in the upper jaw and 62 tooth rows in the lower jaw.