Saddled swellshark
Encyclopedia
The saddled swellshark (Cephaloscyllium variegatum) is a rare species
of catshark
, family
Scyliorhinidae, endemic to eastern Australia
. This bottom-dwelling species is found on the outer continental shelf
and upper continental slope at a depth of 115–605 m (377.3–1,984.9 ft). It is a robustly built shark with a short, broad, flattened head and a capacious mouth. Adults are patterned with saddles on a brownish or grayish background, which varies between tropical and temperate
sharks; juveniles are light-colored with many spots. This shark reaches 74 cm (29.1 in) in length. Like other swellsharks, it can inflate itself as a defensive measure. Reproduction is oviparous.
(CSIRO) chief researchers Peter Last and John Stevens recognized five undescribed swellsharks in Australian waters. Later investigation revealed that the forms provisionally named Cephaloscyllium "sp. B" and "sp. C" may represent clinal variants of a single species, which was described by Peter Last and William White in a 2008 CSIRO publication. The specific epithet variegatum comes from the Latin
word for "various", and refers to the large amount of color variation within this species. The type specimen is 68 cm (26.8 in) long adult male, collected from east of Newcastle, New South Wales
.
and as far south as Tathra
in New South Wales, and perhaps also the Britannia Seamount near Brisbane
. It is a bottom-dwelling species that inhabits the outer continental shelf
and upper continental slope at a depth of 115–605 m (377.3–1,984.9 ft).
s preceded by laterally expanded flaps of skin that do not reach the large mouth. The slit-like eyes are positioned high on the head and followed by tiny spiracle
s. The tooth rows number 68–82 in the upper jaw and 68–80 in the lower jaw. The very small teeth have three cusps, with the central one the longest and sometimes 1–2 additional lateral cusplets. In females the central cusp is smaller than in males. There are no furrows at the corners of the mouth, and the upper teeth are exposed when the mouth is closed. The fourth and fifth gill slit
s lie over the pectoral fin bases and are shorter than the first three.
The pectoral fins are large and broad, with rounded margins. The first dorsal fin
is fairly angular and originates over the middle of the pelvic fin bases. The second dorsal fin is much smaller and lower than the first, originating behind the anal fin origin. The pelvic fins are small, with elongate, relatively short claspers in males. The anal fin is substantially larger and deeper than the second dorsal fin. The caudal fin is deep, with a distinct lower lobe and a strong ventral notch near the tip of the upper lobe. The body is densely covered by minute dermal denticles, each shaped like an arrowhead and bearing a median ridge.
The saddled swellshark is brownish or grayish in color above, with 11 darker saddles of varying width over the body and tail and usually no blotches on the flanks. Individuals from tropical waters ("sp. B") tend to have more defined saddles, while those from temperate waters ("sp. C") have fainter saddles and a smattering of lighter flecks. The underside is a plain light color, often with a few darker marks. The juveniles are pale with many dark brown spots.
at a length of 55–60 cm (21.7–23.6 in).
until more information is available. Currently, little fishing occurs in the region where this shark is found, but should that change it may be vulnerable due to its apparent rarity and benthic habits.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of catshark
Catshark
Catsharks are ground sharks of the family Scyliorhinidae, with over 150 known species. While they are generally known as catsharks, many species are commonly called dogfish....
, family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Scyliorhinidae, endemic to eastern Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
. This bottom-dwelling species is found on the outer continental shelf
Continental shelf
The continental shelf is the extended perimeter of each continent and associated coastal plain. Much of the shelf was exposed during glacial periods, but is now submerged under relatively shallow seas and gulfs, and was similarly submerged during other interglacial periods. The continental margin,...
and upper continental slope at a depth of 115–605 m (377.3–1,984.9 ft). It is a robustly built shark with a short, broad, flattened head and a capacious mouth. Adults are patterned with saddles on a brownish or grayish background, which varies between tropical and temperate
Temperate
In geography, temperate or tepid latitudes of the globe lie between the tropics and the polar circles. The changes in these regions between summer and winter are generally relatively moderate, rather than extreme hot or cold...
sharks; juveniles are light-colored with many spots. This shark reaches 74 cm (29.1 in) in length. Like other swellsharks, it can inflate itself as a defensive measure. Reproduction is oviparous.
Taxonomy
In 1994, Commonwealth Scientific and Industrial Research OrganisationCommonwealth Scientific and Industrial Research Organisation
The Commonwealth Scientific and Industrial Research Organisation is the national government body for scientific research in Australia...
(CSIRO) chief researchers Peter Last and John Stevens recognized five undescribed swellsharks in Australian waters. Later investigation revealed that the forms provisionally named Cephaloscyllium "sp. B" and "sp. C" may represent clinal variants of a single species, which was described by Peter Last and William White in a 2008 CSIRO publication. The specific epithet variegatum comes from the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
word for "various", and refers to the large amount of color variation within this species. The type specimen is 68 cm (26.8 in) long adult male, collected from east of Newcastle, New South Wales
Newcastle, New South Wales
The Newcastle metropolitan area is the second most populated area in the Australian state of New South Wales and includes most of the Newcastle and Lake Macquarie Local Government Areas...
.
Distribution and habitat
The saddled swellshark is found off the eastern coast of Australia, as far north as Rockingham Bay in QueenslandQueensland
Queensland is a state of Australia, occupying the north-eastern section of the mainland continent. It is bordered by the Northern Territory, South Australia and New South Wales to the west, south-west and south respectively. To the east, Queensland is bordered by the Coral Sea and Pacific Ocean...
and as far south as Tathra
Tathra, New South Wales
Tathra is a seaside town on the Sapphire Coast found on the South Coast, New South Wales, Australia in Bega Valley Shire. It has a population of 1,622....
in New South Wales, and perhaps also the Britannia Seamount near Brisbane
Brisbane
Brisbane is the capital and most populous city in the Australian state of Queensland and the third most populous city in Australia. Brisbane's metropolitan area has a population of over 2 million, and the South East Queensland urban conurbation, centred around Brisbane, encompasses a population of...
. It is a bottom-dwelling species that inhabits the outer continental shelf
Continental shelf
The continental shelf is the extended perimeter of each continent and associated coastal plain. Much of the shelf was exposed during glacial periods, but is now submerged under relatively shallow seas and gulfs, and was similarly submerged during other interglacial periods. The continental margin,...
and upper continental slope at a depth of 115–605 m (377.3–1,984.9 ft).
Description
The saddled swellshark reaches a maximum known length of 74 cm (29.1 in). It has a moderately stocky body and a short, variably wide, and strongly flattened head. The snout is broadly rounded, with the nostrilNostril
A nostril is one of the two channels of the nose, from the point where they bifurcate to the external opening. In birds and mammals, they contain branched bones or cartilages called turbinates, whose function is to warm air on inhalation and remove moisture on exhalation...
s preceded by laterally expanded flaps of skin that do not reach the large mouth. The slit-like eyes are positioned high on the head and followed by tiny spiracle
Spiracle
Spiracles are openings on the surface of some animals that usually lead to respiratory systems.-Vertebrates:The spiracle is a small hole behind each eye that opens to the mouth in some fishes. In the primitive jawless fish the first gill opening immediately behind the mouth is essentially similar...
s. The tooth rows number 68–82 in the upper jaw and 68–80 in the lower jaw. The very small teeth have three cusps, with the central one the longest and sometimes 1–2 additional lateral cusplets. In females the central cusp is smaller than in males. There are no furrows at the corners of the mouth, and the upper teeth are exposed when the mouth is closed. The fourth and fifth gill slit
Gill slit
Gill slits are individual openings to gills, i.e., multiple gill arches, which lack a single outer cover. Such gills are characteristic of Cartilaginous fish such as sharks, rays, sawfish, and guitarfish. Most of these have five pairs, but a few species have 6 or 7 pairs...
s lie over the pectoral fin bases and are shorter than the first three.
The pectoral fins are large and broad, with rounded margins. The first dorsal fin
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
is fairly angular and originates over the middle of the pelvic fin bases. The second dorsal fin is much smaller and lower than the first, originating behind the anal fin origin. The pelvic fins are small, with elongate, relatively short claspers in males. The anal fin is substantially larger and deeper than the second dorsal fin. The caudal fin is deep, with a distinct lower lobe and a strong ventral notch near the tip of the upper lobe. The body is densely covered by minute dermal denticles, each shaped like an arrowhead and bearing a median ridge.
The saddled swellshark is brownish or grayish in color above, with 11 darker saddles of varying width over the body and tail and usually no blotches on the flanks. Individuals from tropical waters ("sp. B") tend to have more defined saddles, while those from temperate waters ("sp. C") have fainter saddles and a smattering of lighter flecks. The underside is a plain light color, often with a few darker marks. The juveniles are pale with many dark brown spots.
Biology and ecology
Like other members of its genus, the variegated swellshark can inflate itself with water or air as a defensive measure. This species is oviparous, with its eggs contained in smooth, brownish capsules about 7 cm (2.8 in) long. The egg capsule is thick and rounded, with flanged lateral margins and a pair of horns at each end, which support very long, coiled tendrils. The smallest known free-swimming specimen measured 17 cm (6.7 in) long; males mature sexuallySexual maturity
Sexual maturity is the age or stage when an organism can reproduce. It is sometimes considered synonymous with adulthood, though the two are distinct...
at a length of 55–60 cm (21.7–23.6 in).
Human interactions
The International Union for Conservation of Nature (IUCN) has listed the narrowbar swellshark under Data DeficientData Deficient
Data Deficient is a category applied by the IUCN, other agencies, and individuals to a species when the available information is not sufficient for a proper assessment of conservation status to be made...
until more information is available. Currently, little fishing occurs in the region where this shark is found, but should that change it may be vulnerable due to its apparent rarity and benthic habits.