The blacktip sawtail catshark (''Galeus sauteri'') is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

catshark Catsharks are ground sharks of the family Scyliorhinidae. They are the largest family of sharks with around 160 species placed in 17 genera. Although they are generally known as catsharks, some species can also be called dogfish due to previous ...

, and part of the

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Scyliorhinidae, found off the coasts of

Taiwan Taiwan, officially the Republic of China (ROC), is a country in East Asia, at the junction of the East and South China Seas in the northwestern Pacific Ocean, with the People's Republic of China (PRC) to the northwest, Japan to the nort ...

and the

Philippines The Philippines (; fil, Pilipinas, links=no), officially the Republic of the Philippines ( fil, Republika ng Pilipinas, links=no), * bik, Republika kan Filipinas * ceb, Republika sa Pilipinas * cbk, República de Filipinas * hil, Republ ...

. It is demersal in nature and occurs deeper than . Growing up to long, this slim-bodied species is characterized by its plain brownish dorsal coloration with dark tips on the

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage * Dorsal c ...

and

caudal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as ...

s, and a prominent crest of enlarged dermal denticles on the upper edge of the caudal fin. It is oviparous, with females producing encapsulated eggs two at a time year-round. The blacktip sawtail catshark is caught incidentally in

bottom trawl Bottom trawling is trawling (towing a trawl, which is a fishing net) along the seafloor. It is also referred to as "dragging". The scientific community divides bottom trawling into benthic trawling and demersal trawling. Benthic trawling is tow ...

s and used for

fishmeal Fish meal is a commercial product made from whole wild-caught fish, bycatch and fish by-products to feed farm animals, e.g., pigs, poultry, and farmed fish.R. D. Miles and F. A. Chapman.FA122: The Benefits of Fish Meal in Aquaculture DietsFisheri ...

in Taiwan.

Taxonomy and phylogeny

In 1906, the Carnegie Museum purchased an extensive collection of fishes assembled from the markets of Takao ( Kaohsiung),

by Hans Sauter. American ichthyologists David Starr Jordan and Robert Earl Richardson described several new species from the collection in a 1909 issue of ''Memoirs of the Carnegie Museum'', including a catshark of the genus ''Pristiurus'' that they named in Sauter's honor. Jordan and Richardson referenced six

syntype In biological nomenclature, a syntype is any one of two or more biological types that is listed in a description of a taxon where no holotype was designated. Precise definitions of this and related terms for types have been established as part of ...

s long in their description, of which four survive to the present day. Later authors have recognized ''Pristiurus'' as a junior synonym of the genus ''

Galeus ''Galeus'' is a genus of catshark, belonging to the family Scyliorhinidae, commonly known as sawtail catsharks in reference to a distinctive saw-toothed crest of enlarged dermal denticles, found along the upper edges of their caudal fins. They a ...

''. A 2005

phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

study, based on mitochondrial and

nuclear DNA Nuclear DNA (nDNA), or nuclear deoxyribonucleic acid, is the DNA contained within each cell nucleus of a eukaryotic organism. It encodes for the majority of the genome in eukaryotes, with mitochondrial DNA and plastid DNA coding for the rest. I ...

, found that this species, ''G. eastmani'', and ''G. gracilis'' form a clade apart from ''G. melastomus'' and ''G. murinus''.

Distribution and habitat

The blacktip sawtail catshark is found in the waters around Taiwan, where it is very common, and the

. It was once thought to occur off southern Japan as well, but recent observations by

Kazuhiro Nakaya is a Japanese marine scientist and ichthyologist. He graduated from Hokkaido University with a BA in 1968 and with a PhD in 1972. He is professor of Marine Environment and Resources at the Marine Laboratory for Biodiversity. He specializes in ta ...

have determined that this is not the case. This species is found on or near the bottom over the continental shelf. In the

Taiwan Strait The Taiwan Strait is a -wide strait separating the island of Taiwan and continental Asia. The strait is part of the South China Sea and connects to the East China Sea to the north. The narrowest part is wide. The Taiwan Strait is itself a ...

, it has been recorded over mud at depths of , while off Guishan Island it is known from .

Description

A small species, the blacktip sawtail catshark attains a maximum length of . Its body is slim and firm, with the head comprising roughly one-fifth of the total length. The rather long snout is pointed, with large nostrils divided by triangular flaps of skin on their anterior margins. The large, horizontally oval eyes bear rudimentary nictitating membranes (protective third eyelids) and lack prominent ridges underneath. Behind each eye is a small spiracle. The mouth is large and forms a long, wide arch; the corners of the mouth bear well-developed furrows. There are about 70–78 upper and 82 lower tooth rows. Each tooth is small and usually has five cusps, with the central one the longest. The five pairs of

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 and rays, as well as deep-branching vertebrates such as lampreys. In con ...

s are short, with the fourth and fifth pairs located over the bases of the

pectoral fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as ...

s. Both

dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through c ...

s are rounded; the first is slightly larger and positioned over the latter half of the pelvic fin bases, while the second is positioned over the latter half of the anal fin base. The pectoral fins are medium-sized and blunt-cornered. The small pelvic fins are low and angular; the

claspers In biology, a clasper is a male anatomical structure found in some groups of animals, used in mating. Male cartilaginous fish have claspers formed from the posterior portion of their pelvic fin which serve to channel semen into the female's c ...

of adult males reach the origin of the anal fin. The space between the pelvic and anal fin origins is greater in males than in females. The anal fin is elongated and angular; its base measures 12–15% of the total length, comparable to the distance between the dorsal fins. The

caudal peduncle Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as see ...

is compressed from side to side, and leads to a low

with a small lower fin and a ventral notch near the tip of the upper lobe. The body is covered by small, slightly overlapping dermal denticles, which are leaf-shaped with a median ridge and three marginal teeth. A crest of enlarged denticles is present along the upper edge of the caudal fin. This species is a uniform ochre above and white below, with distinctive dark brown tips on the dorsal and caudal fins; the interior of the mouth is light gray.

Biology and ecology

Reproduction in the blacktip sawtail catshark is oviparous and proceeds throughout the year, without well-defined seasonal patterns. Adult females have a single functional ovary, on the right, and two functional

oviduct The oviduct in mammals, is the passageway from an ovary. In human females this is more usually known as the Fallopian tube or uterine tube. The eggs travel along the oviduct. These eggs will either be fertilized by spermatozoa to become a zygote, o ...

s; a single egg matures within each oviduct at a time. The eggs are enclosed in purse-shaped, translucent golden brown capsules measuring about long and across. The surface of the capsule is smooth and unlined; there are coiled tendrils on the anterior corners and bundles of long fibers on the posterior corners. Half of all males and females are

sexually mature Sexual maturity is the capability of an organism to reproduce. In humans it might be considered synonymous with adulthood, but here puberty is the name for the process of biological sexual maturation, while adulthood is based on cultural definiti ...

at and long respectively. A known

parasite Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...

of this species is the

tapeworm Eucestoda, commonly referred to as tapeworms, is the larger of the two subclasses of flatworms in the class Cestoda (the other subclass is Cestodaria). Larvae have six posterior hooks on the scolex (head), in contrast to the ten-hooked Cesto ...

''Nakayacestus tanyderus''.

Human interactions

In Taiwanese waters, blacktip sawtail catsharks of most sizes are frequently caught incidentally in

s operated by

commercial Commercial may refer to: * a dose of advertising conveyed through media (such as - for example - radio or television) ** Radio advertisement ** Television advertisement * (adjective for:) commerce, a system of voluntary exchange of products and s ...

shrimp fisheries. Captured sharks are processed into

and used in aquaculture. This species is probably also caught incidentally by bottom trawlers in the Philippines, as it has been observed at markets. The

International Union for Conservation of Nature The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of nat ...

(IUCN) has listed the blacktip sawtail catshark as least concern.

References

{{Taxonbar, from=Q1110502 blacktip sawtail catshark Fish of the Philippines Fish of Taiwan blacktip sawtail catshark Taxa named by David Starr Jordan Taxa named by Robert Earl Richardson