The mouse catshark (''Galeus murinus'') is a

species In biology, a species is the basic unit of Taxonomy (biology), 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 ...

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. It is common in the northeastern

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth#Surface, Earth's surface and about 29% of its water surface area. It is known to separate the "Old World" of Afr ...

from

Iceland Iceland ( is, Ísland; ) is a Nordic island country in the North Atlantic Ocean and in the Arctic Ocean. Iceland is the most sparsely populated country in Europe. Iceland's capital and largest city is Reykjavík, which (along with its ...

Western Sahara Western Sahara ( '; ; ) is a disputed territory on the northwest coast and in the Maghreb region of North and West Africa. About 20% of the territory is controlled by the self-proclaimed Sahrawi Arab Democratic Republic (SADR), while ...

. There is much taxonomic confusion regarding this species in Icelandic waters, where it may be confounded with another species of ''

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 ...

'' or ''

Apristurus ''Apristurus'' is a genus of catsharks, the family Scyliorhinidae, commonly known as the ghost or demon catsharks. Species The 39 currently recognized species in this genus are: * '' Apristurus albisoma'' Nakaya & Séret, 1999 (white-bodied c ...

''. Probably not exceeding long, the mouse catshark has a uniformly brown body and is characterized by large, rounded

pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral surface of fish. The paired pelvic fins are homologous to the hindlimbs of tetrapods. Structure and function Structure In actinopterygians, the pelvic fin consists of two e ...

s and crests of enlarged

dermal denticle A fish scale is a small rigid plate that grows out of the skin of a fish. The skin of most jawed fishes is covered with these protective scales, which can also provide effective camouflage through the use of reflection and colouration, as w ...

s along both the dorsal and ventral caudal fin margins. In addition, in adult males the inner margins of the pelvic fins are merged into an "apron".

Demersal The demersal zone is the part of the sea or ocean (or deep lake) consisting of the part of the water column near to (and significantly affected by) the seabed and the benthos. The demersal zone is just above the benthic zone and forms a laye ...

in nature, the mouse catshark inhabits

continental slope A continental margin is the outer edge of continental crust abutting oceanic crust under coastal waters. It is one of the three major zones of the ocean floor, the other two being deep-ocean basins and mid-ocean ridges. The continental marg ...

s at a depth of . It preys mainly on

benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from ancient Greek, βένθος (bénthos), meaning "t ...

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean gro ...

bony fish Osteichthyes (), popularly referred to as the bony fish, is a diverse superclass of fish that have skeletons primarily composed of bone tissue. They can be contrasted with the Chondrichthyes, which have skeletons primarily composed of cartila ...

es, and

cephalopod A cephalopod is any member of the molluscan class Cephalopoda ( Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, ...

s. Reproduction is

oviparous Oviparous animals are animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive method of most fish, amphibians, most reptiles, and all pterosaurs, dinosaurs (including birds), a ...

, with females producing "furry"

egg capsule An egg case or egg capsule, often colloquially called a mermaid's purse, is the casing that surrounds the eggs of oviparous sharks, skates and chimaeras. Egg cases typically contain one embryo, except for big skate and mottled skate egg cases, ...

s. Although it is caught incidentally 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 ...

trawl Trawling is a method of fishing that involves pulling a fishing net through the water behind one or more boats. The net used for trawling is called a trawl. This principle requires netting bags which are towed through water to catch different spe ...

fisheries, this species does not appear to be threatened by fishing activities and has been listed under

Least Concern A least-concern species is a species that has been categorized by the International Union for Conservation of Nature (IUCN) as evaluated as not being a focus of species conservation because the specific species is still plentiful in the wild. Th ...

by 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 natur ...

(IUCN).

Taxonomy and phylogeny

Norwegian

zoologist Zoology ()The pronunciation of zoology as is usually regarded as nonstandard, though it is not uncommon. is the branch of biology that studies the animal kingdom, including the structure, embryology, evolution, classification, habits, and ...

Robert Collett Robert Collett (2 December 1842 – 27 January 1913) was a Norwegian zoologist. Collett was director and curator of the Zoological Museum at University of Oslo. Robert Collett was born at Christiania (now Oslo), Norway. He was the eldest child ...

originally described the mouse catshark as ''Pristiurus murinus'', in a 1904 issue of the

scientific journal In academic publishing, a scientific journal is a periodical publication intended to further the progress of science, usually by reporting new research. Content Articles in scientific journals are mostly written by active scientists such ...

''Forhandlinger i Videnskabs-selskabet i Christiania''; its

specific epithet In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

means "relating to a mouse" in

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power ...

. The

type specimen In biology, a type is a particular specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to anchor or centralizes the ...

is an immature female long, collected northwest of the

Hebrides The Hebrides (; gd, Innse Gall, ; non, Suðreyjar, "southern isles") are an archipelago off the west coast of the Scottish mainland. The islands fall into two main groups, based on their proximity to the mainland: the Inner and Outer Hebrid ...

at a depth of . Later authors have recognized ''Pristiurus'' as a junior synonym of ''

''. Some taxonomic confusion has arisen over ''Pristiurus jensenii'', described from

by Bjarni Sæmundsson in 1922, which has traditionally been considered the same species as ''G. murinus''. Recently reported data for ''G. murinus'' have shown inconsistencies between sharks from Iceland and elsewhere, suggesting that ''P. jensenii'' may in fact be a valid species very similar to ''G. murinus''. However, an alternate possibility is that some of the data may have been confounded with a species of ''

''. The placement of ''G. murinus'' within ''Galeus'' is problematic as it does not much resemble the more typical members of the genus. On the other hand, 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 ...

analysis by Samuel Iglésias and colleagues, based on

mitochondrial A mitochondrion (; ) is an organelle found in the cells of most Eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is us ...

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. ...

, found that ''G. murinus'' forms a clade with ''G. melastomus'', apart from the clade of '' G. eastmani'', ''G. sauteri'', and ''G. gracilis''.

Distribution and habitat

Fairly common, the mouse catshark has recently been found to be more widespread in the northeastern

Atlantic The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the "Old World" of Africa, Europe an ...

than previously thought, occurring from western

and the

Faroe Islands The Faroe Islands ( ), or simply the Faroes ( fo, Føroyar ; da, Færøerne ), are a North Atlantic archipelago, island group and an autonomous territory of the Danish Realm, Kingdom of Denmark. They are located north-northwest of Scotlan ...

to the Hebrides,

Scotland Scotland (, ) is a country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a border with England to the southeast and is otherwise surrounded by the Atlantic Ocean to th ...

, and

Ireland Ireland ( ; ga, Éire ; Ulster Scots dialect, Ulster-Scots: ) is an island in the Atlantic Ocean, North Atlantic Ocean, in Northwestern Europe, north-western Europe. It is separated from Great Britain to its east by the North Channel (Grea ...

, to as far south as

France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of overseas regions and territories in the Americas and the Atlantic, Pacific and Indian Oceans. Its metropolitan ar ...

and

. This species is found on or near the bottom over the

, in water deep.Lorance, P., D. Latrouite, and S. Bernard (2000)
Observations of Chondrichthyan fishes (sharks,rays and chimaeras) in the Bay of Biscay (North-eastern Atlantic) from submersibles
Proceedings of the 3rd European Elasmobranch Association Meeting, Boulogne-sur-Mer, 1999. It has been reported from a depth of off Iceland, but the figure is confounded by taxonomic confusion.

Description

The maximum length of the mouse catshark has been variously reported as and . The larger figure comes from Iceland and is reflective of the aforementioned taxonomic confusion, as the specimen of ''P. jensenii'' described by Bjarni Sæmundsson was long. This species has a firm body with a rather long, blunt snout. The nostrils are divided by triangular flaps of skin in front. The eyes are horizontally oval and equipped with rudimentary

nictitating membrane The nictitating membrane (from Latin '' nictare'', to blink) is a transparent or translucent third eyelid present in some animals that can be drawn across the eye from the medial canthus to protect and moisten it while maintaining vision. All An ...

s (protective third eyelids). A thin ridge is present beneath each eye, and a tiny spiracle behind. The large mouth forms a wide arch, and bears well-developed furrows at the corners. The teeth have a narrow central cusp and multiple lateral cusplets on either side. There are 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 co ...

s. The first

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 ...

has a rounded tip and is positioned over the aft portion of the

s. The second dorsal fin is similar in size and shape as the first, and is positioned over the aft portion of the

anal 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 ...

. 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 are large and broad. The

s are distinctive, being large and wide with an evenly rounded margin. In adult males, the inner margins of the pelvic fins are fused together to form an "apron" partially covering 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 ...

. The anal fin is large and angular; its base measures roughly 12–13% of the total length, much longer than the distance between the dorsal fins. The pelvic, anal, 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 ...

s are all very close to each other. 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 se ...

is cylindrical and the caudal fin is low, with a small lower lobe and a ventral notch near the tip of the upper lobe. The

s are small and overlapping; each has an arrowhead-shaped crown bearing a horizontal ridge and three marginal teeth. There is a prominent crest of enlarged denticles along the dorsal caudal fin margin. Unusually for the genus, there is also a similar denticle crest along the underside of the caudal peduncle, extending to the forward portion of the ventral caudal fin margin. This shark is plain brown, lightening slightly on the underside; the interior of the mouth is dark.

Biology and ecology

The diet of the mouse catshark consists primarily of

shrimp Shrimp are crustaceans (a form of shellfish) with elongated bodies and a primarily swimming mode of locomotion – most commonly Caridea and Dendrobranchiata of the decapod order, although some crustaceans outside of this order are refer ...

such as ''Pasiphaea multidentata'' and ''Sergestes robustus'', other

s such as ''Dorhynchus thomsoni'',

es such as '' Micromesistius poutassou'', and

s. Most prey organisms are captured on or close to the

sea floor The seabed (also known as the seafloor, sea floor, ocean floor, and ocean bottom) is the bottom of the ocean. All floors of the ocean are known as 'seabeds'. The structure of the seabed of the global ocean is governed by plate tectonics. Most of ...

. Reproduction is

; the female has two

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, ...

s, with one egg maturing inside each at a time. The egg capsules are golden yellow and vase-shaped, measuring long and across. The top of the capsule is squared off, while the bottom comes to a short projection. The capsule surface is thickly covered by fibers, giving it a hairy appearance. The young are estimated to hatch at a length of approximately .

Human interactions

The mouse catshark is frequently caught incidentally by

fisheries operating in deep water off Europe and western Africa. However, it may be small enough to escape most nets, and there are likely parts of its wide range that see little fishing activity. Because there are no substantial threats to its population, the

(IUCN) has assessed this species as of

References

{{Taxonbar, from=Q520076 mouse catshark Fish of Iceland Fauna of the Faroe Islands mouse catshark mouse catshark