The lollipop catshark (''Cephalurus cephalus'') is a little-known

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 ...

deep sea The deep sea is broadly defined as the ocean depth where light begins to fade, at an approximate depth of 200 metres (656 feet) or the point of transition from continental shelves to continental slopes. Conditions within the deep sea are a combin ...

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 n ...

, belonging to the

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

Scyliorhinidae, and the only described member of its

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

. A diminutive, bottom-dwelling shark of the outer

continental shelf A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an island ...

and upper

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 margin ...

, this species can be readily identified by its

tadpole A tadpole is the larval stage in the biological life cycle of an amphibian. Most tadpoles are fully aquatic, though some species of amphibians have tadpoles that are terrestrial. Tadpoles have some fish-like features that may not be found i ...

-like shape with a greatly expanded, rounded head and narrow body. The large head houses expanded

gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...

s, which are thought to be an

adaptation In biology, adaptation has three related meanings. Firstly, it is the dynamic evolutionary process of natural selection that fits organisms to their environment, enhancing their evolutionary fitness. Secondly, it is a state reached by the po ...

for hypoxic conditions. This shark

prey Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill the ...

s on

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 group ...

s and

fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of li ...

es. Reproduction is

aplacental viviparous Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a term used as a "bridging" form of reproduction between egg-laying oviparous and live-bearing viviparous reproduction. Ovoviviparous animals possess embryos that develop insi ...

, with females retaining egg cases internally two at a time until they hatch. There is no

fishery Fishery can mean either the enterprise of raising or harvesting fish and other aquatic life; or more commonly, the site where such enterprise takes place ( a.k.a. fishing ground). Commercial fisheries include wild fisheries and fish farms, both ...

interest in this species.

Taxonomy and phylogeny

The lollipop catshark was originally described by American

ichthyologist Ichthyology is the branch of zoology devoted to the study of fish, including bony fish ( Osteichthyes), cartilaginous fish (Chondrichthyes), and jawless fish (Agnatha). According to FishBase, 33,400 species of fish had been described as of Octobe ...

Charles Henry Gilbert Charles Henry Gilbert (December 5, 1859 in Rockford, Illinois – April 20, 1928 in Palo Alto, California) was a pioneer ichthyologist and Fisheries science, fishery biologist of particular significance to natural history of the western Unit ...

as ''Catulus cephalus'', in the 1892 14th volume of ''Proceedings of the United States National Museum''. His description was based on a long adult male caught from a depth of off Clarion Island in the

Revillagigedo Islands The Revillagigedo Islands ( es, Islas Revillagigedo, ) or Revillagigedo Archipelago are a group of four volcanic islands in the Pacific Ocean, known for their unique ecosystem. They lie approximately from Socorro Island south and southwest of C ...

. In 1941, Henry F. Bigelow and William C. Schroeder created the new genus ''Cephalurus'' for this species. One or more yet-undescribed species of ''Cephalurus'' appear to exist off

Panama Panama ( , ; es, link=no, Panamá ), officially the Republic of Panama ( es, República de Panamá), is a transcontinental country spanning the southern part of North America and the northern part of South America. It is bordered by Cos ...

Peru , image_flag = Flag of Peru.svg , image_coat = Escudo nacional del Perú.svg , other_symbol = Great Seal of the State , other_symbol_type = Seal (emblem), National seal , national_motto = "Fi ...

, and

Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the east a ...

, which differ slightly from ''C. cephalus'' in appearance and size. Based on morphological and

molecular phylogenetic Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...

evidence, ''Cephalurus'' is thought to form a

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

with the genera ''

Asymbolus ''Asymbolus'' is a genus of catsharks in 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 mai ...

'', ''

Parmaturus ''Parmaturus'' is a genus of catsharks in the family Scyliorhinidae. Four species were described in 2007 and another in 2019 with more species likely to be described in the near future. Species The following are the currently described species ...

'', ''

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 ...

'', and ''

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 ...

''. However, different authors disagree on the interrelationships within this group; molecular data supports ''Cephalurus'' and ''Parmaturus'' as sister groups.

Distribution and habitat

The range of the lollipop catshark extends from the

Gulf of California The Gulf of California ( es, Golfo de California), also known as the Sea of Cortés (''Mar de Cortés'') or Sea of Cortez, or less commonly as the Vermilion Sea (''Mar Bermejo''), is a marginal sea of the Pacific Ocean that separates the Baja Ca ...

to off the southern Baja peninsula. This

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 ...

species occurs around the outer

and upper

at depths of , where it is reportedly abundant.

Description

The lollipop catshark is so named because of its peculiar

-like shape, with an enormously expanded head and branchial region (containing the

gills A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...

) coupled with a slender, cylindrical body tapering towards the tail. The head is wide, flattened, and rounded, comprising a third of the total length in adults. The snout is very short and blunt, with widely spaced

nostril A nostril (or naris , plural ''nares'' ) is either of the two orifices of the nose. They enable the entry and exit of air and other gasses through the nasal cavities. In birds and mammals, they contain branched bones or cartilages called turbi ...

s flanked by moderately developed flaps of skin. The mouth has a pair of furrows at the corners that curl around from the upper to the lower jaw. The widely spaced teeth have a large central cusp flanked by 1–3 cusplets on both sides; the upper teeth are straight while the lower teeth are curved somewhat outward. There are numerous small

papilla Papilla (Latin, 'nipple') or papillae may refer to: In animals * Papilla (fish anatomy), in the mouth of fish * Basilar papilla, a sensory organ of lizards, amphibians and fish * Dental papilla, in a developing tooth * Dermal papillae, part of ...

e on the tongue and roof of the mouth, and a light-colored membrane lining the inside of the mouth. The large eyes are oval in shape and followed by prominent

spiracle Spiracle or spiraculum may refer to: * Spiracle (arthropods), opening in the exoskeletons of some arthropods * Spiracle (vertebrates), openings on the surface of some vertebrates * Spiraculum, a genus of land snails in family Cyclophoridae Cycl ...

s. 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 distinctive, being strongly arched forward. The body is very soft, almost gelatinous. Unlike in other catsharks, 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 conv ...

originates well in front of the

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 en ...

s. The second dorsal fin is about as long and slightly lower than the first, and is positioned opposite 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 se ...

. The dorsal, pelvic, and anal fins have convex leading and nearly straight trailing margins. 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 angular, twice as long as wide, and originate beneath the fourth gill slit. The

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 se ...

is low, with an indistinct lower lobe and a shallow ventral notch near the tip of the upper lobe. The skin is delicate and sparsely covered by thorn-like

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 we ...

s interspersed with narrower hair-like denticles that become more numerous on the back. The coloration is a plain brownish gray all over, sometimes lightening to almost white at the dorsal, pectoral, and pelvic fin margins. The eyes are an iridescent green. Adults typically attain a length of , but may grow up to long.

Biology and ecology

The enlarged gill region and expanded gill filaments of the lollipop catshark suggest that it is

adapted In biology, adaptation has three related meanings. Firstly, it is the dynamic evolutionary process of natural selection that fits organisms to their environment, enhancing their evolutionary fitness. Secondly, it is a state reached by the po ...

for living in deep-sea basins with very low levels of

dissolved oxygen Oxygen saturation (symbol SO2) is a relative measure of the concentration of oxygen that is dissolved or carried in a given medium as a proportion of the maximal concentration that can be dissolved in that medium at the given temperature. It ca ...

and perhaps also high temperatures and

salinity Salinity () is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal ...

. This shark feeds mainly on

s, followed by

es. The lollipop catshark is

, with birthing apparently taking place in early summer. Females have two functional

ovaries The ovary is an organ in the female reproductive system that produces an ovum. When released, this travels down the fallopian tube into the uterus, where it may become fertilized by a sperm. There is an ovary () found on each side of the body. T ...

and retain pairs of thin-shelled egg cases (one within each

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 ...

) within their bodies until they hatch. Newborns measure about long;

sexual maturation 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 definitio ...

is reached at a length of for males and for females.

Human interactions

The lollipop catshark is of no significance to

fisheries Fishery can mean either the enterprise of raising or harvesting fish and other aquatic life; or more commonly, the site where such enterprise takes place ( a.k.a. fishing ground). Commercial fisheries include wild fisheries and fish farms, both ...

. It may be taken as

bycatch Bycatch (or by-catch), in the fishing industry, is a fish or other marine species that is caught unintentionally while fishing for specific species or sizes of wildlife. Bycatch is either the wrong species, the wrong sex, or is undersized or juve ...

; though the depths at which it occupies may offer some protection from fishing pressure. 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 natu ...

(IUCN) presently assesses it as least concern.

References

{{Taxonbar, from=Q1675845 lollipop catshark Ovoviviparous fish Fish of the Gulf of California lollipop catshark