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

shark Sharks are a group of elasmobranch cartilaginous fish characterized by a ribless endoskeleton, dermal denticles, five to seven gill slits on each side, and pectoral fins that are not fused to the head. Modern sharks are classified within the ...

belonging to the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Pentanchidae Pentanchidae, the deepwater catsharks, is a family of sharks belonging to the order Carcharhiniformes Carcharhiniformes ( from Classical Greek ' (karcharos) 'sharp/jagged' and ' (rhinos) 'nose', plus Latin ''forme'' 'shape'), commonly known a ...

, the deepwater catsharks, and the only described member of its

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

. A diminutive,

bottom-dwelling 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 the Ancient Greek word (), meaning "the depths". ...

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 islan ...

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 margi ...

, this species can be readily identified by its

tadpole A tadpole or polliwog (also spelled pollywog) is the Larva, larval stage in the biological life cycle of an amphibian. Most tadpoles are fully Aquatic animal, aquatic, though some species of amphibians have tadpoles that are terrestrial animal, ...

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

gill A gill () is a respiration organ, respiratory organ that many aquatic ecosystem, 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 r ...

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 p ...

for hypoxic conditions. This shark

prey Predation is a biological interaction in which 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 ki ...

s on

crustacean Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquatic arthrop ...

s and

fish A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...

es. Reproduction is

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

, 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 grounds). Commercial fisheries include wild fisheries and fish far ...

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, 35,800 species of fish had been described as of March 2 ...

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 (, ) 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 Cabo San Lucas, the sout ...

. 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, officially the Republic of Panama, is a country in Latin America at the southern end of Central America, bordering South America. It is bordered by Costa Rica to the west, Colombia to the southeast, the Caribbean Sea to the north, and ...

Peru Peru, officially the Republic of Peru, is a country in western South America. It is bordered in the north by Ecuador and Colombia, in the east by Brazil, in the southeast by Bolivia, in the south by Chile, and in the south and west by the Pac ...

, and

Chile Chile, officially the Republic of Chile, is a country in western South America. It is the southernmost country in the world and the closest to Antarctica, stretching along a narrow strip of land between the Andes, Andes Mountains and the Paci ...

, 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 In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

with the genera ''

Asymbolus ''Asymbolus'' is a genus of catsharks in the Family (biology), family Pentanchidae, the deepwater catsharks. Species The currently recognized species in this genus are: * ''Australian spotted catshark, Asymbolus analis'' (James Douglas Ogilby, ...

'', ''

Parmaturus ''Parmaturus'' is a genus of deepwater catsharks in the Family (biology), family Pentanchidae. 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 cur ...

'', ''

Galeus ''Galeus'' is a genus of deepwater catshark, belonging to the family (biology), family Pentanchidae, commonly known as sawtail catsharks in reference to a distinctive saw-toothed crest of enlarged dermal denticles, found along the upper edges of ...

'', and ''

Apristurus ''Apristurus'' is a genus of catsharks, the family Pentanchidae, the deepwater catsharks. The species in this genus are commonly known as the ghost or demon catsharks. Species The 41 currently recognized species in this genus are: * '' Apristu ...

''. However, different authors disagree on the interrelationships within this group; molecular data supports ''Cephalurus'' and ''Parmaturus'' as sister groups. This taxon was formerly classified in the family

Scyliorhinidae Scyliorhinidae is a Family (biology), family of sharks, one of a few families whose members share the common name catsharks, belonging to the Order (biology), order Carcharhiniformes, the ground sharks. Although they are generally known as cats ...

, but, with most of the other genera previously classified within that family, it is now included in the family Pentanchidae.

Distribution and habitat

The range of the lollipop catshark extends from the

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

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 the Ancient Greek word (), meaning "the depths". ...

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 , : 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 turbinates ...

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 * Papilla (worms), small bumps on the surface of certain worms * Basilar papilla, a sensory organ of lizards, amphibians and fish * ...

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 spiracles. 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 c ...

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 on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...

originates well in front of the

pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral (belly) surface of fish, and are the lower of the only two sets of paired fins (the other being the laterally positioned pectoral fins). The pelvic fins are homologous to the hi ...

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

anal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported o ...

. The dorsal, pelvic, and anal fins have convex leading and nearly straight trailing margins. The

pectoral fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish aquatic locomotion, swim. Apart from the tail or caudal fin, fish fins have no direct connection with the vertebral column ...

s are angular, twice as long as wide, and originate beneath the fourth gill slit. The

caudal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported only ...

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 thornlike

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 scale (zoology), scales, which can also provide effective Underwater camouflage, camouflage through the us ...

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 p ...

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 can ...

and perhaps also high temperatures and

salinity Salinity () is the saltiness or amount of salt (chemistry), 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 dimensio ...

. 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 a gonad in the female reproductive system that produces ova; when released, an ovum travels through the fallopian tube/oviduct into the uterus. There is an ovary on the left and the right side of the body. The ovaries are endocr ...

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

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

) 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 is related to both puberty and adulthood. ''Puberty'' is the biological process of sexual maturation, while ''adulthood'', the condition of being socially recognized as ...

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 grounds). Commercial fisheries include wild fisheries and fish farm ...

. 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) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the stat ...

(IUCN) presently assesses it as least concern.

References

{{Taxonbar, from=Q1675845 lollipop catshark Ovoviviparous fish Fish of the Gulf of California lollipop catshark Taxa named by Charles Henry Gilbert