''Chionodraco'' is a genus of marine

ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fish or actinopterygians, is a class of bony fish that comprise over 50% of living vertebrate species. They are so called because of their lightly built fins made of webbings of sk ...

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 ...

Channichthyidae The crocodile icefish or white-blooded fish comprise a family (biology), family (Channichthyidae) of notothenioid fishes, fish found in the Southern Ocean around Antarctica. They are the only known vertebrates to lack hemoglobin in their blood as ...

, the

crocodile icefish The crocodile icefish or white-blooded fish comprise a family (biology), family (Channichthyidae) of notothenioid fishes, fish found in the Southern Ocean around Antarctica. They are the only known vertebrates to lack hemoglobin in their blood as ...

es. They are found in the

Southern Ocean The Southern Ocean, also known as the Antarctic Ocean, comprises the southernmost waters of the world ocean, generally taken to be south of 60th parallel south, 60° S latitude and encircling Antarctica. With a size of , it is the seco ...

Taxonomy

''Chionodraco'' was first described as a genus in 1905 by the Swedish

zoologist Zoology ( , ) is the scientific study of animals. Its studies include the structure, embryology, classification, habits, and distribution of all animals, both living and extinct, and how they interact with their ecosystems. Zoology is one ...

Einar Lönnberg Axel Johann Einar Lönnberg (24 December 1865 – 21 November 1942) was a Swedish zoologist and conservationist. Lönnberg was born in Stockholm. He was head of the Vertebrate Department of the '' Naturhistoriska Riksmuseet'' (Swedish Natural ...

when he described the ''Chaenichthys hamatus'' which he subsequently placed in a new

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unisp ...

genus. The genus name is a compound of ''chionos'' meaning "snow" and ''draco'' which means "dragon", Lönnberg did not explain this but it may allude to a relationship with the genus '' Cryodraco''.

Species

There are currently three recognized species in this genus: * '' Chionodraco hamatus'' (Lönnberg, 1905) * '' Chionodraco myersi'' H. H. DeWitt & J. C. Tyler, 1960 (Myers's icefish) * '' Chionodraco rastrospinosus'' H. H. DeWitt & Hureau, 1979 (Ocellated icefish)

Characteristics

''Chionodraco'' icefishes may have the spine on the snout present or it is reduced to a small centrally placed knob. The

gill raker Gill rakers in fish are bony or cartilaginous processes that project from the branchial arch (gill arch) and are involved with suspension feeding tiny prey. They are not to be confused with the gill filaments that compose the fleshy part of th ...

s may bear teeth or are vestigial. The upper and lower jaws are of equal length, although the lower jaw may protrude. There are robust spines on the operculum with the other opercular bones each having a pair of spines where they join. The first and second

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 ...

s are separate and there are three

lateral line The lateral line, also called the lateral line organ (LLO), is a system of sensory organs found in fish, used to detect movement, vibration, and pressure gradients in the surrounding water. The sensory ability is achieved via modified epithelia ...

s. In 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 ...

the outermost pair of fin rays are the longest and the tips are covered in thickened skin. 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 rounded. The maximum

total length Fish measurement is the measuring of individual fish and various parts of their anatomies, for data used in many areas of ichthyology, including taxonomy and fishery biology. Overall length Standard length (SL) is the length of a fish measured f ...

of these fishes varies from in ''C. myersi'' to in ''C. rastrospinosus''.

Distribution and habitat

''Chionodraco'' contains two circum-antarctic species, one of which is apparently confined to West Antarctica. They are

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 layer o ...

and

pelagic fish Pelagic fish live in the pelagic zone of ocean or lake waters—being neither close to the bottom nor near the shore—in contrast with demersal fish that live on or near the bottom, and reef fish that are associated with coral reefs. ...

es found on the continental shelf and slope.

Biology

''Chionodraco'' icefishes are predatory, feeding on other fish species and krill. They have a long post larval pelagic phase. In common with many other channichthyid fishes, reproduction in '' Chionodraco hamatus'' involves laying eggs in a nest and parental guarding. Similar morphological features suggest that at least '' Chionodraco rastrospinosus'' has similar reproductive behaviours.

Fisheries

''Chionodraco'' icefishes are targeted by some commercial fisheries and are also taken as bycatch.

References

{{Taxonbar, from=Q2164125 Channichthyidae Perciformes genera Taxa named by Einar Lönnberg