''Cyema atrum'' 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 ...

of deep-water

bobtail snipe eel The bobtail snipe eels are two species of deep-sea eels in the family Cyematidae, one only in each of two genera. They are small elongate fishes, growing up to 16cm (6 in) in length. The family Cyematidae is characterized by thin, short bodies ...

in the family

Cyematidae The bobtail snipe eels are two species of deep-sea eels in the family Cyematidae, one only in each of two genera. They are small elongate fishes, growing up to 16cm (6 in) in length. The family Cyematidae is characterized by thin, short bodies w ...

. It is the only 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 ...

''Cyema''. It is found globally at depths of . Common names include the bobtail eel, snipe eel, scissorjaw eel, and arrow eel. It grows to a possible length of , based on the estimated size for other bobtail eels. There is not much information about this enigmatic fish, because it is so rare and has been encountered a small number of times, but its diet may be composed of tiny

fish larvae Ichthyoplankton (from Greek: ἰχθύς, , "fish"; and πλαγκτός, , "drifter") are the eggs and larvae of fish. They are mostly found in the sunlit zone of the water column, less than 200 metres deep, which is sometimes called the epip ...

zooplankton Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek word for ''animal''). Plankton are aquatic organisms that are unable to swim effectively against currents, and consequently drift or are carried along by ...

copepod Copepods (; meaning "oar-feet") are a group of small crustaceans found in nearly every freshwater and saltwater habitat (ecology), habitat. Some species are planktonic (inhabiting sea waters), some are benthos, benthic (living on the ocean floor) ...

amphipods Amphipoda is an order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods range in size from and are mostly detritivores or scavengers. There are more than 9,900 amphipod species so far descri ...

, sea snow, and tiny

krill Krill are small crustaceans of the order Euphausiacea, and are found in all the world's oceans. The name "krill" comes from the Norwegian Norwegian, Norwayan, or Norsk may refer to: *Something of, from, or related to Norway, a country in n ...

. Instead of gobbling them up, the eel uses the comb-like teeth to swipe the food from the water column by slashing the head to the sides.

Description

This eel has a somewhat strange shaped tail, which gives it some of its names. They have diminutive pectoral fins, long jaws, very small eyes, and an overall dark coloration which probably helps it blend in the dark water where it lives, or maybe absorb the light emitted by other fishes, which is the defense method of the

ridgehead Ridgeheads, also known as bigscales, are a family (Melamphaidae, from the Greek ''melanos'' lackand ''amphi'' y both sides of small, deep-sea stephanoberyciform fish. The family contains approximately 37 species in five genera; their distribut ...

s, which are not related to

eel Eels are ray-finned fish belonging to the order Anguilliformes (), which consists of eight suborders, 19 families, 111 genera, and about 800 species. Eels undergo considerable development from the early larval stage to the eventual adult stage ...

s in any way. The dark coloration of the ridgeheads absorbs up to 95.5% of the light, rendering the fish basically invisible in the dark and barely visible even in lit conditions, with just a silhouette appearing in the ridgehead's place, but this has not been proved with this species. They do not perform any vertical migration at night. They have a worldwide distribution, but they are more commonly found in South Africa, Chile, Panama, the US, New Zealand, and Australia. A remarkable aspect of this small and enigmatic fish is that, as the body narrows, the spine of the eel becomes visible through its skin, giving the tail the aspect of a tree leaf. Another characteristic is that the mouth is very narrow at the end, but very wide at the base on the head, and it goes far beyond the eyes, a vague illusion of a

gulper eel The saccopharyngiformes are a derived lineage of unusual eels within the order Anguilliformes, and includes families Cyematidae, Monognathidae, Eurypharyngidae, Saccopharyngidae, and the proposed family Neocyematidae. Most of the fish in this gro ...

. The genus ''Cyema'' is monotypic, its only species being this one. There is no information about its reproduction.

References

* Cyematidae Monotypic ray-finned fish genera Taxa named by Albert Günther {{Saccopharyngiformes-stub