A leptocephalus is the flat and transparent larva of the eel, marine eels, and other members of the superorder Elopomorpha. This is one of the most diverse groups of teleosts, containing 801 species in 4 orders, 24 families, and 156 genera. This group is thought to have arisen in the Cretaceous period over 140 million years ago.
Eels are any of several long, thin, bony fishes of the order Anguilliformes. They have a catadromous life cycle, that is: at different stages of development migrating between inland waterways and the deep ocean. Because fishermen never caught anything they recognized as young eels, the life cycle of the eel was long a mystery. Of particular interest has been the search for the spawning grounds for the various species of eels, and identifying the population impacts of different stages of the life cycle.
The Notacanthiformes are an order of deep-sea ray-finned fishes, consisting of the families Halosauridae and Notacanthidae.
The superorder Elopomorpha contains a variety of types of fishes that range from typical silvery-colored species, such as the tarpons and ladyfishes of the Elopiformes and the bonefishes of the Albuliformes, to the long and slender, smooth-bodied eels of the Anguilliformes. The one characteristic uniting this group of fishes is they all have leptocephalus larvae, which are unique to the Elopomorpha. No other fishes have this type of larvae.
The name spiny eel is used to describe members of two different families of fish: the freshwater Mastacembelidae of Asia and Africa, and the marine Notacanthidae. Both are so-named because of their eel-like shape and sturdy fin spines. These two families are not related: the Notacanthiformes belong to the Superorder Elopomorpha, whose members are characterized by having leptocephalus larvae. The freshwater Mastacembelids do not share this characteristic and are popular specimens in the aquarium trade.
The spiny-back eel, Notacanthus sexspinis, is a deep-sea spiny eel of the genus Notacanthus, found in all the Southern Hemisphere oceans at depths between 500 and 1,000 m. The length of this fish is up to 60 cm (24 in).
Cyema is a monospecific genus of marine ray-finned fish belonging to the monotypic family Cyematidae. The only species in the genus is Cyema atrum, the arrow eel, bobtail eel, bobtail snipe eel or deepwater eel. This species has circumglobal distribution.
Neocyema erythrosoma is a species of pelagic fish, a deep-water bobtail snipe eel in the family Cyematidae. It is the only member of its genus, Neocyema. It was first described by Peter Castle in 1978 after two specimens were caught at great depths in the south Atlantic Ocean in 1971. Further specimens have since been caught in the North Atlantic.
The New Zealand longfin eel, also known as ōrea, is a species of freshwater eel that is endemic to New Zealand. It is the largest freshwater eel in New Zealand and the only endemic species – the other eels found in New Zealand are the native shortfin eel, also found in Australia, and the naturally introduced Australian longfin eel. Longfin eels are long-lived, migrating to the Pacific Ocean near Tonga to breed at the end of their lives. They are good climbers as juveniles and so are found in streams and lakes a long way inland. An important traditional food source for Māori, who name them ōrea, longfin eel numbers are declining and they are classified as endangered, but over one hundred tonnes are still commercially fished each year.
Leptocephalus is a genus that was used for species of larval eels, called leptocephali. Leptocephali larvae differ so much in appearance from their adults. When first discovered, leptocephali were thought to be a distinct type of fish, not an eel specie. Because of this, the genus designation of Leptocephalus was used for a while for an unidentified leptocephali. After it was known that these were eel larvae, it was identified to be part of a wastebasket taxon, but not anymore in the present classification system. Examples of marine congrid larvae, found in the western Indian Ocean and the Red Sea that were named this way are listed below. Only two species in two families are currently treated as having any validity, though the validity of L. bellottii is strongly in doubt.
The snub-nosed spiny eel is a member of the family Notacanthidae, the deep-sea spiny eels, which are not true eels (Anguilliformes). The snub-nosed spiny eel exists in waters all over the world, except in the tropics, ranging in color from light tan to bluish grey in small ones to dark brown in large ones. Its primary food is sea anemones. The eel usually lives in deep waters, mostly more than 200 m below the surface. Female snub-nosed spiny eels reach maturity around 18 years old, and are larger than 55 cm in length at maturity. Males reach maturity around 14 years and are larger than 66 cm in length.
The Colocongridae, the worm eels or short-tail eels, are a family of eels, containing a single genus, Coloconger.
Eels are ray-finned fish belonging to the order Anguilliformes, which consists of eight suborders, 20 families, 164 genera, and about 1000 species. Eels undergo considerable development from the early larval stage to the eventual adult stage and are usually predators.
Notacanthus is a genus of spiny eels in the family Notacanthidae.
Congriscus is a genus of eels in the family Congridae.
Coloconger eximia is an eel in the family Colocongridae. It was described by Peter Henry John Castle in 1967, originally under the genus Ascomana. It is a marine, deep-water dwelling eel which is known from Cape Peninsula, South Africa, in the southeastern Atlantic Ocean.
Coloconger meadi is an eel in the family Colocongridae. It was described by Robert H. Kanazawa in 1957. It is a marine, deep-water dwelling eel from the Gulf of Mexico and Suriname in the western central Atlantic Ocean. It dwells at a depth range of 650–925 m. Males can reach a maximum total length of 37.7 cm.
The Indo-Pacific shorttail conger, also known as the short-tail conger, is an eel in the family Colocongridae. It was described by Chan William Lai-Yee in 1967. It is a marine, deep-water dwelling eel which is known from the Indo-Pacific, including southern Mozambique, Natal, South Africa, the South China Sea, and eastern Australia. It dwells at a maximum depth of 810 metres (2,660 ft). Males are known to reach a maximum total length of 51 centimetres (20 in).
The shortfin spiny eel, also called Bonaparte's spiny eel, is a member of the family Notacanthidae, the deep-sea spiny eels, which are not true eels (Anguilliformes).
The Pacific bearded brotula also known as the pink bearded cusk-eel or the red bearded cusk-eel is a species of cusk eel found in the Pacific Ocean. It is described as being reddish-brown with dark fins.
