All the extant species and six subspecies in this family are in the genus Anguilla, and are elongated fish of snake-like bodies, with long dorsal, caudal and anal fins forming a continuous fringe.

They have relatively well developed eyes and pectoral fins compared to saltwater eels that they use to navigate and maneuver through river bottoms and shallow water.

The second is Anguilla ignota, which is the fossil that represents the ancestor to all extant freshwater eels and marks the upper boundary of the age of anguillidae.

N. robinsi was found by Italian scientists in 2002 in the Santonian-Campanian Calcari di Melissano, which is a fossil bed located near the town of Nardò.

However, more studies need to be conducted to confirm the placement of freshwater eels within Anguilliformes, and determine the composition of the Anguilloidei subclass.

[19] Threats to these species include: habitat loss/modification, migration barriers, pollution, parasitism, exploitation, and consumption, as eels are a popular food source especially in Asia and Europe.

Fluctuating oceanic conditions associated with climate change also make these species vulnerable, with reduced water quality leading to biodiversity loss among the largest threats.

According to the IUCN Anguillid Eel Specialist Group, or the AESG, the need for conservation of this family is clear given recent declines.

Freshwater eels are carnivores so are fed other wild-caught fish, adding another element of unsustainability to current eel-farming practices.

[18] Some eel species have been observed consuming the eggs of predatory fish such as trout, aiding in population control in these systems.

[23] Ocean-resident eels are the exception of this family, and this behavior may be more common in areas in which the freshwater habitat is of lower quality or productivity.

[25] Tsukamoto and associates found evidence of Japanese eels (A. japonica) may synchronize their breeding cycles during the spawning season with the new moon.

Anguillid eels undergo morphological changes during these developmental stages that are associated with environmental conditions and aid in preparing them for further growth and finally reproduction.

[22] These planktonic (free floating) eggs and translucent, leaf-like larvae are dispersed via ocean currents and migrate sometimes thousands of miles.

Finally, anguillids transition through the silver eel stage into adulthood and migrate to the oceanic breeding grounds to reproduce and begin the cycle anew.

[28] The discovery of the spawning area of the American and European eels in the Sargasso Sea is one of the more famous anecdotes in the history of ichthyology.

Eels in the family Anguillidae are known to be primarily solitary in nature; they are not known to communicate socially or actively school, however large masses of elvers can be found as a result of synchronicity in response to environmental conditions.

[25] These eels are known as generalists and opportunistic feeders; most will consume whatever acceptable prey they happen upon, including things like crustaceans, fishes, and other aquatic fauna.

[30] Aside from their reduced pectoral fins, eels lack of paired appendages: use axial-based lateral undulation as means of locomotion, similar to snakes.

Much is unknown about Anguillid eel behavior and its origins, due to the difficulty in observation, particularly in the context of reproduction, social constructs, and migration.

Lateral lines provide the ability for Anguillidae to sense their surrounding environment through water displacement which aids in predation and hunting especially because they are predominantly nocturnal generalists.

Unlike the other relatives the Anguillidae are catadromous meaning they must migrate for an extended period and depending on what life stage they are in they may be in the open ocean.

Within this experiment they also looked at how the glass eel may rely on the circatidal rhythm in the ocean to work its way back to the coast and into the freshwater systems, but it is not yet fully understood.

Paired frontal bones of skull make for a stronger cranium which aids in their variable burrowing tendencies with mud as well as maneuvering through terrestrial obstacles when hiding under rocks and logs that they encounter at the waters bottom where they spend most of their time during the day.

Ventral lateral gill slits make up eighty-five percent of gas exchange and are highly efficient in converting between salt and freshwater.

It was mistakenly reported that Anguillidae lack a scapular bone but after further research and more advanced staining techniques they have a scapula and coracoid which make up their pectoral girdle.

Since their mouths are not very large, they use their swimming capabilities to aid in feeding where they will bite onto their food and twist/spin rapidly tearing off a piece perfectly sized for them.

The gas bladder adapts for higher pressures which it'll be exposed to in the ocean where it will dive much deeper in search of food and avoiding strong currents.

When held in captivity it was reported that they would hit their heads against the glass or make fast for an escape route most likely looking for the fresh or saltwater they seek.

[citation needed] A. mossambica A. borneensis A. anguilla A. rostrata A. australis A. dieffenbachii A. reinhardtii A. japonica A. celebesensis A. megastoma A. marmorata A. nebulosa A. interioris A. obscura A. bicolor