Common name for an order (Anguilliformes) of voracious, elongate, snakelike teleost fishes.

Anguilla is not a term with a widely accepted medical definition; however, it is the scientific name for the freshwater eel species, and if used in a medical context, it may refer to a rare condition called Anguillula nephria, which is an intestinal infection caused by a roundworm.

Thin-walled sacs or spaces which function as a part of the respiratory system in birds, fishes, insects, and mammals.

A superfamily of nematodes of the suborder CAMALLANINA. Its organisms possess a poorly developed buccal cavity and a rudimentary esophagus and intestine.

A genus of fish, in the family GYMNOTIFORMES, capable of producing an electric shock that immobilizes fish and other prey. The species Electrophorus electricus is also known as the electric eel, though it is not a true eel.

Paired respiratory organs of fishes and some amphibians that are analogous to lungs. They are richly supplied with blood vessels by which oxygen and carbon dioxide are exchanged directly with the environment.

Diseases of freshwater, marine, hatchery or aquarium fish. This term includes diseases of both teleosts (true fish) and elasmobranchs (sharks, rays and skates).