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Hyphessobrycon

Hyphessobrycon is a genus of freshwater ray-finned fish belonging to the family Acestrorhamphidae, the American characins. These species are among the fishes known as tetras. The genus is distributed in the Neotropical realm from southern Mexico to Río de la Plata in Argentina. Many of these species are native to South America; about six species are from Central America, and a single species, H. compressus, is from southern Mexico.

All small fishes, the Hyphessobrycon tetras reach maximum overall lengths of about . Great anatomical diversity exists in this genus. They are generally of typical characin shape, but vary greatly in coloration and body form, many species having distinctive black, red, or yellow markings on their bodies and fins. These species are generally omnivorous, feeding predominantly on small crustaceans, insects, annelid worms, and zooplankton. When spawning, they scatter their eggs and guard neither eggs nor young.

Taxonomy

Hyphessobrycon was first proposed as a monospecific genus in 1908 by the American entomologist and ichthyologist Marion Durbin, with its type species designated as Hemigrammus compressus, a species described in 1904 by Seth Eugene Meek, with its type locality given as the Río Papaloapam basin at El Hule, Oaxaca, Mexico. The genus Hyphessobrycon is the type genus of the subfamily Hyphessobryconinae, within the American characin family Acestrorhamphidae. This family is classified within the suborder Characoidei of the order Characiformes.

This large genus of characins includes nearly 150 species. The systematics of Hyphessobrycon are still largely unresolved. Six groups within this genus have been recognized based on color patterns alone. With no phylogenetic analysis of this genus, species are placed into this genus as anatomically defined by Carl H. Eigenmann in 1917. By this definition, Hyphessobrycon is identified by the presence of an adipose fin, incomplete lateral line, two tooth series in the premaxilla, with the teeth of the external series continuous in a single series, teeth not strictly conical, preventral scales arranged in more than one row and lack of scales in the caudal fin. The characteristic of extension of scales onto the caudal fin that differentiates this genus from Hemigrammus is not satisfactory, as it occurs in intermediate conditions.

This genus, as traditionally defined, was not monophyletic. A monophyletic group within Hyphessobrycon has been hypothesized, termed the rosy tetra clade; this group is based upon coloration pattern and the shape of dorsal and anal fins of males. In 2024, this clade was split from Hyphessobrycon as the revived genus Megalamphodus, and was found to belong to a different tetra subfamily. Recognition of monophyletic groups among Hyphessobrycon species is complicated by the difficulty in finding characters useful for hypothesis of relationships among the species. Traditional characters used to identify Hyphessobrycon are phylogenetically unreliable.

Etymology

The generic name, Hyphessobrycon, is of slightly uncertain origin. The second part derives from the Greek βρύκω (to bite); the first derives from an ostensible Greek hyphesson, which may be an error for υπελάσσων (slightly smaller).

Relationship to humans

Most of the species in the genus have not been rated by the IUCN Red List as Threatened, but many species have small distributions and at least three, H. flammeus, H. coelestinus and H. duragenys, are classified as endangered. One, H. taurocephalus, is categorised as possibly extinct. This species only occurs in a few rivers and streams in Santa Catarina and Paraná states of Brazil.

Many Hyphessobrycon species are popular aquarium fish, and some, including H. flammeus, are bred in large numbers in captivity.

Species

Hyphessobrycon contains the following valid species:

References