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Does Tetra have anything to do witht eh Greek Prefix of 4? That would mean Neon 4 or Lemon 4. Maybe a magical Number? Any Curious minds?

Chris

In a sense, yes, but it' actually a little more complicated than that.

Once upon a time, there was a Genus of fishes called Tetragonopterus. This was derived from Greek as follows: tetra (four), gonia (angle), pteron (wing or fin). The name translates thus as 'four angled fin'. This name was chosen because the fishes in that Genus had an anal fin that was roughly a parallelogram in shape, which is a shape with four angles (tetragon - by way of analogy with pentagon, hexagon etc).

The Genus is still valid, but many of the fishes that were originally classified in that Genus have since been moved elsewhere - an example being Astyanax maximus. Another fish that was originally classified in this once-large Genus was Hemigrammus belotti, a nice small (2.6 cm) Characin that has a golden yellow metallic stripe along the body and an upper half of the iris of the eye that is bright red. However, as taxonomy is still very much a living discipline, the Family Characidae was subject to major revision since the days of the old Innes book, and Tetragonopterus now contains but three species, as opposed to the 121 species originally lumped into that Genus. Many of these fishes were moved to Astyanax, several others ended up in Moenkhausia (with Moenkhausia oligolepis, labelled the "Glass Tetra" on Fishbase being a prime example, along with Moenkhausia sanctaefilomenae, the Red Eye Tetra) and others ended up in Hemigrammus.

If you look at the anal fin of many popular aquarium Characins, you'll find that the shape of the fin is, in many cases, a variation on the same theme - a sort of distorted parallelogram. Admittedly a certain amount of licence was used in the creation of the name, because the fins in question usually have at least one curved edge, but the basic principle remains in place for those wishing to delve into the nuts and bolts of the taxonomy of these fishes.

The Genus Tetragonopterus became the 'type Genus' for a Subfamily of Characins called the Tetragonopterinae, to which the three members of this Genus as constituted in modern times belongs. It is the 'type Genus' because the Genus was used as the basis for describing the characteristics that members of the same Subfamily should possess, in much the same way as a 'type species' within a Genus is used to define the characteristics that other future members of the same Genus should possess in order to be a member. so, for example, in the world of Corydoras, the type species is corydoras punctatus, as that fish was used to define the characteristics that all other members of Corydoras should possess in order to be valid members of the Genus, and in turn, the Genus Corydoras was used as the type Genus to define the characteristics that members of the Subfamily Corydoradinae should possess.

While Tetragonpterus and the Subfamily Tetragonopterinae are still valid taxonomic entities, the problem we now have, after the upheavals that the Family Characidae has undergone, with it being split into several related Families such as the Lebiasinidae (Pencil Fishes) and the Gasteropelecidae (Hatchet Fishes), is that fishes moved out of the Genus Tetragonopterus into other Genera have an uncertain Subfamilial status - they are, to use the taxonomic jargon, "incertae sedis", which means that their Subfamilial placement has yet to be ratified.

Expect to see MUCH more fun and frolics vis-a-vis Characoid taxonomy in the years to come.


Panda Catfish fan and keeper/breeder since Christmas 2002