I just love it when members give me openings like essjay did here
[post #6]. I know not everyone is interested in taxonomy, but there are some who are and the rest can ignore this post. It is all about the names of the four "neon" tetras.
The first species discovered and described was the common Neon Tetra. This species was described by Dr. George S. Meyers in 1936 and named
Hyphessobrycon innesi. The species epithet honours the American aquarist William T. Innes, who, among many other things, authored and published the book
Exotic Aquarium Fishes which appeared in 1935 and has gone through 19 editions [to date]. The genus
Hyphessobrycon--the name derives from the Greek
hyphesson [believed to mean "slightly smaller"] and
brycon [=to bite]--was erected by C.H. Durbin in 1908 and presently contains more than 100 described species. [To avoid cluttering the "neon" saga, I will put related comments on the genus below.]
The cardinal tetra (as it came to be known) was the next "neon" discovered, in the early 1950's; specimens were examined and described by two independent prominent ichthyologists in the United States with the results published in two journals. L.P. Schultz published in the March-April 1956 issue of
Tropical Fish Hobbyist and named the fish
Cheirodon axelrodi, while Dr. George S. Meyers and Dr. Stanley Weitzman published in the
University of Stanford Ichthyological Bulletin and named the fish
Hyphessobrycon cardinalis. It was determined that the Schultz article had been published on February 20, 1956, while the Meyers & Weitzman article was published the day following. Under the rules of the International Code of Zoological Nomenclature, priority must go to the first published name; the fish was therefore officially named
Cheirodon axelrodi. The species epithet honours Dr. Herbert R. Axelrod, although this distinguished scientist had no direct connection with the discovery of this fish.
In 1960, Dr. Jacques Gery erected the genus
Paracheirodon for the type species
P. innesi (Neon Tetra) and Gery also moved the Cardinal Tetra into the new genus. The name
Paracheirodon derives from the Greek; the older genus name
Cheirodon derives from
cheir [= hand] and
odon [= teeth], and the prefix
para means "beside" to distinguish
Paracheirodon from
Cheirodon.
Three years later, Gery--who was arguably the most respected and knowledgeable authority on the characidae during the 20th century--described the third "neon" that was discovered in 1962 from individuals that were mixed in with cardinal tetras. The original description by Gery (1963) placed it in the genus
Hyphessobrycon as
H. simulans; the species epithet
simulans is Latin for "similar" and references the colour pattern similarity to the neon tetra. Fink & Weitzman (1977) placed it in the genus
Paracheirodon with the two other neon species, and subsequent DNA analysis has confirmed this placement. The Cardinal Tetra and the Green/False Neon have 26 and 25 chromosomes respectively, while the common neon tetra has 16.
I mentioned four "neon" tetra. This species was discovered by Heiko Bleher in 2006 and has yet to be described and named. According to preliminary DNA studies, this new species is very close to the true Neon Tetra, whereas the Cardinal Tetra is genetically closer to the Green/False Neon Tetra. Photos of Heiko's collected fish (none of which lived through the journey home unfortunately) suggest this relationship in the close similarity of colour pattern.
Additional comments on Hyphessobrycon:
The classification is deemed
incertae sedis, a Latin term meaning "of uncertain placement" that is applied by taxonomists and biologists when the classification is known to be unreliable or questionable.
Hyphessobrycon was formerly considered within the subfamily Tetragonopterinae, but Javonillo et.al. (2010) suggest that this subfamily should be restricted to species within the genus
Tetragonopterus since they do not share physiological characteristics with species in other genera such as
Hyphessobrycon.
Authors that have recently studied the systematics of the genus
Hyphessobrycon have unanimously pointed out that the group is not well defined and its monophyly is yet uncertain. [A monophyletic genus is one wherein the species share a common ancestor, thus linking them together physiologically.] Mirande (2009) for example has proposed several revisions to the family Characidae based upon phylogenetic diagnosis. Some genera have been moved to a new subfamily, while others are now (temporarily) assigned to a specific clade within the family pending further study. The recognition of groups of species [clades] within
Hyphessobrycon is based primarily on similarities of color patterns; an hypothesis of its intra-relationships is currently unavailable, except for the rosy tetra clade proposed as monophyletic by Weitzman & Palmer (1997).
Hyphessobrycon has until recently been differentiated from
Hemigrammus solely on the basis of the fish in
Hemigrammus possessing a scaled caudal fin; this however is now known to be unreliable, since it occurs in intermediate conditions (de Lucina, 2003). Both genera are polyphyletic [meaning, the species are derived from more than one common evolutionary ancestor or ancestral group and therefore not suitable for placing in the same taxon. Given the number of species, this work will take some time before it is resolved.