Piranha Classifications, why are they such a mess today?

By Frank Magallanes, OPEFE

FROM FRANK MAGALLANES

I dedicate this page to my mentors and friends, Fink, Machado and Jégu. Without them OPEFE would be just another web site. My remarks are my opinions only and not anyone else's. I highly respect the named authors for their contribution to piranha science and its ever changing ways.

INTRODUCTION

Historical authors used to explore just small parts of South America and wrote about the creatures they would find there. Many animals were described and written about. These writings were embellishment of piranha lore and behavior that largely ignored what the fish actually looked like. Many accounts were written having to do with piranhas, without the writer actually checking to see if the reports were true. A scientific name was added and a drawing made of the fish (prior to photography). This portrait of the species would then be colored in by artists at a later date based on what the collector had written. Because of this, species of piranha were described in many different species names, even though it was just one type they were looking at. They did not distinguish juveniles from adults or breeding adults furthering adding to the species names and confusion. Also many specimens were collected that fit only in the jars they were carrying, often small containers. They rarely brought back large specimens for fear of spoilage during transit. Some specimens were stuffed and dried making them appear odd to future systemist. Records of piranha are also a mess, many of the specimens of which the name was based on were poorly labeled. In most cases no locality or collection data was given. In some cases, the label disintegrated. In worst cases, the holotypes disappeared. All that remained was a colored drawing or a photograph when it became fashionable to use that technique.

Carl Eigenmann (1905), an American scientist, was the first author to attempt to clear up the piranha classification mess. His review of the generic ranking helped establish the genus Pygocentrus as having one species P. piraya. Then he erected Pristobrycon for the more innocuous species, following by Pygopristis which contained one historical species, P. denticulatus (= denticulata).  However, even Eigenmann had some errors in classifications. The problem being that under the International Rules of Nomenclature, Eigenmann could not change or delete names. He had to work with what he had and only place dubious species as synonyms if appropriate. For more on this read the genus Pygocentrus.

John Norman (1929), a British scientist, further exacerbated the problem when he reclassified the species into one generic ranking, Serrasalmus. He not only lumped all the species of piranha into this genus (save one, Pygopristis), he also spelled the subfamily wrong. Then the French scientist, Jacques Géry, then revised the genus into subgenera rankings, erected old historical species names and grouped them arbitrarily based on some flawed characters. He also limited the number of species to just a few in the entire continent! While there were many other authors between these 3 gentlemen, these three remained the key scientists that reviewed piranhas, until a young man named Antonio Machado-Allison and William L. Fink entered the arena. These two scientists were in a manner of speaking, in a friendly competition with a French scientist named  Michel Jégu in describing species.

Antonio Machado-Allison, a Venezuela scientist,  in his thesis, authored 4 generic rankings; Pygocentrus, Pristobrycon, Serrasalmus and Pygopristis.

William L. Fink, an American scientist, revised the genus Pygocentrus effectively removing 17 species from the list, and placing just 3 species; piraya, nattereri and cariba. He erected Serrasalmus to hold many of the historical species names, rhombeus, sanchezi, spilopleura, etc. In Pristobrycon, he erected further splitting of the species into its proper species placement (striolatus, calmoni, etc.).  Both the above authors use the Phylogenetic method of classifying species. Based on common evolutionary descent (recency of common ancestry). Now the preferred method because it has predictive value. Based on shared derived characteristics. Phylogeny = the evolutionary history of a group of organisms. Modern phylogeny investigations are based on molecular data, primarily nucleotide sequences. Basically, the more closely related two organisms are, the more nucleotide sequences (genes) they will have in common. The author Jégu follows Géry but does use some of the phylogeny methods and morphometrics. Géry classifications were not built with the Phylogenetic philosophy in mind. 

Michel Jégu, has been revising and rehabilitating species. Some old names have been resurrected, such as S. maculatus. Whether or not his rehabilitations will stand the test of time remains to be seen. Mostly certainly, piranhas are clearly misunderstood, not only by science, but hobbyists and the public-at-large. I can say with some authority, piranha classifications didn't really take off until the last century when piranhas once again became subject to revision. This can be traced to Antonio Machado-Allison (1982) in his thesis and further work (1986) exploring phylogenetics. To completely get a sense of what scientist today have to deal with, all it takes is visiting some of the OPEFE geographical species pages. The types of rehabilitation and revisionism is huge and a project that has only been slightly scratched at the surface. While South America has been vastly explored, there still remain pockets of water that still may hold additional new species of piranha. 

In the meantime visit S. rhombeus and its geo-variations. These are all S. rhombeus, yet they form a complex group. Now look at P. nattereri geo-variations. And try to wrap in your mind  what you just saw in S. rhombeus with these forms.

Now take S. eigenmanni, another widespread species. That species also comes in some different colors and growth differences. It still does not make it a different species. Old historical authors used to classify fish the same way that today's hobbyists look at the species in a narrow picture of South America. The rivers hold a diversity of life that largely remains unanswered. That's why piranha classifications today are a mess, but getting better as more is reviewed and learned. 

You have to look at the big picture not just one locality and not just assign scientific names as it was once historically done.

USE YOUR BACKSPACE TO RETURN OR CLICK HERE TO RETURN RESEARCH PAGE

TO RETURN HOME CLICK HERE.

The OPEFE web site and its contents; is disclaimed for purposes of Zoological Nomenclature in accordance with the International Code of Zoological Nomenclature, Fourth Edition, Article 8.3 and 8.4. No new names or nomenclature changes are available from statements at this web site.

Copyright© 1994-2009 Oregon Piranha Exotic Fish Exhibit (The OPEFE fish exhibit is permanently CLOSED as of 2000) Sutherlin, Oregon. Information posted on this web site is archival data on fish scientific classifications and other information. DISCLAIMER: The copyrighted material may not be used for any purpose other than private study, scholarship or research. Cited information requires credit and this link www.opefe.com. All rights reserved. All images shown  (unless otherwise noted) is property of OPEFE. 

UPDATED: 07/10/2009