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Rio Paraguay - basin Paraña or Piranha Serrasalmo ternetzi Steindachner 1908
FROM FRANK MAGALLANES
Most hobbyists collecting piranhas for the home aquarium do not understand that in order for a species name to be valid, sufficient examples must be available and compared with a holotype. This method is to ensure the species is a valid distinctive species. S. ternetzi was unique and no further examples could be found to justify its placement other than being a synonym of P. nattereri. The species name "nattereri" is older and under The International Rules of Zoological Nomenclature requires when a new species is discovered and described the name of the designated species must be compared with all other valid species to ensure it is indeed a new species.
Fink (1993) places southern populations from that area under the species name P. nattereri which is appropriate for these highly variable populations.
Some piranhas such as my Bent-nosed Piranha, FIG.1 AND FIG.2, P. nattereri, are genetic aberrations but not unreasonable to assume that wild piranhas also create such offspring adding variety to the gene pool. These are then captured by collectors who almost immediately think they have found a new species if there are more than a few when this are fished out. In the fish above, not only is the body more discoid and robust, but it also features an unusual anal fin that begins in-line in front of the adipose fin, the distance from the dorsal to the adipose is very short. I have been fortunate to keep many of these defects in the aquarium over the years. Some are so blunt-headed that no concavity appears over the eyes and the lower jaw can be extremely thick as well. See COMPARISON photo between a red-bellied and a yellow-bellied piranha.
The name Yellow Emperor, Yellow Belly, and Ternetzi is being applied by hobbyist for the yellow-bellied piranhas found in the southern portion of South America. In this photo one can see the high variability of head shapes from a single populations of red-bellied piranhas. Some even have larger lower jaws. Other's smaller depending on age and body shape. Hobbyist generally use their small samples of piranhas in the aquarium to formulate opinions and answers to the question; is there really an S. ternetzi? The answer itself must explored by what is known about this unique species. Then those characters in the description must be followed with sufficient quantities of specimens to reach a conclusion. Hobbyist are not able to secure sufficient examples of P. nattereri in their home aquarium because wholesale collectors do not import from all the areas of South America. Few examples of red-bellies are imported, most are from Argentina and Peru. Majority of the time, due to cost, home grown P. nattereri are offered for sale and since these are generally from the same location with no locality data, little variance is detected particularly to head shape when comparing to the wild caught. Hobbyist use vague terms when trying to compare their piranhas, such as; behavior, temperament, mood, etc., etc,. etc. They forget their fish is living in an unnatural environment which is the aquarium, so the behavior there is dictated by how the hobbyist provides the fishes living conditions. This may include an aquarium too small or overstocked with species (either same or different), water ( ie: pH), and temperature conditions are just a few considerations.
HISTORICAL SCIENCE
The holotype of S. ternetzi is lost to science, and the description itself is broad scoped (except for the unique anal fin), the bionomen nattereri has precedence over the much younger name ternetzi for the locality of where the original holotype was found (see below for more detailed information). If one were to follow Géry (1987) placement of the scientific name; P. nattereri would be appropriate for these southern species while S. altus (Pygocentrus) would be placed for the Amazonian piranhas and S. ternetzi would then become its junior synonym.
Pygocentrus ternetzi, was described by Steindachner (1908) from a single specimen found in the Rio Paraquay and was compared with P. piraya. Steindachner clearly wanted to differentiate the southern populations of Pygocentrus which were not P. piraya (restricted to the Rio São Francisco). However Steindachner did not compare nor mention P. nattereri in this comparison. The unique type specimen of S. ternetzi, now lost, apparently had a damaged anal fin, because it was supposed to have but 12 rays and have its origin on a vertical midway between the dorsal and adipose fins; neither attributes have been found in any other specimens of serrasalmin, and Eigenmann's supposition, supported by Norman, that the specimen was damaged, was reasonable.
In his key, Norman differentiated S. ternetzi from
P. nattereri using three specimens (220-250 mm SL) and 40 specimens
(75-270 mm SL), respectively based on the the anterior profile (strongly
arched vs moderately arched) and a few other features. With the exception of
two specimens from "Rio Plata," the specimens Norman called S.
nattereri were from the Amazon or Guyana. In testing slopes and
intercepts of regressions of these features against SL, no significant
differences between southern and Amazonian populations in these features (as
measured herein) were detected.
Fink, in order to determine if there were any potential discriminators, measured snout length using a sub-sample of both populations of over 60 specimens of equal size and he found no statistical differences in slopes or intercepts of regression of snout length on SL. Distance between the nares being less than or larger than the eye, used by Géry et al. (1987). Géry used a comparison that conflates head width and eye size, one showing positive allometry and one negative allometry (interorbital width). Fink found no differences between southern and Amazonian populations in interorbital width or eye size in the specimens Fink used (determined by slopes and intercepts of each measured in a linear regression on SL). The prepelvic counts were also compared and the numbers garnered from that do not support a hypothesis for independent evolution in those groups. Géry suggested that the name S. altus (Gill 1871) be applied to Amazonian species while S. ternetzi (Steindachner 1908) be used for Paraguayan populations to differentiate them. The problem is, both these names are younger than P. nattereri. Both S. altus and S. ternetzi remain available for upper Amazon and Paraguay populations, respectively should they be found diagnosable (Fink 1993).
In 1997, Fink and Zelditch reviewed the description and all available citations pertaining to S. ternetzi. They could not find reliable characters to distinguish between the two, and consider S. ternetzi as a nonlinear cline (varying body shape) of P. nattereri.
THE SCIENTISTS THAT CLASSIFIED THEM
WHERE HOBBYISTS FIRST LEARNED THE SCIENTIFIC NAME
GEORGE S. MYERS, The Piranha Book (1972) pg 30-34 Serrasalmus ternetzi Myers described four (4) species of Serrasalmus dangerous to man, then listed them on pages 31-35. This list included the Schomburgk (1841) S. niger. Myers also used the common body description (for that time period) of these 4 species having vs. the inoffensive ones... "the broader and much blunter head, the much heavier and apparently shorter lower jaw, and the thicker (less compressed) body" to compare with pirambebas. He also stated, "Two of these species, S. piraya of the Rio São Francisco and S. ternetzi of the Rio Paraguay, have a muzzle so blunt that there is only a very slight concavity in the profile above the eyes, if any at all. S. nattereri of the Orinoco, Amazon, and Paraguay-Paraña systems normally has a slight concavity in the profile at this place, while S. niger of the Guiana region has a deeper concavity and narrower head, thus approaching the appearance of the more innocuous forms."
He also stated; "In size these dangerous species appear to differ from each other," ...."Two of the forms appear to grow larger than the others. Serrasalmus piraya"....."commonly reaches at least 20 United States inches (51 cm.) in total length, and is the largest and most dangerous species. S. niger of Guiana reaches at least 14 ½ inches since the type specimen in the Berlin Museum is that long (365 mm). The largest measured example on record known positively to be S. nattereri is the 27-cm. (10½-inch) example in the British Museum. S. ternetzi of the Rio Paraguay reaches almost 10 inches. Probably all of these four species sometimes grow from 2 to 4 inches longer than the above records would indicate."
Myers went on to describe "S. ternetzi Steindachner" as follows; "is a very blunt-headed species, agreeing in this with preceding" (ie; S. piraya), "known only from the Rio Paraguay in northern Argentina, Paraguay, and presumably in southwestern Brazil and the Rio Paraña. Probably it is common because natives do not distinguish it from the common species" (meaning; Pygocentrus nattereri). "It differs from the following species (i.e. S. nattereri) by the blunter head the shorter distance between the dorsal fin and the adipose. The largest recorded example is just under 10 inches in total length." Myer's made no mention of the "short" 15 rayed (soft spines) anal fin, which is unique to Serrasalmo ternetzi (Eigenmann, 1915 et al). All Pygocentrus species have more than 30 anal fin rays. Myer's further erred by stating the species was from northern Argentina.
Interestingly, when he went on to describe S. nattereri KNER, he said this; "Occasional examples" (meaning S. nattereri) "have fairly well developed rays in the adipose fin." Who knows what he was looking at when he wrote that, since S. nattereri does not have a rayed adipose fin at any time, S. piraya does! He further added; "The fresh-caught fish, especially males at or near the breeding season, are very bright, for the sides show much metallic blue and the underside of the head and the belly are smeared with brilliant red. Because of this the fish is often called piranha vermelha (see above)." What I find interesting here and Fink et al. have already determined by samples of populations from both regions, is what Myers says next; "Presumably the same color is found in the two preceding species" (ie., S. piraya and S. ternetzi). This portion written is largely ignored or overlooked by hobbyist when you try to convince them of the S. ternetzi description errors found in the book and on the internet. Hobbyist assume that "yellow" is the only belly color this form has! The species S. ternetzi if it actually existed would have been from Paraguay.
This yellow-form has been successfully bred in captivity (live home bred example) by a hobbyist in Ohio for quite a few years. The bright yellow belly distinguishes this "home grown P. nattereri" from the other commonly bred red piranhas found in pet stores.
Please read my seed feeding experiment. These piranhas started out with red-bellies later began developing a yellowish-gold tint after ingesting large quantities of seeds as their only food source.
The Paraguayan variety do lack the red found in the eye in some areas, but in science eye color is just one characteristic and cannot be held as a sole indicator of species identification nor head, color or body shape. I hope this finally puts to rest the question, is S. ternetzi a valid species. You cannot simply stick a name on a fish and expect it to have meaning without knowing all the parameters of why a scientific name is placed. And there will always be a few that will argue this point based on their limited knowledge and understanding of scientific methods of placing fish. Some pet stores sell Ternetzi as an Argentina species, but as written above the species was not described from that region. It was Descalvados on the Paraguay. P. nattereri species exhibit the wide range of belly color in that region from yellow-red-orange. In South America all piranhas in the southern portion call these P. nattereri "ternetzi" by fishermen and collectors. This is because of the published Piranha Book by G. S. Myers (1972). That name stuck among those people, but in science, it has no value and not recognized as valid.
By the way, the name Ternetzi derives from Carl Ternetz, a naturalist and this scientific name was erected to honor him
CONTRIBUTOR/ADVISOR
REFERENCES
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