Serrulatus Group

Since the creation of the genera Serrasalmus and Pristobrycon there have been numerous historical taxonomic problems with the species placed within it. Unlike Pygocentrus and Pygopristis where the number of species appears to be fixed and set as of 2011.

Presently there are 28 described species of Serrasalmus, many of which are morphologically similar. Historical authorities originally placed the piranhas as a group in genus Pygocentrus. Then Norman 1929, lumped them all (except Pygopristis denticulata) in genus Serrasalmus. Jacques Géry, the French Ichthyologist further delineated the piranhas into sub-generic ranking. In so doing, Géry recognized only 12 species of piranha in the entire continent of South America (Machado-Allison et al., 1996).

Some species collected from regions are assigned a scientific name without closer examination of the type. This can further present problems on what is actually being collected and catalogued. A few examples are shown below.

Historical authorities placed Serrasalmo aureus as a synonym to S. eigenmanni, but today Pristobrycon aureus is considered a valid species under genus Pristobrycon. Pristobrycon aureus (Spix & Agassiz 1829), though not a member of the humeralis group, also fits closely in appearance to this group. However, there are no types known of this species, only a plate image (see below). It was originally proposed as a Serrasalmo and found in Lower portions of tributaries of lower Amazon River and Guyana rivers: Brazil and Guyana. Today Serrasalmo aureus is valid as Pristobrycon aureus (Spix & Agassiz 1829) (Jégu in Reis et al. 2003).

A few of the species placed within Serrasalmus and Pristobrycon are questionable because no types exist. In the case of Pristobrycon, this genus was erected by Carl Eigenmann 1915 and he used Pristobrycon calmoni as its type. The problem centers on the placement of P. striolatus which does not have ectopterygoid (palatine teeth) or a preanal spine in this genus. It remains unknown why Eigenmann placed this species in the genus. P. careospinus and P. maculipinnis also present problems because like striolatus, these two also lack these key features. The other members of genus Pristobrycon have the key features required of the genus. Freeman and colleagues (2007) have suggested creating a new genus with P. striolatus as the type. So far, this has not gone further than a suggestion. DNA is still in its infancy when it comes to piranhas and it might be years before more is known and decided by future authorities should a new genus be erected as suggested. The rest of the problem seems to be lack of better identifications and specimens.

Serrasalmus scapularis (Günther, A.. 1864) was described from the Essequibo River, Guyana. Géry, 1972 placed it as a synonym of Serrasalmus serrulatus (Valenciennes 1849), but a valid subspecies. This error in study created further taxonomic problems. S. scapularis is presently a synonym to Pristobrycon striolatus. Pristobrycon striolatus is found Amazon and Orinoco River basins and northern and eastern Guiana Shield rivers: Brazil, French Guiana, Guyana, Suriname and Venezuela.

Described below are several species reviewed along with their distribution. Most overlap their respective ranges. All these species present morphological similarities:

Serrasalmus eigenmanni (Norman, J. R.,1929), no types exist and is considered unique. These species has been bounced back and forth between Pristobrycon (Jégu & Santos 2001) and a Serrasalmus (Géry 1972, Machado-Allison 2002, Jégu in Reis et al. 2003, and Machado-Allison et al. 2009). Today this species is valid as Serrasalmus eigenmanni Norman 1929. Distributed over the Amazon River basin and northern and eastern Guiana Shield rivers: Brazil, French Guiana, Guyana, Suriname and Venezuela.

The species is difficult to identify in the field. Samples of S. eigenmanni resembles both S. striolatus and S. hollandi in preservative. However, neither species is found in Peru to my knowledge. Jegu, 1991 suggested that S. eigenmanni could qualify as a twin and synonym to S. hollandi ( 5 & 6, below).

Serrasalmus hollandi, Eigenmann, C. H.. 1915 was described from the Rio Guaporé at Maciél, Brazil. The Holotype is unique (FMNH 56978/ex CM5792). This species presents taxonomic problems on its identity. Jégu & Santos 2001 placed it valid as Serrasalmus hollandi Eigenmann 1915, Lasso et al., 2001, Jegu in Reis et al., 2003, Machado-Allison et al., 2009, Hubert & Renno 2010 concurred. The distribution of the species questionable in its range. Presently it is found in the Madeira River basin and ? Guyana rivers: Brazil and Guiana (?).

S. humeralis (Valenciennes, A., in Cuvier & Valenciennes 1850) is problematic since its type is unique (a radiograph image). The image below for example are specimens catalogued (CAS 71217) as Serrasalmus humeralis. Previous historical authorities have placed different synonym's under this species. Most of which either had a tail band or no humeral blemish. The only known image of S. humeralis is a colored plate drawing by Castelnau 1850 (see 9 below). According to current research, this species is found; Amazonas, Brazil (evidently in error for Araguay River, Tocantins basin). Gery, 1972 considered it valid as Serrasalmus humeralis. Ortega & Vari 1986, Géry et al. 1991, Planquette et al. 1996, Jégu in Reis et al. 2003 all concur it is valid as Serrasalmus humeralis Valenciennes 1850. Distribution range is; Amazon River basin: Bolivia, Brazil and Peru. As a personal note; I have only found images purported to be S. humeralis but incredibly similar to Serrasalmus manueli (Fernández-Yépez, A., & Ramírez, M. V.,1967). Included in my discovery are a couple photos identified by Nicholas Hubert, IRD France, as S. humeralis VIEW. As can be seen, no humeral blemish. More on this interesting species and its problems can be read here. In Zoological record, Volume 101, Issue 14, Part 3 - Issue 20, Part 3, page 83... The key to subgenera, S. ( Pristobrycon) serrulatus, S. (Serrasalmus) humeralis holotypes re-described, Géry (13). In Jegu,1991 it states...

In different occasions, we were able to examine topotypes of Serrasalmus eigenmanni Norman (Guyana), the type of S. humeralis and exemplary topotypes of the Araguia, and many examplary Amazonia of the type, in particular basin of the Rio Madeira and Xingu. We were not able to find any differentiating character allowing separating eigenmanni from humeralis, defined by the type of the Araguaia (well figured by Castelnau, that does not show no marginal band to the tail one) and by the samples collected since in the Araguay (cf. Géry, 1979 pls. VII and VIII). The synonym of S. eigenmanni is therefore more probable. During a recent expedition (7.1989) in the Arataye, flow Approuague, and after the compilation of this work, MM. Boujard, Meunier and Easter discovered a sympatric form of S. humeralis which one could qualify as a twin one if it were not recognizable (in the field only) to its different flows. Examined in the laboratory, the three harvested specimens revealed themselves effectively very similar by the morphometric characters, but they seemed a little more lengthened and could be placed, by way of hypothesis, to S. hollandi. It is necessary to await a more abundant collection and specific knowledge of the live coloration thanks in part to. Also, this form is not fully understood in the account of the types of the Oyapock and Approuague.

N.B. - Serrasalmus rhombeus was not collected or in the Oyapock or in the Approuague: Its ecological niche maybe occupied by S. humeralis. Variance of the same order were noted in certain coastal rivers of Guyana (to see conclusion), and we inspire to go back over the description and the geographic distribution of these types in a future work (Jegu, 1991).

Serrasalmus nalseni, Fernández-Yépez, A.,1969 is described from the Río Uracoa, 9°10'N, 62°27'W, Estado Monagas, Venezuela. The original Holotype (MACLPI 68697) is lost. However a neotype has been erected (MBUCV-V-35389). The species is valid and a new re-description was completed (Machado-Allison et al. 2009).

It is currently valid as Serrasalmus nalseni Fernández-Yépez 1969. Its distribution is Orinoco River basin, Venezuela.

S. serrulatus geographical range maybe synonymous with any one of the species discussed above or even a totally different species. In the present scientific literature S. serrulatus morphology is similar to it's congeners; S. eigenmanni, S. hollandi, S. humeralis and S. nalseni.

Serrasalmus serrulatus, has historically been difficult to delineate within populations and to positively identify it. The problem rests with the growth pattern which is between a Serrasalmus and a Pristobrycon. S. gouldingi also slightly appears to have the same issues of growth pattern. The species gouldingi is more Pristobrycon-like. And there are questions on what its relationship is to S. manueli.

Valenciennes (A.) in Cuvier & Valenciennes 1850 originally placed serrulatus as a Pygopristis. In Fowler (1911) Proceedings of the Academy of Natural Sciences of Philadelphia, Volume 63 (page 428-432) mentions problems distinguishing it from Serrasalmo coccogenis ( = Pristobrycon calmoni ). The authority thought it... may be identical, though the writer does not mention any dark blotches on the side of the body, and yet he does say there are some traces of the dark shoulder-spot. Géry 1972:221, Ortega & Vari 1986:9, Jégu in Reis et al. 2003:192, López et al. 2003:32, Menni 2004:78) revised and placed serrulatus in a different genus (Serrasalmus). Presently, Serrasalmus serrulatus is a valid species with its distribution questionable in some localities; Amazon River basin and ? Essequibo River basin: Amazon (?), Brazil, Guyana (?) and Peru; Argentina.

During rest or stressful periods (such as capture) Serrasalmus serrulatus takes on additional markings on the fin, namely the caudal fin which can show a faint caudal band on the edge. During its growth the shape of the body changes from Serrasalmus-like to Pristobrycon-like along with its body markings. These changes are what has confused authorities in the past in naming piranha fish from South American rivers. As one can ponder, all these species overlap each others range and appear similar.

Plate Image S. serrulatus, Castelnau

Holotype

Serrasalmus serrulatus

j. Gery, 1963 Fig. 2. Type de S. (Pristobrycon) serrulatus, 121 mm sl.

Photo by Michael Goulding

Serrasalmus serrulatus

Field sample S. serrulatus

Pexes de lagos do Medio Rio Solimoes

Serrasalmus serrulatus

Collected rio Nanay, Peru

David M. Schleser

Serrasalmus serrulatus types on the right of screen

Listed as S. serrulatus

Essequibo River, Guyana

Internet fishing photos.

Photographer unknown.

Need name for credit.

Listed as S. serrulatus

Essequibo River, Guyana

Internet fishing photos.

Photographer unknown.

Need name for credit.

This fish was collected in Venezuela. Its a young specimen that somewhat resembles S. eigenmanni. However, I remain uncertain it is that species or one that needs to be described. David Schleser thinks the species might represent S. humeralis. I really don't know, but it might be. But no humeral spot is present in both forms (adult and juvenile).

Collected rio Negro and may represent an adult form of the species on the left (C).

Species on right of screen are unknown species unable to correctly place.

This Pristobrycon type is collected same area as 23.

Pristobrycon-type collected and photographed by David M. Schleser & George Fear. According Dave, this fish was collected at the Tachshacurary river (a blackwater stream) just upstream from the village of Tacshacuraray which is located where the Tachsahcuraray empties into the Napo, Peru. Very certain it might be S. serrulatus. However, N. Hubert and collegues (2006) states this species was misidentified as S. spilopleura by Jegu and dos Santos (2001). The species was determined to be S. eigenmanni instead.

Note midline terminal band

Collected in rio Nanay, Peru (1988) by David M. Schleser. The species resembles P. striolatus a species not recorded in Peru at the present time. This may make this species a first! M. Jégu identified a similar species (Brazil) but called it P. calmoni (see image and accompanying diagram under that species name). Some years ago, David had sent me a slide of this fish and I was of the opinion it might have been a human released specimen as he did not catch anymore since then.

This fish was collected from the rio Negro. It remains undescribed and may be either S. serrulatus or S. eigenmanni.

Serrasalmus species (humeralis?) from the Aruana (rio Vermelho)

Note the V type caudal

Serrasalmus species depicting growth changes and coloration. Aquarium specimen