Pimelodus heraldoi Azpelicueta, 2001, a junior synonym of Pimelodus microstoma Steindachner, 1877 (Siluriformes: Pimelodidae)

Pimelodus heraldoi Azpelicueta, 2001, a junior synonym of Pimelodus microstoma Steindachner, 1877 (Siluriformes: Pimelodidae)

Frank Raynner V. Ribeiro^I; Carlos Alberto S. Lucena^II

^IPrograma de Coleções e Acervos Científicos, Instituto Nacional de Pesquisas da Amazônia. Caixa Postal 478, 69011-970 Manaus, AM, Brazil. [e-mail]

^IISetor de Peixes, Museu de Ciências e Tecnologia, Pontifícia Universidade Católica do Rio Grande do Sul. Av. Ipiranga 6681, 90619-900 Porto Alegre, RS, Brazil. [e-mail]

ABSTRACT

The examination of the holotype and 61 of the 64 paratypes of Pimelodus heraldoi, syntypes of P. microstoma and additional specimens from the upper rio Paraná showed that the former species is a junior synonym of the latter. Both species were originally described from the rio Mogi-Guaçu, upper rio Paraná.

Key words: upper rio Paraná, Taxonomy, Fishes, Catfish.

RESUMO

O exame do holótipo e 61 dos 64 parátipos de Pimelodus heraldoi, dos síntipos de P. microstoma e de exemplares adicionais do alto rio Paraná, mostrou que a primeira espécie é um sinônimo júnior da segunda. Ambas foram descritas originalmente do rio Mogi-Guaçu, rio Paraná superior.

Introduction

The catfish genus Pimelodus LaCépède, 1803, with 33 valid species and a cis- and trans- Andean distribution throughout freshwater drainages of the Neotropical Region from Panama to Argentina, is the largest in the family Pimelodidae (Lundberg & Littmann, 2003; Ferraris, 2007; Eschmeyer & Fricke, 2010).

Pimelodus heraldoi Azpelicueta, 2001 was described from the rio Mogi-Guaçu (type-locality), upper rio Paraná drainage. Azpelicueta (2001: 194) pointed out no exclusive characters to diagnose the new species, namely: (1) small dots irregularly placed (8-9 rows), most occurring in the anterior two-thirds of body, (2) the mouth with striated lips (see Azpelicueta, 2001: fig. 2), and (3) an enlarged posterior branch of the dorsal premaxillary process that articulates with the anterolateral margin of the mesethmoid;(4) a right-angled posterolateral margin of the mesethmoid; (5) and a large pharyngobranchial 3 with a well-developed dorsal crest. Some morphometric characters addressing the differences between P. heraldoi and P. fur (Lütken, 1874) and P. absconditus Azpelicueta, 1995 were included in the diagnosis. Pimelodus microstoma Steindachner, 1877 was recently resurrected from synonymy with P. fur and its type-locality restricted to Irisanga, São Paulo State (rio Mogi-Guaçu drainage, upper rio Paraná) (Ribeiro & Lucena, 2007). The senior author studying the populations of P. microstoma found that the only character distinguishing it from P. heraldoi was the color pattern and that characteristic was included in an identification key for Pimelodus species from the upper portions of the Paraná drainage Ribeiro & Lucena, 2007: 77). However, an in-depth analysis showed that there are no differences between P. microstoma and P. heraldoi.

Material and Methods

The measurements are straight-line distances taken point-to-point with digital calipers and recorded to the nearest 0.1 mm, taken from the left side of the fish whenever possible. Measurements and counts follow Lundberg & McDade (1986) and Lundberg et al. (1991) with the modifications of Lundberg & Parisi (2002) and Ribeiro & Lucena (2006). Fin-ray counts include all rays. The two posteriormost anal-fin rays that are inserted at the same base were counted as separate rays. Gill rakers were counted on the first branchial arch (ceratobranchial and epibranchial). Osteological preparations were cleared and stained (c&s) for cartilage and bone using the method of Taylor & van Dyke (1985). Osteological terminology follows Lundberg & Luckenbill (2007).

Examined specimens belong to the American Museum of Natural History, New York (AMNH); Museu de Ciências e Tecnologia, Pontifícia Universidade Católica do Rio Grande do Sul, Porto Alegre (MCP); Museu de Zoologia da Universidade de São Paulo, São Paulo (MZUSP); and Naturhistorisches Museum, Vienna (NMW). In this study the Holotype, four lots of paratypes of P. heraldoi and two cited in the "Additional material" section of Azpelicueta (2001) (see Material examined and Note below) were examined.

Results

As mentioned in Introduction, Azpelicueta pointed out 8-9 irregular rows of dark dots on sides of the body in P. heraldoi. An examination of a series of specimens of P. heraldoi showed a wider range, with 6-9 irregular rows of dark dots on sides of the body (sometimes very weak or absent, e. g., MZUSP 105395), more evident on the anterolateral region of the body. A similar pattern is demonstrated by P. microstoma (see Figs. 1b-c and Ribeiro & Lucena, 2007: fig. 3). The other character mentioned previously by Azpelicueta (2001), presence of striated lips in P. heraldoi, is likewise present in P. microstoma.

 

We also examined the bone characters given by Azpelicueta (2001) to look for any difference between P. heraldoi and P. microstoma. The two unique characters absent in the c&s specimen of P. microstoma examined and pointed out by Azpelicueta as diagnostic for P. heraldoi, but not exclusive, is an enlarged posterior branch of the dorsal premaxillary process which articulates [completely] with the anterolateral margin of the mesethmoid and a large pharyngobranchial 3 with a well-developed dorsal crest. Nevertheless, one c&s specimen of P. heraldoi (MZUSP 105395, 111.0 mm SL) collected with the holotype showed some differences with respect to these characters. The posterior branch of the dorsal premaxillary process is not as enlarged as that shown by Azpelicueta (2001: figs. 3a-c) and does not completely articulate with the mesethmoid. On the contrary, it is short, slender and only partially articulates with the mesethmoid. Besides that, the pharyngobranchial 3 of the right side has two crests, one on the anterior region and other on a middle region of the dorsal margin of the bone. In the pharyngobranchial 3 of the left side a crest is present on the anterior margin of the bone in a position similar to that shown for P. heraldoi, illustrated by Azpelicueta (2001: fig. 5a). With respect to this bone, a juvenile c&s specimen of P. microstoma (MZUSP 23077, 65.0 mm SL) shows that the pharyngobranchial 3 bone of the left side has a small crest, while the crest is absent on the right side.

The morphometric data were calculated and compared between the syntypes of P. microstoma and the types of P. heraldoi. The only difference found is on body width (18.2 and 18.4, in syntypes of P. microstoma vs. 16.5-17.9, in types of P. heraldoi). This difference may be due to the poor condition of the syntypes of P. microstoma (see Morris & Sabaj, 2010 for images of the syntypes). The morphometric data did not show any other differences when comparing types of P. heraldoi, syntypes of P. microstoma and a population of the former species from the upper rio Paraná drainage (Table 1).

Note about "Additional material" of Azpelicueta (2001)

We found some mistakes regarding the additional material used by Azpelicueta (2001). It is important to mention them for future taxonomic studies of the genus. The lot MZUSP 22713 included as P. heraldoi (collected with the holotype) had the same catalog number as the holotype. Therefore, another catalog number, MZUSP 105395, was given to the 21 specimens. In addition, two lots cited in the same section (MZUSP 22489 and MZUSP 22559) contain mixed specimens that are representatives of the species P. heraldoi (now P. microstoma) and P. platicirris Borodin, 1927. The lot MZUSP 22489 was split to: MZUSP 22489, with nine specimens of P. heraldoi, and MZUSP 105677, with 25 specimens of P. platicirris. The lot MZUSP 22559 has 101 specimens (FRVR pers. obser.) and not 74 as mentioned by Azpelicueta (2001). This discrepancy was probably by division of the lot into two jars. The lot MZUSP 22559 has 70 specimens of P. heraldoi and 16 of P. platicirris, plus 15 specimens on loan not reviewed.

Discussion

This study allowed us to conclude that there is a wide variation in the color pattern of P. microstoma. We found specimens with no dots; specimens with dots restricted to the anterior region of the body, and specimens with dots reaching to gently beyond the half of the body (Fig. 1). This variation includes the pattern displayed by the holotype of P. heraldoi (Fig. 1a and Azpelicueta, 2001: fig. 1), where the spots are small and arranged in larger number of rows. This seems to be a rare pattern to the species (see specimen figured in Graça & Pavanelli, 2007:155). With the recognition of the variability in the color pattern of P. microstoma, it is possible that the species is more widely distributed than actually reported.

The variations observed in mesethmoid and pharyngobranchial 3, including different states in the same specimen, lead us to reject them as diagnostic for the species. The same applies to the morphometric data (Table 1), as they did not show significant differences when comparing the types of P. heraldoi, specimens from upper rio Paraná and syntypes of P. microstoma. The difference in body width between the syntypes of P. microstoma and the types of P. heraldoi may be a consequence of the poor condition of the syntypes of P. microstoma.

Based on the results obtained herein, we conclude that P. heraldoi is not distinct from P. microstoma, and a junior synonym of the latter.

Acknowledgements

We thank Osvaldo Oyakawa and José Lima de Figueiredo for their assistance provided to FRVR during his visit to MZUSP collection, help in searching the type-series of P. heraldoi, and loan of specimens. FRVR received a doctoral scholarship from CNPq.

Material examined: Pimelodus absconditus: MCP 18919, c&s, 120.0 mm SL, rio Uruguay. Pimelodus heraldoi: MZUSP 22713, holotype, 179.0 mm SL, Brazil, rio Mogi-Guaçu, rio Paraná; MZUSP 22712, paratypes, 29, 72.4-151.3 mm SL, Pirassununga, rio Mogi-Guaçu, Emas; MZUSP 38915, paratypes, 7, 104.6-116.1 mm SL, Brazil, rio Paranaíba; MZUSP 22695, paratypes, 7, not measured, Pirassununga, rio Mogi-Guaçu, Cachoeira de Emas; MZUSP 22696, paratypes, 18, 90.5-171.5 mm SL, c&s 89.0 mm SL, rio Mogi-Guaçu. Additional material of Azpelicueta (2001): MZUSP 22559, 70 of 101, not measured, Pirassununga, rio Mogi-Guaçu, Emas; MZUSP 22489, 9, not measured, Pirassununga, rio Mogi-Guaçu; MZUSP 22603, 2, not measured, rio Paraíba do Sul; MZUSP 105395, 21, not measured, 1 c&s, 111.0 mm SL, rio Mogi-Guaçu. Pimelodus maculatus: MZUSP 1188, 1, 211.7 mm SL, rio Itaqui; MZUSP 44776, 2, 82.9-128.2 mm SL, rio de La Plata; MZUSP 24456, 1, 61.8 mm SL, ilha Solteira, rio Paraná. Pimelodus microstoma: NMW 45823, syntype, photograph, Orissanga, upper rio Paraná; NMW 45824, 2 syntypes, 140.0-125.8 mm SL, Orissanga, upper rio Paraná; MZUSP 22443, 15, 88.2-149.2 mm SL, Porto Cabral, rio Paraná; MZUSP 23144, 4, 89.8-102.5 mm SL, rio Tietê; MZUSP 23077, 35, 91.1-107.5 mm SL, c&s 65.0 mm SL, rio Paraná; MZUSP 23204, 42, 108.1-122.6 mm SL, rio Paraná; MZUSP 54567, 1, not measured, Ilha Solteira, rio Paraná. Pimelodus paranaensis: MZUSP 23089, holotype, 235.0 mm SL, rio Paraná; MZUSP 24454, 1, 121.4 mm SL, rio Paraná; MZUSP 284+31, 1, 99.3 mm SL, rio Paraná; MZUSP 28432, 1, 71.1 mm SL, rio Paraná; MZUSP 28434, 1, 70.4 mm SL, Brazil, rio Paraná. Pimelodus platicirris: AMNH 8628, 1, 190.0 mm SL, photograph, rio Mogi-Guaçu; MZUSP 105677, not measured, Pirassununga, rio Mogi-Guaçu; MZUSP 22716, 76, 108.6-170.0 mm SL, rio Mogi-Guaçu; MZUSP 79838, 26, 111.8-140.3 mm SL, rio Mogi-Guaçu; MZUSP 58655, 4, 128.5-200.9, rio Mogi-Guaçu.

Literature Cited

Accepted May 12, 2010

Published June 25, 2010

References

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• Lundberg, J. G., F. Mago-Leccia & P. Nass. 1991. Exallodontus aguanai, a new genus and species of Pimelodidae (Pisces: Siluriformes) from deep river channels of South America, and delimitation of the subfamily Pimelodinae. Proceedings of the Biological Society of Washington, 104(4): 840-869.
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Publication Dates

• Publication in this collection
  14 July 2010
• Date of issue
  2010

History

• Received
  12 May 2010
• Accepted
  25 June 2010