CompCytogen 6(4): 443–452, doi: 10.3897/CompCytogen.v6i4.4028
Karyotypic diversity and evolutionary trends in the Neotropical catfish genus Hypostomus Lacépède, 1803 (Teleostei, Siluriformes, Loricariidae)
Anderson Luis Alves 1, Rafael Splendore de Borba 2, Claudio Oliveira 3, Mauro Nirchio 4, Angel Granado 4, Fausto Foresti 3
1 Embrapa Pesca e Aquicultura (CNPASA), Palmas, Tocantins, Brazil
2 Laboratório de Citogenética, Univ Estadual Paulista “Julio de Mesquita Filho” - UNESP, Rio Claro, São Paulo State, Brazil
3 Departamento de Morfologia, Instituto de Biociências, Univ Estadual Paulista Julio de Mesquita Filho, Botucatu, SP, Brasil
4 Instituto Limnológico, Universidad de Oriente, Caicara del Orinoco, Estado Bolívar, Venezuela

Corresponding author: Anderson Luis Alves (anderson.alves@embrapa.br)

Academic editor: N. Golub

received 24 September 2012 | accepted 21 November 2012 | Published 15 December 2012


(C) 2012 Anderson Luis Alves. This is an open access article distributed under the terms of the Creative Commons Attribution License 3.0 (CC-BY), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.


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Abstract

The family Loricariidae with 813 nominal species is one of the largest fish families of the world. Hypostominae, its more complex subfamily, was recently divided into five tribes. The tribe Hypostomini is composed of a single genus, Hypostomus Lacépède, 1803, which exhibits the largest karyotypic diversity in the family Loricariidae. With the main objective of contributing to a better understanding of the relationship and the patterns of evolution among the karyotypes of Hypostomus species, cytogenetic studies were conducted in six species of the genus from Brazil and Venezuela. The results show a great chromosome variety with diploid numbers ranging from 2n=68 to 2n=76, with a clear predominance of acrocentric chromosomes. The Ag-NORs are located in terminal position in all species analyzed. Three species have single Ag-NORs (Hypostomus albopunctatus (Regan, 1908), Hypostomus prope plecostomus (Linnaeus, 1758), and Hypostomus prope paulinus (Ihering, 1905)) and three have multiple Ag-NORs (Hypostomus ancistroides (Ihering, 1911), Hypostomus prope iheringi (Regan, 1908), and Hypostomus strigaticeps (Regan, 1908)). In the process of karyotype evolution of the group, the main type of chromosome rearrangements was possibly centric fissions, which may have been facilitated by the putative tetraploid origin of Hypostomus species. The relationship between the karyotype changes and the evolution in the genus is discussed.

Keywords

Armoured-catfish, Loricariidae, Hypostomus, karyotype evolution, Ag-NORs, centric fission, polyploidy

Introduction

The subfamily Hypostominae with about 386 species (Reis et al. 2006) is the largest one in the family Loricariidae. The subfamily Hypostominae can only be recognized as monophyletic with the inclusion of the old subfamily Ancistrinae and the exclusion of some genera more related to the subfamily Neoplecostominae (Armbruster 2004). This subfamily is divided into five tribes: Corymbophanini, Rhinelepini, Hypostomini, Ancistrini, and Pterygoplichithini (Armbruster 2004) (Fig. 1). The tribe Hypostomini, with the only genus Hypostomus, has the greatest number of Hypostominae species (Reis et al. 2003).

Figure 1.

Phylogeny of the family Loricariidae proposed by Armbruster (2004).

The genus Hypostomus is the most representative in the family (Weber 2003, Hollanda Carvalho et al. 2010) with 126 species distributed from Central America to southern South America (Zawadzki et al. 2010). Species of the genus display phenotypic plasticity that makes difficult to obtain diagnostic characters for the group (Armbruster 2004).

Recent studies suggested that the genus Hypostomus might be composed of some monophyletic groups (Muller and Weber 1992, Montoya-Burgos 2003, Armbruster 2004, Zawadzki et al. 2004, Alves et al. 2006). This suggestion is confirmed by extensive morphological variation in the genus combined with a largest variety of diploid numbers and karyotype formulae in Loricariidae (Artoni and Bertollo 1996, Alves et al. 2006), with diploid numbers ranging from 2n=52 in Hypostomus emarginatus (Valenciennes, 1840) (Artoni 1996) to 2n=84 in Hypostomus sp. 2 (Cereali et al. 2008) (Table 1).

Table 1.

A summary of the cytogenetic data available for the genus Hypostomus. 2n = diploid number; M = metacentric; SM = submetacentric; ST = subtelocentric; A = acrocentric.

Species Locality 2n Karyotypic formulae References
Hypostomus affinis (Steindachner, 1877) Paraitinga River, São Paulo, Brazil 66 14M, 14SM, 12ST, 26A Kavalco et al. (2004)
Jacuí stream (SP) 66 14M, 14SM, 12ST, 26A Fenerich et al. (2004)
Hypostomus albopunctalus (Regan,  1908) Mogi-Guaçu River, São Paulo, Brazil 74 10M, 20SM, 44ST/A Artoni and Bertollo (1996)
Corumbataí River, São Paulo, Brazil 74 10M, 20M, 16ST, 28A Present study
Hypostomus ancistroides (Ihering,  1911) -- 68 10M, 28SM, 30ST/A Michelle et al. (1977)
Araquá River, São Paulo, Brazil 68 18M, 10SM, 12ST, 28A Alves et al. (2006)
Corumbataí River, São Paulo, Brazil 68 16M, 4SM, 16ST, 32A Present study
Mogi-Guaçu River, São Paulo, Brazil 68 16M, 18SM, 34ST/A Artoni and Bertollo (1996)
Paranapanema River, São Paulo, Brazil 68 10M, 26SM, 32ST/A Rubert et al. (2011)
Hypostomus prope auroguttatus (Kner, 1854) Mogi-Guaçu River, São Paulo, Brazil 76 8M, 30SM, 38ST/A Artoni and Bertollo (1996)
Hypostomus cochliodon (Kner, 1854) Salobra river and Salobrinha stream (MS) 64 16M, 20SM, 28ST-A (male)/ 16M, 19SM, 27ST-A (female) Cereali (2006)
Hypostomus emarginatus (Valenciennes, 1840) Araguaia River, Mato Grosso, Brazil 52 16M, 30SM, 6ST Artoni (1996)
Hypostomus goyazensis (Regan,  1908) Vermelho River, Goiás, Brazil 72 10M, 16SM, 10ST, 36A Alves et al. (2006)
Hypostomus prope iheringi (Regan,  1908) Corumbataí River, São Paulo, Brazil 74 10M, 14M, 20ST, 30A Present study
Hypostomus macrops (Eigenmann & Eigenmann, 1888) -- 68 10M, 14SM, 44ST/A Michelle et al. (1977)
Hypostomus nigromaculatus (Schubart, 1964) Tibagi River, Paraná, Brazil. 76 6M, 20SM, 50ST/A Rubert et al. (2008)
Mogi-Guaçu River, São Paulo, Brazil 76 8M, 20SM, 48ST/A Rubert et al. (2008)
Hypostomus paulinus (Ihering, 1905) -- 74 10M, 20SM, 44ST/A Michelle et al. (1977)
Hypostomus prope paulinus (Ihering, 1905) Corumbataí River, São Paulo, Brazil 76 6M, 18M, 12ST, 40A Present study
Hypostomus prope paulinus (Ihering, 1905) Corumbataí River, São Paulo, Brazil 76 6M, 18M, 12ST, 40A Present study
Hypostomus plecostomus (Linnaeus,  1758) -- 54 24M/SM, 12ST, 18A Muramoto et al. (1968)
Hypostomus prope plecostomus (Linnaeus, 1758) Orinoco River, Bolivar, Venezuela 68 12M, 16M, 12ST, 28A Present study
Hypostomus regani (Ihering, 1905) Mogi-Guaçu River, São Paulo, Brazil 72 10M, 20SM, 42ST/A Artoni and Bertollo (1996)
Paranapanema River, São Paulo, Brazil 72 10M, 18SM, 44ST/A Rubert et al. 2011
Araguá River, São Paulo, Brazil 72 12M, 18SM, 26ST, 16A Alves et al. (2006)
Hypostomus strigaticeps (Regan,  1908) Corumbataí River, São Paulo, Brazil 74 10M, 14M, 14ST, 36A Present study
Mogi-Guaçu River, São Paulo, Brazil 74 8M, 4SM, 62ST/A Michelle et al. (1977)
Paranapanema River, São Paulo, Brazil 72 10M, 16SM, 46ST/A Rubert et al. (2011)
Hypostomus sp. 2 Salobrinha stream, Mato Grosso do Sul, Brazil 84 6M, 16SM, 62ST/A Cereali et al. (2008)
Hypostomus sp. 3 Perdido River, Mato Grosso do Sul, Brazil 82–84 6M, 16SM, 64ST/A - 6M, 12SM, 66ST/A Cereali et al. (2008)
Hypostomus sp. A Rincão Stream, São Paulo, Brazil 70 18M, 14SM, 38ST/A Artoni and Bertollo (1996)
Hypostomus sp. B Mogi-Guaçu River, São Paulo, Brazil 72 12M, 18SM, 42ST/A Artoni and Bertollo (1996)
Hypostomus sp. C Mogi-Guaçu River, São Paulo, Brazil 68 10M, 18SM, 40ST/A Artoni and Bertollo (1996)
Hypostomus sp. D1 Mogi-Guaçu River, São Paulo, Brazil 72 10M, 26SM, 36ST/A Artoni and Bertollo (1996)
Hypostomus sp. D2 Mogi-Guaçu River, São Paulo, Brazil 72 14M, 20SM, 38ST/A Artoni and Bertollo (1996)
Hypostomus sp. E Mogi-Guaçu River, São Paulo, Brazil 80 8M, 16SM, 56ST/A Artoni and Bertollo (1996)
Hypostomus sp. F São Francisco River, Minas Gerais, Brazil 76 10M, 16SM, 50ST/A Artoni (1996)
Hypostomus sp. G Araguaia River, Mato Grosso, Brazil 64 14M, 24SM, 26ST/A Artoni (1996)
Hypostomus sp. Xingu-1 Xingu River, Pará, Brazil 64 32M/SM, 32ST/A Milhomem et al. (2010)
Hypostomus sp. Xingu-2 Xingu River, Pará, Brazil 66 32M/SM, 34ST/A Milhomem et al. (2010)
Hypostomus sp. Xingu-3 Xingu River, Pará, Brazil 65 38M/SM, 26ST/A, 1b Milhomem et al. (2010)

Cytogenetic studies in Hypostomus are relatively well documented (Table 1). In a review of genus cytogenetic data by Bueno et al. (2011) the relations between diploid number and karyotypic formulae of genus were established. However, several problems were not yet solved, including the pattern of karyotype evolution in Hypostomini. In the present study, six species of Hypostomus were karyotyped and the results employed to discuss the karyotype evolution of the genus.

Material and methods

Cytogenetic analyses were performed on chromosomal preparations obtained from six species. Five species were collected in the Corumbataí River, São Paulo, Brazil: Hypostomus ancistroides (Ihering, 1911) (6 males and 4 females) (LBP 2544), Hypostomus albopunctatus (Regan, 1908) (5 males and 6 females) (LBP 2547), Hypostomus strigaticeps (Regan, 1908) (6 males and 7 females) (LBP 2545), Hypostomus prope iheringi (Regan, 1908) (5 males and 4 females) (LBP 1674), and Hypostomus prope paulinus (Ihering, 1905) (5 males and 6 females) (LBP 2548). One species of Hypostomus prope plecostomus (Linnaeus, 1758) (3 males and 2 females) (LBP 2198) was collected in the Orinoco River, Bolivar, Venezuela. Vouchers were deposited in the fish collection of Laboratório de Biologia e Genética de Peixes (LBP), UNESP, Botucatu, São Paulo, Brazil.

Chromosome preparations were obtained from kidney tissues using the technique described by Foresti et al. (1993). Silver staining of the nucleolus organizer regions (Ag-NORs) was performed according to the technique proposed by Howell and Black (1980). Chromosome morphology was determined on the basis of arm ratio, as proposed by Levan et al. (1964) and the chromosomes were classified as metacentrics (M), submetacentrics (SM), subtelocentrics (ST) and acrocentrics (A).

Results and discussion

Hypostomus ancistroides has karyotype with 2n=68 (16M, 4SM, 16ST, 32A) and terminal Ag-NORs on the short arm of the chromosome pair 1 (M) and pair 10 (SM) (Fig. 2a).

Figure 2.

Giemsa stained karyotypes of Hypostomus a Hypostomus ancistroides, 2n=68 b Hypostomus albopunctatus, 2n=74. Ag-NOR-bearing chromosome pairs in the insets. Bar = 10µm.

Hypostomus albopunctatus has 2n=74 (10M, 20SM, 16ST, 28A) and terminal Ag-NORs on the short arm of the chromosome pair 15 (SM) (Fig. 2b).

Hypostomus prope iheringi has 2n=74 (10M, 14SM, 20ST, 30A) and terminal Ag-NORs on the long arms of the chromosome pairs 23, 24, 25, 30 (A) (Fig. 3a).

Figure 3.

Giemsa stained karyotypes of Hypostomus a Hypostomus prope iheringi, 2n=74 b Hypostomus strigaticeps, 2n=74. Ag-NOR-bearing chromosome pairs in the insets. Bar = 10µm.

Hypostomus prope paulinus has 2n=76 (6M, 18SM, 12ST, 40A) and terminal Ag-NORs on the long arm of the chromosome pair 20 (A) (Fig. 4b).

Figure 4.

Giemsa stained karyotypes of Hypostomus a Hypostomus prope plecostomus, 2n=68 b Hypostomus prope paulinus, 2n=76. Ag-NOR-bearing chromosome pairs in the insets. Bar = 10µm.

Hypostomus prope plecostomus has 2n=68 (12M, 16SM, 12ST, 28A) and terminal Ag-NORs on the short arm of the chromosome pair 16 (ST) (Fig. 4a).

Hypostomus strigaticeps has 2n=74 (10M, 14SM, 14ST, 36A) and terminal Ag-NORs on the short arm of the chromosome pair 14 (ST) and on the long arm of the chromosome pairs 21, 22 e 24 (A) (Fig. 3b).

The genus Hypostomus seems to be the karyotypically most derived genus in Loricariidae (Rubert et al. 2011), the variation of diploid number observed in the six species of Hypostomus analyzed (2n=68 to 2n=76) confirms this hypothesis. All species analyzed exhibited a large number of acrocentric chromosomes, reinforcing the hypothesis that higher diploid numbers are positively related to higher number of acrocentric chromosomes in Hypostomus (Artoni and Bertollo 2001). According to Oliveira and Gosztonyi (2000), high diploid numbers may represent a derived characteristic in siluriforms.

Three species had single Ag-NORs (Hypostomus albopunctatus, Hypostomus prope plecostomus, and Hypostomus prope paulinus); and the three others had multiple Ag-NORs (Hypostomus ancistroides, Hypostomus prope iheringi, and Hypostomus strigaticeps). All species presented terminal Ag-NORs, a marked characteristic of the species of this genus. The occurrence of multiple Ag-NORs is the most common characteristic among the Hypostomini, however, this phenotype is considered a derived characteristic among siluriforms (Oliveira and Gosztonyi 2000), which usually predominate single Ag-NORs.

Differences in the karyotype formulae or in the number and position of Ag-NORs are common in species that do not present extensive migration behaviour, since isolated populations are more commonly involved in inbreeding processes, which makes the fixation of chromosome rearrangements easier (Almeida-Toledo et al. 2000). This kind of phenomenon has been extensively documented in fishes as in Astyanax scabripinnis (Jenyns, 1842) (Moreira-Filho and Bertollo 1991, Maistro et al. 1998, Alves and Martins-Santos 2002). On the other hand one of the most important problems associated with the study of the genus Hypostomus is the correct species identification due to the large number of species as well as the close morphological similarity among species (Armbruster 2004). Thus, Table 1 shows many samples identified as Hypostomus sp., which reflects our poor taxonomic knowledge of the group. Among the Hypostomus species, the high diploid number is coincident with a high the number of uniarmed chromosomes (Table 1), suggesting the occurrence of a large number of centric fissions in the karyotypic evolution of the group (Artoni and Bertollo 1996). This hypothesis is reinforced considering that the species of Rhinelepini, the sister group of Hypostomini, has 2n=54 chromosomes (Alves et al. 2003, Alves et al. 2005, Alves et al. 2006). The occurrence of a polyploidy event in the origin of the tribe Hypostomini may explain the existence of duplicated centromeres and telomeres that could have been activated in the centric fissions rearrangements.

Thus, in the ancestor of Hypostomini an extensive process of chromosome fusions should have occurred changing a putative original karyotype with 2n=108 chromosomes into a karyotype with 2n=54 chromosomes. The alternative hypothesis that species of Hypostomus with high diploid numbers are the most primitive, suggesting that new chromosome fusions are reducing the diploid numbers in the genus, is not corroborated by the phylogenies available for the genus (Montoya-Burgos 2003, Armbruster 2004). Considering that the available phylogenies for the genus Hypostomus are very limited regarding the number of species and precise fish identification, further phylogenetic studies including karyotyped fishes are fundamental for a better understanding of the chromosome evolution in Hypostomus.

Acknowledgments

The authors are grateful to Renato Devidé for his technical assistance and to C.H. Zawadzki for the taxonomic identification of the species. This research was supported by the Brazilian agencies FAPESP (Fundação de Apoio à Pesquisa do Estado de São Paulo) and CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico).

References
Almeida-Toledo LF, Foresti F, Toledo-Filho SA (2000) Karyotypic evolution in Neotropical freshwater. Chromosomes Today 13: 169-182.
Alves AL, Martins-Santos IC (2002) Cytogenetics studies in two populations of Astyanax scabripinnis with 2n=48 chromosomes (Teleostei, Characidae). Cytologia 67: 117-122. doi: 10.1508/cytologia.67.117
Alves AL, Oliveira C, Foresti F (2003) Karyotype variability in eight species of the subfamilies Loricariinae and Ancistrinae (Teleostei, Siluriformes, Loricariidae). Caryologia 56: 57-63.
Alves AL, Oliveira C, Foresti F (2005) Comparative cytogenetic analysis of eleven species of subfamilies Neoplecostominae and Hypostominae (Siluriformes: Loricariidae). Genetica 124: 124-127. doi: 10.1590/S1415-47572011005000038
Alves AL, Oliveira C, Nirchio M, Granado A, Foresti F (2006) Karyotypic relationships among the tribes of Hypostominae (Siluriformes: Loricariidae) with description of XO sex chromosome system in a Neotropical fish species. Genetica 128: 1-9. doi: 10.1007/s10709-005-0715-1
Armbruster JW (2004) Phylogenetic relationships of the suckermouth armoured catfishes (Loricariidae) with emphasis on the Hypostominae and the Ancistrinae. Zoological Journal of the Linnean Society 141: 1-80. doi: 10.1111/j.1096-3642.2004.00109.x
Artoni RF (1996) Cytogenetics studies in the Loricariidae family, with emphasis in the genera Hypostomus Lacépède (1803) (Pisces, Siluriformes). Master Thesis. Universidade Federal de São Carlos, São Carlos, SP, 130 pp.
Artoni RF, Bertollo LAC (1996) Cytogenetic studies on Hypostominae (Pisces, Siluriformes, and Loricariidae). Considerations on karyotype evolution in the genus Hypostomus. Caryologia 49: 81-90.
Artoni RF, Bertollo LAC (2001) Trends in the karyotype evolution of Loricariidae fish (Siluriformes). Hereditas 134: 201-210. doi: 10.1111/j.1601-5223.2001.00201.x
Bueno V, Zawadzki CH, Margarido VP (2011) Trends in chromosome evolution in the genus Hypostomus Lacépède, 1803 (Osteichthyes, Loricariidae): a new perspective about the correlation between diploid number and chromosomes types. Reviews in Fish Biology and Fisheries. doi: 10.1007/s11160-011-9215-9
Cereali SS, Pomini E, Rosa R, Zawadzki CH, Froehlich O, Giuliano-Caetano L (2008) Karyotype description of two species of Hypostomus (Siluriformes, Loricariidae) of the Planalto da Bodoquena, Brazil. Genetics and Molecular Research 7: 583-591. doi: 10.4238/vol7-3gmr404
Fenerich PC, Foresti F, Oliveira C (2004) Nuclear DNA content in 20 species of Siluriformes (Teleostei: Ostariophysi) from Neotropical region. Genetics and Molecular Biology 27: 350-354. doi: 10.1590/S1415-47572004000300008
Foresti F, Oliveira C, Almeida-Toledo LF (1993) A method for chromosome preparations from large specimens of fishes using in vitro short treatment with colchicine. Experientia 49: 810-813. doi: 10.1007/BF01923555
Hollanda Carvalho P, Lima FCT, Zawadzki CH (2010) Two new species of the Hypostomus cochliodon group (Siluriformes: Loricariidae) from the rio Negro basin in Brazil. Neotropical Ichthyology 8 (1): 39-48.
Howell WM, Black DA (1980) Controlled silver staining of Nucleolus Organizer Regions with a protective colloidal developer: a 1-step method. Experientia 36: 1014-1015. doi: 10.1007/BF01953855
Kavalco KF, Pazza R, Bertollo LAC, Moreira–Filho O (2004) Gene mapping of 5S rDNA sites in eight fish species from the Paraíba do Sul river Basin, Brazil. Cytogenetic and Genome Research 106: 107-110. doi: 10.1159/000078567
Levan A, Fredga K, Sandberg AA (1964) Nomenclature for centromeric position on chromosomes. Hereditas 52: 201-220. doi: 10.1111/j.1601-5223.1964.tb01953.x
Maistro EL, Oliveira C, Foresti F (1998) Comparative cytogenetic and morphological analysis of Astyanax scabripinnis paranae (Pisces, Characidae, Tetragonopterinae). Genetic and Molecular Biology 21 (2): 201-206. doi: 10.1590/S1415-47571998000200005
Michelle JL, Takahashi CS, Ferrati I (1977) Karyotypic study of some species of the family Loricariidae (Pisces). Cytologia 42: 539-546. doi: 10.1508/cytologia.42.539
Milhomem SSR, Castro RR, Nagamachi CY, Souza ACP, Feldberg E, Pieczarka JC (2010) Different cytotypes in fishes of the genus Hypostomus Lacépède, 1803 (Siluriformes: Loricariidae) from Xingu river (Amazon region, Brazil). Comparative Cytogenetics 4 (1): 45-54. doi: 10.3897/compcytogen.v4i1.31
Montoya-Burgos JI (2003) Historical biogeography of the catfish genus Hypostomus (Siluriformes: Loricariidae), with implications on the diversification of Neotropical ichthyofauna. Molecular Ecology 12: 1855-1867. doi: 10.1046/j.1365-294X.2003.01857.x
Moreira-Filho O, Bertollo LAC (1991) Astyanax scabripinnis (Pisces: Characidae): a “species complex”. Brazilian Journal of Genetics 14: 331-357.
Muller S, Weber C (1992) Les dents des sous-familles Hypostominae et Ancistrinae (Pisces, Loricariidae) et leur valeur taxonomique. Revue Suisse Zoologie 99: 747-754.
Oliveira C, Gosztonyi AE (2000) A cytogenetic study of Diplomystes mesembrinus (Teleostei, Siluriformes, Diplomystidae) with a discussion of chromosome evolution in Siluriformes. Caryologia 53: 31-37.
Reis RE, Kullander SO, Ferraris Jr CJ (2003) Check list of the freshwater fishes of South America. Edipucrs, Porto Alegre, RS, 729 pp.
Reis RE, Pereira EHL, Armbruster JH (2006) Delturinae, a new loricariid catfish subfamily (Teleostei: Siluriformes), with revisions of Delterus and Hemipsilichthys. Zoological Journal of the Linnean Society 143: 277-299. doi: 10.1111/j.1096-3642.2006.00229.x
Rubert M, Rosa R, Jerep FC, Bertollo LAC, Giuliano-Caetano L (2011) Cytogenetic characterization of four species of the genus Hypostomus Lacépède, 1803 (Siluriformes, Loricariidae) with comments on its chromosomal diversity. Comparative Cytogenetics 5 (5): 397-410. doi: 10.3897/CompCytogen.v5i5.1589
Rubert M, Zawadzki CH, Giuliano-Caetano L (2008) Cytogenetic characterization of Hypostomus nigromaculatus (Siluriformes: Loricariidae). Neotropical Ichthyology 6: 93-100. doi: 10.1590/S1679-62252008000100011
Weber C (2003) Subfamily Hypostominae (Armored catfishes). In: Reis RE, Kullander SO, Ferraris Jr CJ (Eds) Check list of the freshwater fishes of South America, Edipucrs, Porto Alegre, RS, 351–372.
Zawadzki CH, Renesto E, Paiva S, Lara-Kamei MCS (2004) Allozyme differentiations of Hypostomus (Teleostei: Loricariidae) from Ribeirão Keller, a small stream in the upper Rio Paraná basin, Brazil. Genetica 121: 251-257. doi: 10.1023/B:GENE.0000039852.65610.4f
Zawadzki CH, Weber C, Pavanelli CS (2010) A new dark-saddled species of Hypostomus (Siluriformes: Loricariidae) from the upper Paraguay river basin. Neotropical Ichthyology 8: 719–725. doi: 10.1590/S1679-62252010000400003