Identification key and pictures of the Hypostomus Lacépède , 1803 ( Siluriformes , Loricariidae ) from the rio Ivaí , upper rio Paraná basin

The rio Ivaí flows through the left margin of the upper rio Paraná basin with 798 km of extension, being one of its largest tributaries. In this study, we analyzed 586 specimens of Hypostomus Lacépède, 1803 from the rio Ivaí basin deposited in the Coleção de Peixes do Núcleo de Pesquisas em Limnologia, Ictiologia e Aquicultura da Universidade Estadual de Maringá (NUP) and Coleção Ictiológica do Grupo de Pesquisas em Limnologia e Recursos Pesqueiros (CIG). Herein, 14 species of Hypostomus were recorded from the rio Ivaí basin (10 already described and 4 possible new). The most representative species was H. ancistroides, corresponding to 23.5% of all the specimens, followed by Hypostomus sp. 3, with 15.2%, and Hypostomus sp. 2, with 13.8%. Considering Hypostomus, this study suggests that the rio Ivaí has high species richness compared with adjacent basins, such as rio Paranapanema, rio Tibagi, rio Piquiri and rio Iguaçu. Knowing the difficulties founded by many ichthyologists and researchers in identifying species within this genus, we also present here an identification key for its species present in the rio Ivaí basin.


Introduction
The rio Ivaí is the largest river that runs entirely through the Paraná state, in southeastern Brazil, and it is one of the tributaries that contributes most to the rio Paraná basin (Parolin et al. 2010).With 798 km of extension, the rio Ivaí is formed by the confluence of the rio Patos with rio São João in the municipality of Prudentópolis, southeastern Paraná state, and reaches the rio Paraná in the municipality of Icaraíma, northwestern Paraná state (Maack 2012).Through its extension, the rio Ivaí ranges from 1316 m to 216 m in elevation, and it is considered an upland river filled with rapids and waterfalls (Parolin et al. 2010).
Hypostomus Lacépède, 1803 (Siluriformes, Loricariidae) has about 135 valid species (Eschmeyer and Fong 2017) in Central to South America (Zawadzki et al. 2016a).The taxonomy of most species of the genus is usually difficult due to old type materials, poor morphological descriptions and the great morphological variation found in local populations, especially regarding the widely distributed species.Moreover, another obstacle encountered by researchers to correctly identify species of Hypostomus is the presence of several cryptic species with large intraspecific variation in morphology and body pigmentation patterns (Reis et al. 1990).These problems are intensified by the lack of detailed knowledge of the distribution of many species (e.g.H. strigaticeps (Regan, 1908)).Consequently, a large amount of the species of this genus found in fish collections and museums is misidentified or identified only to generic level.Most of valid species of Hypostomus are distributed in Amazon and La Plata systems (85%) (Zawadzki et al. 2016b).From the 25 species documented for the upper rio Paraná basin (Jerep et al. 2007, Langeani et al. 2007, Zawadzki et al. 2008), 10 species are found in the rio Ivaí basin, along with at least 4 probably new to science.
To help solving these problems and to clarify the differences among the Hypostomus species, this work provides a photographic identification key to catalog the ichthyofauna diversity of Hypostomus from the rio Ivaí basin, one of the biggest tributaries from rio Paraná, and the most representative in species richness of Hypostomus among the rio Paraná tributaries in the Paraná state.

Methods
Study area.The rio Ivaí is a direct tributary of the rio Paraná and constitutes 97.5% of the drainage area of Paraná state (Parolin et al. 2010).In its 798 km length, the rio Ivaí basin (Fig. 1) runs through many municipalities from the confluence of the rio Patos and rio São João, until the upper rio Paraná, between municipalities of Querência do Norte and Icaraíma (Maack 2012).The rio Ivaí is classified as a typical plateau river and can be divided into upper, middle and lower courses, according to the gradient unevenness of the river, that ranges from 1316 m above sea level (a.s.l.) at the upper course to 216 m a.s.l. at the lower course.The upper course region, located in the municipality of Prudentópolis, is the longest part of the river with about 440 km.It harbors several prominent waterfalls, some above 100 m high, such as the Salto São Francisco (196 m) and the Salto Sebastião (130 m) (Parolin et al. 2010).The rio Ivaí receives numerous tributaries during its course, especially the rio Patos, which is classified by the Ministério do Meio Ambiente and Secretaria de Biodiversidade e Florestas as an area important for biodiversity conservation due its rich ichthyofauna.Nevertheless, the rio Ivaí has much agricultural activity throughout its entire course (Maack 2012).
The middle course of the rio Ivaí, which extends for about 170 km, has a medium gradient and mineral rich soil that allows high productivity of grains, such as soybean, corn, and wheat.Here, there poor attention to environmental preservation, with only small remnants of forest in the municipalities of Cianorte and Tuneiras do Oeste (Parolin et al. 2010).
The lower course of the rio Ivaí basin is about 164 km long and is characterized by sandy soils with low fertility (Parolin et al. 2010).This region has advanced cultivation of sugar cane and rice.The lower course also have large grazing areas for cattle.In this region, there are very few forest remnants (e.g.Parque Estadual do Lago Azul, municipality of Campo Mourão; Parque Estadual de Vila Rica do Espírito Santo, municipality of Fenix) (Destefani 2005, Parolin et al. 2010).
Data collection.The morphometric analysis was based on inspections of previously fixed specimens in formaldehyde and preserved in 70% alcohol, deposited in the Coleção Ictiológica do Núcleo de Pesquisas em Limnologia, Ictiologia e Aquicultura da Universidade Estadual de Maringá (NUP), municipality of Maringá, Paraná state, Brasil; and in the Coleção Ictiológica do Grupo de Pesquisas em Limnologia e Recursos Pesqueiros (CIG), municipality of Toledo, Paraná state.
All measurements and counts were taken from the left side of the body (when possible).A digital caliper accurate to 0.1 mm was used to collect the morphometric and meristic data, point to point, according to Boeseman (1968) and Weber (1985).The specimens were studied under a stereoscopic microscope when necessary.Schaefer (1987) was followed for the classification of bony plates, with modifications from Zawadzki et al. (2010).
The list of materials examined present information in the following order: acronym of the collection, number of tipping, number of specimens in the lot, amplitude (mm) of the standard length (SL), river where the species occur, and geographical coordinates.

Discussion
The rio Ivaí basin recently has become the subject of scientific studies related to fish populations, due to increasing efforts in the sampling of its ichthyofauna (Luiz et al. 2003, Zawadzki et al. 2004, Luiz et al. 2005, Portela-Castro et al. 2007, Graça and Pavanelli 2008, Maier et al. 2008, Araújo et al. 2011, Delariva and Silva 2013, Paiva et al. 2013, Viana et al. 2013, Roxo et al. 2014, Tencatt et al. 2014, Frota et al. 2016, Zawadzki et al. 2016a, b).The recognition of areas of endemism is essential for species preservation (Löwenberg-Neto and Carvalho 2004).As previously mentioned in the literature (e.g.Langeani et al. 2007, Frota et al. 2016), the rio Ivaí contains species not yet scientifically described, as well as possibly endemic species, such as Characidium heirmostigmata da Graça &Pavanelli, 2008 andCorydoras lacrimostigmata Tencatt, Britto &Pavanelli, 2014, and the possible new species Hypostomus sp. 1, 2, and 3 are some of the most representative species of this study (Fig. 2), which are probably endemic to the river basin.
Of the 25 species that can be found in the upper rio Paraná system, we recognized 14 species of Hypostomus in the rio Ivaí basin, including 10 that are already described and at least 4 that are probably new to science and endemic to this system.Our results corroborates a previous study (Frota et al. 2016), which suggested that the rio Ivaí has the highest species richness compared to adjacent basins.In the rio Paranapanema basin, 6 species of Hypostomus were recorded (Hoffmann et al. 2005), 5 in the rio Tibagi (Shibatta et al. 2002) and rio Piquiri basins (Gubiani et al. 2006), and only 4 species in the rio Iguaçu basin (Baumgartner et al. 2012).
It is common among ichthyologists and taxonomists to find some level of difficulty in the identification of species of Hypostomus (Gosline 1947, Reis et al. 1990, Jerep et al. 2007), and this has generated several misidentifications in the literature.A possible explanation is that species of this genus exhibit high intraspecific variability, highly similar body shapes, and variable colour patterns of brown, black and yellow, with spots of different shapes and sizes all over the body (Armbruster 2004).Furthermore, Hypostomus is the largest genus of the Hypostominae and the second largest of order Siluriformes.In general, this group has a wide distribution, almost the same distribution as the entire family (Loricariidae).Species of Hypostomus can be found from the rio La Plata in Argentina to southern Costa Rica (Ferraris et al. 2003, Armbruster 2004).The representativeness of H. ancistroides shown in rio Ivaí basin (Fig. 2) is a constant in the La Plata system and also in streams of all upper rio Paraná basin (Oliveira et al. 2009, Gubiane et al. 2010, Araújo et al. 2011).Many species of Hypostomus were described based on a single specimen, which was often lost or poorly preserved, losing essential diagnostic features that are absent in the original descriptions, like those related to color pattern.In other cases, despite existence of the type material, species may have uncertain locality, which makes the collection of topotypes difficult.The original descriptions of the majority of species are too simple and often without figures.
The presence of endemic Hypostomus species in the rio Ivaí basin and several records of unidentified species, in addition to the abundance of poorly determined species, reveals that taxonomic revision of the genus and redescription of many species is needed, with designation of lectotypes when necessary.There are, in this river basin, common species still undescribed or with unresolved taxonomic status, which reveals that knowledge of the fish community from one of the largest tributaries of the upper rio Paraná basin is still lacking.More scientific research and environmental protection in headwater streams of this basin is needed.