The cascudos of the genus Hypostomus Lacépède ( Ostariophysi : Loricariidae ) from the rio Iguaçu basin

We reviewed several large collections of the genus Hypostomus from the rio Iguaçu basin summing up to 793 specimens mainly from the Laboratório de Ictiologia do Departamento de Ecologia e Biologia Evolutiva from Universidade Federal de São Carlos, from fish collection of Núcleo de Pesquisas em Limnologia, Ictiologia e Aquicultura da Universidade Estadual de Maringá, and from the Museu de História Natural do Capão da Imbuia. Hypostomus albopunctatus, H. commersoni, H. derbyi, and H. myersi are redescribed and Hypostomus nigropunctatus is described as a new species. A practical key for identification of Hypostomus species from the rio Iguaçu is also provided.


Introduction
This review of Hypostomus from the rio Iguaçu basin was conducted as part of a larger effort to revise the taxonomy of genus from the whole rio Paraná hydrographic system.Catfishes of the genus Hypostomus are benthic and have a broad distribution across most aquatic habitats in tropical South American river basins.According to Weber (2003) the greatest species richness of Hypostomus comes from the Paraná-Paraguay basin.
The rio Iguaçu is a tributary of the rio Paraná in southern Brazil and there has been considerable confusion regarding the species of Hypostomus that occur there.The rio Iguaçu basin has near 1.080 km of extension declining almost 830 meters from its origins to Cataratas do Iguaçu.Its headwaters are located in Serra do Mar near Curitiba in a region geologically known as First Paranean Plateau, the rio Iguaçu between Engenheiro Blay and Porto Amazonas cities, includes fast and extensive rapids attached with ample flooded areas, marking the known route to the Second Paranean Plateau.At this place, Maack (1981) identified their beds dated from Devonian times.Continuing downriver, when running through Serra da Boa Esperança it ingress to Third Paranean Plateau, an area geologically dated from Tertiary beds.Again, it includes rapids and waterfalls in cascade to get the Cataratas do Iguaçu in Brazil, just before to flows into the rio Paraná just downstrem Itaipu reservoir.The water volume greatly varies along the year, depending of rainfalls and according to Maack (1981) the rio Iguaçu was characterized by rich vegetation of araucaria trees (Araucaria angustifolia) in the past.Meanwhile, the forest devastation was so hard in the middle 1960's when nearly 2/3 of those forests were removed and succeeded by secondary vegetation or agriculture.The places where the Hypostomus species were collected in rio Iguaçu usually include extensive waterfalls and rapids which are variable in depth, but most frequently with rocky bottom forming torrential environments.
The first Hypostomus species described from the rio Paraná system was Hypostomus commersoni Valenciennes, 1836 with type locality given as La Plata (Argentina) and rio São Francisco (Brazil).A second species, Hypostomus auroguttatus Kner, 1854, was described with only "Brasil Oriental" given as the type locality.Miranda Ribeiro (1918) determined that the type locality for this species was probably in the Mogi-Guaçu and Tietê river basins in São Paulo State, Brazil.Hypostomus emarginatus Valenciennes, 1840 was also described with only "Brasil" given as the type locality, but this species, along with H. alatus Castelnau (type locality: Sabará, Minas Gerais) and H. garmani Regan (type locality: rio das Velhas, São Francisco basin) were all recorded from the Tietê, Pardo, and Piracicaba river basins by Miranda Ribeiro (1918).It seems likely that these were all misidentifications since the author did not provide a list of examined material and none of these species have been observed in the upper rio Paraná basin since then (Langeani et al., 2007).Ihering (1905Ihering ( , 1911)), Regan (1908), and Gosline (1945) all made major contributions to the systematics of Hypostomus in the upper rio Paraná basin; however, at no point has the taxonomy of this fauna been reviewed.Ihering (1905) described Plecostomus hermanni, P. paulinus, and P. regani based on specimens from the rio Piracicaba and P. tietensis from the upper stretches of the rio Tietê basin and Regan (1908) described P. albopunctatus, P. iheringii, P. margaritifer, and P. strigaticeps, also from the rio Piracibaba.Thereafter, Ihering (1911) described P. ancistroides from Tietê basin and P. lexi, P. margaritifer butantanis, and P. variipictus from Mogi-Guaçu river basins.Marini et al. (1933) described P. meleagris and P. niger from rio Mogi-Guaçu, based on specimens sent by Ihering from Pirassununga and, finally, Nichols (1919) described P. scaphyceps from Cerqueira Cesar (all localities at São Paulo State).
In the rio Iguaçu basin, Haseman (1911) described Plecostomus derbyi and in his revision of loricariid ichthyofauna from southeastern Brazil, Gosline (1945) described Hypostomus myersi, both species coming from União da Vitória, Paraná State.Since this time no more Hypostomus species have been described from rio Iguaçu basin.However, the rio Iguaçu fish fauna is also known to include H. albopunctatus (Regan) and H. commersoni Valenciennes (Zawadzki et al., 1999, 2001), plus another undescribed and probably endemic species.
Herein, we examined 793 specimens of Hypostomus from rio Iguaçu deposited in the Laboratório de Ictiologia do Departamento de Ecologia e Biologia Evolutiva from Universidade Federal de São Carlos, from fish collection of Núcleo de Pesquisas em Limnologia, Ictiologia e Aquicultura da Universidade Estadual de Maringá, and from the Museu de História Natural do Capão da Imbuia.The four nominal species of Hypostomus from rio Iguaçu are redescribed and Hypostomus nigropunctatus is described as new.We provide a key for the identification of Hypostomus species from the rio Iguaçu and an appraisal of all Hypostomus species present in rio Iguaçu basin.

Material and Methods
From the examined material, meristic and morphometric data were obtained point-to-point with a 0.01 mm digital caliper according to procedures of Boeseman (1968) and Weber (1985).Counts were obtained for all fins, teeth, and plates and are included with the descriptions of species.Bone and plate nomenclature follow Schaefer (1997).Other qualitative data, e.g.color pattern, teeth design, position of abdominal plates, were examined in a comparative manner and are included with the descriptions of species.The morphometric data of Hypostomus tapijara used in the diagnosis of H. commersoni was those from Oyakawa et al. (2005).
Institutional abbreviations are: AMNH, American Museum of Natural History, New York; ANSP, Academy of Natural Sciences of Philadelphia, Philadelphia; BMNH, British Museum of Natural History, London; LISDEBE, Laboratório de Ictiologia do Departamento de Ecologia e Biologia Evolutiva, 1. Head wide and depressed; usually no keels or thin odontode rows along the lateral plate series.bridge and with inconspicuous keel running to caudal peduncle.Dorsal, mid-dorsal, middle and ventral series of plates without conspicuous keels.Mid-ventral series of plates angled just to pelvic-fin insertion region.Rostral margin of snout aciculate with dense irregular series of odontodes; tip of snout with a naked area at ventral region; irregular series of small dermal bones covering the snout from anterior region of orbit to limits of supraoccipital and pterotic-supracleithrum. Scapular bridge totally covered by skin; dense covering of small plates with odontodes on almost whole abdomen, even on juveniles; only a narrow naked area in front of anal opening; an unpaired plate between anus and the anal-fin insertion.Twenty eight plates in the lateral line.Lips gross and with dense papillae; a membrane joining the short and wide labial barbel to labial border.Premaxilla with 26 to 51, and dentary with 26 to 44 moderate to robust teeth; internal cusps shorter than external ones.
Color pattern.Ground color of head and trunk uniformly dark brown; head, trunk and fins with pale spots.Some specimens having spots on each lateral plate and on interradial membranes of all fins.Pale vermiculate spots on head and trunk forming conspicuous longitudinal rows along body and caudal peduncle in some specimens.Abdominal region light brown with dark brown spots or vermiculate on whole abdomen.Fins uniformly dark brown; unbranched rays of pelvic, anal and lower caudal fin light brown.
Distribution.Known from rio Paraná-Paraguay basin including rio Iguaçu.In the rio Iguaçu basin H. albopunctatus is found mainly in the main channel of the rio Iguaçu, from its upper stretches to the lower ones, including a population below Iguaçu Falls.It was also found in a few tributaries of the rio Iguaçu as the rio Três Barras and rio Guarani in the municipality of Três Barras; in the córrego Passo do Aterrado and rio Jordão at its mouth, both in the municipality of Foz do Jordão; and in the rio Timbó in the municipality of Porto União.

Hypostomus commersoni Valenciennes, 1836
Fig. 2 Hypostomus commersoni Valenciennes, 1836:(266)  Description.Dorsal profile of head slightly curved from tip of snout to anterior orbit; supraoccipital profile high and curved to the dorsal-fin insertion.Head elevated and slightly compressed, totally covered by dermal bones with dense covering of odontodes.A conspicuous keel on posterior region of pterotic-supracleithrum behind orbit, followed by continuous keel of odontodes along each lateral series of plates to caudal peduncle; two inconspicuous and divergent keels from median region of supraoccipital; followed by dorsal series of plates Body covered by five longitudinal series of large plates, four of them forming conspicuous keels along whole body and with pungent odontodes on median region of each keel.Rostral margin of snout aciculate.Tip of snout covered by irregularly dispersed platelets and with odontodes extending to upper limits of supraoccipital and posterior pteroticsupracleithrum.Scapular bridge totally covered by small plates with odontodes covering practically whole abdomen; only a small naked area in front of each pelvic-fin insertion; two pair of small plates between anal-fin base and anus.Twenty eight plates in lateral line.Lips with dense papillae; labial barbel elongate and free from the labial border; 23-48 teeth on premaxilla and 24-53 on dentary; teeth slender and long with internal cusps larger than external ones.
Color pattern.Ground color of head and trunk reddish dark brown, irregularly black spotted with small spots on head and larger and more spaced spots on dorsum.All fins dark brown and interradial membranes hyaline and irregularly black spotted with small spots; unbranched rays dark brown.Abdominal region light brown, usually without spots but some species exhibit dark spots.
Distribution.Known from Paraná-Paraguay basin, rio Iguaçu, rio Uruguay and coastal rivers from south Brazil.In the rio Iguaçu basin H. commersoni is found mainly in the main channel of the rio Iguaçu, where it was frequently captured in the several reservoirs from the rio Iguaçu as Foz do Areia, Jordão, Salto Caxias, Salto Santiago and Segredo reservoirs.
Hypostomus commersoni was also captured in some direct tributaries of the rio Iguaçu as rios Cavernoso, Jaracatiá, and Jordão as well as, in a tributary of rio Jordão the córrego Passo do Aterrado.(Haseman, 1911) Figs.

3, 4
Plecostomus derbyi Haseman, 1911:384, pl    Body covered by five lateral series of plates.Dorsal, middorsal, median and ventral series of plates not bearing conspicuous keels.Mid-ventral series of plates moderately keeled on lateral abdomen through six plates from scapular bridge.Rostral margin of snout aciculate and with dense series of odontodes; lips deeply forked at insertion.Snout tip formed by irregular series of plates covering from snout to anterior orbit, to limits of upper supraoccipital and lateral pteroticsupracleithrum.Scapular bridge totally covered by gross skin and small plates with odontodes, covering the whole abdomen; only a small naked region on insertion of pelvic fins and in the region in front of anus.Two pair of narrow plates not meeting at median region between anal-fin insertion and anus and with a naked area between them.Twenty eight to twenty nine plates in the lateral line.Lips and oral region semicircular, with dense papillae; labial barbel elongate and joined to labial border by a gross membrane.Premaxilla with 21 to 42 and dentary with 23 to 43 teeth of moderate length, with two cusps nearly equal in size.
Color pattern.Ground color of head and trunk brown uniform; dorsal region of head, trunk, and fins densely black spotted with small spots on head and larger spots on flanks and whole fins.Interradial membranes hyaline and the black spots forming transversal lines through fins, mainly on dorsal fin.Branched rays of whole fins dark brown uniform.Abdominal region light brown, irregularly black spotted or vermiculated on whole abdomen and ventral caudal peduncle.Unbranched ray of pectoral, pelvic, anal, and caudal fins light brown in ventral regions but black spotted on upper regions.
Distribution.Known from rio Iguaçu basin, Paraná and Santa Catarina States, Brazil.Hypostomus derbyi is the more widespread and abundant species of Hypostomus within the basin.Besides being abundant in the main channel of the rio Iguaçu it is also common in the small to medium streams of the basin.In some streams as the rio das Antas, rio das Pedras, rio dos Padres, and rio Pinhaozinho, among others, it was the sole Hypostomus captured.(Gosline, 1947) Figs   Body covered by five series of longitudinal plates; median series with origin at posterior region of scapular bridge and with a salient keel of odontodes decreasing in size on posterior plates of series.Some rows of odontodes running at median region of all plates on first and second dorsal series of plates; becoming inconspicuous on posterior plates of caudal peduncle.Rostral margin of snout in ventral view aciculate.Tip of snout formed by upper lip in part; snout tip with a naked area without odontodes.Irregular series of small bones between upper snout and orbit running to posterior limits of supraoccipital and pterotic-supracleithrum. Scapular bridge totally covered by gross skin and with dense covering of odontodes on small plates.Numerous small plates and platelets in juveniles covering scapular bridge to pelvic-fin insertion and almost whole abdomen.Abdomen almost totally covered by minute plates, with minute odontodes, leaving naked areas at anterior region of pelvic-fin insertion, around anus and in front of anal-fin insertion; region between anal fin and anus covered only by skin.Twenty six plates in lateral line.Lip gross, ovate and with numerous small papillae; labial barbel short and broad, with no membrane between barbel and lip.Premaxilla with 65-89 and dentary with 64-90 thin and elongate teeth; internal cusp of each tooth shorter than external.

Hypostomus myersi
Color pattern.Ground color of head, trunk and fins dark brown uniform; light brown in lower abdomen.Head, trunk and fins spotted with minute pale spots mainly along plates and interradial membranes; series of pale spots also on median region of each trunk plate, in some specimens forming rows of pale spots more conspicuous on caudal peduncle base.All fins dark brown; branched rays of pectoral, pelvic and lower lobe of caudal fin light brown; distal region of caudal fin bounded with pale brown pigment.

Discussion
This article deals with redescriptions and comparisons between the rio Iguaçu species (Fig. 8) and those from rio Paraná.Despite the Hypostomus species from Iguaçu probably remained in considerable isolation from the Paranean species by the Iguaçu falls, only H. derbyi and Hypostomus nigropunctatus n. sp.seems to be actually restricted to Iguaçu river basin.The species identified by Miquelarena et al. (1997) as H. derbyi from arroyo Urugua-í is herein put in doubt.Some populations of H. ancistroides Ihering, a widespread species from the upper rio Paraná basin, could be misidentified as H. derbyi.Besides, usually reaching a smaller length than H. derbyi, H. ancistroides has more prominent keels on compound pterotic-supracleitrum and along lateral series of plates.Hypostomus derbyi has also an exclusive combination of characters as dark-spotted trunk, compressed head and body without keels on lateral plate series.Some other morphologically similar species as H. agna, H. isbrueckeri, H. interruptus and H. luetkeni have more evident depressed head and body.On the other hand, Hypostomus nigropunctatus n. sp.combines some characteristics of H. derbyi but with a more numerous and fine-closed dark spots on head and three plates bordering supraoccipital (vs.usually one in H. derbyi).
Hypostomus myersi, which occurs at rio Iguaçu, upper and downstream of the Iguaçu Falls is detached by its exclusive association of head and trunk depressed, dental formulae 65 to 89 on premaxillar and 64 to 90 teeth on dentary, and distinctive ground color dark brown, combined with pale vermiculations and punctuations.This combination of characters makes H. myersi very easy to be recognized among the species of rio Paraná basin.Hypostomus derbyi and H. myersi whereas very common at rio Iguaçu basin, they are currently unregistered in the upper rio Paraná basin.This fact was also recognized by Gomes et al. (1990) concerning to Iguaçu at Argentina.
From the nominal species from the rio Iguaçu, only Hypostomus albopunctatus and H. commersoni were also registered in the upper rio Paraná basin.Hypostomus albopunctatus, show the head and trunk strong depressed, combined with a robust teeth design with internal cusps about twice in length than the external cusp; and color pattern dark brown with numerous circular to semicircular pale spots.However, the pectoral-fin spine equal to shorter than the pelvic-fin unbranched ray is the main character to differ H. albopunctatus from the other species of Hypostomus.Hypostomus commersoni from rio Iguaçu is also very different from its congeners from rio Paraná, characterized by lateral series of plates ending in pungent keels, mainly those on the lateral line.Also, its slender and long teeth in the premaxilla (23 to 48) and in dentary (24 to 53), the exclusive reddish color pattern, and the three plates bordering supraoccipital are the distinctive features for H. commersoni.Therefore, while the H. derbyi and H. nigropunctatus might be considered exclusive from the rio Iguaçu, H. albopunctatus, H. myersi and H. commersoni occur in other tributaries of rio Paraná.
The general pattern of rio Iguaçu basin, according to Petri & Fúlfaro (1983) is similar to those of Paraná basin, aged from Mesozoic times.Otherwise, some tributary rivers of Iguaçu were likely established during Tertiary.This supposition is due to intense tectonic activities that among other events formed the Iguaçu Falls in rio Iguaçu and the Sete Quedas Falls in rio Paraná (this last fall is currently covered by waters of the Itaipu hydroelectric Dam).Following Petri & Fúlfaro (1983), in both cases the tectonic elevation was nearly one hundred meters, isolating both the rio Iguaçu and upper rio Paraná basins from the lower stretches of the rio Paraná, which resulted in three ichthyofaunistic areas.
As the Neotropical ichthyofauna is normally older than those geological events, we may comfortably understand a former consensus between the Iguaçu and Paraná basins.On the other hand, by the characteristic geographic isolation imposed for Iguaçu basin in relation to upper rio Paraná basin by the rising of the large falls in Tertiary times, we may believe that the species of Hypostomus, alike other endemic fish groups of the rio Iguaçu, present some relevant degree of endemism.
along caudal peduncle, giving to upper caudal peduncle a quadrangular aspect.Snout narrow and compressed, covered by irregular series of small plates.Mesethmoid forming inconspicuous bulge from snout tip to upper region of orbit.Orbit elevated, almost lateral; orbit diameter 11.4-14.3% in head length.Posterior region of head between supraoccipital and dorsal fin formed by two pair of large plates followed by an unpaired nuchal plate enclosing the first dorsal-fin spinelet.Supraoccipital and pterotic-supracleithrum densely covered with odontodes; larger odontode rows on keels of pteroticsupracleithrum just behind orbit on each side.Dorsal profile of trunk arched at dorsal-fin insertion, slightly declining to caudal fin.Adipose-fin spine short, joined to dorsal caudal peduncle by a slim membrane.Dorsal, mid-dorsal, middle, and mid-ventral series of plates in bent plates forming a keel of hypertrophied odontodes from posterior region of scapular bridge to caudal fin; ventral series of plates moderately angled from posterior region of pelvic fin to lower trunk, giving to caudal peduncle a rectangular aspect.Maximum width slightly decreasing from scapular bridge to caudal fin in dorsal view.Dorsal fin II,7; its origin slightly anterior to vertical through pelvic-fin insertion; elongate, surpassing the adipose-fin spine when adpressed; its distal margin convex.Pectoral fin I,6; elongate, surpassing the pelvic-fin insertion; first ray with large odontodes at upper distal region; its distal margin almost straight.Pelvic fin i,5; surpassing half of anal-fin first ray; its distal border slightly convex.Anal fin, i,5; distal border slightly rounded.Caudal fin i,14,i; slightly concave, lower unbranched ray longer than upper.
, H. nigromaculatus, H. nigropunctatus, H. ternetzi,  H. topavae, and H. wuchereri, by the absence of keels on pteroticsupracleitrhum, pre-dorsal plates and on lateral series of plates (vs.having moderate to developed keels on pteroticsupracleitrhum, pre-dorsal plates, and lateral series of plates).
albopunctatus, H. chrysostiktos, H. faveolus, H. francisci, H.  lexi, H. luteus, H. luteofrenatus, H. margaritifer, H. microstomus,  H. multidens, H. regani, H. roseopunctatus, H. scaphiceps, H.  strigaticeps, H. tietensis, and H. variipictusit is distinguished by having dark spots over body and fins (vs.pale spots).It is distinguished from the remaining congeners, except H. agna, H. brevicauda, H. brevis, H. garmani, H. goyazensis, H. heraldoi,H.hermanni,H. iheringii, H. johnii, H. lima, H. luetkeni, H.  macropsDescription.Dorsal profile of head almost straight from tip of snout to supraoccipital; supraoccipital concave from this point through pre-dorsal plates to origin of dorsal-fin insertion.Head elevated and compressed, totally covered by plates with dense covering of odontodes.A slender keel on upper Hypostomus myersi can be distinguished from the species of the H. cochliodon group, except H. hemicochliodon, by having bifid not spoon-shaped teeth and with the lateral cups not fused to the mesial one (vs.spoon-shaped teeth with lateral cups usually fused to the mesial one).odontodes on small platelets (vs.scapular bridge usually naked).From H. albopunctatus by pelvic-fin unbranched ray smaller than pectoral-fin unbranched ray (vs.pelvic-fin unbranched ray equal to larger than pectoral-fin unbranched ray).From H. chrysostiktos by having seven branched ray on dorsal fin (vs.eight).From H. multidens by having asymmetric bicuspid teeth (vs.symmetric).Dorsal profile of head from tip of snout to dorsalfin insertion slightly concave and elevated at supraoccipital region.Head broad and depressed, totally covered by large dermal bones with fine odontodes; rows of dense odontodes on posterior region of orbit and on median supraoccipital, forming a slightly depression between this bone and orbit.Snout broad and depressed.Mesethmoid forming an inconspicuous bulge from snout tip to upper region of orbit.Orbit narrow, almost dorsal; orbital diameter 14.6-21.7% in head length.Posterior region of head between supraoccipital and dorsal-fin insertion covered by three unpaired and narrowed pre-dorsal plates with a dense series of odontodes in median region forming a divergent keel from supraoccipital.A small platelet on first dorsal-fin ray.Nares narrow, nearly four times in intranasal distance.Body profile slightly straight from dorsalfin insertion to caudal peduncle.Adipose fin elevated and inserted five plates after dorsal-fin posterior insertion.Caudal peduncle with longitudinal series of odontodes at median region of each plate; upper region of caudal peduncle slightly concave and lower region almost straight.

Table 1 .
Morphometric data and counts of Hypostomus albopunctatus, H. commersoni and H. derbyi from the rio Iguaçu basin, Brazil.SD = standard deviation.spaceto space on upper region and light brown in lower regions.Unbranched rays and interradial membranes of caudal fin black spotted, forming six transversal black bars crossing both lobes of caudal fin.Abdominal region light brown, irregularly black spotted or vermiculated on whole abdomen and lower caudal peduncle.Unbranched ray of pectoral, pelvic, anal and caudal fins light brown in lower regions but black spotted on upper regions.Distribution.Known from rio Iguaçu, Paraná State, Brazil.Hypostomus nigropunctatus is known from the middle stretches of the rio Iguaçu, at Salto Segredo reservoir and at the mouth of rios Covó and Jordão. from