Hypostomus Lacepede

Osvaldo T. Oyakawa, Alberto Akama & Angela M. Zanata, 2005, Review of the genus Hypostomus Lacépède, 1803 from rio Ribeira de Iguape basin, with description of a new species (Pisces, Siluriformes, Loricariidae)., Zootaxa 921, pp. 1-27 : 23-25

[[Genus Hypostomus Lacepede ]]

Discussion

Four nominal species of Hypostomus are cited in the literature for rio Ribeira de Iguape basin: Hypostomus agna (Miranda-Ribeiro, 1907) , Hypostomus commersonii Valenciennes, 1840 , Hypostomus interruptus (Miranda-Ribeiro, 1918) , and Hypostomus lacerta (Nichols, 1919) . Hypostomus lacerta was recently transferred to the genus Kronichthys by Armbruster & Page (1997). Hypostomus commersonii was described for the La Plata river basin, Uruguay, and to rio São Francisco, Brazil. Subsequent authors registered the species in other Brazilian drainages (e.g., rio Paraíba do Sul (Steindachner, 1876; MirandaRibeiro, 1911, 1918), rio Paraná (Miranda-Ribeiro, 1911), and rio Ribeira de Iguape (Miranda-Ribeiro, 1907, 1908a, b, 1918)), broadening the distribution of H. commersonii . Weber (1986), on the contrary, restricted the area of occurrence of H. commersonii to the La Plata river system and Mazzoni et al. (1994) corroborated the absence of this species in the rio Paraíba do Sul drainage. Similarly, we herein confirm the absence of H. commersonii in the Ribeira de Iguape river system. Our analysis revealed that the loricariids collected in the Ribeira do Iguape basin and previously identified in the literature as H. commersonii , have several distinctive features when compared to the La Plata river form. In fact, this material represents a new species and is described herein as H. tapijara , sp. n. Besides having a relatively distinct overall body form, H. tapijara can be also distinguished from H. commersonii on the basis of several characters including the presence of larger and more numerous dark spots distributed over body and fins, and absence of oblique inconspicuous bands over flanks. These two species can be further distinguished from each other by the relatively higher degree of development of ridges and keels in H. commersonii .

As noted in the ‘Introduction’ some authors provided regional revisions of the genus Hypostomus . From those revisions, only Mazzoni et al. (1994) examined species from eastern Brazilian basins, recognizing only two valid species for lower portion of rio Paraíba do Sul basin: Hypostomus affinis (Steindachner, 1877) and Hypostomus auroguttatus Kner, 1854 , senior synonym of H. luetkeni (Steindachner, 1877) (see Weber, 2003:356). According to Mazzoni et al. (1994) both species are only in the rio Paraíba do Sul or northern Brazilian drainages. Furthermore, those species were not cited in the literature for the rio Ribeira de Iguape basin. Examination of specimens of H. affinis in the present study revealed some similarities in coloration with H. interruptus and H. tapijara . However, H. affinis have body comparatively more elongated than H. interruptus and also have larger and more conspicuous dark spots distributed over body and fins (compare Fig. 6 with fig. 2 of Mazzoni et al., 1994). Hypostomus affinis differs from H. tapijara by the absence of broad dorsal fin and absence of strongly developed keels characteristic of the later species (compare Fig. 7 with fig. 2 of Mazzoni et al, 1994). According to Bizerril (1994), there is another species from rio Paraíba do Sul basin, H. punctatus , which belongs to the H. commersoni group, and can be readily distinguished from H. tapijara by having smaller spots over body and fins, four dark brown inconspicuous oblique bands, absence of a broad dorsal fin and body not so elongated.

In the case of Hypostomus auroguttatus , comparisons with species of Hypostomus from rio Ribeira de Iguape basin revealed several similarities with H. agna , mainly related to the body shape, alignment of series of plates in anterior and posterior portion of trunk, absence of keels, and coloration (compare Fig. 2 with fig. 3 of Mazzoni et al, 1994).

Although H. agna is endemic to the rio Ribeira de Iguape system (Weber, 2003:355) and H. auroguttatus was never reported in the literature to occur in this river basin, the distinction between the two species based on the examination of the available material of both species is apparently problematic. In fact, taxonomic difficulties involving H. auroguttatus were previously emphasized by Weber (2003:364), under his comments of Hypostomus vermicularis (Eigenmann & Eigenmann) . According to the author, H. vermicularis needs a revision, a task beyond the scope of this study. Considering the known geographic distribution of H. auroguttatus , the undoubted presence of H. agna in rio Ribeira de Iguape basin and the limited focus of the present study we defer to propose a synonymization of these two species and maintain H. agna as the species present in the rio Ribeira de Iguape basin.

Thus the four species found to occur in rio Ribeira do Iguape basin includes those two previously cited in the literature and confirmed to be present in this study, recognized as H. agna and H. interruptus , one species recorded for the first time in this system that is Hypostomus ancistroides , and the new species H. tapijara .