Héctor Samuel Vera-Alcaraz

Paraguay is a landlocked country with a central position in South America, and two main rivers of the La Plata Basin run through the country: Paraná and Paraguay rivers. This is the second-largest basin in South America and harbors an important molluscan fauna (Strong et al., 2008 Strong, E.E., Gargominy, O., Ponder, W.F., & Bouchet, P., 2008. Global diversity of gastropods (Gastropoda; Mollusca) in freshwater. Hydrobiologia 595(1), 149-166. http://dx.doi.org/10.1007/s10750-007-9012-6. http://dx.doi.org/10.1007/s10750-007-901... ; Pereira et al., 2014 Pereira, D., Mansur, M.C.D., Duarte, L.D.S., Oliveira, A.S., Pimpão, D.M., Callil, C.T., Ituarte, C., Parada, E., Peredo, S., Darrigran, G., Scarabino, F., Clavijo, C., Lara, G., Miyahira, I.C., & Lasso, C., 2014. Bivalve distribution in hydrographic regions in South America: historical overview and conservation. Hydrobiologia 735(1), 15-44. http://dx.doi.org/10.1007/s10750-013-1639-x. http://dx.doi.org/10.1007/s10750-013-163... ; Cuezzo et al., 2020 Cuezzo, M.G., Gregoric, D.E.G., Pointier, J.P., Vázquez, A.A., Ituarte, C., Mansur, M.C.D., Arruda, J.O., Baker, G., Santos, S.B., Ovando, X.M., Fernandez, M.A., Thiengo, S.C., Mattos, A.C., Silva, E.F., Berning, M.I., Collado, G.A., Miyahira, I.C., Antoniazzi, T.N., Pimpão, D.M., & Damborenea, C., 2020. Phylum Mollusca. In: Damborenea, C., Rogers, D.C. & Thorp, J.H., eds. Thorp and Covich’s Freshwater Invertebrates. London: Academic Press, 261-430, 4 ed., vol. 5: Keys to Neotropical and Antartic Fauna. http://dx.doi.org/10.1016/B978-0-12-804225-0.00011-3. http://dx.doi.org/10.1016/B978-0-12-8042... ). A total of 16 freshwater species of molluscs were reported as non-native from South America by Darrigran et al. (2020) Darrigran, G., Agudo-Padrón, I., Baez, P., Belz, C., Cardoso, F., Carranza, A., Collado, G., Correoso, M., Cuezzo, M.G., Fabres, A., Gregoric, D.E., Letelier, S., Ludwig, S., Mansur, M.C.D., Pastorino, G., Penchaszadeh, P., Peralta, C., Rebolledo, A., Rumi, A., Santos, S., Thiengo, S., Vigidal, T., & Damborenea, C., 2020. Non-native mollusks throughout South America: emergent patterns in an understudied continent. Biol. Invasions 22(3), 853-871. http://dx.doi.org/10.1007/s10530-019-02178-4. http://dx.doi.org/10.1007/s10530-019-021... . These authors reported the presence of seven non-native species in the La Plata Basin, from which were highlighted Corbicula fluminea (Müller, 1774), the Asiatic clam; and Limnoperna fortunei (Dunker, 1857), the golden mussel. Corbicula species arrived in South America in the 1970s and Limnoperna fortunei some years later (around the 1990s), both are widespread now (Darrigran et al., 2020 Darrigran, G., Agudo-Padrón, I., Baez, P., Belz, C., Cardoso, F., Carranza, A., Collado, G., Correoso, M., Cuezzo, M.G., Fabres, A., Gregoric, D.E., Letelier, S., Ludwig, S., Mansur, M.C.D., Pastorino, G., Penchaszadeh, P., Peralta, C., Rebolledo, A., Rumi, A., Santos, S., Thiengo, S., Vigidal, T., & Damborenea, C., 2020. Non-native mollusks throughout South America: emergent patterns in an understudied continent. Biol. Invasions 22(3), 853-871. http://dx.doi.org/10.1007/s10530-019-02178-4. http://dx.doi.org/10.1007/s10530-019-021... ; Miyahira et al., 2020 Miyahira, I.C., Pereira, L.S., & dos Santos, L.N., 2020. Non-native freshwater molluscs in the Neotropics: what can be learned from Brazilian reservoirs? Aquat. Invasions 15(3), 455-472. http://dx.doi.org/10.3391/ai.2020.15.3.06. http://dx.doi.org/10.3391/ai.2020.15.3.0... ; Hermes-Silva et al., 2021 Hermes-Silva, S., Ribolli, J., Ávila-Simas, S.D., Zaniboni-Filho, E., Cardoso, G.F.M., & Nuñer, A.P.D.O., 2021. Limnoperna fortunei-Updating the geographic distribution in the Brazilian watersheds and mapping the regional occurrence in the Upper Uruguay River basin. Biota Neotrop. 21(3), e20201175. http://dx.doi.org/10.1590/1676-0611-bn-2020-1175. http://dx.doi.org/10.1590/1676-0611-bn-2... ). Invasive species can promote modification of environmental and biological aspects of the invaded habitat (e.g., Darrigran & Damborenea, 2011 Darrigran, G., & Damborenea, C., 2011. Ecosystem engineering impacts of Limnoperna fortunei in South America. Zool. Sci. 28(1), 1-7. PMid:21186940. http://dx.doi.org/10.2108/zsj.28.1. http://dx.doi.org/10.2108/zsj.28.1... ; Sousa et al., 2014 Sousa, R., Novais, A., Costa, R., & Strayer, D.L., 2014. Invasive bivalves in fresh waters: impacts from individuals to ecosystems and possible control strategies. Hydrobiologia 735(1), 233-251. http://dx.doi.org/10.1007/s10750-012-1409-1. http://dx.doi.org/10.1007/s10750-012-140... ; Boltovskoy & Correa, 2015 Boltovskoy, D., & Correa, N., 2015. Ecosystem impacts of the invasive bivalve Limnoperna fortunei (golden mussel) in South America. Hydrobiologia 746(1), 81-95. http://dx.doi.org/10.1007/s10750-014-1882-9. http://dx.doi.org/10.1007/s10750-014-188... ), affecting not only native molluscs, but also other taxonomic groups. Understanding the distribution of invasive species is the first step to proposing strategies to mitigate the negative impacts.

The Characiform fish species from the Tapyta Reserve and surrounding area, Caazapa, Paraguay, were inventoried during a year with electrofishing, netting, and trapping. A total of 20 species were registered, being Characidae the richest family. We also report three species as new records to the Paraguayan ichthyofauna and discuss the update of the inventory of fishes from Paraguay.

A new species of Corydoras is described from the rio São Francisco basin in northeastern Brazil, Minas Gerais and Bahia States. The new species is distinguished from most of its congeners by the anterior portion of the infraorbital 1 very large, conspicuously expanded towards the anteroventral margin of the snout and almost entirely covering its lateral margin. Other characters that distinguish the new species are the infraorbital 2 slender on its dorsal tip, contacting only sphenotic and not compound pterotic; and the presence of two laterosensory canals on trunk. A phylogenetic analysis including the new species found it sister-group of C. flaveolus, and both species sister-group of C. paleatus. An identification key to the species of the rio São Francisco basin is also provided

Species of the genus Rineloricaria from the Paraguay River basin were revised, the following species and geographic distributional patterns were found: R. aurata, Paraguay River basin in Brazil and Paraguay, rio Guaporé in Brazil; R. cacerensis, Paraguay River near Cáceres in Brazil; R. lanceolata, Paraguay River basin in Brazil and Paraguay, Guaporé, Ji-Paraná, Purus, Solimões, and Araguaia rivers in Brazil, Marañón and Madre de Dios rivers in Peru; R. parva, Paraguay River basin in Brazil and Paraguay, Paraná River in Argentina, Uruguay River in Brazil. Loricaria hoehnei is proposed as a new junior synonym of R. lanceolata. A key to the species of Rineloricaria from the Paraguay River basin is provided.

Astyanax jordanensis, new species, is described from the rio Jacu and rio das Torres, both tributaries to the lower rio Jordão, in the rio Iguaçu basin, Paraná, Brazil. The new species is a member of the A. scabripinnis species complex. Astyanax jordanensis differs from its congeners by several meristic and morphometric characters. Mature males possess bony hooks in the dorsal, pectoral, pelvic, and anal fins, and mature females have a few small bony hooks on the first rays of the anal fin. The presence of these bony hooks in females and the endemism of the ichthyofauna in the rio Jordão are discussed.

Microglanis carlae, new species, is described from the río Paraguay basin and distinguished from its congeners by the following combination of characters: paired and anal fins mottled or with thin faint bands, trunk with dark-brown saddles, anterior margin of pectoral spine with serrations retrorse proximally and antrorse distally, tip of pectoral spine as a distinct bony point, continuous portion of lateral line reaching vertical through last dorsal-fin ray, caudal peduncle with irregularly shaped, faint to dark blotch, maxillary barbel surpassing vertical through dorsal-spine origin, and dark bar on posterior flank continuous from base of adipose fin to that of anal fin. The new species is included in the Microglanis parahybae species complex on the basis of color pattern.