Trophic ecology and metabolism of two species of nonnative freshwater stingray (Chondrichthyes: Potamotrygonidae)

The stingrays Potamotrygon amandae and Potamotrygon falkneri are nonnative species established in the Upper Paraná basin. Although they are widely distributed, few studies on their diets or respective metabolic responses exist. Therefore, the aim was to evaluate the dietary composition, trophic niche breadth and lipid/protein concentrations in muscle and hepatic tissues of these two species, as well as the interrelationships between them. The individuals were collected in two areas on the Upper Paraná River. The stomachs and samples of muscle and liver tissues were taken for analysis. A broad dietary spectrum was observed for both species, along with differences in dietary composition, with a higher consumption of detritus by P. amandae and Baetidae by P. falkneri. No differences were observed in the trophic niche breadth. Regarding the metabolic variables, differences were only found in the hepatic protein, with a higher content observed in P. falkneri. A significant positive correlation was observed between items of animal origin and detritus with muscle protein for this species. This shows that such feeding habits, which are characteristic of a generalist, influenced the metabolism of the species and possibly contributed to the successful adjustment of the species to new habitats in the Upper Paraná River.

     

Phylogenetic relationships of species of Crenicichla (Teleostei: Cichlidae) from southern South America based on the mitochondrial cytochrome b gene

Phylogenetic analysis using Bayesian inference, likelihood and parsimony methods was conducted on 60 complete mitochondrial cytochrome b sequences from 21 species of Crenicichla, including all species known from Uruguay (Crenicichla celidochilus, Crenicichla lepidota Crenicichla minuano, Crenicichla missioneira, Crenicichla punctata, Crenicichla scottii, Crenicichla vittata), Crenicichla compressiceps, Crenicichla empheres, Crenicichla geayi, Crenicichla iguassuensis, Crenicichla macrophthalma, Crenicichla menezesi, Crenicichla notophthalmus, Crenicichla regani, Crenicichla cf. regani, Crenicichla semifasciata, Crenicichla sveni, Crenicichla tendybaguassu, two unidentified species, and also two species of Teleocichla. Bayesian analysis resulted in a trichotomy with three major groups: (1) The C. missioneira species group (C. celidochilus, C. empheres, C. minuano, C. missioneira, C. tendybaguassu, and an undescribed species analyzed); (2) a group of southern species (C. iguassuensis, C. punctata, C. scottii, C. vittata); and (3) a rather heterogeneous group comprising the type species C. macrophthalma, members of the Crenicichla reticulata species group (C. geayi, C. semifasciata), members of the Crenicichla wallacii species group (C. compressiceps, C. notophthalmus, C. regani, C. cf. regani), members of the Crenicichla saxatilis species group (C. lepidota, C. menezesi, C. sveni, C. sp.), and two species of Teleocichla. Parsimony jackknifing resulted in a quadritomy with: (1) C. macrophthalma, (2) Teleocichla, (3) the saxatilis + wallacii group species, and (4) the rest, which include C. geayi and C. semifasciata as sister group to a dichotomy with the C. missioneira group and the remaining southern species. The sequence variation within the C. missioneira group is remarkably minor despite considerable morphological differences, supporting the conclusion that it forms an endemic species flock in the Uruguay River basin. Previously proposed species groups within the speciose genus Crenicichla (more than 90 species known) are partly corroborated. However, C. celidochilus was not previously associated with the C. missioneira species group, and C. vittata has not previously been associated with C. scottii, C. iguassuensis, or C. punctata. Crenicichla lepidota, C. sveni, C. menezesi and C. sp. represent the C. saxatilis group. Species of small size, representing the C. wallacii species group and Teleocichla are characterized by very long branches, and the position of Teleocichla differed considerably between the Bayesian and parsimony trees. This finding does not invalidate Teleocichla but rather suggests that the several monophyletic major clades within Crenicichla may need nominal recognition. A putative hybrid specimen with a morphology combining components from C. vittata and C. scottii, but with a cytochrome b sequence from C. scottii was found in a sample from the Rio Quaraí/Cuareim. Another putative hybrid specimen with a unique morphology but a cytochrome b sequence agreeing with C. scottii was found in a sample from Maldonado, but no other Crenicichla species than C. scottii is known from that locality.     

Multilocus phylogeny of Crenicichla (Teleostei: Cichlidae), with biogeography of the C. lacustris group: species flocks as a model for sympatric speciation in rivers

First multilocus analysis of the largest Neotropical cichlid genus Crenicichla combining mitochondrial (cytb, ND2, 16S) and nuclear (S7 intron 1) genes and comprising 602 sequences of 169 specimens yields a robust phylogenetic hypothesis. The best marker in the combined analysis is the ND2 gene which contributes throughout the whole range of hierarchical levels in the tree and shows weak effects of saturation at the 3rd codon position. The 16S locus exerts almost no influence on the inferred phylogeny. The nuclear S7 intron 1 resolves mainly deeper nodes. Crenicichla is split into two main clades: (1) Teleocichla, the Crenicichla wallacii group, and the Crenicichla lugubris-Crenicichla saxatilis groups (“the TWLuS clade”); (2) the Crenicichla reticulata group and the Crenicichla lacustris group-Crenicichla macrophthalma (“the RMLa clade”). Our study confirms the monophyly of the C. lacustris species group with very high support. The biogeographic reconstruction of the C. lacustris group using dispersal-vicariance analysis underlines the importance of ancient barriers between the middle and upper Paraná River (the Guaíra Falls) and between the middle and upper Uruguay River (the Moconá Falls). Our phylogeny recovers two endemic species flocks within the C. lacustris group, the Crenicichla missioneira species flock and the herein discovered Crenicichla mandelburgeri species flock from the Uruguay and Paraná/Iguazú Rivers, respectively. We discuss putative sympatric diversification of trophic traits (morphology of jaws and lips, dentition) and propose these species flocks as models for studying sympatric speciation in complex riverine systems. The possible role of hybridization as a mechanism of speciation is mentioned with a recorded example (Crenicichla scottii).     

Patterns of population differentiation in annual killifishes from the Paraná–Uruguay–La Plata Basin: the role of vicariance and dispersal

Aim To elucidate the role of vicariance versus dispersal at the microevolutionary scale in annual killifish populations belonging to the Austrolebias bellottii species complex (Rivulidae). Within this complex, A. bellottii and A. apaii have low vagility and occur widely within the study area, making them excellent models for testing biogeographic hypotheses of differentiation. Location South America, in the Paraná–Uruguay–La Plata river basin. Methods Molecular data and morphometric analyses were used to reconstruct the phylogeographic history and morphological variation of 24 populations of two taxa of the A. bellottii species complex. Phylogenetic analyses using maximum likelihood (ML) and Bayesian inference (BI) model‐based methods, estimates of clade divergence times implemented in beast , non‐metric multidimensional scaling, analysis of molecular variance results, and morphological analyses elucidated the role of vicariance versus dispersal hypotheses in population differentiation in the aforementioned river basin. Results In the A. bellottii species complex from the Paraná–Uruguay–La Plata river basin, past allopatric fragmentation from vicariance events seems to be the most plausible scenario for diversification since the Late Miocene and more recently since the Plio‐Pleistocene. The Plio‐Pleistocene vicariance produced the differentiation of three major clades in A. bellottii populations. One clade from the eastern Uruguay River drainage was separated from another in western Uruguay and the Paraná–La Plata River drainages. A later vicariance event split populations to the south (lower Paraná–La Plata Basin) and north (middle Paraná) of the western Paraná River drainage. However, our results do not exclude the possibility of dispersal events among A. bellottii populations from both the Uruguay and Paraná river drainages, which could occur in these river basins during hypothesized connectivity cycles of the Late Pliocene and Pleistocene. Main conclusions Past allopatric fragmentation caused by different vicariance events seems to be the main driver of diversification in the A. bellottii species complex since the Plio‐Pleistocene. However, the current molecular data suggest that populations from both drainages of the Paraná–Uruguay rivers may have experienced cycles of connectivity during the Pleistocene, perhaps including multiple vicariance or dispersal events from populations located in the western lower Uruguay River drainage, which encompassed climatic and geological changes in the Paraná–Uruguay–La Plata Basin.     

First observations on longitudinal succession of Zooplankton in the main course of the Paraná River between Santa Fe and Buenos Aires Harbour

The material was been collected in 1972 during a field trip performed by the research vessel of the National Institute of Limnology, Argentina, along the main course of the Paraná River from the Santa Fe harbor down to the Río de la Plata. Sixty sampling stations were covered. In the lower course of the river sampling was carried out in the Paraná Guazú and the Paraná Bravo branches down to its confluence with the Uruguay River, and the Paraná de las Palmas and the Rio de la Plata down to the Buenos Aires harbor. Water samples for chemical analysis were collected and some physical parameters were measured.

Due to the characteristics of the part of the river under consideration, we have divided it into four sectors.

Sixty six species were seen. The rotifers were always the most important. Trichocerca rattus was the predominant species.

The Zooplankton density and specific diversity showing differences between those from industrialized areas and not industrialized ones.     

Length-weight relationships for seven endemic fish species from streams of the last two large remaining dam-free tributaries of the Upper Paraná River Floodplain in the Paraná State,Brazil

This study reports the length-weight relationships (LWR) for seven endemic fish species from streams in the Ivaí (Characidium heirmostigmata, Corydoras lacrimostigmata, Curculionichthys oliveirai, Hisonotus pachysarkos, and Cambeva horacioi) and Ivaí and Piquiri (Apareiodon vladii and Planaltina kaingang) River basins, Paraná State, Brazil. Fish specimens measured and weighed were collected between November 1994 and July 2019, fixed with 10% formalin, and are preserved in 70% alcohol. Measurements were done for standard length (SL—0.1 cm precision) and total weight (TW—0.01 g precision). All coefficient of allometry obtained is within the general range for fishes representing useful tentatives for LWR parameters. We highlight the importance of information about the biology of the endemic fish species in a crucial area for the biodiversity conservation of the Upper Paraná River system.     

The genus Potamolithus Pilsbry, 1896 (Gastropoda: Tateidae) on the Somuncurá Plateau,Patagonia, Argentina

The genus Potamolithus (Gastropoda: Tateidae) is endemic to South America where it is distributed mainly in the Ribeira, Itajaí-açú and Jacuhy Rivers in southern Brazil and the Uruguay River, part of the Paraná and Río de la Plata drainage systems. An exception to the pattern of distribution is Potamolithus valchetensis Miquel, 1998, which is endemic to the Valcheta Stream, Somuncurá Plateau, Patagonia, Argentina. Here we provide a review of Potamolithus from this plateau based on new samples and review of material deposited in collections. A new species, Potamolithus elenae, is named. The shell, head-foot, penis, pallial organs and radula are described. Differences between the new species and P. valchetensis include details in the shell, radula, body pigmentation and penis. A phylogeny using mitochondrial gene cytochrome c oxidase subunit I is provided which shows that Potamolithus is related to species in New Caledonia (Australasia), suggesting that the Tateidae has a Gondwanan distribution.     

Highly segregated trophic niche of two congeneric fish species in Neotropical floodplain lakes

The diets of two sympatric, morphologically similar species of Moenkhausia were studied to investigate whether the manner in which they exploit food resources can help to explain their coexistence. Fish diets were evaluated during the low‐water season in six lakes of the upper Paraná River floodplain (Brazil). The results indicate that these two species segregate in relation to food resources and that the differential use of resources is probably a strategy that reduces competition during periods of a potential food shortage (the low‐water season).     

Sympatry between <Emphasis Type="Italic">Alouatta caraya</Emphasis> and <Emphasis Type="Italic">Alouatta clamitans</Emphasis> and the rediscovery of free-ranging potential hybrids in Southern Brazil

Records of sympatry between Alouatta caraya and A. clamitans are rare despite their extensive range overlap. An example of their current sympatry and the rediscovery of free-ranging potential hybrids of A. caraya and A. clamitans in the forests of the Upper Paraná River, Southern Brazil, are reported in this paper. Eight groups were observed in the study area: five monospecific groups of A. caraya, two of A. clamitans, and a group containing two adult males and two adult females of A. caraya and a sub-adult male and two adult females identified as Alouatta sp. The color of the last three individuals was a mosaic between the two species; this is consistent with previously described variations in museum specimens collected in the Paraná River in the 1940s that had been identified as potential hybrids. The results from this study emphasize the need for scientific studies in the region of the Ilha Grande National Park, one of the few regions in the Paraná River that currently harbors both howler species. Contribution number 1637 of the Departamento de Zoologia, Universidade Federal do Paraná, Caixa Postal 19020, 81531-980, Curitiba, Paraná, Brasil.     

Transcontinental dispersal,ecological opportunity and origins of an adaptive radiation in the Neotropical catfish genus Hypostomus (Siluriformes: Loricariidae)

Ecological opportunity is often proposed as a driver of accelerated diversification, but evidence has been largely derived from either contemporary island radiations or the fossil record. Here, we investigate the potential influence of ecological opportunity on a transcontinental radiation of South American freshwater fishes. We generate a species‐dense, time‐calibrated molecular phylogeny for the suckermouth armored catfish subfamily Hypostominae, with a focus on the species‐rich and geographically widespread genus Hypostomus. We use the resulting chronogram to estimate ancestral geographical ranges, infer historical rates of cladogenesis and diversification in habitat and body size and shape, and test the hypothesis that invasions of previously unoccupied river drainages accelerated evolution and contributed to adaptive radiation. Both the subfamily Hypostominae and the included genus Hypostomus originated in the Amazon/Orinoco ecoregion. Hypostomus subsequently dispersed throughout tropical South America east of the Andes Mountains. Consequent to invasion of the peripheral, low‐diversity Paraná River basin in southeastern Brazil approximately 12.5 Mya, Paraná lineages of Hypostomus, experienced increased rates of cladogenesis and ecological and morphological diversification. Contemporary lineages of Paraná Hypostomus are less species rich but more phenotypically diverse than their congeners elsewhere. Accelerated speciation and morphological diversification rates within Paraná basin Hypostomus are consistent with adaptive radiation. The geographical remoteness of the Paraná River basin, its recent history of marine incursion, and its continuing exclusion of many species that are widespread in other tropical South American rivers suggest that ecological opportunity played an important role in facilitating the observed accelerations in diversification.     

Description of a second species of Nannogonalia Young, 1977 (Insecta: Hemiptera: Cicadellidae: Cicadellini) from the Atlantic Forest of south Brazil

A second species of the poorly known sharpshooter genus Nannogonalia Young, 1977 is described and illustrated from the Atlantic Forest of south Brazil (state of Paraná). Types are deposited in DZUP. Nannogonalia inusitata n. sp. can be distinguished from the type-species (Tettigonia circumcincta Signoret, 1855) mainly by the color pattern and form of the male subgenital plates and female sternite VII. Nannogonalia circumcincta is newly recorded from the state of Paraná. The female genitalia of Nannogonalia are described in detail for the first time, based on the type-species and the new species. We discuss some peculiar features of the first and second ovipositor valvulae of this genus that were previously observed in Versigonalia Young, 1977.     

Distribution of non‐native suckermouth armoured catfish Pterygoplichthys ambrosettii in the upper Paraná River basin,Brazil

This study describes the invasion of the upper Paraná River basin by Pterygoplichthys ambrosettii based on a literature review and field samples. Pterygoplichthys ambrosettii has been reported in 42 localities throughout the upper Paraná River basin, including the Tietê, Paranapanema, Paraná, Grande and Aguapeí rivers. The ascent of P. ambrosettii after the inundation of the Sete Quedas Falls on the Paraná River and the release of individuals by aquarium hobbyists were the primary drivers of this invasion.     

Yellow-eyed piranhas produce louder sounds than red-eyed piranhas in an invasive population of Serrasalmus marginatus

Serrasalmus marginatus is a piranha species native from the lower Paraná River basin and has been invasive in the upper Paraná River basin since the 1980s. In piranhas, sounds of different species have different features. The aim of this study was to investigate if the sounds produced by this species could be used to distinguish two morphotypes: red- and yellow-eyed S. marginatus from the Araguari River (upper Paraná River basin). All the temporal and frequency features of the sounds were equivalent in both groups of eye colour; it corresponds to the species-specific signature described for S. marginatus. Nonetheless, the amplitude features were all statistically different between red- and yellow-eyed piranhas. Yellow-eyed specimens produced louder sounds. In different fish species, colour change in eyes can be due to the absence or the presence of a dominant allele. It can also be involved in social rank or during reproduction. Different hormones and neuropeptides can modulate vocal features. It is hypothesized that a mutation or different hormonal concentrations could explain both sound amplitude and eye colour playing a role in animal communication in S. marginatus.     

Influence of large South American rivers of the Plata Basin on distributional patterns of tropical snakes: a panbiogeographical analysis

Aim The main drainages of the Plata Basin – the Paraná, Paraguay and Uruguay rivers – begin in tropical latitudes and run in a north–south direction into subtropical–temperate latitudes. Consequently, the biota of these rivers has tropical elements that contrast with temperate biomes through which the rivers run. We apply a panbiogeographical approach, to test whether the large rivers of the Plata Basin have a differential influence on distributional patterns of tropical snakes in subtropical and temperate latitudes of South America. Location Subtropical and temperate sections of the major Plata Basin rivers, South America. Methods We compared the individual tracks of 94 snake taxa. The track analysis consisted of: (1) plotting the localities of each taxon on maps, (2) connecting the localities of each taxon using a minimal geographical proximity determinant of the ‘individual tracks’, and (3) superimposing the individual tracks to determine generalized tracks. To detect tropical snakes that reach higher latitudes through the rivers we used the preferential direction of distribution concept. For each taxon we measured the angular deviations between the line of its individual track and the course of the rivers in a 100 × 100 km scaled grid. Average angular values < 45° indicated a positive association with the rivers. Results Thirty‐five of 94 taxa showed distributions associated with the major rivers of the Plata Basin, including fauna from distinct biogeographical lineages, supported by the occurrence of five generalized tracks as follows: (1) the Paraguay–Middle Paraná, (2) the Paraguay–Paraná fluvial axis, Upper Paraná and Middle Paraná to Upper Delta, (3) the Lower Paraguay, Paraná and Uruguay rivers, excluding the sectors High Paraná and High Uruguay, (4) the Uruguay River and Upper Paraná, and (5) the High Paraná. The Atlantic species occurred with significantly higher frequency in the Uruguay River and High Paraná river sections, the Amazon species were found with significantly higher frequency in the Paraguay and Middle Paraná sections, and the species with a Pantanal distribution were found in all sections. Main conclusions The observed distributional patterns may be explained by the interaction of ecological, geographical and historical factors. Previous authors have developed ecological (hydrological or environmental similarity) or dispersalist (effect of rivers as migration routes) explanations. The coincidence between generalized tracks and past geomorphological events that caused displacements and changed relationships between the Paraguay, Paraná and Uruguay river sections supports hypotheses involving the strong influence of historical factors in the present configuration of tropical snake distribution in temperate latitudes.     

A new species of Cambeva (Siluriformes,Trichomycteridae) from the Rio Ivaí basin,Upper Rio Paraná basin,Paraná State,Brazil

A new species of Cambeva endemic to the Rio Ivaí basin, Upper Paraná basin, is described combining morphological and molecular data. This new species is distinguished from all congeners by characters related to the number of pectoral-fin rays, to the colour pattern of the dorsal and lateral surface of the body, to the presence of diffuse blotches in the ventral surface of body, to the presence of a pelvic-fin and pelvic girdle, to the number of odontodes in the inter-opercular and opercular patches, to the number of dorsal and ventral procurrent rays. In addition, the analysis of mitochondrial DNA sequences identified a satisfactory genetic distance between this new species and its congeners. The new species from the Rio Ivaí reinforces its characteristics as an area of endemism for fishes in the Upper Rio Paraná basin.     

Oldest record of the Great White Shark (Lamnidae,Carcharodon; Miocene) in the Southern Atlantic

Lamnid teeth close to but more plesiomorph than Carcharodon carcharias were collected in the late Miocene beds of the Paraná Formation in the central eastern Argentina. We propose, as other authors, that some species formerly assigned to Isurus or to Cosmopolitodus should be included in Carcharodon. Some workers suggested that C. carcharias originated by phyletic evolution in the Pacific basin. The teeth from Paraná could pertain to a new species of Carcharodon already known from Perú. In contrast with the Pacific basin, Carcharodon sp. was sympatric with the wide toothed species Carcharodon plicatilis in central Argentina. This is the oldest record of Carcharodon in the southern Atlantic.     

Microstachys crassifolia sp. nov. (Euphorbiaceae) from Chapada dos Veadeiros,Goiás,Brazil

Microstachys crassifolia, a new species from Chapada dos Veadeiros region in the State of Goias, central Brazil, is here described and illustrated. Its habit and general morphology resembles that of M. nana Silva & Esser, an endemic species from the State of Paraná, southern Brazil. Both species are hemicryptophytes from grasslands, with a well‐developed underground system, glabrous leaves and reddish inflorescences and fruits, but M. crassifolia has fleshy leaves without glands while M. nana has membranaceous leaves with pateliform, submarginal glands.     

<Emphasis Type="Italic">Monticellia santafesina</Emphasis> n. sp. (Cestoda: Proteocephalidea), a parasite of <Emphasis Type="Italic">Megalonema platanum</Emphasis> (Günther) (Siluriformes: Pimelodidae) in the Paraná River basin,Argentina

The proteocephalidean tapeworm Monticellia santafesina n. sp. is described from the siluriform catfish Megalonema platanum (Günther) (Siluriformes: Pimelodidae) in the Paraná River basin, Argentina. The new species is allocated to Monticellia La Rue, 1911 (Proteocephalidae: Monticelliinae) because of the cortical position of the testes, ovary, vitelline follicles and uterus, a globular scolex without a metascolex and uniloculate suckers. The new species differs from all other species of Monticellia (except for M. lenha Woodland, 1933) in possessing a vaginal canal opening anterior or posterior to the cirrus-sac. M. santafesina can be distinguished from M. lenha by the following characteristics: a larger body size; a weakly developed internal longitudinal musculature arranged in 15–35 slim bundles of muscle fibres; vitelline follicles not interrupted at the level of the cirrus-sac and vaginal canal, and with a few paramuscular and/or medullary follicles; the absence of large spinitriches on the anterior margin of the suckers; and the utilisation of Megalonema platanum (in the Paraná River basin) as its host, rather than Sorubimichthys planiceps (Spix & Agassiz) (in the River Amazon). Monticellia santafesina exhibits low values of prevalence (9%) and intensity of infection (1). Megalonema platanum was parasitised by two proteocephalidean cestodes, Rudolphiella cf. lobosa (Riggenbach, 1895) and the new species described in this paper.