Otávio Froehlich

Nuclear DNA content determination in Characiformes fish (Teleostei, Ostariophysi) from the Neotropical region

In the present study, nuclear DNA content was analyzed in 53 species of Characiformes fish from the Neotropical region. Diploid number ranged from 2n = 48 in Astyanax fasciatus, Gymnocorymbus ternetzi and Hyphessobrycon griemi to 2n = 102 in Potamorhina squamoralevis, with a modal number of 54 chromosomes. Nuclear DNA content ranged from 1.70 ± 0.04 pg of DNA per diploid nucleus in Acestrorhynchus pantaneiro to 3.94 ± 0.09 pg in Tetragonopterus chalceus. A general analysis showed a mean value of 2.9 pg of DNA per diploid nucleus. Very similar DNA content values were observed in the species of the family Cynodontidae which showed a variation of 3% between the two genera studied. Small variations were observed between populations of Gymnocorymbus ternetzi, Astyanax fasciatus and Moenkhausia sanctaefilomenae (Characidae, Tetragonopterinae). The subfamilies Tetragonopterinae and Acestrorhynchinae (Characidae) presented the widest range, about 96%. Even in those families in which diploid number and karyotypic formulae were conserved such as the families Anostomidae, Curimatidae, and Prochilodontidae, episodes leading to losses or gains of genetic material became fixed in their evolutionary history.

Riggia acuticaudata sp. nov. (Isopoda, Cymothoidae) from the body cavity of a reshwater fish of Mato Grosso do Sul State, Brazil

Riggia acuticaudata sp. nov. is described on the basis of 10 female specimens recovered from the body cavity of the freshwater catfish, Ancistrus sp. The fish were caught in a stream called the Corrego Piraputanga, a tributary of the Paraguai River. The new species differs from the others in the genus by being smaller and less convex and by having a pleotelson that tapers abruptly rather than being the same width throughout. Also, the pereopods and dactyls are much smaller, the maxillule has two terminal and three subterminal spines and the first two pleopods are elongate and acute. Additionally, R. acuticaudata sp. nov. is from a different Order of fish host and a new geographic area.

A new unicuspid-toothed species of Hypostomus Lacépède, 1803 (Siluriformes: Loricariidae) from the rio Paraguai basin

A new unicuspid-toothed armored catfish species of Hypostomus is described from the Bodoquena Plateau, rio Paraguai basin, Mato Grosso do Sul State, Brazil. The new species is distinguished from its congeners, with exception of H. fonchii, by having unicuspid teeth (vs.bicuspid teeth); from H. fonchii it is distinguished by having median series of lateral plates with 26-27 (vs. 28); by lower number of premaxillary and dentary teeth (7-10 vs. 18-21; 8-13 vs. 18-25, respectively); for possessing more depressed head (head depth 15.8-18.1% SL vs. 19.1-22.0% SL); and by the presence of median buccal papilla (vs. absence).

First record of the camboatá Megalechis picta (Müller & Troschel, 1849) (Siluriformes: Callichthyidae) for the Pantanal, Brazil

Herein we report the first record of Megalechis picta in the Brazilian Pantanal based in a single specimen captured in a tributary to the rio Miranda, municipality of Corumba, rio Paraguay basin, State of Mato Grosso do Sul, Brazil. Additional discussion about its co-occurrence with M. thoracata is also provided.

Ecomorphology and diet reflect the spatial segregation between two Siluriformes species inhabiting a stream of the Bodoquena Plateau, in Central Brazil

Pimelodella taenioptera Miranda Ribeiro, 1914 and Imparfinis schubarti (Gomes, 1956) are two of the most common fish species in Bodoquena Plateau streams, Paraguay basin. These species have benthic habits and subaquatical observations suggested that they present differentiation in their preference for mesohabitat types. Pimelodella taenioptera shows preference for slow waters, such as pools, while I. schubarti is associated to riffles. In this study we investigated if the known patterns of mesohabitat use of P. taenioptera and I. schubarti can be predict by their ecomorphological and trophic traits. We described the dietary habits and ecomorphological attributes of P. taenioptera and I. schubarti individuals, captured in the Parque Nacional da Serra da Bodoquena (PNSB), Mato Grosso do Sul state, central Brazil. Pimelodella taenioptera presented a more generalist diet, consuming a total of 23 different food items. Imparfinis schubarti have a diet based exclusively on aquatic insects. The ecomorphological analysis revealed that the species differed in relation to five morphological traits associated to habitat use (p <0.01). The results of this study reveal a clear functional dissimilarity between P. taenioptera and I. shubarti. The observed trophic and ecomorphological patterns are congruent with the known habitat use for these species and probably reflect the spatial and temporal variability on conditions and resources present in riffles and pools. Therefore, as expected, the morphological and feeding attributes represent predictive information related to mesohabitat use.

The Poorly Known Riggia acuticaudata (Crustacea: Isopoda) Parasitizing Ancistrus sp. (Siluriformes: Loricariidae) from the Paraguay River Basin, Brazil, with Comments on its Reproductive Biology

ABSTRACT: Here we provide a new record of Riggia acuticaudata parasitizing the armored catfish, Ancistrus sp., from the Paraguay River basin, Brazil. On May and July 2010, 27/47 (57.4%) specimens of Ancistrus sp. collected in 2 streams at Corguinho municipality in the state of Mato Grosso do Sul, were found to be parasitized by R. acuticaudata. This is the second time R. acuticaudata has been reported parasitizing Ancistrus sp. from the Paraguay River basin. In addition, it represents an important record for the known distribution of this isopod species, which was previously known only from the type locality. We also provide information on the reproductive biology of this isopod species.

Cleaning behaviour of the cichlid Mesonauta festivus in the Pantanal wetlands: evidence of a potential freshwater cleaning station

Abstract Cleaning interactions are known among several groups of fishes, with a higher number of records for marine fish species. These temporary associations occur between one species that acts as the cleaner and the other species as the client. The interaction usually takes place within the boundaries defined by the cleaner. This site, known as the cleaning station, allows the client fish to strike a typical pose allowing the cleaner to approach, such as wide-open fins and inclined, motionless body. Few studies have reported on the cleaning behaviour of freshwater fish species, and none has reported on behaviour that could be interpreted as establishing a cleaning station. Herein we present a new record of the cleaning interaction in the Neotropics, between the cichlid Mesonauta festivus as the cleaner and three species of anostomid (Leporinus macrocephalus, Leporinus friderici and Schizodon borellii) as clients on Pantanal wetlands, as well as the establishment of a defined cleaning station.

Two new species of the Hypostomus cochliodon group (Siluriformes: Loricariidae) from the rio Paraguay basin, with a redescription of Hypostomus cochliodon Kner, 1854

Hypostomus cochliodon group is a monophyletic clade of 20 valid species of Neotropical armored catfishes that is widely distributed throughout South America. Recently, specimens identified as H. cochliodon from the type locality and nearby localities were examined, and found to include representatives of more than one species. A redescription of H. cochliodon is provided, with a description of two new species, one from the Bodoquena Plateau and another from several localities of the rio Paraguay basin. A lectotype for H. cochliodon is designated herein, since the previous designation is invalid. Hypostomus cochliodon is diagnosed from all other species of the H. cochliodon group by having the opercle almost completely covered laterally by thick layer of skin, the absence of buccal papilla, weak to moderately developed keels on the lateral plates of the body and by the color pattern of its body and fins. Hypostomus basilisko, new species, is distinguished from the remaining species of the H. cochliodon group by the absence of spots on the body, highly developed keels and spoon-shaped teeth. Hypostomus khimaera, new species, is distinguished from the other species of the H. cochliodon group by having a dark tan stripe along the midline of the flank, black spots on the body and/or fins and teeth with mesial cusp and not spoon-shaped.