Differential expression for tissue-specific isozymes in three species of Hypostomus Lacépède, 1803 (Teleostei: Loricariidae)

Molecular inferences about the genus Hypostomus Lacépède, 1803 (Siluriformes: Loricariidae): a review

This review compiles and discusses the use of genetic markers applied in the study of the fish genus Hypostomus Lacépède, 1803 (Siluriformes: Loricariidae). The database comprises 51 peer-review articles that were published in the last 52 years (1968-2020) and that approach analysis based on different classes of genetic markers. The use of cytogenetic and enzymatic markers was predominantly especially in population studies with the genus Hypostomus, while mitochondrial markers were the majority in phylogenetic studies. Although significant methodological advances have occurred for molecular evaluation, they are still modestly applied to the study of neotropical fish genera, in which Hypostomus is included. New perspectives, especially on integrative approaches, are needed to improve our knowledge of the genetic functionality of fishes.

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.

Genetic variability in four samples of Neoplecostomus yapo (Teleostei: Loricariidae) from the rio Paranapanema basin, Brazil

Four samples of Neoplecostomus yapo were analyzed through the allozyme electrophoresis technique in corn starch gel. The allozyme pattern was similar to those found in N. paranensis with 24 loci scored. Two samples (ribeirão Atlântico and ribeirão Uraí) showed monomorphic bands for all 24 loci, whereas the other two (rio Verde and rio Fortaleza) showed 8.3% of polymorphic loci. The He genetic variability estimates for the rios Verde and Fortaleza populations were 0.0195 and 0.0179, respectively, too much inferior to the mean heterozygosity summed to species from the whole world (0.051). The Wright statistical values F IS = 0.5181, F IT = 0.5681 and F ST = 0.1039 and the genetic distance of Nei values showed that the four samples are genetically very similar to each other and that there is homozygote excess in the polymorphic loci.

Genetic variability in three species of Gymnotus Linnaeus, 1758 (Gymnotiformes: Gymnotidae) from Caracu stream of the upper Paraná River basin, Brazil

The genetic variability of three Gymnotus species from the Caracu stream, a small tributary of the left margin of Paraná River (Brazilian upper Paraná River floodplain), was estimated with data of 17 putative allozyme loci, which were obtained by using corn starch gel electrophoresis of 10 enzymatic systems: Aspartate aminotransferase (E. C. 2.6.1.1), Alcohol dehydrogenase (E. C. 1.1.1.1), Esterase (E. C. 3.1.1.1), Glucose dehydrogenase (E. C. 1.1.1.118), Glycerol-3-phosphate dehydrogenase (E. C. 1.1.1.8), Isocitrate dehydrogenase (E. C. 1.1.1.42), L-Lactate dehydrogenase (E. C. 1.1.1.27), Malate dehydrogenase (E. C. 1.1.1.37), Superoxide dismutase (E. C. 1.15.1.1) and Sorbitol dehydrogenase (E. C. 1.1.1.14). The genetic diversity was estimated as He = 0.3458 for G. pantanal, He = 0.2481 for G. inaequilabiatus, and He = 0.3152 for G. sylvius. The most divergent species were G. sylvius and G. pantanal (D = 0.117), and the most similar were G. inaequilabiatus and G. pantanal (D = 0.051). The data indicates that the observed genetic variability was very low and the expected variability estimated for these three species is very high, and the genetic differences among them are small. The data suggest that the process of speciation which produced these three species is recent.

Biochemical comparison of two Hypostomus populations (Siluriformes, Loricariidae) from the Atlântico Stream of the upper Paraná River basin, Brazil

Two syntopic morphotypes of the genus Hypostomus - H. nigromaculatus and H. cf. nigromaculatus (Atlântico Stream, Paraná State) - were compared through the allozyme electrophoresis technique. Twelve enzymatic systems (AAT, ADH, EST, GCDH, G3PDH, GPI, IDH, LDH, MDH, ME, PGM and SOD) were analyzed, attributing the score of 20 loci, with a total of 30 alleles. Six loci were diagnostic (Aat-2, Gcdh-1, Gpi-A, Idh-1, Ldh-A and Mdh-A), indicating the presence of interjacent reproductive isolation. The occurrence of few polymorphic loci acknowledge two morphotypes, with heterozygosity values He = 0.0291 for H. nigromaculatus and He = 0.0346 for H. cf. nigromaculatus. F_IS statistics demonstrated fixation of the alleles in the two morphotypes. Genetic identity (I) and distance (D) of Nei (1978) values were I = 0.6515 and D = 0.4285. The data indicate that these two morphotypes from the Atlântico Stream belong to different species.

Cytogenetic characterization of Hypostomus nigromaculatus (Siluriformes: Loricariidae)

Hypostomus is the most speciose genus in the family Loricariidae, with approximately 120 species. These fish show a wide morphological and color variation, which hinders the identification of species, mainly of widely distributed representatives. The aim of this study was to contribute to the current knowledge on cytogenetic features of Hypostomus nigromaculatus. Three specimens of H. nigromaculatus, collected in two tributaries of rio Tibagi, Paraná, and in Cachoeira de Emas, rio Mogi-Guaçu, São Paulo, the latter being the type locality of H. nigromaculatus, were studied. Chromosomal preparations were submitted to Giemsa staining, silver nitrate impregnation, C-banding and CMA3 and DAPI fluorochromes staining. All samples presented 2n = 76, but the rio Mogi-Guaçu sample differed from those from tributaries of rio Tibagi in relation to karyotype formulae, distribution and composition of heterochromatin, and NOR location. The silver nitrate staining revealed the presence of multiple Ag-NORs for all samples, but with differences on the location on chromosomes. CMA3 staining reveled bright signals equivalent to NOR-bearing chromosomal segments; such sites were characterized by negative, i.e. unstained, marks after DAPI staining. The pattern of heterochromatin distribution was distinctive among samples from rio Mogi-Guaçu and tributaries of rio Tibagi. The differences observed between the sample from rio Mogi-Guaçu and the ones from tributaries of rio Tibagi allow us to suggest that these samples are presently isolated. Further analyses are necessary to ascertain whether such isolation refers to distinct populations or characterizes true different species.

Antioxidant enzyme activity in endemic Baikalean versus Palaearctic amphipods: Tagma- and size-related changes

The activities of key antioxidant enzymes in two endemic Baikalean amphipod species: Pallasea cancelloides (Gerstf), Eulimnogammarus verrucosus (Gerstf) and the widely distributed Palearctic species Gammarus lacustris (Sars) were studied. This work was done to prove or disprove the hypothesis that Baikalean endemics have specifics in antioxidants system different from Palearctic species. The activities of antioxidant enzymes peroxidase, catalase and glutathione-S-transferase were measured in different sections (tagmata) of the amphipods' bodies as well as in different size groups. Well expressed tagma-related differences in peroxidase activity as well as smaller differences in catalase activity were shown in all studied species. There were no measured differences in glutathione-S-transferase activity among body sections. The existence of size-related changes in some antioxidant enzymes and the difference in such changes between Baikalean and Palearctic amphipods were noted. A significant increase in peroxidase activity with the size was found in both Baikalean species while a significant decrease in peroxidase activity was observed in the Palearctic G. lacustris. In Baikalean P. cancelloides, a significant decrease of catalase activity with the increase in age of crustaceans was noted, while in E. verrucosus no such relationship was found. In the Palearctic G. lacustris, a significant increase in catalase activity with the increase in size was noted. All species are shown to have no size-related differences in glutathione-S-transferase activity. The differences between species as well as between both different tagmata and size-classes within a particular species were estimated. It was assumed that the estimated differences in enzymes activity most likely depend on interspecific variation, rather than on conditional specifics in Lake Baikal.

Allozyme relationships in hypostomines (Teleostei: Loricariidae) from the Itaipu Reservoir, Upper Rio Paran� basin, Brazil

In an allozyme electrophoresis survey of 15 hypostomine species from the Itaipu Hydroelectric Reservoir, 25 loci from 14 enzyme systems were scored. Allozyme data allowed recording diagnostic genetic markers for all species analyzed and for some species groups within Hypostomus, a taxon which is taxonomically still unresolved in the Upper Rio Paraná basin. The mean expected heterozygosity of the species was considerably variable and hypotheses to tentatively explain this variation are discussed. A cladogram based upon the allelic frequencies of the species analyzed was produced by the continuous maximum likelihood method: Rhinelepis aspera and M. parananus were separated from the species of Hypostominae by a long branch length. Pterygoplichthys anisitsi was the sister of all the representatives of the genus Hypostomus. Within Hypostomus, two main clades were produced: in the first, H. cochliodon was the sister of the species comprising the H. plecostomus group, and in the second, the tree showed the following relationships: (H. albopunctatus (H. regani + Hypostomus sp. 3) + (H. margaritifer (H. microstomus (Hypostomus sp. 1 (H. ternetzi + Hypostomus sp. 2)). Hypostomus ternetzi and Hypostomus sp. 2 are referred to here as representatives of the H. ternetzi group.