Hypostomus sertanejo (Siluriformes: Loricariidae), new armoured catfish species from north-eastern Brazil.

A re-evaluation of the armoured catfish species of Hypostomus in the Rio Jaguaribe, north-eastern Brazil, was prompted by the discovery of specimens with pale spots on a dark background collected from that basin c. 1936 and deposited at the Academy of Natural Sciences of Philadelphia. Recent field collections in the Rio Jarguaribe basin confirmed the presence of the pale-spotted specimens and its distinctiveness as a new species. Hypostomus sertanejo n. sp. is diagnosed from other species of Hypostomus by having fins and dermal-plated regions of head and body with pale spots or vermiculations on darker background, teeth slender, asymmetrically bicuspid and numerous (34-75) on dentary and premaxilla, depressed dorsal-fin spine not reaching adipose spine, unbranched pectoral-fin spine longer than unbranched pelvic-fin ray, seven branched dorsal-fin rays and one (rarely two) predorsal plate(s) bordering supraoccipital. Ancistrus salgadae Fowler 1941 is hypothesized to be a junior synonym of Hypostomus carvalhoi (Miranda-Ribeiro, 1937), a dark-spotted Hypostomus described from the Rio Granjeiro, a tributary to the upper Rio Salgado.

Karyotypic diversity of the armoured catfish genus Hypostomus (Siluriformes: Loricariidae) in the context of its occurrence and distribution.

This study taxonomically reviewed the specimens studied by Artoni & Bertollo (1996) and assimilated species of Hypostomus into three groups according to their cytogenetic characteristics, vagility and occurrence environments.

Karyotype structure of Hypostomus cf. plecostomus (Linnaeus, 1758) from Tapajós River basin, Southern Amazon: occurrence of sex chromosomes (ZZ/ZW) and their evolutionary implications.

Hypostomus is a group of fish with numerical and struc-tural karyotypic variability. Among them, only six species, three of which belong to the Amazon basin, show a sex chromosome. In this study, we present the karyotype structure of Hypostomus cf. plecos-tomus from the Teles Pires river basin in the municipality of Alta Flo-resta, MT. The species has 2n = 68 and the karyotype formula 14m+ 24sm+ 14st+ 16a [fundamental number (FN) = 120] in males and 15m+ 24sm+14st+15a (FN = 121) in females and sex chromosomes ZZ/ZW. Argyrophilic nucleolar organizer regions (AgNORs) were identified in two pairs of chromosomes at different positions: short arm of the pair 21and long arm of the pair 27, matching the signals displayed by 18S FISH and indicating multiple NORs. Analysis of band C detected few blocks of constitutive heterochromatin in the pericentromeric regions of most chromosomes and the telomeric regions of some pairs, includ-ing the nucleolar pair 21. However, large blocks on the long arm of the nucleolar pair 27 still stood out. GC-rich heterochromatin (CMA3) was visualized only coincidently with nucleolar sites. Mapping of 5S rDNA sites with FISH revealed markings in eight chromosomes, demonstrat-ing synteny between the 18S and 5S sites. The data obtained for H. cf. plecostomus are important for taxonomic studies of this Amazon com-plex "H. plecostomus group". The occurrence of sex chromosomes in Amazon species of Hypostomus suggests an evolutionary event that is independent of other species in the group.

Cytogenetic description of Ancistrus abilhoai (Siluriformes: Loricariidae) from Iguaçu River basin, southern Brazil.

The Iguaçu River basin is a tributary to the upper Paraná River in southern Brazil, and is considered an important aquatic ecoregion that, although having few species of fish, 51-71% of these are apparently endemic. Ancistrus abilhoai is one of three recently described species for this basin and is currently considered endemic to the basin. In this study, we present the chromosomal structure of two populations of Ancistrus abilhoai one collected in the Iguaçu River, in Paraná State, and another collected in the Timbó River, a tributary of the Iguaçu River, in the State of Santa Catarina. Karyotype analyzes were performed in 11 specimens from the Iguaçu River (four females and seven males) and 12 specimens (all males) from Timbó River, revealing 2n = 48 chromosomes with a karyotype formula of 22m + 14sm + 6st + 6a in both populations. Analysis of active nucleolar organizer regions (Ag-NORs) and fluorescent in situ hybridization (FISH) with 18S rDNA probes revealed the submetacentric pair 13 bearing marks at terminal positions on the short arms. Considered as plesiomorphic chromosomal markers in Loricariidae, asynteny 18S and 5S rDNA, and small amounts of heterochromatin were observed. In this study, the first chromosomal data of A. abilhoai are presented with comments on karyotypic characteristics of the genus.

The occurrence of Austrodiplostomum compactum (Lutz, 1928) (Digenea: Diplostomidae) metacercariae in the eyes of loricariid fish (Siluriformes: Osteichthyes: Loricariidae) from Brazil.

The aim of this study was to report the occurrence of Austrodiplostomum compactum metacercariae in the eyes of 98 specimens of loricariid fish (Hypostomus ancistroides, H. hermanni, H. iheringii, H. margaritifer, H. regani, H. strigaticeps, Hypostomus sp. and Megalancistrus parananus) from the Chavantes reservoir (23°07'36″S and 49°37'35″W) located in the rio Paranapanema, upper Paraná river basin, municipality of Ipaussu, São Paulo State, Brazil. Fish were collected from October 2007 to February 2009 using nylon monofilament gill nets and transported to the field laboratory where they were euthanized and the eyes were taken and examined under a stereomicroscope. Hypostomus ancistroides and M. parananus were not infected by this diplostomid. Hypostomus hermanni and H. margaritifer were represented by only one specimen but both had a high intensity of A. compactum metacercarie (27 and 35, respectively). Hypostomus strigaticeps (n = 45) and H. iheringii (n = 28) were the most representative specimens and the prevalence, mean intensity of infection and mean abundance were 24.4%, 10.3 and 2.7, and 64.2%, 13.1 and 8.4, respectively. No correlation was observed between the intensity of infection and the standard length (r = - 0.223; P = 0.827) and weight (r = 0.03; P = 0.779) of studied fish. Similarly, linear regression among these variables showed a poor correlation and indicated that the infection by A. compactum metacercariae occurs similarly in small and large fish specimens. A seasonal pattern of infection was not observed. Hypostomus hermanni, H. iheringii, H. margaritifer and H. strigaticeps were new hosts recorded for A. compactum metacercariae. A review of morphometric data of A. compactum metacercariae is presented.

Karyotype description of two species of Hypostomus (Siluriformes, Loricariidae) of the Planalto da Bodoquena, Brazil.

Hypostomus sp 3-Córrego Salobrinha NUP 4247 and Hypostomus sp 2-Rio Perdido NUP 4249, collected in the Planalto da Bodoquena, Paraguay River basin, Brazil, were characterized cytogenetically. Hypostomus sp 3-Córrego Salobrinha showed two modal numbers. This polymorphism consists of the presence of two extrachromosomes. It was not possible to define the diploid number in four specimens, where cell lineages had 2n = 83 and 2n = 84 chromosomes in one individual, and 2n = 82, 2n = 83 and 2n = 84 chromosomes in the others. These results reveal the existence of a genetic mosaic due to the occurrence of one or two extrachromosomes in this species. Hypostomus sp 2-Rio Perdido NUP 4249 showed a 2n = 84, FN = 106 with size heteromorphism in one pair of chromosomes stained with AgNO3. In both species, C banding showed a pattern of heterochromatin distribution with a few small bands in the centromeric and pericentromeric regions coinciding with chromomycin A3 staining. Until now, the major diploid number for the genus Hypostomus was 2n = 80, but the species studied here had chromosomes that in creased this number and the variation for this genus. Our results are also the first cytogenetic data on Hypostomus from the Paraguay River basin.

Ichthyofauna from the Emas National Park region: composition and structure.

The relationship between habitats and the ichthyofauna composition in the Parque Nacional das Emas (PNE) and adjacent areas (the Araguaia and Sucuriú rivers) are provided and could be applied in determining the Park's future zoning. Samples of the ichthyofauna and limnological parameters were obtained during both dry (September 1999) and wet (December 1999) seasons. Ichthyofauna collections resulted in the capture of 4,740 specimens of 22 species. The most abundant species in the Araguaia River during the two sampling seasons were Astyanax sp. 2 and Hasemania sp. In the Sucuriú River and PNE, Astyanax scabripinnis cf. paranae and Hoplias aff. malabaricus were the most frequent species. The largest number of species and diversity index were recorded for the Araguaia River. However, sound management policies require more detailed studies on the fish communities of the Cerrado biome.

Ichthyofauna from the Emas National Park region: composition and structure

Com o objetivo de obter informações básicas para o futuro zoneamento do Parque Nacional das Emas (PNE), foram realizadas amostragens ictiofaunísticas e de parâmetros limnólógicos durante o período de seca (setembro/1999) e de chuvas (dezembro/1999) em estações de coletas localizadas no interior do Parque e em áreas adjacentes (rios Araguaia e Sucuriú). Foram capturados 4.740 indivíduos, distribuídos em 22 espécies. Entre as espécies mais abundantes destacam-se Astyanax sp. 2 e Hasemania sp. no rio Araguaia e Astyanax scabripinnis cf. paranae e Hoplias aff. malabaricus no rio Sucuriú e PNE. A maior diversidade de espécies foi constatada para o rio Araguaia. Entretanto, para que medidas de manejo possam ser tomadas de forma criteriosa, estudos ecológicos mais detalhados das comunidades de peixes do cerrado devem ser conduzidos.

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

The expression patterns of 14 enzymatic systems in skeletal muscle, liver and heart tissues of three species of Hypostomus from the Iguaçu River basin (Brazil) were investigated. Although the patterns were similar for the three species, different tissues showed differential expressions, and the data showed that differential tissue expressions of isoperoxidases may be due to preferential combination or association of polypeptide subunits. The detected patterns for SOD isozymes showed that the quaternary structures of these enzymes were in disagreement with the subunit number reported for the majority of other vertebrate groups. Tissue-specific restriction on heterotetramer formation also were described in LDH and MDHP isozymes. Thus, these tissue-specific gene expression character in the species of Hypostomus have the greatest potential to be recognized and applied in systematic studies among species of Hypostomus.