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Example of the sampled habitat of Rivulus giarettai in Uberlândia, Minas Gerais, Brazil. In the first plane a dam reservoir of a Vereda stream. The palm trees (Mauritia flexuosa L.) in the second plane are at the original margins of the streamlet (free flowing water)

Example of the sampled habitat of Rivulus giarettai in Uberlândia, Minas Gerais, Brazil. In the first plane a dam reservoir of a Vereda stream. The palm trees (Mauritia flexuosa L.) in the second plane are at the original margins of the streamlet (free flowing water)

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We present data on the habitat, density, and spatial distribution of Rivulus giarettai, and discuss some biotic and abiotic variables related to its abundance in Free Flowing Waters (FFW) and Dam Reservoirs (DR) in palm grove (Mauritia flexuosa) marshes (Veredas) in Uberlândia, Minas Gerais, southeastern Brazil. The mean density (individuals/plot)...

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... were predominantly taken in July (winter) 2008. Complementary quantitative data (A. A. Giaretta, unpubl. data) gathered in winter months of 2004 within a study on tadpole ecology ( Muniz et al. 2008) in the same sampled sites and using the same sampling methods, were also considered. On Septem- ber 2004 (after the first sampling), a fire severely destroyed vegetation at CP, including Vereda habitats. Sampling plots were spatially defined by an enclosure (a metal ring, 56 cm diameter × 45 cm height, 0.25 m 2 ) randomly placed in water (stovepipe sampling, see Shaffer et al. 1994). To homogenize the disturbance prior to plot establishment, two people came from opposite directions and converged to the exact point of the plot establishment. The metal ring was dropped and pressed against the substrate; lower borders were checked for sealing. We took 99 plots along Veredas, 60 in Free Flowing Waters (FFW) and 39 in Dam Reservoirs (DR) (<3 m from the margin). Plots in the drainage channels (described above) in the CP were established only in 2008. In DR, the maximum sampled depth was limited by the height of the metal ring. Specimens, plant material and detritus were removed from each plot by hand and with a sieve (4 mm mesh) and stored in plastic bags with 5% formaldehyde for subsequent laboratory analysis. All samples were taken during daylight periods. During the sampling, air temperature ranged between 15 and 25°C. At the lab, plant material was washed out with a 4 mm mesh sieve for fine sediment removal and separation of arthropods, and then dried (90°C) to a constant mass. Variables determined for each plot were: 1) maximum water depth, 2) dry mass of plants (substrate), 3) number of arthropods, 4) number and mass of tadpoles [Hypsiboas albopunctatus (Spix, 1824)], and 5) num- ber of individuals and mass of R. giarettai and of other two teleost species [Astyanax paranae (Eigenmann, 1914) and Phalloceros harpagos (Lucinda, 2008)]. Biomass (nearest 0.1 g) was obtained after drying individuals with absorbent towel paper. Differences in quantitative variables between aquatic habitats (FFW × DR) and between years (2004 and 2008) were tested using Mann-Whitney U test. The proportions of plots with at least one specimen of R. giarettai were compared between both habitats using Chi-square (χ 2 ) tests with Yates correction (Zar 1999 (Fig. 2) was essentially restricted to open Veredas habitats (FFW and DR) (Fig. 3), being rare (1 specimen) in their forested (shaded) portions. It was absent in adjacent habitats, such as the firm- bottomed streamlet along pasture and temporary ponds (n=10). In addition to R. giarettai, other vertebrates found in plots were three species of teleosts and one frog species (tadpole) ( Table 1). The size of R. giarettai in samples ranged from 13.3 to 45.3 mm in total length (mean ± SD: 26.5± 7.1 mm); and weight ranged from 0.03 to 1.39 g (mean ± SD: 0.31±0.25 ...

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... However, species which inhabit degraded and fragmented systems would seem to be most vulnerable to fire and firerelated disturbances (Dunham et al. 2003). In this study, a fire was observed in June, but it seemed to have no effect on the variables studied here, as no significant changes were observed immediately after the fire on the population structure of Melanorivulus giarettai (Costa 2008) from Bvereda^habitats (Oliveira et al. 2012). As pointed out by Minshall et al. (2001), fire may affect aquatic organisms over the long term, suggesting that this population should be monitored over a long time course to determine the real effects of fire and other significant environmental disturbances. ...
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Species of Melanorivulus present behaviour and physiological traits that allow them to live in marginal aquatic habitats. In particular, Melanorivulus rossoi is a small nonannual fish only known from its type locality in the Brazilian Cerrado. In this study, we aimed to characterize the distribution and temporal variation in body size, sex ratio, density, length-weight relationship (LWR) and condition factor (CF) of M. rossoi in its natural habitat. To accomplish this, fish samples were taken monthly for a year using sieve nets every 30 min. Body size of males and females increased throughout the year until early summer. LWR was significant, and general coefficient of determination (r²) was 92%. Juveniles showed negative allometric growth, but adults showed positive allometric growth. Both sexes presented the same tendency of temporal variation in CF, with lower values in October and January and peaks in September and February. Fire occurred in June, but no difference in population parameters was observed after this event. A decrease in the abundance of Melanorivulus was related with an increase in the abundance of Erythrinidae juveniles. This might be explained by an increased predation of this species over the M. rossoi individuals, when the population was reduced to about 30% of that in the previous months. We report four new locations where this species was recorded; thus, similar to most Rivulidae members, M. rossoi has a restricted distribution area and is threatened with extinction. Therefore, our results may be useful in developing management strategies aimed at conservation of this species and its habitat in Brazil.
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