Rotifera na bacia hidrográfica do Rio Una, Valença, baixo sul da Bahia

Abstract

The Phylum Rotifera comprises a group of invertebrate pseudocoelomate with size between 100 and 1000μm. These organisms body is divided into head, trunk and terminal foot. They present a muscular pharynx and a set of hard parts such as – mastax – and a ciliary crown which aids in the locomotion and food intake, these characteristics differ them from the others animal’s groups. The aim of this study was to generate information about the ecological attributes of Una River Hydrographic Basin Rotifera community. This project was developed in Valença, BA municipality, in 4 separate collection points, identified as Lower South (LS 1, 3, 4, 5), at the geographical coordinate 13° 17’ 07.6” S e 039° 04' 40.1" W. The biological samples were collected with 64μm mesh size cylindrical-conic plankton net. The samples were fixed in 4% formaldehyde and visualized in an Olympus CX31 microscope for identification based on specific bibliographical description. The abiotic variables data were obtained with a HANNA 9828 multi-parameter probe. A total of 57 taxa were recorded of them distributed in 10 Families of the Monogononta Class, with Lecanidae and Brachionidae major representativeness. The other taxon belonged to the Digononta Class, Bdelloidea Order. The highest richness was detected in the BS3 and BS1 collection points, with 29 and 28 taxa respectively. These points were located in the mountain range region in the rural zone of Valença municipality. Families more abundant were Lecanidae (19.157 org./m3), Brachionidae (2.725 orgs./m3), Trichotriidae (2.346 org./m3) and Euchlanidae (2.314 orgs./m3). Lecane bulla (86.5%), Lecane lunaris (61.5%) and Trichotria tetractis (57.7%) were the most frequent species in the samples. Lecane bulla (10.212 org./m3), Lecane lunaris (4.265 org./m3), Trichotria tetractis (1.505 org./m3) and Lecane luna (1.382 org./m3) registered the highest pick of abundance in the collected samples. Data obtained for temporal dynamic showed highest values in april/2011 (5.000 org./m3) and the lowest in september/2011(1.167 org./m3) and august/2011 (1.365 orgs./m3). Spatial dynamics data were highest in LS 4 point (22.589 orgs./m3) and lowest in LS 5 point (6.027 org./m3). The main diversity value observed was 2.45 Bits. ind.-1 in april/2011 in BS 3 point. During the study period, the equitability showed homogenous distribution of the species. Regarding the abiotic variables data, water temperature oscillate between 20.99°C in august/2011 at BS 1 point and 28.3°C in december/2010 at LS 5 point. pH varied among 9.19 in march/2011 and 6.18 in april/2011, both in BS1 point. Diluted oxygen (ppm) maximum and minimum values were 31,72 in February/2011 at LS 1 point and 80.17 in november/2010 at BS4 point respectively. Electricity conductivity varied between 18.13 at BS1 point and 7306,39 in BS5 point both in september/2011. The water analyzed had salinity in the range of 0.01 ppm at BS1, BS3 and BS4 points and 4.15 ppm at BS5 point in september/2011. In sum, a correlation between the abiotic variables and the community attributes analyzed was observed during the study period. In terms of richness and abundance, Lecanidae and Brachionidae presented predominance in Una river hydrographic basin points studied. Furthermore, BS4 point showed the highest population density.