Acta Scientiarum 22(2):343-346, 2000. ISSN 1415-6814. Species composition of rotifers in different habitats of an artificial lake, Mato Grosso do Sul State, Brazil Juan Carlos Cisneros Martínez 1 , Angela Canesin 1 and Cláudia Costa Bonecker 2 * 1 Departamento de Ciências Exatas e Biológicas, Universidade Federal de Mato Grosso do Sul-Centro Universitário de Dourados, Dourados-Mato Grosso do Sul, Brazil. 2 Nupélia, Universidade Estadual de Maringá, Av. Colombo, 5790, 87020-900, Maringá-Paraná, Brazil. *Author for correspondence. e-mail: bonecker@nupelia.uem.br ABSTRACT. Rotifers are small filter-feeders that are important in food chains and nutrient cycling in aquatic environments. Little is known of the rotifer fauna in the State of Mato Grosso do Sul. We investigated the occurrence and distribution of rotifers in different habitats of an artificial lake near the city of Dourados, from May through November 1997. We recorded 36 taxa belonging to 15 families, mainly Brachionidae. In the different environments sampled, the presence of vegetation was an important factor determining the occurrence of the taxa. Key words: rotifers, composition, State of Mato Grosso do Sul, Brazil. RESUMO. Composição de rotíferos em diferentes habitats de um lago artificial, estado do Mato Grosso do Sul, Brasil. Os rotíferos são pequenos filtradores importantes para as cadeias tróficas dos ambientes aquáticos, bem como na ciclagem dos nutrientes. No Estado do Mato Grosso Sul pouco se conhece sobre a fauna desses invertebrados. Dessa forma, procurou-se, neste estudo, investigar a ocorrência e distribuição do grupo nessa região. As coletas foram realizadas em diferentes habitats de um lago artificial, próximo à cidade de Dourados, no período de maio a novembro/97. Foi registrada a ocorrência de 36 táxons, pertencentes a 15 famílias, destacando-se Brachionidae. Em relação aos diferentes ambientes amostrados, verificou-se que a presença da vegetação foi um fator importante para determinação da ocorrência dos táxons. Palavras-chave: rotíferos, composição, Estado do Mato Grosso do Sul, Brasil. The ecological importance of rotifers derives from the fact that they are small filter-feeders that play a relevant role in energy transfer and nutrient cycling of continental aquatic environments. Generalists, they participate in herbivore as well as detritus food chains. In part because they are r- strategists with a high rate of population growth, they are also rapid colonizers. Studies of the composition and distribution of rotifers in South America are few. Those of Koste (1972), Green (1972), Hardy (1980), Bozelli (1992) in the Amazon basin, and of José de Paggi (1989, 1996), Turner and da Silva (1992), Campos et al. (1996), Espíndola et al. (1996), Bonecker et al. (1997, 1998), Lansac-Tôha et al. (1997), Heckman (1998), and Koste (1999) in the Paraná-Paraguay basin are prominent. The purpose of this study is to assess the occurrence and spatial distribution of rotifers in different habitats of an artificial lake located at Dourados city, Mato Grosso do Sul State. There are no information on this group in that location. Another interesting aspect of the area it is situated that is in the boundary area of two basins (Paraná and Paraguay). Material and methods The study was carried out in an artificial lake and its terrestrial area (22° 12'S; 54 54'W) belonging to the company Sementes Guerra S.A., at Dourados city, Mato Grosso do Sul (Fig. 1). The lake was constructed in 1981. Its area is about 140,000 m 2 , volume about 424,000 m 3 , mean depth 2 meters, and maximum depth 5 meters. Banks of aquatic macrophytes, Eichhornia crassipes (Mart.) Solms., occur along part of the shore, and grassland surrounds the lake. This grassy area becomes part of the lake during the rainy season, it is a seasonally flooded wetland adjacent to the lake.