Diversity of aquatic invertebrates in rice fields in southern Brazil

Abstract

Irrigated rice fields have been cultivated for thousands of years, and a high diversity of invertebrate species has been associated with these agricultural areas. Investigations on the structure and diversity of aquatic invertebrates in rice fields are scarce in southern Brazil. Thus, the main goal of this study was to conduct an inventory of the aquatic invertebrate diversity in rice fields and irrigation canals in an important rice  ultivation area in Rio Grande do Sul to preserve the biota in these agroecosystems. Six collections were carried out along a cultivation cycle (June 2005 – June 2006) in six rice fields and four irrigation canals in the Coastal Plain of Rio Grande do Sul. A total of 26,579 individuals in 119 invertebrate taxa distributed among seven Phyla were collected over the cultivation cycle investigated in rice fields and irrigation canals. The arthropods were the invertebrates which showed the greatest amount of sampled taxa. Collectors, predators, and omnivores were the prevalent functional feeding groups in this study. Naididae, Chironomidae, Spongillidae, Libellulidae, and Tubificidae families were those which showed the highest number proof genera and species. The invertebrate composition was different between rice fields and irrigation canals over the rice cultivation cycle. Besides, some ere more frequent over the rice cultivation period whereas other ones were more associated with the non-cultivation period. Rice fields and irrigation canals are systems colonized by a variety of aquatic and terrestrial invertebrates, and they present a high biologic diversity which can be hardly found in other cultivation areas.

Key words: artificial wetlands, arthropods, biodiversity, functional feeding groups.