1. The effect of habitat structural features and physicochemical characteristics of the water on the composition and richness of fish assemblages in temporary ponds near streams were examined at three spatial scales: among ponds, among streams and between drainage basins, in a 'terra-firme' (not subject to long-term flooding) forest reserve in Central Amazonia. 2. The fish assemblage in temporary ponds was composed of subsets of 18 small-bodied species widely distributed in the reserve. The assemblages had a nested subset structure, where smaller ponds contained subgroups of the species found in larger ponds. 3. Species composition and richness in temporary ponds were similar between drainage basins, although the fish assemblages in streams differed between basins. 4. Fish assemblage structure was influenced by local factors related to habitat structure, such as pond area and depth, canopy cover and hydroperiod. Physicochemical characteristics of the water in the ponds were similar between drainage basins and had little detectable effect on the structure of pond fish assemblages. 5. No correspondence was found between the composition, richness or abundance of fishes in the ponds and in stretches of the streams adjacent to the ponds. Therefore, it is not possible to predict the composition of these temporary pond fish assemblages from the fish assemblages found in adjacent streams.

In the Amazon, a large number of native and exotic toxic plants and of suspected toxicity has been described (see Tokarnia et al., 2007). Amazonian aquatic and semi-aquatic plants are consumed by a variety of aquatic organisms, including the Amazonian manatee, an herbivorous aquatic mammal of wide distribution in the Amazonian ecosystem. This species has been historically hunted by local communities until current days. In a recent study about the diet of Amazonian manatees in the Mamirauá and Amanã sustainable development reserves, Guterres-Pazin (2010) reported on up to 49 plant species consumed by the manatee, most of which previously undescribed in the literature. Here we identify those plants of the Amazonian manatee diet that contain toxic principles and the effects of the toxic components on other (terrestrial) mammals. RESUMONa Amazônia, um grande número de plantas tóxicas, nativas e exóticas, e de toxicidade suspeita, tem sido descrito (ver TOKARNIA et al., 2007). Plantas aquáticas e semi-aquáticas da Amazônia são ingeridas por uma variedade de organismos aquáticos, incluindo o peixe-boi amazônico (Trichechus inunguis), um mamífero aquático herbívoro de ampla distribuição no ecossistema amazônico. Animais dessa espécie têm sido historicamente caçados pelas comunidades humanas locais, até os dias de hoje. Em um estudo recente sobre a dieta de T. inunguis nas reservas de desenvolvimento sustentável Mamirauá e Amanã, Guterres-Pazin (2010) relatou 49 espécies de plantas ingeridas, a maioria das quais ainda não descritas na literatura. Nesta nota, identificamos algumas plantas componentes da dieta do peixe-boi amazônico que contêm princípios tóxicos e os efeitos dos componentes tóxicos em outros mamíferos (terrestres).