This study describes the application of a protocol for biological assessment of water quality at first to third order streams at Serra dos Ó rgã os, an area covered by Atlantic Forest in Rio de Janeiro State, Brazil. Major impacts in the region are domestic effluents and deforestation. Our main objective is to establish biocriteria for the establishment of the Serra dos Ó rgã os Multimetric Index (SOMI) based on benthic macroinvertebrates. We used data from previous studies, sampled by experienced biologists, from 1999 through 2002. The benthic macroinvertebrate community was sampled in 12 reference sites and seven impaired sites in three river basins: Guapimirim, Macaé and Grande, all from the same bioregion. From the 22 tested metrics, 6 were included in the SOMI (% Diptera, % Coleoptera, Family Taxa, EPT Taxa, BMWP-CETEC and % Shredders). Scores (5, 3 or 1) were developed for these metrics to allow for aggregation into the index. Seven intermediately impaired sites were used for evaluating the applicability of the multimetric index. We concluded that the SOMI is a robust easy-to-apply tool for biomonitoring programs in the Serra dos Ó rgã os region, south-east Brazil.

No abstract

The aim of this study was to determine the toxicity of niclosamide (Bayluscide ®) on Melanoides tuberculata and Biomphalaria glabrata under laboratory conditions. The latter species is the intermediate host of Schistosoma mansoni (Sambon 1917). M. tuberculata was successfully used as competitor of B. glabrata in biological control programs in French West Indies. Both molluscicide and biological control using M. tuberculata have proved to be successful in reducing the population density of B. glabrata. The associated use of molluscicide in this area would be an effective measure if M. tuberculata were less susceptibility to the molluscicide than B. glabrata. Three hundreds individuals each of B. glabrata and of M. tuberculata, collected in Sumidouro, State of Rio de Janeiro, were used in the experiment. The molluscs were exposed to 14 different concentrations of niclosamide as recommended by the World Health Organization. Probit analysis was used to determine the LC 50 and LC 90. The LC 50 and LC 90 values for B. glabrata were 0.077 mg/l and 0.175 mg/l, respectively and the LC 50 and LC 90 values for M. tuberculata were 0.082 mg/l and 0.221 mg/l respectively. As the lethal concentrations of niclosamide were approximately the same to both species, this could be a disadvantage when controlling B. glabrata with niclosamide in an area of M. tuberculata occurrence. It migth therefore be preferable to utilize the latex extracted from the Euphorbia splendens, which presented a much higher efficiency for B. glabrata than to M. tuberculata

Interactions between two species that result in reduced growth

(WHO 1984, Madsen 1990, Sturrock 1995, Pointier & Giboda 1999. In the West Indies, the thiarid Melanoides tuberculata was effective in the elimination or reduction of populations of Biomphalaria glabrata, the intermediate host in the cycle of schistosomiasis , 1991a, Pointier & McCullough 1989, Pointier & Guyard 1992, Pointier 1993, Schlegel et al. 1997. However, in Venezuela M. tuberculata was introduced in 20 sites, but only in three sites was Biomphalaria spp. eliminated or effectively reduced (Pointier et al. 1991c). In Brazil, the first occurence of M. tuberculata was reported in 1967, in Santos, State of São Paulo. After that, this snail has spread to other localities, probably as a result of successive accidental introductions associated with fish farms (Vaz et al. 1986). However, there are few reports of interaction between M. tuberculata and species of the genus Biomphalaria in Brazil. glabrata reached a larger size and produced more cercaria of S. mansoni (Moné 1991). These results point to the dangers of species introductions for biological control based on poor knowledge and weak assumptions of species interactions. The effectiveness of M. tuberculata for biological control of B. glabrata in a specific environment can be evaluated only when the ecology of these species and the nature of their interactions are understood.Here, our objectives were to test two hypotheses: that M. tuberculata has a negative effect on the growth and demography of B. glabrata (H1), and that a substance liberated by M. tuberculata causes this negative effect (H2). The second hypothesis was proposed previously for Thiara granifera, another thiarid (Prentice 1983, Gomez et al. 1990, Perez et al. 1991. Two laboratory experiments were performed to test these hypotheses. MATERIALS AND METHODSIndividuals of M. tuberculata and B. glabrata were collected in streams of two valleys in the municipality of Sumidouro, RJ, Brazil (22 o 02'59"S, 42 o 40'29"W). In laboratory, these individuals were raised in 74 x 237 x 330 mm plastic containers with 2 l of dechlorinated tap water. Dehydrated lettuce and rodent food pellets (3-4 mm large) were provided ad libitum, and temperature varied between 22 and 27 o C during the study. Containers were checked at least every two days to remove dead individuals, to guarantee ad libitum food, and that rodent pellets stayed on the bottom. The water was changed every fortnight to avoid any crowding effect, when the number of egg masses, embryos, young and adults was counted. These