16 research outputs found
Molluscicidal activity of Moringa oleiferaon Biomphalaria glabrata: integrated dynamics to the control of the snail host of Schistosoma mansoni
The ground seed of Moringa oleifera Lam., Moringaceae, has been evaluated for its molluscicidal activity against the snails Biomphalaria glabrata, Physa marmorata and Melanoides tuberculatus. The results show that M. oleifera is active against B. glabrata (LC50 0.419 g/l; LC90 1.021 g/l and P. marmorata (LC50 0.339 g/l; LC90 0.789 g/l) but has no effect against M. tuberculatus. The great innovation of the use of M. oleifera, in addition to being innocuous to humans, is the present nutritional potential for humans and animals as well as providing an ecosystemic service as water purifier
Interaction between the Intermediate Host of Schistosomiasis in Brazil Biomphalaria glabrata (Planorbidae) and a Possible Competitor Melanoides tuberculata (Thiaridae): I. Laboratory Experiments
The biological control of Biomphalaria glabrata, intermediate host of Schistosoma mansoni, is one the accepted options to fight schistosomiasis. One of the most promising candidates to control B. glabrata is the snail Melanoides tuberculata, a potential competitor. However, the mechanisms of interaction between the two species are not clear. Our objective is to determine if M. tuberculata indeed compete with B. glabrata, using two laboratory experiments. In Experiment 1, we tested the effect of the presence of M. tuberculata on the fecundity and mortality rates of B. glabrata. In Experiment 2, we tested if there was a direct or indirect interaction between the two species. In Experiment 1, M. tuberculata was eliminated after the peak in reproductive activity of B. glabrata. In Experiment 2, B. glabrata produced more egg masses when raised with M. tuberculata. The conditions leading to this unexpected positive effect of M. tuberculata on the fecundity of B. glabrata need further clarification, but emphasize that detailed studies of the interaction between these species in the conditions of the local environment should be considered
SHORT COMMUNICATION - Apparent Competition Through Facilitation between Melanoides tuberculata and Biomphalaria glabrata and the Control of Schistosomiasis
Interactions between two species that result in reduced growth rates
for both and extinction of one of the species are generally considered
cases of asymmetric interspecific competition. Exploitative or
interference competition is the usual mechanism invoked. Here we
describe another mechanism producing the same result, named apparent
competition through facilitation (ACF), observed between Melanoides
tuberculata and Biomphalaria glabrata populations.
The superior competitor actually gives some benefit to the other
species, whose population becomes unstable with progressively
increasing oscillations, leading to extinction. A model of ACF using
difference equations suggests initial dynamics distinct from
traditional interspecific competition. The dynamics of two freshwater
snails in the field and in laboratory experiments suggest ACF, and
these relations should be considered in studies of schistosomiasis
control. ACF could occur in natural populations, but might have gone
undetected because the final result is similar to traditional
interspecific competition
The Molluscicidal Activity of Niclosamide (Bayluscide WP70®) on Melanoides tuberculata (Thiaridae), a Snail Associated with Habitats of Biomphalaria glabrata (Planorbidae)
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