Comparative toxicity of Euphorbia milii latex and synthetic molluscicides to Biomphalaria glabrata embryos

Abstract

Plant molluscicides have been regarded as possible alternatives to the costly and environmentally hazardous molluscicides currently available. This study was undertaken to compare the developmental toxicity of a plant molluscicide (Euphorbia milii latex, LAT) with that of three synthetic molluscicidal compounds. Biomphalaria glabrata egg masses (0-15 h after spawning) were exposed to molluscicides for 96 h and thereafter examined up to the 14th day after spawning. Embryo deaths, abnormal embryo development (malformations) and the day of hatching were recorded. Although exhibiting a weak ovicidal effect, LAT markedly impaired the development of snail embryos at concentrations 1000 microg L(-1) and produced anomalies (EC(50)=2040 microg L(-1)) such as abnormal shells, hydropic embryos, cephalic and non-specific malformations. Embryolethal potencies of molluscicides were as follows: triphenyltin hydroxide (TPTH; LC(50)=0.30 microg L(-1))>niclosamide (NCL; LC(50)=70 microg L(-1))>copper sulphate (CuSO(4); LC(50)=2190 microg L(-1)) >>> LAT (LC(50)=34030 microg L(-1)). A few malformations were recorded in embryos exposed to concentrations of TPTH within the range of lethal concentrations, while almost no anomalies were noted among those treated with NCL or CuSO(4). A hatching delay (hatching on day 10 after spawning or later) was observed among LAT-exposed embryos. The effects of NCL, TPTH and CuSO4 on hatching were to some extent masked by their marked embryolethality. The no-observed effect concentrations (NOEC) for embryotoxicity were as follows: TPTH, 0.1 microg L(-1); NCL, 25.0 microg L(-1); CuSO(4), 500.0 microg L(-1) and LAT, 500.0 microg L(-1). Results from this study suggest that, although LAT was not acutely embryolethal after a short-term exposure, it markedly disrupted snail development. The marked embryotoxicity of E. milii possibly contributes to its effectiveness as a molluscicide.

OVICIDAL EFFECT OF PIPERACEAE SPECIES ON Biomphalaria glabrata, Schistosoma mansoni HOST

“…Studies with molluscicides compounds show that it is usual to obtain the death of B. glabrata snail but not the embryos 18 23 25 . The lack of ovicidal activity allows the permanence of the snail host in the environment, maintaining the transmission of schistosomiasis.…”

Molluscicidal activity of some marine substances against the snail Biomphalaria glabrata (Mollusca, Planorbidae)

“…We observed that snail embryos became abnormal, presenting shell and cephalic malformations with disaggregated cells or hatching delay, when exposed to L. farinosa apolar extract, probably due the antimitotic action of this extract previously observed by Mendonça et al (1997). Oliveira-Filho et al (2010) observed that a substance that induces embryotoxicity can lead to reduced viability of exposed eggs. Moreover, if these malformed embryos can hatch, a hatching delay itself may damage post-hatching growth and survival and reduce the snail population in an infested region.…”

“…The normal embryonic development has been described in detail (Camey and Verdonk 1970;Kawano et al 1992) and showed well-defined and easily recognizable stages allowing the detection of morphogenetic effects. It has been used at the Butantan Institute for more than 30 years to evaluate the mutagenicity and toxicity of chemical (Estevam et al 2006;Kawano et al 1979;Kawano and Simões 1986;Nakano et al 2003;Oliveira-Filho et al 2010;Rapado et al 2011;Ré and Kawano 1987) and physical agents (Okazaki et al 1996;Tallarico et al 2004). In this work, crude extracts of marine organisms from northern coastline of São Paulo State (Brazil) were assessed to detect molluscicidal and ovicidal properties against B. glabrata.…”

Usnic Acid Potassium Salt: An Alternative for the Control of Biomphalaria glabrata (Say, 1818)

“…It is estimated that more than 7000 chemicals have been tested for mollusk control, such as copper sulfate, gramoxone, calcium hydroxide, N-tritylmorpholin (Frescon) and niclosamide [6], [7]. Niclosamide is highly efficient in all stages of the mollusk lifecycle, killing 100% of adults and embryos at a concentration of less than 1.5 µg/ml after 2 h of exposure [8].…”