Effects of Niclosamide and Plant Extract Molluscicides on theDifferent Developmental Stages of Freshwater Snails Physa acuta

The effect of synthetic molluscicide(Niclosamide) of different concentrations on the survival of fresh water snails, Physa acuta (Draparnaud), Lymnaea auricularia(L)- [pulmonats] and Melanopsis praemorsa (Linnaeus)-[Prosobranchates] in Mosul area was investigated, with emphases on the comparative effects of Niclosamide and botanical molluscicides (Euphorbia helioscopia [EE] and Melia azedirachta [MA] on fecundity and developmental rate of Physa acuta. There were variable lethal effects of different Niclosamide concentrations on the fresh water snails as well as on Mosquito fish(Gambusia affinis). The doses used in this study (5 ppm – 50 ppm) had more effect on Pulmonate snails (L. auricularia and P. acuta), that were with out operculum than did on the Prosobranchia snail (M. praemorsa) that possess operculum. The Mosquito fish was affected by synthetic Molluscicide in a very short duration of time. The ovicidal action of Niclosamide as well as the botanical molluscicide (E. helioscopia and M. azedirachta) against the fecundity of P. acuta was found to have an negative effect on the eggs survival period, as the molluscicide concentration increased. Physa acuta snails treated with (2 ppm) Niclosamide showed an increase in shell length during the first four days of the beginning of experiment reaching (1.0,mm). Snails died by the 6th day of the experiment. Snails treated with (5 ppm) Niclosamide showed a slight increase in shell length (0.5 mm) from the 2nd to the 5th day of experiment after which they all died. Individuals treated with(5 ppm) E. helioscopia extract showed an increase in the shell length reaching (0.5 mm) within a couple of days, then died after 7th day of the experiment, while those treated with same dose of M. azedirachta, reached 0.9 mm shell length by the 7th day, but the increase in shell length continued up to the 21st day of the experiment reached 6.74 mm, after which all died. No side effects of the botanical extracts were observed on concomitantly exposed Mosquito fish, however Niclosamide was lethal to the fish within 30 minutes at concentrations that were non-lethal to snails.