The role of behavior in the survival of Biomphalaria glabrata in biossays with the plant molluscicide Phytolacca dodecandra

Abstract

This work examines the role of behavior in the survival of Biomphalaria glabrata exposed to 25, 50, 75 and 100 mg l-1 of Phytolacca dodecandra. Time-lapse cinematography was used to quantify accurately the following parameters: (a) frequency of exits from the solution, (b) time spent out of the solution and (c) time elapsed until the first exit from the solution. These behavior patterns were statistically compared between surviving snails and those which later died. The proportion of surviving snails leaving the liquid medium was significantly higher than that of dying snails. In addition, the surviving group spent significantly more time out of the solution than the group which died, except for the 100 mg l-1 concentration. However, no significant difference was detected in the time elapsed until the first exit from the solution. It can be concluded that both the tendency to leave the P. dodecandra solutions, and the time spent out of them, contributed significantly to snail survival. Molluscicide bioassays should take into account the possibility that some behavior patterns of planorbids might contribute to the protection of the snails.

Effects of Bayluscide WP 70® on the Survival and Water-leaving Behaviour of Biomphalaria straminea, Snail Host of Schistosomiasis in Northeast Brazil

“…This is not unexpected, as leaving the water prevents prolonged contact with molluscicide. Increased survival due to water-leaving behaviour was also reported for B. glabrata exposed to the plant molluscicide Phytolacca dodecandra (Jurberg et al 1988).…”

“…Thus, it is likely that some snails may escape mollusciciding by leaving the water and survive long enough to recolonize the transmission foci after the toxic effects are over. The epidemiological importance of water-leaving behaviour by snail hosts of schistosomiasis in relation to molluscicides has been well emphasized (Pieri & Thomas 1986, Jurberg et al 1988, Dussart 1991, Green et al 1992, Dannemann & Pieri 1993. However, the occurrence of other patterns of protective behaviour which could hamper the chemical control of snail hosts should also be considered.…”

Laboratory assessment of molluscicidal and cercariacidal effects of Glinus lotoides fruits

“…Azare et al [ 13 ] also observed movement of snails to the side of the container in an attempt to escape from the test media containing Althernanthera sessils treated water. The mechanism of B. pfeifferi partially leaving the treated water has been found to increase the survival of B. straminae exposed to sub lethal doses of niclosamide [ 36 ] and B. glabrata exposed to Phytolacca dodecandra [ 37 ].…”

A laboratory assessment of the potential molluscicidal activity of some Nigerian plant species used as anthelmintics

“…Such behaviour, by which the snails tended to avoid continuous contact with extract, has been found to increase the survival of Biomphalaria species exposed to sub-lethal doses of toxic substances (Jurberg et al 1988, Sarquis et al 1997.…”