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WP3 Aquatic Toxicology
(433) Pokeweed (Phytolacca americana) as a Potential Molluscicide for Use in Aquaculture.
Allen-Gil, S1, Aldea, M1, 1 Biology Department, Ithaca College, Ithaca, NY, USA
ABSTRACT- The aquatic snail Viviparus georgianus is an invasive species of mollusk in the Eastern United States. Ripe berries of the putative molluscicidal plant pokeweed (Phytolacca americana L.) were used in toxicity tests on V. georgianus and fathead minnow larvae (Pimephales promelas). Static toxicity tests were conducted on the snails and the fish separately to assess acute and chronic toxicity at two levels of exposure (200 mg L-1 and 500 mg L-1). Dry pokeweed berries were applied to the experimental tanks in three identical applications, two days apart, each meant to maintain the desired concentration, accounting for natural degradation rates. At 7 days the snail mortality for the 500 mg/L treatment (55%, P<0.01) was significantly higher than the 200 mg/L (10%, P<0.01) and control (0%) (P<0.001). At 30 days after the initial exposure (same snails used for the 7-day) the treatment effect was still significant with a snail mortality of 95% (P<0.001) for the highest concentration, 75% (P<0.01) for the 200 mg/L and 15% for control (P<0.001). In an 8-day exposure test identical to the one used on the snails, there was no significant increase in mortality (P=0.39) at any of the tested concentrations on larval (30 days old) fathead minnows (P. promelas). There were, however, indications of sublethal effects for the 500 mg L-1 treatment, manifested as impaired growth (P=0.04). Pokeweed is the American variety of the Ethiopian plant Endod (Phytolacca dodecandra), which has been reported to contain the highly potent molluscicidal substance oleanolic acid glucoside. Yet, LC/MS/MS investigations of pokeweed berry extracts showed no definitive evidence to support that any type of oleanolic acid glycoside or oleanolic acid itself were present in the preparations. We conclude that pokeweed berries have significant molluscicidal properties, but in concentrations far too high for use in practical applications.
Key words: molluscicide, Phytolacca americana, Viviparus georgia, Pimephales promelas
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