Discussion
The majority of Biomphalaria and Bulinus snails, withdrawn into their shell through the initial 24 hours, were found to have died at the end of the experiment. None of the snails survived 20mg/ml extract concentration except for Biomphalaria juveniles. The significant difference between susceptibility of juveniles and adults to the ethanol extracts agrees with the results from previous studies by Anto et al. (2005); Omobhudhe (2017) and Ping et al. (2017). Throughout the study, high concentrations of both ethanolic and water extracts of pumpkin seeds showed substantial molluscicidal activities with LC50 values that were clear-cut below the upper threshold of 40 mg/L set for a potential molluscicide by the WHO (WHO, 1993). 100% mortalities were observed in adult Biomphalaria and Bulinus exposed to the highest concentration of both water and ethanol extracts. The susceptibility of Biomphalaria snails to the extracts could be attributed to the fact that they have no operculum; thus, their cephalopodia were continuously in contact with the molluscicide during the assays (Ping et al., 2017).
The present outcomes might have been due to metabolic disorders, loss of muscle coordination which prompts snail's death (Labe et al., 2012). As is valid for the mechanism of action of many insecticides, the activity of a molluscicide may possibly be a multi-part process, influencing more than one of the snails’ internal systems. Various such reactions that provide evidence for this have been recorded in the literature, for example; decrease in heart rate, swelling of tissues and change in the water balance (McCullough et al., 1980; WHO 2017).