Biomphalaria pfeifferi, (Krauss, 1848) (Krauss, 1848)

Ataev, Gennady L., 2023, ЭкспериментаΛьное изучение вΛияния метацеркарий Echinostoma caproni на выживаемость моΛΛюсков Biomphalaria pfeifferi, Amurian Zoological Journal XV (4), pp. 712-723 : 714-716

Mortality of B. pfeifferi due to metacercariae autoinfection

The first deaths of B. pfeifferi snails from Group 1 were registered 3 weeks PI. This is when the release of cercariae first began. More than half of the snails died a month PI ( Fig. 2 ). The last snail from Group 1 died 38 days PI. By contrast, only 3 uninfected snails (6%) from the control group (Group 5) died during the experiment.

As we mentioned earlier, the density of cercariae in the aquaria of Groups 2 and 4 was lowered artificially by either frequent filtration of water (Group 2) or by using uninfected snails (Group 4) as a biological cercarial filter in the aquarium with infected snails (Group 3).

This artificial decrease of cercarial density led to the extension of the lifespan of infected snails (Group 2 — up to 56 days, Group 3 — up to 60 days). The experiment also confirmed the pathogenicity of metacercariae since snails from Group 4 died within 58 days. Therefore, the results of the experiments on Groups 2, 3, and 4 indicate that the mortality of snails is attributed to metacercarial infection. The analysis of the survivorship curves of different experimental groups confirms this assumption ( Fig. 2 ). The graph shows that snails from Group 1 started dying sooner and faster than snails from the other groups. At the same time, survivorship curves for Groups 2–4 look very similar.

These findings are also confirmed by statistical analysis. According to the Friedman test, the conditions of the experiment significantly affect the mortality dynamics of B. pfeifferi snails. A pairwise comparison of death times between Groups 1–4 (Wilcoxon test, including the Bonferroni correction) shows that the findings on Group 1 are different from the findings on Groups 2, 3, and 4 (p <0.001). At the same time, survivorship curves for Groups 2, 3 and 4 are statistically indistinguishable (p> 0.05).

Thus, the analysis of survivorship curves of B. pfeifferi snails from different groups confirmed our assumption that E. caproni metacercariae are pathogenic to snails regardless of whether they were initially exposed to rediae or not.

Figures

Fig. 2. Dynamics of mortality of Biomphalaria pfeifferi molluscs. Group 1* — red line / 38 days PI; Group 2* — green line / 56 days PI; Group 3* — blue line / 60 days PI; Group 4 — lilac line (magenta) / 58 days PI Рис. 2. Àинамика смертности моΛΛюсков Biomphalaria pfeifferi. Серия 1* — красная Λиния /38 Δней P. I.; Серия 2* — зеΛёная Λиния / 56 Δней P. I.; Серия 3* — гоΛубая Λиния / 60 Δней P. I.; Серия 4 — ΛиΛовая Λиния (magenta) / 58 Δней P. I.