Aquatic snails from mining sites have evolved to detect and avoid heavy metals

Area of Science:

• Ecotoxicology
• Behavioral Ecology
• Environmental Science

Background:

• Pollutants are often unevenly distributed in the environment.
• Organisms can evolve to detect and avoid toxicants, rather than passively absorb them.
• Physella columbiana, an aquatic pulmonate snail, thrives in heavy-metal-polluted sites where it is rare at reference locations.

Purpose of the Study:

• To investigate the avoidance behavior of Physella columbiana snails exposed to heavy metals.
• To determine if the ability to avoid heavy metals is an evolved, heritable trait.
• To assess the potential of these snails as a bio-indicator for aquatic pollution.

Main Methods:

• A Y-maze flow tank was used to test snail avoidance of polluted sediments and solutions of cadmium, zinc, and lead.
• Behavioral assays were conducted on snails from a polluted site, their lab-reared offspring, and snails from a reference site.
• Sensitivity to heavy metals was compared across these different snail populations.

Main Results:

• All tested snails could detect low concentrations of heavy metals.
• Snails from the polluted site were most sensitive, followed by their offspring, and then snails from the reference site.
• Avoided metal concentrations were below those found in polluted hotspots, suggesting active avoidance contributes to survival.

Conclusions:

• The ability of Physella columbiana to avoid heavy metals is influenced by both genetic and environmental factors.
• Snails may persist in polluted areas by actively moving to less contaminated zones.
• The Y-maze assay using aquatic snails presents a cost-effective, sensitive method for detecting aquatic pollution, particularly in resource-limited regions.