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How does urbanization shape shell phenotype, behavior, and parasite prevalence in the snail Cornu aspersum?
Maxime Dahirel1, Youna de Tombeur2, Claudia Gérard2
1Department of Biology, Ghent University, B-9000, Ghent, Belgium.
Current Zoology
|April 6, 2026
Summary
Urbanization impacts snail size, but not shell color or behavior. Snails with larger shells or paler coloration were more susceptible to parasites, affecting their feeding and movement.
Area of Science:
- Ecology
- Environmental Science
- Zoology
Background:
- Urbanization causes significant environmental changes, including habitat loss and altered climate, impacting organismal traits.
- Organismal responses to urbanization are often studied in isolation, hindering a holistic understanding of adaptation.
- The brown garden snail (Cornu aspersum) is a model organism for studying urbanization effects due to its widespread distribution.
Purpose of the Study:
- To investigate the effects of urbanization on multiple phenotypic traits of Cornu aspersum, including shell size, shell reflectance, behavior, and parasite prevalence.
- To determine how urbanization gradients influence the interplay between snail phenotype and parasite infection.
- To assess the ecological consequences of urbanization on snail populations.
Main Methods:
- Studied Cornu aspersum along an urbanization gradient in Rennes, France.
- Measured shell size, shell reflectance, food intake, mobility, and metazoan parasite prevalence.
- Analyzed the relationship between urbanization levels and phenotypic traits, as well as parasite infection status.
Main Results:
- Snails from more urbanized areas were significantly smaller.
- Urbanization did not have a detectable effect on shell reflectance, parasite prevalence, or general behavior.
- Larger snails and those with paler shells showed higher infection rates with specific parasites (trematode metacercariae and Nemhelix bakeri).
- Parasitized snails exhibited altered behaviors: trematode-infected snails ate less, while N. bakeri-infected snails moved slower.
Conclusions:
- Urbanization, potentially via the Urban Heat Island effect and reduced resource availability, drives a decrease in snail size.
- The lack of urbanization effects on other traits may stem from scale mismatches in how urbanization is perceived at different environmental levels.
- Further research is needed to understand the complex interactions between urbanization, snail phenotype, life-history traits, and parasitism.
