Background: Gastropods are significant vectors of human infectious diseases and are exposed to a wide range of soil parasites and micro-organisms. To defend against infection, we hypothesized that the slug produces both soluble and cellular defense mechanisms.
Material/Methods: In the gastropod Lehmannia nyctelia, soluble antimicrobial activity was measured by disk diffusion assay and phagocytosis was measured by in vitro and in vivo uptake of fluorescent Escherichia coli bioparticles.
Results: In disk diffusion assays we failed to observe either methanol or dimethylsulfoxide soluble material in the slug secretions and tissues. However, isolation of the slug skin cells demonstrated phagocytic morphology in vitro when exposed to Escherichia coli and Staphylococcus aureus and internalization of fluorescent Escherichia coli bioparticles. Further, examination of histological sections of a slug exposed to fluorescent Escherichia coli bioparticles revealed a subset of skin cells which had cytoplasmic accumulations of the bioparticles.
Conclusions: These data suggest that the Lehmannia nyctelia skin contains active phagocytic cells that may affect the set of parasites and microbes for which slugs can serve as vectors of disease.

Keywords: Phagocytosis - physiology, Immune System - physiology, Gastropoda - physiology, Escherichia coli - pathogenicity, Epithelial Cells - immunology, Disk Diffusion Antimicrobial Tests, Anti-Infective Agents - pharmacology, Skin - immunology, Staphylococcus aureus - pathogenicity, Tissue Extracts - pharmacology