Mucus Trail Proteins May Infer Reproductive Readiness for Land Snails

Mucus trails are defining features of the class Gastropoda, which includes snails and slugs. While several studies have shown that mucus trails are followed by conspecifics, the detectable elements in the mucus have not been clearly identified. This is particularly relevant during periods of reproduction, whereby conspecific cues are critical for mate finding. A better understanding of the mucus' molecular components, including proteins differentially represented between the reproductive and non-reproductive stages, could aid the development of novel eco-friendly biocontrol approaches. In this study, we investigated the mucus trails of the globally invasive land snail Cernuella virgata, which has become a significant pest to the grain industry. We conducted a comparative proteomic analysis of the non-reproductive- and reproductive-stage trail mucus, whereby 533 proteins were identified, including 191 and 226 stage-exclusive proteins, respectively. Subsequent comparative tissue transcriptomic analysis found that the albumen gland, which is the key gland for the preparation of fertilized eggs prior to egg laying, was the primary source of secreted proteins present in the reproductive stage trail mucus. This included leukocyte elastase inhibitors, achacin, perlucin, and other proteins without any known function (uncharacterized). In summary, our results strongly implicate the albumen gland as a source for snail trail mucus proteins deposited during the reproductive stage, suggesting a mechanism that could convey their reproductive status to conspecifics. Further research testing their bioactivity related to chemical communication is paramount and may assist in the development of a novel biocontrol strategy.