The protein and volatile components of trail mucus in the Common Garden Snail, Cornu aspersum

Abstract

The Common or Brown Garden Snail, Cornu aspersum, is an invasive land snail that has successfully colonized a diverse range of global environments. Like other invasive land snails, it is a significant pest of a variety of agricultural crops, including citrus, grapes and canola. Cornu aspersum secretes a mucus trail when mobile that facilitates locomotion. The involvement of the trail in conspecific chemical communication has also been postulated. Our study found that anterior tentacle contact with conspecific mucus elicited a significant increase in heart rate from 46.9 to 51 beats per minute. In order to gain a better understanding of the constituents of the trail mucus and the role it may play in snail communication, the protein and volatile components of mucus trails were investigated. Using two different protein extraction methods, mass spectrometry analysis yielded 175 different proteins, 29 of which had no significant similarity to any entries in the non-redundant protein sequence database. Of the mucus proteins, 22 contain features consistent with secreted proteins, including a perlucin-like protein. The eight most abundant volatiles detected using gas chromatography were recorded (including propanoic acid and limonene) and their potential role as putative pheromones are discussed. In summary, this study has provided an avenue for further research pertaining to the role of trail mucus in snail communication and provides a useful repository for land snail trail mucus components. This may be utilized for further research regarding snail attraction and dispersal, which may be applied in the fields of agriculture, ecology and human health.

Comparative Mucomic Analysis of Three Functionally DistinctCornu aspersumSecretions

“…Epiphragmin was identified in the adhesive mucus, which is used to create the epiphragm -the persistent glue that maintains bonds between the snail's shell and substrate. 36 This protein has been found previously in other snail species, such as the vineyard snail, Cernuella virgata, and is localized to the pedal surface of the foot, 18 suggesting it is conserved in mollusks and has important function in snail adhesion. Notably, 30% of the adhesive mucus is composed of only two tenascin glycoproteins.…”

“…From the 179,552 transcripts, 71 provided coding sequences for proteins based on the standard criteria of having a minimum of two identified peptides and a false discovery rate of less than 1.0 %. 18,28 All proteins were quantified based on MS/MS proteomic abundance (Supplementary Figures 5–7, Supplementary Table 2). Many of the proteins had sequence similarity ( E -value < 10 ‒ 4 ) to known proteins from snails or other mollusks, and were thus assigned identities corresponding to the specific proteins with which they shared highest similarity (Supplementary Table 3).…”

“…Using the Scaffold Local FDR (false discovery rate) algorithm, probability thresholds for peptide identifications and protein identifications were set at 95.0% and 5.0%, respectively, to achieve an FDR less than 1.0%, as per proteomic research standards. 18,28 Additionally, accepted sequences must have contained at least 2 identified peptides. Peptides were quantified by MS/MS counts.…”

“…16 These studies found that proteins in the mucus secretions of C. aspersum contain overabundances of Ser/Thr residues, N -acetylgalactosamine (GalNAc), galactose (Gal), and fucose (Fuc) glycans, and the proteins had average molecular masses of 30 kDa, while mammalian mucins are typically 100 kDa to 1 MDa with an abundance of sialic acids. 17 Broad proteomic analyses and profiling of snail mucus, focused on C. aspersum snail-snail signaling, 18 microbial interactions, 19 and comparison of proteins between multiple snail species. 20 These studies illustrate that molluscan mucus contain proteins and glycans that are not found in mammalian mucus.…”

Messages in the mucus: Selection of land snail resting sites based on the presence of mucus from conspecifics and other species

“…Secreted mucous trails of land snails differ from insect scent trails because the primary uses of mucous trails are locomotion and adhesion. Water comprised 90% or more of fresh land snail mucus and the remainder includes a wide variety of substances, including many glycoproteins, proteins, and some volatiles, such as limonene (Ballard et al, 2021).…”