The Bioactivity and Functionality of the Molecular and Microbial Components of the Trail Mucus in the Invasive Land Snails Theba pisana and Cernuella virgata
Creators: name: Ballard, Kaylene
Publisher: name: University of the Sunshine Coast, Queensland
Year: 2023
Subjects: subject: mollusc
subject: snail
subject: mucus
subject: pheromone
subject: chemical communication
subject: transcriptomics
subject: proteomics
subject: metabolomics
subject: microbiomics
subject: Agricultural biotechnology
subject: FOS: Agricultural biotechnology
subject: Other biological sciences

description: Invasive land snails have become significant global pests to a variety of agricultural crops, including grains, canola, grapes citrus and lucerne. In Australia, the Mediterranean snails Theba pisana and Cernuella virgata are the 8th most damaging agricultural pests, causing millions of dollars of economic losses annually to the grains industry. These snails contaminate the grain harvest, leading to a downgrade or rejection by potential buyers. Although several different kinds of control methods are employed, snail numbers remain high and more innovative solutions are sought. Towards achieving that, this Thesis research used a multi-disciplinary approach to identify, compare and characterise the components of land snail trail mucus, including proteins, volatiles, metabolites and microbes, which helped inform functional bioassays.
description: Initial analysis of a land snail trail mucus was performed on the common garden snail, Cornu aspersum, which provided a basis for the development of technical approaches for identification of proteins and volatiles (Chapter 2). Subsequent investigation focussed on T. pisana and C. virgata, including during non-reproductive and reproductive stages. In Chapter 3, over 50 different proteins were identified in the snail trail mucus, some of which appeared to be species-specific, and exclusive to the reproductive stage. Based on comparative RNA-sequencing analysis, the albumen gland was a major source of trail mucus proteins at reproductive stage (Chapter 4), suggesting these proteins may relay information to conspecifics associated with reproductive maturation status.
description: In Chapter 5, snail trail mucus volatiles were profiled used 4 different methods of extraction, yet failed to provide consistent results; however, solid-phase microextraction did suggest the presence of sulcatone, undecene and an unidentified 12C hydrocarbon in the reproductive mucus trail of both species. Behavioural assays using two concentrations of sulcatone failed to elicit any observable response from snails.
description: Metabolomic profiling of trail mucus also provided evidence of species variation, as well as differences between non-reproductive and reproductive stages (Chapter 6). Metabolites upregulated during reproductive stage included caffeine, xanthine, L-tryptophan and p-hydroxyphenylacetic acid, stearic acid, palmitic acid and phenylethylamine. Preliminary behaviour assays using the aforementioned compounds indicated that snails showed a significant preference to the amino acid L-tryptophan over either water or any other location in the dish. In contrast, 5% phenylethylamine induced an aversion response, with snails significantly preferring both the water and other location in the dish. Finally, a preliminary analysis of the microbial components of trail mucus proved that numerous bacteria and fungi were present, some of which are potential crop pathogens (e.g. Fusarium spp, Macrophomina phaseolina, Mycosphaerella tassiana and Phaetheca triangularis) that could negatively impact the grain industry (Appendix I).
description: In summary, this Thesis research has provided the most comprehensive molecular analysis of land snail mucus trails, which opens the door to further research that will assist in the development of a sustainable and effective control strategy for invasive pest snails.