Invasive snails

Unveiling dietary preferences of Theba pisana between green and decaying leaves : the potential of Fecal Near-Infrared Spectroscopy

Imagine a snail so troublesome it can take down an entire harvest. Urgency grips us to devise more precise control methods, doesn't it ? This study is crucial because it proposes a new method to investigate snails' diet : Fecal-NIRS. Our study aims to investigate Theba pisana preferences between green and decaying leaves. We compared wild snail's faecal hyperspectral images to those of control snails fed, either only with living or decaying leaves. We also aim to investigate the link between Theba pisana’s shell size and diet. Unlocking the secrets of Theba pisana's diet, could pave the way for crafting more effective pest management strategies.

MATERIEL AND METHODS

NIRS images of snail’s faeces from S3-D group (left) and one sampling of the S3-D group (right).

Centralisation and normalisation

Noise reduction

Spectrum pre-treatment

Multiplicative & additive effects reduction

RESULTS AND INTERPRETATIONS

Spectra of the faeces from the two control groups of snails, fed either with green leaves of Malva setigera or decaying ones are different : There is a statistical relationship between the reflectance of snails’ faeces in the near infrared region and their diet : Faecal-NIRS appears as a promising technology in investigating snails’ diet

Evidence of spectral signatures from green and senescent leaves in spectra faeces from control snails fed either on green or decaying leaves : Snails ingested leaves but assimilated very little Presence of cholrophyll reflectance peak at 680 nm in the faeces spectra of control snails : Chlorophyll is not degraded during the snail’s digestion process.

Accuracy (86%) of the PLS-DA model in predicting wild snails diet when calibrated with control snails' diet : Theba pisana is mainly feeding on decaying leaves of Malva setigera in the sampling area

Inaccuracy (45%) of the PLS-DA model in predicting wild snails diet when calibrated with control snails' shell size : The diet of Theba pisana between living and decaying leaves Malva setigera is not influenced by its age