Assessment of MALDI-TOF MS for Arthropod Identification Based on Exuviae Spectra Analysis

MALDI-TOF MS is an innovative tool for identifying hematophagous and non-hematophagous arthropods at various life stages. However, identification by MALDI-TOF MS currently requires euthanizing of the specimen, hindering further phenotypic tests. All arthropods have a common factor, molting of their exoskeletons leaving a remaining structure known as the exuviae. This phenomenon is indispensable for their growth and can evidence past arthropod presence. This study assessed the performance of MALDI-TOF MS biotyping for arthropod identification using exuviae from nine distinct laboratory-reared species (Aedes aegypti, Anopheles coluzzii, Cimex lectularius, C. hemipterus, Pediculus humanus humanus, Triatoma infestans, Rhodnius prolixus, Supella longipalpa and Blattella germanica) compared its efficiency with a molecular identification approach using DNA sequencing. Molecular analysis showed low DNA quantity in exuviae (n = 108) across species, resulting in low success of COI, 16s, and 18s amplification (50.0%), depending on the species and sequencing (10.2%). The establishment of an exuviae protocol for MS submission yielded spectra of high reproducibility and specificity per species. After upgrading a homemade reference MS database with exuviae spectra, a query with remaining spectra revealed that 100% of samples were correctly identified, with 85.8% (278/324) exceeding the threshold score value for reliable identification. MALDI-TOF MS showed high efficiency in identifying various arthropod species based on their exuviae. This approach is a groundbreaking development in the field of entomology underlining that MALDI-TOF outperformed traditional methods of exuviae identification, including morphological and molecular tools. It also prevents specimen sacrifice which could be used for complementary analyses.