Whole animal matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry of ticks – Are spectra of Ixodes ricinus nymphs influenced by environmental, spatial, and temporal factors?

by Axel Karger, Barbara Bettin, Joern M. Gethmann, Christine Klaus

In the recent years matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) has become a useful tool to characterize arthropod species and their different stages of development. It was reported for sand flies and mosquitoes at immature stages and also assumed for ticks that geographic location can have a subtle influence on MALDI-TOF mass spectra which allows the discrimination of animals with specific local variations of the MALDI-TOF MS phenotype. It is so far uncertain, however, if these mass-spectrometric differences are based on genetic variation or on spectral features which depend on environmental or temporal features. The aim of this study was to analyze the influence of the geographic location, environmental factors and the season of the year on the MALDI-TOF mass spectra of Ixodes (I.) ricinus nymphs and if spectral variation would allow to draw conclusions with respect to the tick’s provenience or conditions that influence the tick life cycle. Application of multivariate statistical models on spectra of ticks collected in different seasons and different habitats and locations within Germany showed that the impact of the location seemed to be small while season and habitat seemed to have stronger impact on the MALDI-TOF mass spectra. Possibilities and limitations of MALDI-TOF mass spectra to draw conclusions on the tick life cycle are discussed.