A Mass Spectrometry Study of Populational Changes in the Amphibian Skin Peptidomes on an Example of Moor Frog Rana arvalis Belonging to the Siberian, Slovenian, and Moscow Populations

Amphibian skin secretion provides the primary defense for frogs against various threats, including predators and pathogens. The composition of this secretion, which is rich in peptides, is unique to each amphibian species and may serve as a taxonomic biomarker, not only for frog species but also for their populations. In this study, we sequenced the components of the skin peptidome of frogs from the Novosibirsk population of Rana arvalis using a range of tandem mass spectrometry techniques, including CID, HCD, ETD, and EThcD. For the first time, we applied an alternative method for collecting secretion in field conditions, which involved manual stimulation to release the secretion. We also evaluated the applicability of the Novor.Cloud program for automatic peptide sequencing in Ranid frogs, focusing on the Novosibirsk population of R. arvalis. The skin peptidomes of the Novosibirsk, Moscow, and Central Slovenian populations of moor frogs were compared. Brevinin 1AVa, brevinin 1AVb, and the melittin-related peptide FQ-22-1, found in the skin secretion of all three populations, may serve as biomarkers for the moor frog, Rana arvalis.