Seasonal Changes in the Seminal Plasma Proteome of the Crab-Eating Fox ( <i>Cerdocyon thous</i> )

The objective was to analyze seasonal changes in the seminal plasma proteome of crab-eating fox (<i>Cerdocyon thous</i>). Semen was collected in Brazil from March 2021 to March 2022 from five healthy adult males housed individually. Collections were performed without chemical or physical restraint by digital manipulation of the penis, and seminal plasma proteomics were assessed by mass spectrometry (ESI Q-Tof MS/MS) on 43 ejaculates from the reproductive season and four from the nonreproductive season. A total of 408 proteins were identified: 219 exclusives to the reproductive season (June-September), 90 to the nonreproductive season (October-May), and 99 shared between both. Protein abundance differed significantly between seasons. Proteins related to enzymatic and oxidoreductase functions predominated in the nonreproductive season, whereas those linked to sperm metabolism and reproductive processes were more abundant in the reproductive season. Among these, olfactory receptor, strawberry notch homologue, and zinc finger protein were considered potential reproductive season biomarkers, with AUC > 0.80 in the receiver operating characteristic analysis. This is the first study describing the seminal plasma proteome and its seasonal variation in the crab-eating fox, identifying biomarkers with potential applications in conservation and reproductive management of this and other endangered canids.