LAUSR

Abstract An understanding of how seasonality impacts amphibian's sperm quality is crucial for the development and implementation of assisted reproductive technologies for threatened species. We analysed sperm quality both within and outside the breeding season for the common natterjack toad (Epidalea calamita) in a population close to Madrid (Spain). Fresh hormonally induced sperm samples were assessed for sperm concentration, total activated sperm (TAS), forward motility (FM), quality of motility (QM) and DNA integrity (DNAi). Motility and DNAi were re-evaluated after cold-storage at 5 °C for 24 h. After freezing and thawing DNAi was re-analysed and a fertilization trial performed to test post-thaw sperm functionality. More males presented sperm after hormone administration during the breeding season compared to out of season (78.3 vs. 52.2%), although the difference was not significant. Fresh sperm motility and DNAi were not affected by season (p > 0.05). However, sperm concentration was higher (p = 0.037) during the breeding season (5.2 vs. 2.9 × 106 sperm/ml). After cold-storage sperm obtained in the breeding season presented higher FM (36.1 ± 4.6 vs. 22.0 ± 3.5%; p = 0.013) and QM (1.28 ± 0.2 vs. 0.68 ± 0.2; p = 0.017) than samples from out of season. DNAi decreased after freeze-thawing in both seasons (p