McLennan, H.J.Sutton-McDowall, M.L.Heng, S.Abell, A.D.Thompson, J.G.2021-01-132021-01-132020Reproduction, Fertility and Development, 2020; 32(14):1223-12381031-36131448-5990http://hdl.handle.net/2440/129527Oocyte activation, the dynamic transformation of an oocyte into an embryo, is largely driven by Ca²⁺ oscillations that vary in duration and amplitude across species. Previous studies have analysed intraoocyte Ca²⁺ oscillations in the absence of the oocyte’s supporting cumulus cells. Therefore, it is unknown whether cumulus cells also produce an ionic signal that reflects fertilisation success. Time-lapse confocal microscopy and image analysis on abattoir-derived cattle cumulus–oocyte complexes coincubated with spermatozoa revealed a distinct discharge of fluorescence from the cumulus vestment. This study demonstrated that this Ca²⁺ fluorescence discharge was an artefact induced by the imaging procedure independently of oocyte activation success. The fluorescence discharge was a direct result of cumulus cell membrane integrity loss, and future studies should consider the long-term effect of fluorescent labels on cells in time-lapse imaging. However, this study also demonstrated that the distinctive pattern of a coordinated fluorescence discharge was associated with both the presence of spermatozoa and subsequent embryo development to the morula stage, which was affected by Ca²⁺ chelation and a reduction in the active efflux of the fluorophore. This indicates that the cumulus vestment may have a relationship with oocyte activation at and beyond fertilisation that requires further investigation.enJournal compilation © CSIRO 2020Calcium oscillations; confocal imaging; embryo development; fertilisation; fluorescent probes; oocyte activationJournal article100002732210.1071/RD201430005759756000012-s2.0-85093513882550802McLennan, H.J. [0000-0002-2058-2488]Sutton-McDowall, M.L. [0000-0002-4121-0202]Abell, A.D. [0000-0002-0604-2629]Thompson, J.G. [0000-0003-4941-7731]