The ability of whale haploid spermatogenic cells to induce calcium oscillations and its relevance to oocyte activation.

Interspecies microinsemination assay was applied to examine the ability of minke whale haploid spermatogenic cells to induce Ca2+ oscillations and oocyte activation. Populations of round spermatids (RS), early-stage elongating spermatids (e-ES), late-stage elongating spermatids (1-ES) and testicular spermatozoa (TS) were cryopreserved in the presence of 7.5% glycerol on board ship in the Antarctic Ocean. Repetitive increases of intracellular Ca2+ concentration occurred in 0, 65, 81 and 96% of BDF1 mouse oocytes injected with the postthaw RS, e-ES, 1-ES and TS, respectively. A normal pattern of the Ca2+ oscillations was observed in 26-47% of the responding oocytes. Most oocytes that exhibited Ca2+ oscillations, regardless of the oscillation pattern, resumed meiosis (83-94%). These results indicate that whale spermatogenic cells acquire SOAF activity, which is closely related to their Ca2+ oscillation-inducing ability at the relatively early stage of spermiogenesis.