Asian elephant (Elephas maximus) seminal plasma: establishing the proteome and effect on spermatozoa when added to cryomedium

Abstract

Context. The removal or supplementation of ejaculates with seminal plasma (SP) can affect cryotolerance and post-thaw survival of spermatozoa in many species. In the Asian elephant (Elephas maximus), elucidation of the SP proteome and investigation of how it affects spermatozoa may enable improvement of cryopreservation protocols. Aims. Herein, we characterise the Asian elephant SP proteome and investigate the impacts of SP on sperm cryotolerance in the presence of conspecific or heterospecific SP. Methods. Proteomic analysis of Asian elephant SP was performed using mass spectrometry on nine samples from three individuals. In a separate study, SP was removed from six ejaculates and spermatozoa were resuspended in Tris extender supplemented with: no seminal plasma (NOSP), conspecific SP from ejaculates exhibiting ‘good’ (GSP, >60%) or mixed sperm total motility (MSP), or horse SP (HSP). Samples underwent cryopreservation, and sperm parameters were compared prior to cryopreservation and after thawing (0 and 2 h). Key results. Mass spectrometry identified 155 proteins from an array of families. Significant differences were observed in post-thaw sperm quality between SP treatments: high concentrations of MSP (25%, v/v) displayed greater average path and straight-line velocity immediately after thawing (P < 0.05) and greater sperm motility index and beat cross frequency than NOSP after 2 h post-thaw incubation (P < 0.05). The addition of HSP improved sperm kinematic parameters compared to NOSP and GSP treatments (P < 0.05). Conclusions and implications. These preliminary findings suggest the potential of SP to enhance the cryosurvival of Asian elephant spermatozoa, with HSP showing particularly promising results compared to conspecific SP (GSP). Further research into the specific effects of Asian elephant SP proteins is warranted.