Artificial seminal plasma improves motility and fertilisation capacity of common carp Cyprinus carpio L. sperm during one hour of storage

The quality of fish sperm is characterized by relatively high individual variation. Moreover, under artificial conditions, the collected sperm loses its motility and viability very rapidly, which may decrease fertilisation success. Therefore, techniques able to secure and maintain a high biological value of collected fish sperm are needed in hatchery practice. Herein, we used previously composed artificial seminal plasma (ASP) containing 2mM CaCl2, 1mM Mg2SO4, 20mM Tris, 110mM NaCl and 40mM KCl (pH 7.5 and 310 mOsm kg(-1)) to dilute common carp sperm samples for 1 h storage prior to fertilisation. Sperm was collected from mature males and, after checking its motility (MOT) using the CASA system, was divided into high (range 55-65%) and low (range 5-10%) quality. Samples of both sperm qualities (high/low) were diluted tenfold (1: 9; sperm: extender) in ASP and stored for 24 h at 10 degrees C. Motility (MOT, PRG) and velocity (VCL, VSL) of low- and high-quality sperm diluted in ASP increased after 1 h of storage compared to undiluted sperm. Moreover, the fertilisation capacity of low-quality sperm (previously diluted and stored for 1 h in ASP) increased three times compared to undiluted sperm of the same quality. Prolonging the time of sperm storage in ASP to 24 h results in the further increase of MOT, PRG and VCL in the low quality samples and PRG in the high quality samples. The results of the presented study confirm the possibility of common carp sperm revitalisation using ASP. The utilisation of such sperm in hatchery practice is possible since the fertilisation capacity of sperm, previously diluted and stored for 1 h in ASP, was over 90% regardless of the initial sperm quality (high/low).