Practical use of extender and activation solutions for short-term storage of common carp (Cyprinus carpio) milt in a hatchery

Highlights

• Fertilization and hatching rate were 85–87% and 78–81% after 7 days of sperm storage in a carp artificial seminal plasma.

• Less than 1% sperm motility, fertilization and hatchery rate were observed in undiluted sperm with a carp artificial seminal plasma.

• The fertilization success of old sperm confirmed that the sperm may have good prospect to use in common carp aquaculture.

ABSTRACT

The purpose of this study was to investigate the effect of an activation solution (AS) (hatchery water (pH 7.9 and 4 mOsm/kg), Perchec solution (5 mM KCl, 45 mM NaCl, 30 mM Tris-HCl; pH 8.0 and 130 mOsm/kg) and Cheng solution (40 mM NaCl, 20 mM Tris; pH 8.0 and 100 mOsm/kg) on aging sperm of common carp (Cyprinus carpio) after storage in a carp artificial seminal plasma (carp ASP: 2 mM CaCl₂, 1 mM MgSO₄, 40 mM KCl, 110 mM NaCl, 20 mM Tris; pH 7.5 and 310 mOsm/kg) for 7 days without antibiotics at 4 °C. Fresh milt and undiluted aging milt were used as the control groups. Milt (5 ml) was collected and diluted 1:1 in a carp ASP in 50 ml containers and stored at 4 °C under aerobic conditions. The highest sperm motility was found 45% and 36% at 15 s and 45 s post sperm activation (PSA) in hatchery water. Additionally, the curvilinear velocity (VCL, μm/s) and straight-line velocity (VSL, µm/s) of sperm were the highest in hatchery water and the solution with 5 mM KCl, 45 mM NaCl, 30 mM Tris and pH 8.0, which were above 122 µm/s and 87 µm/s at 15 PSA. Sperm concentration in aging sperm of common carp is known to decrease rapidly, so prior to fertilization, sperm concentration was determined and accurately set to 200,000 sperm per egg. The fertilization of eggs and hatching rate after 7 days of sperm storage in carp ASP were 85–87% and 78–81% in both ASs of hatchery water and Perchec solution. Less than 1% sperm motility, fertilization and hatching rate were observed in undiluted sperm (control). In conclusion, the fertilization ability of aging common carp sperm in carp ASP within different ASs was confirmed for practical use in aquaculture.