Sperm dilution ratio affects post-thaw motility rate and velocity of Prochilodus lineatus (Characiformes) sperm

Abstract

There is a lack of standardization in sperm cryopreservation of aquatic organisms and, thus, a necessity of more accurate investigations in all steps of this process. In this study, the effects of sperm dilution ratio on post-thaw sperm quality of Prochilodus lineatus were evaluated. Sperm was diluted in a standard freezing medium (glucose and methyl glycol) at four different ratios (sperm to final volume = 1:5, 1:10, 1:50 or 1:100), frozen in a nitrogen vapour vessel at -170°C and then stored in liquid nitrogen vessel at -196°C. Post-thaw motility rate and velocities (curvilinear = VCL; average path = VAP; straight line = VSL) were determined using a Computer-Assisted Sperm Analyzer (CASA) at 10 and 40 s post-activation. The highest motility rates were observed when sperm was frozen at a ratio of 1:5 (76%) and 1:10 (75%). The highest VCL (225 μm/s) and VAP (203 μm/s) were observed at a ratio of 1:10, while VSL was similar among samples frozen at 1:5, 1:10 and 1:50 (97-124 μm/s). When those parameters were evaluated again 30 s later, motility decreased significantly in samples frozen at a ratio of 1:5 (57%) and 1:10 (61%), while velocities decreased significantly in all samples regardless of dilution ratio (75-85 μm/s of VCL, 38-53 μm/s of VAP and 25-39 μm/s of VSL). P. lineatus sperm should be frozen at a ratio of 1:10, where both the number of loaded sperm per straw and the post-thaw quality are maximized.

Quality assessment of cryopreserved black-lip pearl oyster Pinctada margaritifera spermatozoa

“…Suquet et al (2016) reported 75% lower velocity in frozen/thawed spermatozoa of the great scallop compared to fresh. Linhart et al (2005) (Figueroa et al 2016), 97 µm s -1 to 134 µm s -1 in Prochilodus lineatus (Viveiros and Leal 2016;Viveiros et al 2017), 57 µm s -1 in rainbow trout Oncorhynchus mykiss (Suquet et al 2012b) and µm s -1 in Siberian sturgeon Acipenser baerii spermatozoa (Sarosiek et al 2014). VSL of sea urchin spermatozoa was shown to be 170-240 µm sec -1 in Hemicentrotus pulcherrimus (Hiramoto and Baba 1978) and 150-200 µm sec -1 in Paracentrotus lividus (Fabbrocini and D'Adamo 2017).…”

Optimization of sperm freezability in Bactrian camel using various dilution rates and equilibration times

“…Conversely, a higher DR might cause more glycerol to penetrate sperm cells, as a higher glycerol ratio per sperm cell is available, and consequently sperm quality would be diminished. Higher DRs may also reduce sperm post-thaw quality through dilution of several proteins or antioxidants present in seminal plasma that protect sperm against freezing-thawing (Viveiros and Leal, 2016).…”