Use of Hypertonic Media to Cryopreserve Sauger Spermatozoa

Abstract

The objective of this study was to determine the effects of extender osmolality on postthaw sperm quality and fertility in Sauger Sander canadensis. Fresh milt from 10 male Saugers was diluted by using base extenders with osmolalities of 350, 500, or 750 mOsm/kg (E350, E500, and E750, respectively) containing 10% dimethyl sulfoxide, frozen in LN 2 vapor, and stored. Sperm parameters (total motility, progressive motility, velocity, and viability) were assessed at different steps of the cryopreservation process (extended, equilibrated, and postthaw). Fertilization rates were compared between fresh and frozen sperm and at two sperm-to-egg ratios. All of the parameters that were measured, except for progressive motility, were reduced by cryopreservation. Extender 500 yielded the highest postthaw progressive motility (32.20 ± 3.86% [mean ± SD]) and velocity (84.97 ± 16.82 μm/s), whereas both E350 and E500 displayed the highest total motility (65.30 ± 4.24 and 68.70 ± 6.46%) and viability (80.60 ± 4.84 and 78.80 ± 3.91%), respectively. By contrast, E750 yielded the lowest postthaw velocity, viability, and total and progressive motility. Despite the increase in the motility parameters, fertilization in E350 (13.93%) was approximately double that in E500 (6.58%), although not statistically different. In conclusion, traditional isosmotic base extenders (E350) were found to be superior to hypertonic base extenders in the preservation of Sauger milt. These results serve as a starting point for future investigations of cryopreservation potential for Sauger spermatozoa that work toward developing a freezing protocol that is more suitable for large-scale application.

Spatial and Temporal Changes in Testis Morphology and Sperm Ultrastructure of the Sportfish Sauger (Sander canadensis)

“…Sperm concentrations were highest in the distal portion of the testis, intermediate in the middle section and lowest in the proximal portion of the testis and strip‐spawned spermatozoa (Table 1). Motility was significantly reduced in stripped spermatozoa compared with testicular spermatozoa but is most likely a result of urine contamination as they are not consistent with previous values for this species (Blawut et al., 2018; Blawut, Wolfe, Moraes, Ludsin, et al., 2020).…”

“…Each section was macerated in 1.0 ml Rathbun extender to release spermatozoa and then thoroughly mixed. Samples were then assessed using computer‐assisted sperm analysis (CASA) and densimetry to determine motility and sperm concentration according to previously published methods (Blawut, Wolfe, Moraes, Ludsin, et al., 2020).…”

“…As saugeye production is highly variable due to limited sperm production per individual sauger compounded by fluctuations in populations and weather conditions, assisted production strategies are necessary for sustaining the multimillion dollar recreational fishery industry in Ohio reservoirs. Previous research has focused on managing sperm use (Blawut et al., 2018), long‐term storage of excess spermatozoa using cryopreservation (Blawut et al., 2020) and utilizing testicular harvest to enhance sperm yield (Blawut, Wolfe, Moraes, Sweet, et al., 2020). However, sperm quality (i.e., morphology, maturation and motility) can vary as a result of the unintended consequences of these assisted reproduction techniques and thus could adversely impact saugeye production.…”

Evaluation of Kappa‐carrageenan supplementation in extender for post‐thaw Kajli ram sperm quality

“…Polysaccharides, k‐carrageenan in this case, are impermeable cryoprotectants that can increase the osmolarity of the extracellular environment (Oldenhof et al., 2013). This increased osmolarity draws water out of the sperm cells, preventing the cell from bursting and reducing the chances of crystal formation (Blawut et al., 2020). This leads to better viability rates as well as improved integrity of the sperm (Khudyakov et al., 2015).…”