The effect of different gaseous environments on the motility of spermatozoa from striped bass Morone saxatilis after 2 and 48 h of storage at 3 Ϯ 1ЊC was examined. Storage in a 1.5-mL polypropylene snapcap vial versus a 50-mL polystyrene tissue culture flask was also examined for any influence on motility. Motility declined with time within each treatment group and in comparison with the motility of freshly collected undiluted semen. After 2 h, there was no significant difference in the motility of sperm stored under ambient air or oxygen. After 48 h, however, semen stored under an oxygen atmosphere had a significantly (P Ͻ 0.0444) greater percentage of motile sperm (13 Ϯ 2.4%) than did semen stored under ambient air (9 Ϯ 1.9%) or nitrogen (4 Ϯ 1.7%). These results suggest the importance of oxygen to the motility of striped bass sperm stored for short periods. After both 2 and 48 h of storage, the percentage of motile sperm obtained from semen stored in the 1.5-mL snap-cap vials was higher than that of sperm obtained from semen stored in the 50-mL tissue culture flasks in the same gaseous environment.
Abstract.— Two experiments were designed to improve upon existing methods for cryopreserving striped bass Morone saxatilis, semen. In the first experiment, two extenders, two cryoprotectant concentrations, and two freezing rates were evaluated on the basis of post‐thaw semen motility after 1, 7, and 30 d of storage at −196 C. Semen samples cryopreserved at a freezing rate of −40 C/m resulted in a significantly higher percentage of motile sperm (P < 0.001) and longer duration of spermatozoa motility (P < 0.001) than samples cryopreserved at a freezing rate of ‐30 Chin. Also, the cryoprotectant dimethyl‐sulfoxide yielded a significantly higher percentage of motile sperm (P < 0.001) and longer duration of spermatozoa motility (P < 0.001) when a 5% concentration was used instead of 7.5%. In the second experiment, the two extenders from Experiment I were re‐evaluated and a new extender, which was a modified version of Extender 1, was tested. The samples were cryopreserved at ‐40 C/min with 5% DMSO and thawed in a 25 C water bath. Spermatozoa motility and fertilization ability were evaluated, and semen cryopreserved in Extender 2 yielded the longest duration of spermatozoa motility (P < 0.001). the highest percentage of motile sperm (P < 0.001). and the highest percentage of fertilized eggs (P < 0.002) in comparison to Extenders I and 3.
Six extenders were evaluated in two experiments for use in the short‐term, refrigerated storage of the milt of striped bass Morone saxatilis. In each experiment, milt samples were collected weekly. The percentage of motile sperm obtained from each extended milt sample and each undiluted milt sample (control) were measured after 1, 2, and 7 d of storage at 3 ± 1°C (mean ± SE). In the first experiment, there were significant changes in the percentage of motile sperm obtained across the spawning season with respect to the day of storage, the extender used, and the day × extender combination. Extender 1 yielded the highest percentage of motile sperm after 2 and 7 d of storage but was not significantly different from extender 4 after 1 d of storage. In the second experiment, two modified versions of extender 1 were compared with the original. Extenders 5 and 6 contained the same ingredients as extender 1 except that their sodium chloride concentrations were increased to obtain osmolalities more closely resembling that of striped bass milt. Extender 6 was closest to the osmolality of striped bass milt and yielded the highest percentage of motile sperm after 2 and 7 d of storage but was not significantly different from extender 5 after 1 d of storage. As in experiment 1, there were significant changes in the percentage of motile sperm obtained across the spawning season with respect to the day of storage, the extender used, and the day × extender combination. Sperm motility in the undiluted control samples and the extended milt samples significantly changed over the course of the spawning season, indicating a seasonal change in milt quality. At the beginning and end of the spawning season, milt quality was low and there was little, if any, significant difference in the performance of the various extenders. In the middle of each spawning season, when milt quality was highest, significant differences in the percentages of motile sperm obtained from the extended samples were evident.
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