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Title: The effect of freezing rate on the quality of Striped Bass Spermatozoa

item FRANKEL, TYLER - University Of Maryland
item THEISEN, DANIEL - University Of Maryland
item Guthrie, Howard
item Welch, Glenn
item WOODS, III, L - University Of Maryland

Submitted to: Theriogenology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/21/2013
Publication Date: 4/1/2013
Citation: Frankel, T.E., Theisen, D.D., Guthrie, H.D., Welch, G.R., Woods, III, L.C. 2013. The effect of freezing rate on the quality of Striped Bass Spermatozoa. Theriogenology. 79(6):940-945.

Interpretive Summary: Utilization of striped bass spermatozoa for in vitro fertilization of white bass eggs to produce hybrid striped bass for aquaculture would be much more efficient if the semen was stored in frozen form as soon as it was collected so that it could be stored for a period of weeks before it was transported to the laboratory location where the eggs were collected. One of the major problems for sperm freezing is the determination of the rate of cooling during the freezing process. In this study, we determined that cooling sperm at a rate of -40ºC/minute permitted more sperm (55%) to survive freezing and thawing. The hybrid striped bass industry is dependent upon wild individuals for a source of spermatozoa and eggs. Coupled with a genetic improvement program the adoption of this technology will permit the development of domesticated striped and white bass brood stock for the hybrid striped bass producers.

Technical Abstract: Several studies have been conducted in an attempt to determine the optimal freezing rate for the cryopreservation of striped bass (Morone saxatilis) spermatozoa. In this study, the effects of freezing rate (-10, -15, -20 and -40oC/minute) on gamete quality including, viability, motion characteristics and ATP concentration were examined. We utilized Sybr-14 and propidium iodide to confirm viability (sperm cell membrane integrity), ATP concentration, using a luciferin-luciferase bioluminescence assay and a Hamilton-Thorne CEROS™ system to characterize striped bass sperm motion. Adult male striped bass (n = 12) were sampled once a week for five weeks. Collected samples were extended, cryo-protected using a 7.5% DMSO final concentration solution and frozen at various rates using a Planer Kryosave controlled-rate freezer. The samples were stored in liquid nitrogen for 49 days, after which sperm quality was re-evaluated post-thaw utilizing the same methods. Sperm cryopreserved using -40ºC/minute resulted in significantly higher levels of total and progressive motility, ATP concentration and percentage of viable cells based on the total population collected over the five weeks. These results demonstrate that -40ºC/minute was the optimal freezing rate among those tested for the cryopreservation of striped bass spermatozoa.