The ability to store gametes in perpetuity requires in-depth knowledge of the mechanisms which govern gamete survival during the freezing and thawing process. In our lab, we not only develop “cutting edge techniques” to preserve genetic resources (for sperm, spermatogonia, and oogonia), but also define underlying physiological principles that influence gamete survival during low-temperature storage.

 

Variation in the ability of cells to withstand cryogenic freezing and thawing has been reported among individuals within species. For instance, we (Butts et al. 2011, 2013) found considerable variability in sperm traits after cryopreservation, depending on the donor male; i.e. inter-male frozen-thawed fertilization success ranged from 19 to 90% for Atlantic cod, Gadus morhua. This male-to-male variation poses a problem where “bad” sperm donors might be of high genetic value. Males with “bad” cryopreservation potential also require higher sperm to egg ratios to compensate for lower frozen-thawed quality, jeopardize the enhancement of sperm cryopreservation protocols, and put at risk experimental designs that rely on a specific number of individuals.

Recent research in mammalian species has identified several semen quality indices (i.e., antioxidants, seminal proteins, sperm motility and kinematic patterns) which can be used to discriminate between “good” vs. “bad” sperm donors. On the contrary, there have been only a handful of studies addressing this aspect in bivalves or fishes. 

 

It is therefore of utmost importance that we continue to understand the physiological processes associated with cryopreservation of gametes and develop models that predict, prior to freezing, those individuals which are able and/or unable to endure the freezing and thawing process. Together, this will allow us to address these male-to-male short-comings in the cryogenic process so we can i.e. transform a “bad” sperm donor into a “good” sperm donor and sustain a more effective germplasm repository to support selective breeding, aquaculture, and conserva-tion efforts.