Sperm freezability is neither associated with the expression of aquaporin 3 nor sperm head dimensions in dromedary camel (Camelus dromedarius)

The expression of aquaglyceroporin 3 (AQP-3) has been demonstrated in the spermatozoa of several mammalian species and its role has been associated with cryotolerance. Post-thaw sperm quality from individual dromedary males with different response to freezing-thawing process was evaluated through sperm head morphometry. In order to understand the cellular mechanisms affected by cryoinjury we have explored the presence and distribution of sperm AQP-3 using western blotting and immunocytochemistry. WB showed different intensity of the specific signal bands at 28 kDa. Immunofluorescence assessments allowed us to identify five different and clear AQP-3 distribution patterns of labelling in the sperm plasma membrane; acrosome, post-acrosome, mid-piece, and principal and final tail. Although expression of AQP-3 varied among male ejaculates, the individual sperm response to freeze-thawing was not associated with AQP-3 expression. Thus, AQP3 expressions do not seem like a reliable predictor of sperm response to freeze-thawing process in this species. This work is the first to describe the morphometric characteristics of the heads of dromedary spermatozoa. No correlation was found between sperm head dimensions and sperm quality variables after freeze-thawing suggesting that dromedary camel sperm head morphometry is also not a reliable predictor of cryosurvival.