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The long and the short of sperm selection in vitro and in vivo : swim‐up techniques select for the longer and faster swimming mammalian sperm
Author(s) -
HOLT W. V.,
HERNANDEZ M.,
WARRELL L.,
SATAKE N.
Publication year - 2010
Publication title -
journal of evolutionary biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.289
H-Index - 128
eISSN - 1420-9101
pISSN - 1010-061X
DOI - 10.1111/j.1420-9101.2010.01935.x
Subject(s) - biology , sperm , sperm competition , andrology , flagellum , sexual selection , in vivo , boar , sperm motility , anatomy , zoology , genetics , gene , medicine
Sperm competition and sexual selection outcomes are sometimes reported as depending on sperm velocity and flagellar length, suggesting that sperm shape may be optimized for maximum efficiency. This is a largely unexamined assumption regarding sperm performance. Here, we examine this idea using a ‘swim‐up’ selection technique as a proxy for sperm transport within the female tract, testing the hypothesis that variation in sperm tail length should be reduced by this procedure. We detected small but significant ( P < 0.001) increases in mean flagellar length in brown hare, pig and bull spermatozoa without reduction in variance. Applying the swim‐up technique to boar ejaculates confirmed that the selected populations were enriched for fast motile spermatozoa. These effects were also reflected in vivo where boar spermatozoa with both short and long flagellae were able to reach and colonize the oviductal sperm reservoir. The benefits of possessing a longer flagellum thus appear to be marginal, suggesting that sperm selection in vivo is based on more complex criteria.