Abstract
Sperm conjugation is an unusual variation in sperm behavior where two or more spermatozoa physically unite for motility or transport through the female reproductive tract. Conjugation has frequently been interpreted as sperm cooperation, including reproductive altruism, with some sperm advancing their siblings toward the site of fertilization while ostensibly forfeiting their own ability to fertilize through damage incurred during conjugate break-up. Conversely, conjugation has been proposed to protect sensitive regions of spermatozoa from spermicidal conditions within the female reproductive tract. We investigated the possibility of dissociation-induced sperm mortality and tested for a protective function of conjugation using the paired sperm of the diving beetle, Graphoderus liberus. Sperm conjugates were mechanically dissociated and exposed to potentially damaging tissue extracts of the female reproductive tract and somatic tissue. We found no significant difference in viability between paired sperm and dissociated, single sperm. The results further indicate that the reproductive tract of female G. liberus might not be spermicidal and conjugation is not protective of sperm viability when damaging conditions do exist. Our results support the interpretation that, at least in some taxa, sperm conjugation is neither protective nor damaging to sperm viability.
Highlights
Sperm conjugation is a rare, but taxonomically widespread, adaptation to postcopulatory sexual selection where two or more spermatozoa physically unite for motility or transport through the female reproductive tract before dissociating prior to fertilization [1]
We tested two non-mutually exclusive hypotheses regarding sperm conjugation, i) conjugation is protective of sperm viability in damaging environments, and ii) conjugation reduces viability of some participating sperm due to the mechanism of conjugate breakup
Conjugated sperm exposed to damaging conditions died in the same proportion as single sperm and at a rate far lower than the 50% mortality predicted if the death of one sperm was required for pair break-up
Summary
Sperm conjugation is a rare, but taxonomically widespread, adaptation to postcopulatory sexual selection where two or more spermatozoa physically unite for motility or transport through the female reproductive tract before dissociating prior to fertilization [1]. Conjugates are stabilized by cell-cell or cell-matrix interactions, and while the mechanisms of conjugate dissociation are unknown, the break-up of such intimately associated cells might disrupt cell membrane integrity resulting in a loss of fertilizing ability or death of a proportion of the participating sperm while leaving others unharmed [7]. Conjugation has the potential to be protective of sperm viability only to the extent that conditions within the female reproductive tract are damaging [19,20]. We investigate the possibility of dissociation-induced sperm mortality and test for a protective function of conjugation against spermicidal conditions in the diving beetle Graphoderus liberus. The results indicate that conjugation was neither protective in damaging environments, nor was conjugate break-up associated with increased sperm mortality
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
