title: No evidence of sperm conjugate formation in an Australian mouse bearing sperm with three hooks.
abstract: Sperm conjugation occurs when two or more sperm physically unite for motility or transport through the female reproductive tract. In many muroid rodent species, sperm conjugates have been shown to form by a single, conspicuous apical hook located on the sperm head. These sperm "trains" have been reported to be highly variable in size and, despite all the heads pointing in roughly the same direction, exhibit a relatively disordered arrangement. In some species, sperm "trains" have been shown to enhance sperm swimming speed, and thus have been suggested to be advantageous in sperm competition. Here, we assessed the behavior of sperm in the sandy inland mouse (Pseudomys hermannsburgensis), a muroid rodent that bears sperm with three apical hooks. First, we accrued genetic evidence of multiple paternity within "wild" litters to unequivocally show that sperm competition does occur in this species. Following this we utilized both in vitro and in vivo methodologies to determine whether sandy inland mouse sperm conjugate to form motile trains. Our observations of in vitro preparations of active sperm revealed that sandy inland mouse sperm exhibit rapid, progressive motility as individual cells only. Similarly, histological sections of the reproductive tracts of mated females revealed no in vivo evidence of sperm conjugate formation. We conclude that the unique, three-hooked morphology of the sandy inland mouse sperm does not facilitate the formation of motile conjugates, and discuss our findings in relation to the different hypotheses for the evolution of the muroid rodent hook/s.
authors.affiliation: Centre for Evolutionary Biology, School of Animal Biology, University of Western Australia Crawley, Western Australia, 6009, Australia.
authors.forename: Renée C
authors.initials: RC
authors.lastname: Firman
authors.forename: Blair
authors.initials: B
authors.lastname: Bentley
authors.forename: Faye
authors.initials: F
authors.lastname: Bowman
authors.forename: Fernando García-Solís
authors.initials: FG
authors.lastname: Marchant
authors.forename: Jahmila
authors.initials: J
authors.lastname: Parthenay
authors.forename: Jessica
authors.initials: J
authors.lastname: Sawyer
authors.forename: Tom
authors.initials: T
authors.lastname: Stewart
authors.forename: James E
authors.initials: JE
authors.lastname: O'Shea
keywords: Multiple paternity; Muridae; polyandry; sperm competition; sperm morphology
references.citation: J Morphol. 2004 Jul;261(1):52-69
references.pmid: 15164367
references.citation: Biol Rev Camb Philos Soc. 2011 Feb;86(1):249-70
references.pmid: 20608927
references.citation: Proc Biol Sci. 2003 Oct 7;270(1528):2079-86
references.pmid: 14561298
references.citation: Proc Biol Sci. 1999 Sep 7;266(1430):1759-64
references.pmid: 10577160
references.citation: Evolution. 2008 Oct;62(10):2580-91
references.pmid: 18691259
references.citation: J Evol Biol. 2011 Apr;24(4):856-62
references.pmid: 21306461
references.citation: Biol Rev Camb Philos Soc. 1992 Nov;67(4):551-93
references.pmid: 1463811
references.citation: Nature. 2002 Jul 11;418(6894):174-7
references.pmid: 12110888
references.citation: Proc Natl Acad Sci U S A. 2009 Jan 27;106(4):1128-32
references.pmid: 19164576
references.citation: Evolution. 1973 Mar;27(1):106-110
references.pmid: 28563668
references.citation: Proc Natl Acad Sci U S A. 2006 Oct 10;103(41):15113-7
references.pmid: 16990431
references.citation: Curr Biol. 2004 Jan 6;14(1):44-7
references.pmid: 14711413
references.citation: Proc Biol Sci. 1991 Mar 22;243(1308):181-5
references.pmid: 1675796
references.citation: Proc Biol Sci. 1993 Apr 22;252(1333):7-12
references.pmid: 8389048
references.citation: Evolution. 1997 Jun;51(3):937-945
references.pmid: 28568571
references.citation: Evolution. 2013 Oct;67(10):3061-70
references.pmid: 24094355
references.citation: Proc Biol Sci. 2009 Mar 22;276(1659):1175-81
references.pmid: 19129098
references.citation: Curr Biol. 2002 Jan 22;12(2):121-3
references.pmid: 11818062
references.citation: PLoS One. 2010 Aug 13;5(8):e12146
references.pmid: 20730092
references.citation: Biol Reprod. 1990 Mar;42(3):450-7
references.pmid: 2340331
references.citation: Nature. 2010 Feb 11;463(7282):801-3
references.pmid: 20090679
references.citation: J Evol Biol. 2009 Dec;22(12):2505-11
references.pmid: 19878408
references.citation: Am Nat. 1997 May;149(5):933-54
references.pmid: 18811256
references.citation: Biol Reprod. 1996 Apr;54(4):783-8
references.pmid: 8924497
references.citation: Cell Tissue Res. 1983;229(3):611-25
references.pmid: 6839354
references.citation: Mol Ecol. 1999 Jan;8(1):107-11
references.pmid: 12187947
references.citation: J Reprod Fertil. 1991 Mar;91(2):567-73
references.pmid: 2013880
references.citation: BMC Evol Biol. 2011 Jan 20;11:19
references.pmid: 21251249
references.citation: PLoS One. 2007 Jan 24;2(1):e170
references.pmid: 17245446
references.citation: Evolution. 2010 May;64(5):1245-56
references.pmid: 19922447
references.citation: Biol Reprod. 1987 Feb;36(1):203-10
references.pmid: 3567275