Sperm traits differ between winged and wingless males of the ant Cardiocondyla obscurior.

Size and shape of sperm cells vary tremendously throughout the animal kingdom. The adaptive significance of this variation is not fully understood. In addition to sperm-female interactions and the environmental conditions, the risk of sperm competition might affect number, morphology and other "quality" traits of sperm. In the male-diphenic ant Cardiocondyla obscurior, winged sneaker males have limited sperm number, because their testes degenerate shortly after adult emergence, as is typical for males of social Hymenoptera. In contrast, wingless fighter males continuously replenish their sperm supply due to their exceptional lifelong spermatogenesis. While winged males usually have to compete with several other winged males for virgin queens, wingless males are able to monopolize queens by killing all other rivals. Hence, this presents a unique system to investigate how alternative reproductive tactics and associated physiology affect sperm morphology and viability. We found that sperm-limited males invest into sperm number instead of sperm size. Variance in sperm length is smaller in winged males, probably reflecting that they have to compete with several other males. Finally, sperm viability is equally high in both male phenotypes.

[1]  L. Schärer,et al.  The evolutionary ecology of testicular function: size isn't everything , 2014, Biological reviews of the Cambridge Philosophical Society.

[2]  R. Jehle,et al.  Evolution of sperm morphology in anurans: insights into the roles of mating system and spawning location , 2014, BMC Evolutionary Biology.

[3]  P. Berg,et al.  Modern maize varieties going local in the semi-arid zone in Tanzania , 2014, BMC Evolutionary Biology.

[4]  M. Gomendio,et al.  POSTCOPULATORY SEXUAL SELECTION INCREASES ATP CONTENT IN RODENT SPERMATOZOA , 2013, Evolution; international journal of organic evolution.

[5]  T. Pitcher,et al.  Reproductive investment patterns, sperm characteristics, and seminal plasma physiology in alternative reproductive tactics of Chinook salmon (Oncorhynchus tshawytscha) , 2013 .

[6]  J. Belote,et al.  How Multivariate Ejaculate Traits Determine Competitive Fertilization Success in Drosophila melanogaster , 2012, Current Biology.

[7]  K. A. Segraves,et al.  Female reproductive tract form drives the evolution of complex sperm morphology , 2012, Proceedings of the National Academy of Sciences.

[8]  L. Simmons,et al.  Ejaculate Economics: Testing the Effects of Male Sexual History on the Trade-Off between Sperm and Immune Function in Australian Crickets , 2012, PloS one.

[9]  J. Fitzpatrick,et al.  POLYANDRY REDUCES SPERM LENGTH VARIATION IN SOCIAL INSECTS , 2011, Evolution; international journal of organic evolution.

[10]  W. M. Wheeler.  Ants Collected by Professor F. Silvestri in Formosa, the Malay Peninsula and the Philippines , 2011 .

[11]  Kogiku Shiba,et al.  Why small males have big sperm: dimorphic squid sperm linked to alternative mating behaviours , 2011, BMC Evolutionary Biology.

[12]  G. Parker,et al.  Resolving variation in the reproductive tradeoff between sperm size and number , 2011, Proceedings of the National Academy of Sciences.

[13]  K. Ota,et al.  Sperm phenotypic plasticity in a cichlid: a territorial male's counterstrategy to spawning takeover , 2010 .

[14]  R. J. Robertson,et al.  Intraspecific Variation in Sperm Length is Negatively Related to Sperm Competition in Passerine Birds , 2008, Evolution; international journal of organic evolution.

[15]  L. Simmons,et al.  Male crickets adjust ejaculate quality with both risk and intensity of sperm competition , 2007, Biology Letters.

[16]  J. Heinze,et al.  Mating success and potential male-worker conflict in a male-dimorphic ant , 2007, BMC evolutionary biology.

[17]  L. Simmons,et al.  Male Crickets Adjust the Viability of Their Sperm in Response to Female Mating Status , 2007, The American Naturalist.

[18]  T. Birkhead,et al.  Postcopulatory Sexual Selection Is Associated with Reduced Variation in Sperm Morphology , 2007, PloS one.

[19]  L. Simmons,et al.  SHORTER SPERM CONFER HIGHER COMPETITIVE FERTILIZATION SUCCESS , 2007, Evolution; international journal of organic evolution.

[20]  S. Pitnick,et al.  Influence of developmental environment on male‐ and female‐mediated sperm precedence in Drosophila melanogaster , 2007, Journal of evolutionary biology.

[21]  I. Folstad,et al.  Rapid adjustments of sperm characteristics in relation to social status , 2006, Proceedings of the Royal Society B: Biological Sciences.

[22]  D. Hosken,et al.  Co‐evolution of male and female reproductive characters across the Scathophagidae (Diptera) , 2005, Journal of evolutionary biology.

[23]  J. Boomsma,et al.  The evolution of male traits in social insects. , 2005, Annual review of entomology.

[24]  R. Snook.  Sperm in competition: not playing by the numbers. , 2005, Trends in ecology & evolution.

[25]  Robin J Stuart,et al.  Lethal fighting among dimorphic males of the ant, Cardiocondyla wroughtonii , 1987, Naturwissenschaften.

[26]  R. Montgomerie,et al.  Sperm swimming speed and energetics vary with sperm competition risk in bluegill (Lepomis macrochirus) , 2004, Behavioral Ecology and Sociobiology.

[27]  J. Heinze,et al.  Stress Grows Wings Environmental Induction of Winged Dispersal Males in Cardiocondyla Ants , 2003, Current Biology.

[28]  J. Millar,et al.  Intraspecific variation of testis size and sperm length in the yellow-pine chipmunk (Tamias amoenus): implications for sperm competition and reproductive success , 2003, Behavioral Ecology and Sociobiology.

[29]  T. Birkhead,et al.  Sperm Viability and Sperm Competition in Insects , 2002, Current Biology.

[30]  T. Vladić.  Sperm quality in the alternative reproductive tactics of Atlantic salmon: the importance of the loaded raffle mechanism , 2001, Proceedings of the Royal Society of London. Series B: Biological Sciences.

[31]  J. L. Tomkins,et al.  Sperm competition games played by dimorphic male beetles , 1999, Proceedings of the Royal Society of London. Series B: Biological Sciences.

[32]  S. Ward,et al.  Larger sperm outcompete smaller sperm in the nematode Caenorhabditis elegans , 1998, Proceedings of the Royal Society of London. Series B: Biological Sciences.

[33]  R. Shine,et al.  Is sperm really so cheap? Costs of reproduction in male adders, Vipera berus , 1997, Proceedings of the Royal Society of London. Series B: Biological Sciences.

[34]  J. Radwan.  Intraspecific variation in sperm competition success in the bulb mite: a role for sperm size , 1996, Proceedings of the Royal Society of London. Series B: Biological Sciences.

[35]  S. Pitnick.  Investment in Testes and the Cost of Making Long Sperm in Drosophila , 1996, The American Naturalist.

[36]  G. Parker,et al.  Effects of alternative male mating strategies on characteristics of sperm production in the Atlantic salmon (Salmo salar): theoretical and empirical investigations , 1995 .

[37]  T. Markow,et al.  Delayed male maturity is a cost of producing large sperm in Drosophila. , 1995, Proceedings of the National Academy of Sciences of the United States of America.

[38]  M. Gage.  Associations between body size, mating pattern, testis size and sperm lengths across butterflies , 1994, Proceedings of the Royal Society of London. Series B: Biological Sciences.

[39]  J. Heinze,et al.  Fighting for a harem of queens: physiology of reproduction in Cardiocondyla male ants. , 1993, Proceedings of the National Academy of Sciences of the United States of America.

[40]  P. Ward,et al.  Variation in sperm length in the yellow dung fly Scathophaga stercoraria (L) , 1993 .

[41]  W. Voorhies.  Production of sperm reduces nematode lifespan , 1992, Nature.

[42]  M. Gomendio,et al.  Sperm competition influences sperm size in mammals , 1991, Proceedings of the Royal Society of London. Series B: Biological Sciences.

[43]  G. Parker.  Sperm competition games: raffles and roles , 1990, Proceedings of the Royal Society of London. Series B: Biological Sciences.

[44]  Norm Johnson,et al.  The males of Cardiocondyla Emery (Hymenoptera: Formicidae), with a description of the winged male of Cardiocondyla wroughtoni (Forel). , 1984 .

[45]  G. Parker,et al.  Why are there so many tiny sperm? Sperm competition and the maintenance of two sexes. , 1982, Journal of theoretical biology.

[46]  D. Dewsbury,et al.  Ejaculate Cost and Male Choice , 1982, The American Naturalist.

[47]  G. Parker,et al.  SPERM COMPETITION AND ITS EVOLUTIONARY CONSEQUENCES IN THE INSECTS , 1970 .