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1 October 2009 Sperm Competition and Reproductive Mode Influence Sperm Dimensions and Structure Among Snakes
Maximiliano Tourmente, Montserrat Gomendio, Eduardo R. S. Roldan, Laura C. Giojalas, Margarita Chiaraviglio
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Abstract

The role of sperm competition in increasing sperm length is a controversial issue, because findings from different taxa seem contradictory. We present a comparative study of 25 species of snakes with different levels of sperm competition to test whether it influences the size and structure of different sperm components. We show that, as levels of sperm competition increase, so does sperm length, and that this elongation is largely explained by increases in midpiece length. In snakes, the midpiece is comparatively large and it contains structures, which in other taxa are present in the rest of the f lagellum, suggesting that it may integrate some of its functions. Thus, increases in sperm midpiece size would result in more energy as well as greater propulsion force. Sperm competition also increases the area occupied by the fibrous sheath and outer dense fibers within the sperm midpiece, revealing for the first time an effect upon structural elements within the sperm. Finally, differences in male-male encounter rates between oviparous and viviparous species seem to lead to differences in levels of sperm competition. We conclude that the influence of sperm competition upon different sperm components varies between taxa, because their structure and function is different.

© 2009 The Society for the Study of Evolution.
Maximiliano Tourmente, Montserrat Gomendio, Eduardo R. S. Roldan, Laura C. Giojalas, and Margarita Chiaraviglio "Sperm Competition and Reproductive Mode Influence Sperm Dimensions and Structure Among Snakes," Evolution 63(10), 2513-2524, (1 October 2009). https://doi.org/10.1111/j.1558-5646.2009.00739.x
Received: 11 July 2008; Accepted: 1 May 2009; Published: 1 October 2009
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KEYWORDS
mating systems
reproductive strategies
selection-sexual
snakes
sperm competition
sperm structure
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