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. 2014 Nov;4(21):4080-92.
doi: 10.1002/ece3.1262. Epub 2014 Oct 7.

Variability in sperm form and function in the context of sperm competition risk in two Tupinambis lizards

Cecilia S Blengini  1 , Naretto Sergio  1 , Cardozo Gabriela  1 , Laura C Giojalas  2 , Chiaraviglio Margarita  1
Affiliations

Variability in sperm form and function in the context of sperm competition risk in two Tupinambis lizards

Cecilia S Blengini et al. Ecol Evol. 2014 Nov.

Abstract

In polyandrous species, sperm morphometry and sperm velocity are under strong sexual selection. Although several hypotheses have been proposed to explain the role of sperm competition in sperm trait variation, this aspect is still poorly understood. It has been suggested that an increase in sperm competition pressure could reduce sperm size variation or produce a diversity of sperm to maximize male fertilization success. We aim at elucidating the variability of sperm morphometric traits and velocity in two Tupinambis lizards in the context of sperm competition risk. Sperm traits showed substantial variation at all levels examined: between species, among males within species, and within the ejaculate of individual males. Sperm velocity was found to be positively correlated with flagellum: midpiece ratio, with relatively longer flagella associated with faster sperm. Our results document high variability in sperm form and function in lizards.

Keywords: Postcopulatory sexual selection; Squamata; sperm evolution; sperm morphometry; sperm velocity.

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Figures

Figure 1
Figure 1
Males of Tupinambis lizards. (A) Tupinambis merianae; (B) Tupinambis rufescens.
Figure 2
Figure 2
Within- and among-male variation in sperm morphometric traits in Tupinambis lizards. (A) Tupinambis merianae (black squares); (B) Tupinambis rufescens (gray dots). Squares and dots represent individual mean lengths (±standard deviation) ranked in order of magnitude.
Figure 3
Figure 3
Within- and among-male variation in sperm dynamic traits in Tupinambis lizards. (A) Tupinambis merianae (black squares); (B) Tupinambis rufescens (gray dots). Squares and dots represent individual mean lengths (±standard deviation) ranked in order of magnitude.
Figure 4
Figure 4
Relationship between sperm straight line velocity and sperm morphometric traits in Tupinambis. (A) Tupinambis merianae; (B) Tupinambis rufescens. Similar slopes between species were found (Dummy variable midpiece F = 0.48; P = 0.6204; flagellum: midpiece ratio F = 0.00062, P = 0.9803).
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