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

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

doi:10.1002/ece3.1262

Cardozo Gabriela, Chiaraviglio Margarita + Show 3 more

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https://doi.org/10.1002/ece3.1262

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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.

Highlights

Polyandry can promote the spatial and temporal overlap of ejaculates from multiple males within the female reproductive tract, promoting postcopulatory sexual selection and male adaptations that ensure success during sperm competition (Parker 1970; Snook 2005; Pizzari and Parker 2009)
Ecology and Evolution published by John Wiley & Sons Ltd
We found that Tupinambis rufescens had greater relative testis mass (ANCOVA F1,117 = 5.17; P = 0.0248) than T. merianae

Summary

Introduction

Polyandry can promote the spatial and temporal overlap of ejaculates from multiple males within the female reproductive tract, promoting postcopulatory sexual selection and male adaptations that ensure success during sperm competition (Parker 1970; Snook 2005; Pizzari and Parker 2009). In taxa with high risk of sperm competition, females are more likely to mate with multiple males within a single reproductive cycle Because sperm competition often favors the evolution of larger testes, relative testis mass is considered a reliable index of sperm competition risk (Tourmente et al 2009, 2013; Snook and Pizzari 2012).

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