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

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.

The Diversity, Plasticity, and Evolution of Sperm Morphology in Anolis Lizards

“…In fact, there are only two studies that have tested for an association between sperm morphology and velocity in lizards (Blengini et al 2014). In contrast to our findings, sperm with a longer tails and shorter midpieces have a higher sperm velocity in…”

“…Tupinambis lizards (Blengini et al 2014). The difference in the relationship between morphology and velocity in these two species of lizards highlights the need to conduct intraspecific tests for the functional morphology of sperm, as the patterns may be speciesspecific.…”

“…Though we know little about the relationships between sperm morphology and function in Anolis lizards, sperm velocity increases with sperm tail length in Tupinambis lizards (Blengini et al, 2014).…”

“…2). The midpiece, which is the area of the cell containing the mitochondria, and the tail, which influences sperm velocity in other lizards (Blengini et al, 2014), are likely targets of selection because of these links to function and performance . These consistent changes in sperm morphology and testis size argue against a role of random factors such as genetic drift and founder effects, instead suggesting that either the process of introduction or the local environment in Miami has consistently favored the same adaptive changes or induced the same plastic responses in each of these three species.…”

Modification of sperm quality after sexual abstinence in Seba's short-tailed bat,Carollia perspicillata

“…Sperm quality may be increased by modifications of sperm structure. Larger flagella or mid-pieces, as well as more flexible membranes, may allow spermatozoa to move faster (Blengini et al, 2014;Firman and Simmons, 2010;Safarinejad et al, 2010). Changes in sperm structure may, however, require the duration of a spermatogenesis cycle or of epididymal maturation period before they become conspicuous.…”