The Cost of Sex: Quantifying Energetic Investment in Gamete Production by Males and Females

Abstract

The relative energetic investment in reproduction between the sexes forms the basis of sexual selection and life history theories in evolutionary biology. It is often assumed that males invest considerably less in gametes than females, but quantifying the energetic cost of gamete production in both sexes has remained a difficult challenge. For a broad diversity of species (invertebrates, reptiles, amphibians, fishes, birds, and mammals), we compared the cost of gamete production between the sexes in terms of the investment in gonad tissue and the rate of gamete biomass production. Investment in gonad biomass was nearly proportional to body mass in both sexes, but gamete biomass production rate was approximately two to four orders of magnitude higher in females. In both males and females, gamete biomass production rate increased with organism mass as a power law, much like individual metabolic rate. This suggests that whole-organism energetics may act as a primary constraint on gamete production among species. Residual variation in sperm production rate was positively correlated with relative testes size. Together, these results suggest that understanding the heterogeneity in rates of gamete production among species requires joint consideration of the effects of gonad mass and metabolism.

Spermless males elicit large-scale female responses to mating in the malaria mosquito Anopheles gambiae

“…It also shows that the number of insects that will be required for successful control depends on the relative competitiveness of manipulated and wild-type males, something that must be assessed under field conditions. There is evidence from other systems that sperm production is metabolically costly (25), and there is thus a possibility that manipulated males might even be at an advantage compared with wild-type individuals.…”

Diet-Mediated Pheromones and Signature Mixtures Can Enforce Signal Reliability

“…Numerous studies demonstrate a role of diet quality for mate assessment pheromones across a wide range of taxa, including insects (Shelly et al, 2007;South et al, 2011;Fedina et al, 2012;Weddle et al, 2012;Liedo et al, 2013); mammals (Ferkin et al, 1997;Havlicek and Lenchova, 2006); reptiles (Kopena et al, 2011(Kopena et al, , 2014Chouinard, 2012); arachnids (Cross et al, 2009;Baruffaldi and Andrade, 2015); and fish (Giaquinto, 2010;Giaquinto et al, 2010;Hayward and Gillooly, 2011 ; Table 1). Nonetheless, comprehensive studies that include both behavioral and chemical assays are largely limited to insect systems.…”

Protein and carbohydrate intake influence sperm number and fertility in male cockroaches, but not sperm viability

“…For example, sperm number is reduced by 65% in large male sea slugs (Chelidonura sandrana) across four successive matings [15]. Third, sperm production has been associated with an elevated metabolic rate within [16] and across [8] species. In some species, this elevation in metabolic rate is likely to represent a significant cost to the daily energy budget.…”