Sperm Traits Negatively Covary with Size and Asymmetry of a Secondary Sexual Trait in a Freshwater Crayfish

Abstract

In species where females mate promiscuously, the reproductive success of males depends both on their ability to acquire mates (pre-copulatory sexual selection) and ability of their ejaculates to outcompete those of other males (post-copulatory sexual selection). Sperm competition theory predicts a negative relationship between investment in body traits favouring mate acquisition (secondary sexual characters, SSCs) and investment in ejaculate size or quality, due to the inherent costs of sperm production. In contrast, the phenotype-linked fertility hypothesis posits that male fertilizing efficiency is reliably reflected by the phenotypic expression of male SSCs, allowing females to obtain direct benefits by selecting more ornamented males as copulation partners. In this study, we investigated the relationships between male SSCs and size and quality (viability and longevity) of ejaculates allocated to females in mating trials of the freshwater crayfish Austropotamobius italicus. We showed that the relative size of male weapons, the chelae, was negatively related to ejaculate size, and that chelae asymmetry, resulting from regeneration of lost chelipeds, negatively covaried with sperm longevity. Moreover, males allocated more viable sperm to mates from their own rather than different stream of origin. Our findings thus suggest that, according to sperm competition theory, pre-copulatory sexual selection for large weapons used in male fighting may counteract post-copulatory sperm competition in this crayfish species, and that investment in cheliped regeneration may impair ejaculate quality.

Female monopolization mediates the relationship between pre- and postcopulatory sexual traits

“…Intraspecifically, male investment in weaponry used in male-male competition (for example, horns, large male size relative to females, or grasping forearms) appears to be negatively associated with testes size or ejaculate size in most species examined (for example, dung beetles Onthophagus nigriventris 14 , dung flies Sepsis punctum 15 , myobatrachid frogs Crinia georgiana 13 and freshwater crayfish Austropotamobius italicus 16 ). However, antler size covaries positively with relative testes size and sperm quality in the red deer Cervus elaphus 17 , and relative testes size does not differ between male tree weta Hemideina crassidens exhibiting small and large mandibular weaponry, respectively 18 .…”

Post-mating morphological changes in the spermatozoon and spermatophore wall of the crayfish Astacus leptodactylus: Insight into a non-motile spermatozoon

“…Thereafter, during transit of the sperm mass to the distal portion of the vas deferens, a spermatophore wall is added by secretions of the vas deferens epithelium (Vogt, 2002). A three layered spermatophore wall was reported for crayfish (Dudenhausen and Talbot, 1983;Galeotti et al, 2012). Although the basic function of the spermatophores is the transfer of spermatozoa from male to female (Dudenhausen and Talbot, 1983), the complex ultrastructure of the spermatophore layers and their post-mating morphological changes may indicate additional functional significance in crayfish.…”

“…In the crayfish, spermatozoa are packaged into spermatophores (Galeotti et al, 2012) that are transferred from the male to female during mating. Crayfish spermatophores are deposited either on the ventral surface (in Astacidae and Parastacidae) of the female or into the Annulus ventralis (in Cambaridae).…”

“…Additionally, the decapod spermatozoon lacks a true flagellum and is non-motile (Jamieson and Tudge, 2000;Tudge, 2009), providing opportunities for comparison with motile spermatozoa.…”

Beneficial effect and potential molecular mechanism of chloroquine on sperm motility and fertilizing ability in yellow catfish

“…Under the pressure from sexual selection and sperm competition, interest for sperm quality analysis has been aroused to increase the reproductive success and maintain the genetic diversity of the lineages (Mehlis et al, 2015;Galeotti et al, 2012). Multiple quality indexes including motility, spermatocrit, viability and fertilization success have been used to define the quality of the sperm.…”