Article

Social competitiveness associated with rapid fluctuations in sperm quality in male fowl.

Edward Grey Institute of Ornithology, Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK.
Proceedings of the Royal Society B: Biological Sciences (Impact Factor: 5.29). 04/2007; 274(1611):853-60. DOI: 10.1098/rspb.2006.0080
Source: PubMed

ABSTRACT When females copulate with multiple males, paternity is determined by the competitive ability of a male to access females and by the ability of its ejaculates to out-compete those of other males over fertilization. The relationship between the social competitiveness of a male and the fertilizing quality of its sperm has therefore crucial implications for the evolution of male reproductive strategies in response to sexual selection. Here, we present a longitudinal experimental study of the relationship between social status and sperm quality. We monitored sperm quality in socially naive male domestic fowl, Gallus gallus domesticus, before and after exposure to a social challenge which comprised two stages. In the first stage, social dominance was established in male pairs divergent in sperm quality, and in the second, social status was experimentally manipulated by re-shuffling males across pairs. We show that sperm quality fluctuates within males both before and after a social challenge. Importantly, such fluctuations followed consistently different patterns in males that displayed different levels of social competitiveness in the social challenge. In particular, following the social challenge, sperm quality dropped in males that won both contests while the sperm quality of males that lost both contests remained constant. Together, these results indicate that males of different social competitiveness are predisposed to specific patterns of fluctuations in sperm quality. These rapid within-male fluctuations may help explain the recent findings of trade-offs between male social and gametic competitive abilities and may help maintain phenotypic variability in these traits.

Download full-text

Full-text

Available from: Tommaso Pizzari, Jul 03, 2015
1 Follower
 · 
90 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The general decline in wild Iberian populations of the red-legged partridge (Alectoris rufa) has been accompanied by an increase in game-farm facilities producing hybrids with chukar partridges (Alectoris chukar). Genetic introgression from chukar partridges is thought to modify male red-legged partridge reproductive indicators. The aim of the present study was to determine the effects of such genetic introgression on seasonal reproductive patterns by comparing the sperm and plasma testosterone concentrations of males from pure red-legged and hybrid red-legged/chukar populations. Semen was collected twice monthly over a 12-mo period using a massage technique. Both types of bird showed a clear seasonal pattern of spermatogenic activity. The proportion of males ejaculating sperm was higher (P < 0.05) among the pure red-legged birds. The greatest sperm production was recorded in March to May among the pure birds and April to May among the hybrids. Reproductive activity in both groups decreased in June, to reach a minimum in August to December among the hybrids and in September to December among the pure birds. Spermatogenic activity resumed in January in both groups. The sperm concentration produced by the pure birds was smaller than that of the hybrids (P < 0.001), but the percentage of motile sperm was higher in the pure birds (P < 0.001). The sperm of the hybrids showed greater straight-line velocity (P < 0.05), linearity (P < 0.001), straightness (P < 0.001), sperm wobble (P < 0.05), and beat-cross frequency values (P < 0.001). The length and area of the sperm head were smaller in the pure birds (P < 0.05). The seasonal plasma testosterone concentration pattern followed a trend roughly parallel to the ejaculatory response. The present results suggest that genetic introgression influences the reproductive variables of the red-legged partridge. © 2015 Poultry Science Association Inc.
    Poultry Science 01/2015; 94(1):80-7. DOI:10.3382/ps/peu020 · 1.67 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Sperm competition, whereby sperm from multiple males compete to fertilize an egg, selects for adaptations that increase fertilization success. Because fertilization success is related to sperm number, size, and quality, both interspecific and intraspecific variation in these traits are predicted to correlate with the level of sperm competition. Specifically, species and individuals that experience high sperm competition are predicted to produce more sperm per ejaculate, produce longer sperm, and exert higher quality control, resulting in reduced numbers of morphologically abnormal sperm and reduced size variation via selection for the most successful sperm phenotype. However, the causes of sperm morphological and size variation and its consequences for sperm competition remain poorly understood, especially within species. We quantified variation in sperm morphology, size, and number in the Lance-tailed Manakin (Chiroxiphia lanceolata), a Neotropical suboscine passerine with a cooperative lek mating system. Although alpha-status males sire almost all chicks, the numbers of sperm produced per ejaculate by betas, nonterritorial adults, and subadult males were similar to those produced by alphas. Sperm counts declined with age in alphas, which may explain the decreased siring success of older alphas. Most ejaculates contained both normal helical sperm and abnormal sperm with rounded heads. The proportion of morphologically normal sperm per ejaculate was unrelated to social status or age. The coefficients of variation in sperm component length (head, tail, and total) both between and within alpha males were comparable to variation reported in asserines with low sperm competition. Total sperm length was shorter than in the majority of avian species studied to date, and cloacal protuberance and relative testis size were small. These results indicate low sperm competition, despite evidence for multiple paternity, or that sperm number rather than sperm morphology may be a major postcopulatory mediator of male reproductive success in this species. This work represents the first thorough quantification of intraspecific sperm variability in a suboscine passerine.
    The Auk 09/2014; 131:660-671. DOI:10.1642/AUK-14-38.1 · 2.63 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Oxidative stress is emerging as a key factor underpinning life history and the expression of sexually selected traits. Resolving the role of oxidative stress in life history and sexual selection requires a pluralistic approach, which investigates how age affects the relationship between oxidative status (i.e., antioxidants and oxidative damage) and the multiple traits contributing to variation in reproductive success. Here, we investigate the relationship between oxidative status and the expression of multiple sexually selected traits in two-age classes of male red junglefowl, Gallus gallus, a species which displays marked male reproductive senescence. We found that, irrespective of male age, both male social status and comb size were strongly associated with plasma oxidative status, and there was a nonsignificant tendency for sperm motility to be associated with seminal oxidative status. Importantly, however, patterns of plasma and seminal antioxidant levels differed markedly in young and old males. While seminal antioxidants increased with plasma antioxidants in young males, the level of seminal antioxidants remained low and was independent of plasma levels in old males. In addition, old males also accumulated more oxidative damage in their sperm DNA. These results suggest that antioxidant allocation across different reproductive traits and somatic maintenance might change drastically as males age, leading to age-specific patterns of antioxidant investment.
    Ecology and Evolution 09/2012; 2(9):2155-67. DOI:10.1002/ece3.300 · 1.66 Impact Factor