scholarly journals Sperm competition and sperm length influence the rate of mammalian spermatogenesis

2009 ◽  
Vol 6 (2) ◽  
pp. 219-221 ◽  
Author(s):  
Steven A. Ramm ◽  
Paula Stockley
Keyword(s):  
Sperm Competition ◽  
Negative Relationship ◽  
Interspecific Variation ◽  
Sperm Length ◽  
Testis Size ◽  
Sperm Production ◽  
Selection For ◽  
High Level ◽  
Sperm Size ◽  
Numerical Advantage

Sperm competition typically favours an increased investment in testes, because larger testes can produce more sperm to provide a numerical advantage in competition with rival ejaculates. However, interspecific variation in testis size cannot be equated directly with variation in sperm production rate—which is the trait ultimately selected under sperm competition—because there are also differences between species in the proportion of spermatogenic tissue contained within the testis and in the time it takes to produce each sperm. Focusing on the latter source of variation, we provide phylogenetically controlled evidence for mammals that species with relatively large testes (and hence a high level of sperm competition) have a shorter duration of the cycle of the seminiferous epithelium and consequently a faster rate of spermatogenesis, enabling males to produce more sperm per unit testis per unit time. Moreover, we identify an independent negative relationship between sperm length and the rate of spermatogenesis, such that spermatogenesis takes longer in species with longer sperm. We conclude that sperm competition selects for both larger testes and a faster rate of spermatogenesis to increase overall sperm production, and that an evolutionary trade-off between sperm size and numbers may be mediated via constraints on the rate of spermatogenesis imposed by selection for longer sperm.

scholarly journals Sperm competition leads to functional adaptations in avian testes to maximize sperm quantity and quality

Reproduction ◽  
2011 ◽  
Vol 141 (5) ◽  
pp. 595-605 ◽  
Author(s):  
Stefan Lüpold ◽  
Joachim Wistuba ◽  
Oliver S Damm ◽  
James W Rivers ◽  
Tim R Birkhead
Keyword(s):  
Sperm Competition ◽  
Relative Number ◽  
Cell Types ◽  
Sperm Length ◽  
Testis Size ◽  
Trade Offs ◽  
Competition Level ◽  
Selection For ◽  
Sperm Output

The outcome of sperm competition (i.e. competition for fertilization between ejaculates from different males) is primarily determined by the relative number and quality of rival sperm. Therefore, the testes are under strong selection to maximize both sperm number and quality, which are likely to result in trade-offs in the process of spermatogenesis (e.g. between the rate of spermatogenesis and sperm length or sperm energetics). Comparative studies have shown positive associations between the level of sperm competition and both relative testis size and the proportion of seminiferous (sperm-producing) tissue within the testes. However, it is unknown how the seminiferous tissue itself or the process of spermatogenesis might evolve in response to sperm competition. Therefore, we quantified the different germ cell types and Sertoli cells (SC) in testes to assess the efficiency of sperm production and its associations with sperm length and mating system across 10 species of New World Blackbirds (Icteridae) that show marked variation in sperm length and sperm competition level. We found that species under strong sperm competition generate more round spermatids (RS)/spermatogonium and have SC that support a greater number of germ cells, both of which are likely to increase the maximum sperm output. However, fewer of the RS appeared to elongate to mature spermatozoa in these species, which might be the result of selection for discarding spermatids with undesirable characteristics as they develop. Our results suggest that, in addition to overall size and gross morphology, testes have also evolved functional adaptations to maximize sperm quantity and quality.

scholarly journals Patterns of sperm damage in Chernobyl passerine birds suggest a trade-off between sperm length and integrity

2013 ◽  
Vol 9 (5) ◽  
pp. 20130530 ◽  
Author(s):  
Ignacio G. Hermosell ◽  
Terje Laskemoen ◽  
Melissah Rowe ◽  
Anders P. Møller ◽  
Timothy A. Mousseau ◽  
...  
Keyword(s):  
Sperm Competition ◽  
Acrosome Reaction ◽  
Interspecific Variation ◽  
Passerine Bird ◽  
Sperm Length ◽  
Passerine Birds ◽  
Trade Off ◽  
Sperm Abnormalities ◽  
Trade Offs ◽  
Sperm Competition Risk

Interspecific variation in sperm size is enigmatic, but generally assumed to reflect species-specific trade-offs in selection pressures. Among passerine birds, sperm length varies sevenfold, and sperm competition risk seems to drive the evolution of longer sperm. However, little is known about factors favouring short sperm or constraining the evolution of longer sperm. Here, we report a comparative analysis of sperm head abnormalities among 11 species of passerine bird in Chernobyl, presumably resulting from chronic irradiation following the 1986 accident. Frequencies of sperm abnormalities varied between 15.7 and 77.3% among species, more than fourfold higher than in uncontaminated areas. Nonetheless, species ranked similarly in sperm abnormalities in unpolluted areas as in Chernobyl, pointing to intrinsic factors underlying variation in sperm damage among species. Scanning electron microscopy of abnormal spermatozoa revealed patterns of acrosome damage consistent with premature acrosome reaction. Sperm length, but not sperm competition risk explained variation in sperm damage among species. This suggests that longer spermatozoa are more susceptible to premature acrosome reaction. Therefore, we hypothesize a trade-off between sperm length and sperm integrity affecting sperm evolution in passerine birds.

scholarly journals Long sperm fertilize more eggs in a bird

2015 ◽  
Vol 282 (1799) ◽  
pp. 20141897 ◽  
Author(s):  
Clair Bennison ◽  
Nicola Hemmings ◽  
Jon Slate ◽  
Tim Birkhead
Keyword(s):  
Sperm Competition ◽  
Reproductive Traits ◽  
Fertilization Success ◽  
Swimming Velocity ◽  
Sperm Length ◽  
Complex Interactions ◽  
Female Reproductive Traits ◽  
Sperm Size ◽  
The Relationship ◽  
Main Factor

Sperm competition, in which the ejaculates of multiple males compete to fertilize a female's ova, results in strong selection on sperm traits. Although sperm size and swimming velocity are known to independently affect fertilization success in certain species, exploring the relationship between sperm length, swimming velocity and fertilization success still remains a challenge. Here, we use the zebra finch ( Taeniopygia guttata ), where sperm size influences sperm swimming velocity, to determine the effect of sperm total length on fertilization success. Sperm competition experiments, in which pairs of males whose sperm differed only in length and swimming speed, revealed that males producing long sperm were more successful in terms of (i) the number of sperm reaching the ova and (ii) fertilizing those ova. Our results reveal that although sperm length is the main factor determining the outcome of sperm competition, complex interactions between male and female reproductive traits may also be important. The mechanisms underlying these interactions are poorly understood, but we suggest that differences in sperm storage and utilization by females may contribute to the outcome of sperm competition.

scholarly journals How sperm competition shapes the evolution of testes and sperm: a meta-analysis

2020 ◽  
Vol 375 (1813) ◽  
pp. 20200064
Author(s):  
Stefan Lüpold ◽  
Raïssa A. de Boer ◽  
Jonathan P. Evans ◽  
Joseph L. Tomkins ◽  
John L. Fitzpatrick
Keyword(s):  
Sperm Competition ◽  
Meta Analysis ◽  
Empirical Studies ◽  
Reproductive Behaviour ◽  
Analytical Framework ◽  
Sperm Length ◽  
Other Information ◽  
Theoretical Predictions ◽  
Testes Size ◽  
Sperm Size

Females of many species mate with multiple males, thereby inciting competition among ejaculates from rival males for fertilization. In response to increasing sperm competition, males are predicted to enhance their investment in sperm production. This prediction is so widespread that testes size (correcting for body size) is commonly used as a proxy of sperm competition, even in the absence of any other information about a species' reproductive behaviour. By contrast, a debate about whether sperm competition selects for smaller or larger sperm has persisted for nearly three decades, with empirical studies demonstrating every possible response. Here, we synthesize nearly 40 years of sperm competition research in a meta-analytical framework to determine how the evolution of sperm number (i.e. testes size) and sperm size (i.e. sperm head, midpiece, flagellum and total length) is influenced by varying levels of sperm competition across species. Our findings support the long-held assumption that higher levels of sperm competition are associated with relatively larger testes. We also find clear evidence that sperm competition is associated with increases in all components of sperm length. We discuss these results in the context of different theoretical predictions and general patterns in the breeding biology and selective environment of sperm. This article is part of the theme issue ‘Fifty years of sperm competition’.

Relationships of basal metabolic rate, relative testis size and cycle length of spermatogenesis in shrews (Mammalia, Soricidae)

2008 ◽  
Vol 20 (3) ◽  
pp. 431 ◽  
Author(s):  
Roumen Parapanov ◽  
Sébastien Nusslé ◽  
Jacques Hausser ◽  
Peter Vogel
Keyword(s):  
Metabolic Rate ◽  
Mating System ◽  
Sperm Competition ◽  
Basal Metabolic Rate ◽  
Cycle Length ◽  
System Level ◽  
Testis Size ◽  
Suncus Murinus ◽  
Sperm Production ◽  
Sorex Minutus

The aim of the present study was to determinate the cycle length of spermatogenesis in three species of shrew, Suncus murinus, Sorex coronatus and Sorex minutus, and to assess the relative influence of variation in basal metabolic rate (BMR) and mating system (level of sperm competition) on the observed rate of spermatogenesis, including data of shrew species studied before (Sorex araneus, Crocidura russula and Neomys fodiens). The dynamics of sperm production were determined by tracing 5-bromodeoxyuridine in the DNA of germ cells. As a continuous scaling of mating systems is not evident, the level of sperm competition was evaluated by the significantly correlated relative testis size (RTS). The cycle durations estimated by linear regression were 14.3 days (RTS 0.3%) in Suncus murinus, 9.0 days (RTS 0.5%) in Sorex coronatus and 8.5 days (RTS 2.8%) in Sorex minutus. In regression and multiple regression analyses including all six studied species of shrew, cycle length was significantly correlated with BMR (r2 = 0.73) and RTS (r2 = 0.77). Sperm competition as an ultimate factor obviously leads to a reduction in the time of spermatogenesis in order to increase sperm production. BMR may act in the same way, independently or as a proximate factor, revealed by the covariation, but other factors (related to testes size and thus to mating system) may also be involved.

Human sperm competition: testis size, sperm production and rates of extrapair copulations

2004 ◽  
Vol 68 (2) ◽  
pp. 297-302 ◽  
Author(s):  
Leigh W. Simmons ◽  
Renée C. Firman ◽  
Gillian Rhodes ◽  
Marianne Peters
Keyword(s):  
Sperm Competition ◽  
Human Sperm ◽  
Testis Size ◽  
Sperm Production

scholarly journals Larval social cues influence testicular investment in an insect

2021 ◽  
Author(s):  
Junyan Liu ◽  
Xiong Z He ◽  
Xia-Lin Zheng ◽  
Yujing Zhang ◽  
Qiao Wang
Keyword(s):  
Body Weight ◽  
Sperm Competition ◽  
Growth And Development ◽  
Social Cues ◽  
Social Setting ◽  
Testis Size ◽  
Sperm Production ◽  
Competition Level ◽  
Fine Tune ◽  
Paternity Share

Abstract Socio-sexual environment can have critical impacts on reproduction and survival of animals. Consequently, they need to prepare themselves by allocating more resources to competitive traits that give them advantages in the particular social setting they have been perceiving. Evidence shows that a male usually raises his investment in sperm after he detects the current or future increase of sperm competition because relative sperm numbers can determine his paternity share. This leads to the wide use of testis size as an index of the sperm competition level, yet testis size does not always reflect sperm production. To date, it is not clear whether male animals fine-tune their resource allocation to sperm production and other traits as a response to social cues during their growth and development. Using a polygamous insect Ephestia kuehniella, we tested whether and how larval social environment affected sperm production, testis size, and body weight. We exposed the male larvae to different juvenile socio-sexual cues and measured these traits. We demonstrate that regardless of sex ratio, group-reared males produced more eupyrenes (fertile and nucleate sperm) but smaller testes than singly reared ones, and that body weight and apyrene (infertile and anucleate sperm) numbers remained the same across treatments. We conclude that the presence of larval social, but not sexual cues is responsible for the increase of eupyrene production and decrease of testis size. We suggest that male larvae increase investment in fertile sperm cells and reduce investment in other testicular tissues in the presence of conspecific juvenile cues.

scholarly journals Fisher vs. The Worms: Extraordinary Sex Ratios in Nematodes and the Mechanisms That Produce Them

Cells ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 1793
Author(s):  
Justin Van Goor ◽  
Diane C. Shakes ◽  
Eric S. Haag
Keyword(s):  
Sex Ratio ◽  
Sperm Competition ◽  
Sex Chromosomes ◽  
Sex Ratios ◽  
Environmental Sex Determination ◽  
Fitness Advantage ◽  
Selection For ◽  
Facultative Parthenogenesis ◽  
Multicellular Organisms ◽  
Inbred Populations

Parker, Baker, and Smith provided the first robust theory explaining why anisogamy evolves in parallel in multicellular organisms. Anisogamy sets the stage for the emergence of separate sexes, and for another phenomenon with which Parker is associated: sperm competition. In outcrossing taxa with separate sexes, Fisher proposed that the sex ratio will tend towards unity in large, randomly mating populations due to a fitness advantage that accrues in individuals of the rarer sex. This creates a vast excess of sperm over that required to fertilize all available eggs, and intense competition as a result. However, small, inbred populations can experience selection for skewed sex ratios. This is widely appreciated in haplodiploid organisms, in which females can control the sex ratio behaviorally. In this review, we discuss recent research in nematodes that has characterized the mechanisms underlying highly skewed sex ratios in fully diploid systems. These include self-fertile hermaphroditism and the adaptive elimination of sperm competition factors, facultative parthenogenesis, non-Mendelian meiotic oddities involving the sex chromosomes, and environmental sex determination. By connecting sex ratio evolution and sperm biology in surprising ways, these phenomena link two “seminal” contributions of G. A. Parker. 

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