Archive

Sperm competition

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This year’s edition of Advances in the Study of Behavior will be published shortly, to which Paula Stockley and I have contributed an in-depth review of male adaptations to sperm competition in rodents. The review pulls together many of the different research strands we have ourselves been working on over the past several years, covering aspects such as copulatory behaviour, sperm production, sperm allocation, sperm quality, seminal fluid and genitalia, as well as the wider context of sperm competition studies by considering topics such as cryptic female choice, sexual conflict and multivariate selection and trade-offs. We argue that allied to traditional behavioural and morphological studies, recent molecular and genome-based approaches are transforming our understanding of traits that contribute to male competitive fertilization ability, closing the gap between genotypic and phenotypic perspectives on their adaptive evolution.

Hopefully the review will be a useful synthesis of where we’ve got to with respect to understanding sperm competition in this important vertebrate model group, and can serve as a guide to where we need to go next. The advance online version can be found here.

Integrating perspectives on rodent sperm competition.
Ramm SA, Stockley P (2016)
Advances in the Study of Behavior 48, in press. 
DOI: 10.1016/bs.asb.2016.02.003

Photo credit: Joad Hughes, via Unsplash.

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Our latest experimental results in Macrostomum lignano flatworms demonstrate that individuals are able to produce sperm faster under conditions of higher sperm competition, presumably contributing to stronger sperm competitiveness. The findings are important because they imply that the speed of spermatogenesis is not a fixed property of a species or a genotype, but rather a malleable parameter that varies according to the prevailing environmental conditions. Whether or not other animals are capable of modulating the speed of spermatogenesis in this manner is currently unknown, but it could be that speeding up and slowing down spermatogenesis based on sperm competition cues is a taxonomically widespread – but until now largely overlooked – mechanism underlying phenotypic plasticity in sperm production.

The paper is based on experiments conducted by Athina Giannakara for her Master Thesis with me here in Bielefeld,  in collaboration with Lukas Schärer in Basel, and has just been published in BMC Evolutionary Biology.

Sperm competition-induced plasticity in the speed of spermatogenesis.
Giannakara A, Schärer L, Ramm SA (2016)
BMC Evolutionary Biology 16: 60. doi: 10.1186/s12862-016-0629-9

Picture: Detail from Fig. 1 in Giannakara et al. (2016).

Spermatozoons_42 The journal Molecular Human Reproduction has just published a special series on the theme of sperm competition, which the editor-in-chief Chris Barratt and I devised as a way of trying to bridge the divide between evolutionary and biomedical researchers interested in reproduction. I introduce the series in this Editorial and there are four reviews in total: Jussi Lehtonen and Geoff Parker writing on the evolution of anisogamy, a review I wrote together with Lukas Schärer, Jens Ehmcke and Joachim Wistuba on the evolution of spermatogenesis, John Fitzpatrick and Stefan Lüpold writing about the evolution of sperm quality and Ellen Kosman and Don Levitan reviewing the evolution of gametic compatibility. Thanks to all involved – enjoy!

Ramm SA. 2014.
Sperm competition and the evolution of reproductive systems
Mol. Hum. Reprod., doi:10.1093/molehr/gau076 PDF

Lehtonen J, Parker GA. 2014.
Gamete competition, gamete limitation, and the evolution of the 
two sexes
Mol. Hum. Reprod., doi:10.1093/molehr/gau068

Ramm SA, Schärer L, Ehmcke J, Wistuba J. 2014.
Sperm competition and the evolution of spermatogenesis
Mol. Hum. Reprod., doi:10.1093/molehr/gau070 PDF

Fitzpatrick JL, Lüpold S. 2014.
Sexual selection and the evolution of sperm quality
Mol. Hum. Reprod., doi:10.1093/molehr/gau067

Kosman ET, Levitan DR. 2014.
Sperm competition and the evolution of gametic compatibility in 
externally fertilizing taxa
Mol. Hum. Reprod., doi:10.1093/molehr/gau069

Update 19 November 2014: The Special Issue has now been published, and all of the reviews are freely available to download here.

Image: Nevit Dilmen via Wikimedia Commons (CC BY-SA 3.0)