Archive

Rodents

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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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Owing to its complex composition, the mixture of sperm and seminal fluid substances that comprise an ejaculate has recently been likened to a musical symphony. In a new study I conducted with former colleagues at the University of Liverpool and published this week in BMC Biology, we used proteomics techniques to ask whether male mammals can plastically adjust ejaculate composition. We discovered that the “seminal symphony” males produce indeed depends strongly upon the prevailing “social milieu”. Under more competitive conditions, males produce more sperm and a different blend of seminal fluid proteins than they do under less competitive conditions. This is presumably because high sperm numbers and large amounts of certain seminal fluid proteins enhance male competitive fertilization success, but aren’t needed when there are no competitors around, and so plasticity in ejaculate composition is selectively favoured.

Ramm SA, Edward DA, Claydon AJ, Hammond DE, Brownridge P, Hurst JL, 
Beynon RJ, Stockley P (2015) 
Sperm competition risk drives plasticity in seminal fluid composition
BMC Biology 13:87. doi: 10.1186/s12915-015-0197-2

Image credit: from Beethoven’s Symphony No. 5. Licensed under Public Domain via Wikimedia Commons.