Evolution and co-evolution of the suck behaviour, a postcopulatory female resistance trait that manipulates received ejaculate

Abstract Background Sexual conflicts over the post-mating fate of received ejaculate can favour traits in one sex that are costly to the other. Reciprocally mating hermaphrodites face unique challenges as they mate simultaneously in both the male and female role, potentially leading to receipt of un...

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Main Authors: Pragya Singh, Jeremias N. Brand, Lukas Schärer
Format: Article
Language:English
Published: BMC 2025-03-01
Series:BMC Biology
Subjects:
Online Access:https://doi.org/10.1186/s12915-025-02171-5
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author Pragya Singh
Jeremias N. Brand
Lukas Schärer
author_facet Pragya Singh
Jeremias N. Brand
Lukas Schärer
author_sort Pragya Singh
collection DOAJ
description Abstract Background Sexual conflicts over the post-mating fate of received ejaculate can favour traits in one sex that are costly to the other. Reciprocally mating hermaphrodites face unique challenges as they mate simultaneously in both the male and female role, potentially leading to receipt of unwanted ejaculate. Reciprocal mating can then give rise to postcopulatory female resistance traits that allow manipulation of received ejaculate. A putative example is the suck behaviour, observed in the flatworm genus Macrostomum. It involves the sperm recipient placing its pharynx over its own female genital opening and appearing to suck, likely removing received ejaculate after mating. The genus also contains hypodermically inseminating species that presumably exhibit unilateral mating and have not been observed to suck. Results Here, we examine the evolution of the suck behaviour in the Macrostomum genus, aiming to document the mating behaviour in 64 species. First, we provide videographic evidence that ejaculate is indeed removed during the suck behaviour in a reciprocally mating species, Macrostomum hamatum. Next, we show positive evolutionary correlations between the presence, duration and frequency of reciprocal mating behaviour and the suck behaviour, providing clear evidence that the suck behaviour co-evolves with reciprocal mating behaviour. Finally, we show an association between reproductive behaviour and reproductive morphology, suggesting that the reproductive morphology can be used to infer a species’ mating behaviour. Conclusions Together, our study demonstrates sexually antagonistic coevolution leading to the evolution of a postcopulatory behavioural trait that functions as a female counter-adaptation allowing individuals to gain control over received ejaculate in a hermaphroditic sexual system.
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spelling doaj-art-211cea079fec4cd0a3efaf08b048b4d72025-08-20T02:10:14ZengBMCBMC Biology1741-70072025-03-0123111910.1186/s12915-025-02171-5Evolution and co-evolution of the suck behaviour, a postcopulatory female resistance trait that manipulates received ejaculatePragya Singh0Jeremias N. Brand1Lukas Schärer2Department of Environmental Sciences, University of Basel, Zoological InstituteDepartment of Environmental Sciences, University of Basel, Zoological InstituteDepartment of Environmental Sciences, University of Basel, Zoological InstituteAbstract Background Sexual conflicts over the post-mating fate of received ejaculate can favour traits in one sex that are costly to the other. Reciprocally mating hermaphrodites face unique challenges as they mate simultaneously in both the male and female role, potentially leading to receipt of unwanted ejaculate. Reciprocal mating can then give rise to postcopulatory female resistance traits that allow manipulation of received ejaculate. A putative example is the suck behaviour, observed in the flatworm genus Macrostomum. It involves the sperm recipient placing its pharynx over its own female genital opening and appearing to suck, likely removing received ejaculate after mating. The genus also contains hypodermically inseminating species that presumably exhibit unilateral mating and have not been observed to suck. Results Here, we examine the evolution of the suck behaviour in the Macrostomum genus, aiming to document the mating behaviour in 64 species. First, we provide videographic evidence that ejaculate is indeed removed during the suck behaviour in a reciprocally mating species, Macrostomum hamatum. Next, we show positive evolutionary correlations between the presence, duration and frequency of reciprocal mating behaviour and the suck behaviour, providing clear evidence that the suck behaviour co-evolves with reciprocal mating behaviour. Finally, we show an association between reproductive behaviour and reproductive morphology, suggesting that the reproductive morphology can be used to infer a species’ mating behaviour. Conclusions Together, our study demonstrates sexually antagonistic coevolution leading to the evolution of a postcopulatory behavioural trait that functions as a female counter-adaptation allowing individuals to gain control over received ejaculate in a hermaphroditic sexual system.https://doi.org/10.1186/s12915-025-02171-5Sexual conflictSexual selectionSimultaneous hermaphroditeCo-evolutionReproductive traitsPostcopulatory mechanisms
spellingShingle Pragya Singh
Jeremias N. Brand
Lukas Schärer
Evolution and co-evolution of the suck behaviour, a postcopulatory female resistance trait that manipulates received ejaculate
BMC Biology
Sexual conflict
Sexual selection
Simultaneous hermaphrodite
Co-evolution
Reproductive traits
Postcopulatory mechanisms
title Evolution and co-evolution of the suck behaviour, a postcopulatory female resistance trait that manipulates received ejaculate
title_full Evolution and co-evolution of the suck behaviour, a postcopulatory female resistance trait that manipulates received ejaculate
title_fullStr Evolution and co-evolution of the suck behaviour, a postcopulatory female resistance trait that manipulates received ejaculate
title_full_unstemmed Evolution and co-evolution of the suck behaviour, a postcopulatory female resistance trait that manipulates received ejaculate
title_short Evolution and co-evolution of the suck behaviour, a postcopulatory female resistance trait that manipulates received ejaculate
title_sort evolution and co evolution of the suck behaviour a postcopulatory female resistance trait that manipulates received ejaculate
topic Sexual conflict
Sexual selection
Simultaneous hermaphrodite
Co-evolution
Reproductive traits
Postcopulatory mechanisms
url https://doi.org/10.1186/s12915-025-02171-5
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