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CIBER research published in Science

Boris Baer Seminal fluid from one male can damage the sperm of other males in insect species where females mate with several males but female secretions seem to inhibit this effect. Research conducted at the University of Western Australia, the University of Copenhagen and the Smithsonian Tropical Research Institute (STRI) investigated the effects of the seminal fluid of two species of bees – the multiple-mating honeybee and the single-mating bumble bee – and three species of Panamanian leaf-cutting ants, of which two have queens that mate multiply. The results now published in Science indicate that only the seminal fluid of the multiple-mating species appears to have the capacity to damage the sperm of competitors. In the single-mating bumblebees, the male inserts a ‘plug’ into the female once she is mated which seems to prevent her re-mating, so ejaculates from different males never get into contact with each other and appear not to have evolved a system of sperm warfare.

Download and read the paper

The work was published on the 18th of March in Science. (Volume 327, pages 1506-1509).

To download the paper click here.

Read the abstract of the paper.

Seminal fluid mediates ejaculate competition in social insects

Den Boer, S. P. A., Baer, B. & Boomsma, J. J. Science 327, 1506-1509 (2010)


Queens of ants and bees normally obtain a lifetime supply of sperm on a single day of sexual activity and sperm competition is expected to occur in lineages where queens receive sperm from multiple males. We compared singly-mated (monandrous) and multiply-mated (polyandrous) sister groups of ants and bees and show that seminal fluid of polyandrous species has a more positive effect on the survival of a male's own sperm than on other males' sperm. This difference was not observed in the monandrous species, suggesting that incapacitation of competing sperm may have independently evolved in both bees and ants. In Atta leafcutter ants the negative effect of the seminal fluid of other males was negated by secretion from the queen sperm-storage organ, suggesting that queens may control ejaculate competition after sperm storage.

A commentary about the work in the same issue of Science can be found here.

More information

To download a press release from the University of Western Australia click here

To download a press release from STRI click here

To download a press release in Danish click here.

A commentary about the work has also been published in Nature and can be found here.

Author contacts

University of Western Australia:
Boris Baer: +61 8 6488 4495 /+61 4 2465 2911
E-mail: boris.baer[at]uwa.edu.au
University of Copenhagen:
Susanne den Boer: +45 4118 8436
E-mail: spadenboer@bio.ku.dk
Koos Boomsma:+45 3532 1340 /+45 2043 6771
E-mail: jjboomsma[at]bio.ku.dk

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