video: double amplexus in Gammarus pulex

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In Gammarus pulex, the pair formation is characterized by a long-lasting mate guarding behaviour, named amplexus, in which a male grasps a female for up to 20 days until the sexual receptiviy of the female. In this video recorded in laboratory conditions, a male is attempting to handle two females, possibly in order to compare the two mating options. 

> Galipaud M., Bollache L., Oughadou A., Dechaume-Moncharmont F.-X. (2015) Males do not always switch females when presented to a better reproductive option. Behavioral Ecology 26:359–366 [pdf]