The causal and functional organization of mating behaviour in Gammarus pulex (Amphipoda)

The causal and functional organization of mating behaviour in male Gammarus pulex was investigated using Principal Components Analysis. Males were presented with 1) unmoulted novel females and 2) moulted females ready for insemination. Composite measures of behaviour were derived from an array of often correlated behavioural measures and activities. Three factors describe Precopulatory behaviour and are labelled according to the activities which define them as; "decisiveness", "courtship" and "tenacity". Three factors describe Copulatory behaviour; "decisiveness", "preparation" and "copulation". These factors reflect the internal organization of male behaviour and motivational state. In addition, they allow for investigation of the functional significance of behaviour. Correlation analysis showed clear relationships between Precopula behaviour and female reproductive quality. As the time from moult of offered females decreased, males became more "decisive" in their actions and were more "tenacious" towards females, whereas the "courtship" component remained constant. No aspect of Copulatory behaviour was influenced by the absolute or relative size of copulating animals. These results are discussed with reference to activities displayed by other Gammarus spp. and compared with other studies that employ factor analyses.