Body-generated hydrodynamic flows influence male–male contests and female mate choice in a freshwater fish

Abstract

The lateral line system of fishes is composed of neuromast mechanoreceptors that detect movement through vibration and changes in pressure gradients in the water. Although mechanosensory information has been shown to be important in the contexts of predator escape and foraging, little is known about the role of the lateral line system during intraspecific interactions, such as reproduction. However, many species of fish demonstrate complex courtship and aggressive repertoires that involve movement of the body and fins, resulting in local displacement of the surrounding water. This displacement has the potential to function as a signal that contains information about the sender. In this study, we conducted two behavioural experiments using fathead minnows, Pimephales promelas, to test the hypothesis that the outcomes of male–male contests and male–female courtship interactions are influenced by hydrodynamic flows generated during conspecific interactions. In the first experiment, we pitted control males against those with an ablated lateral line system and assessed both overall aggression and the likelihood of territory acquisition. In the second experiment, we conducted dual-choice female mate choice experiments to determine whether control females and those without access to mechanosensory information (ablated females) differed in patterns of discrimination and the use of courtship as a criterion of choice. In experiment 1, control males won a significantly greater proportion of territorial contests than expected by chance and were more likely to use noncontact threat displays during aggressive interactions compared with ablated males. In experiment 2, females with access to the mechanosensory information channel showed enhanced mate discrimination compared to ablated females. These data are among the first to show that mechanosensory signals are an important criterion of territorial and reproductive success in fishes and are likely important contributors to multimodal communication in this group.