JEB Fighting cichlids size up opposition with lateral line

When sizing each other up before a confrontation, most males depend on all of their senses to learn more about their opponent – listening, watching and sniffing out strengths and weaknesses. However, Karen Maruska and Julie Butler, from Louisiana State University, USA, explain that fish also explore their surroundings with an additional sense: the lateral line system responds to the ebb and flow of water surrounding the fish’s body. Could fish also use this ‘touch at a distance’ system to learn more about a foe? Maruska and Butler explain that fish adversaries often waft water around while posturing in preparation for an encounter and add, ‘The lateral line is poised to provide crucial information for opponent assessment’. However, no one had ever tested whether fish resort to the specialised sense in preparation for combat. ‘Astatotilapia burtoni males use a variety of aggressive behaviors, such as lateral displays, border fights, biting and mouth fights to defend their spawning territory,’ says Butler, so the scientists selected this aggressive species to test their theory.