Signalling function of long wavelength colours during agonistic male-male interactions in the wrasse Coris julis

Abstract

Long wavelength colours (λ > 580 nm) often serve as visual signals during inter- and intrasexual interactions in various species of freshwater fish. However, while long wavelength colours are also prevalent in many marine fish, their functional importance remains largely unknown. Here, we demonstrate that the presence of long wavelength colours mediate intraspecific aggressive interactions in the Mediterranean rainbow wrasse Coris julis. By manipulating the relative mixture of red (λmax = 628 nm) and blue (λmax = 454 nm) light in experimental tanks, we created conditions in which discrimination of long wavelength colours from colours of shorter wavelength was either possible or prevented. We found that resident males were significantly more likely to attack conspecific intruder males when discrimination was enabled compared to conditions where no such discrimination was possible. Aggression from residents was associated with the display of a red (λ max = 611 nm) colour patch on the dorsal fin of intruders, but not the size of the putative signal. Our findings suggest that long wavelength colours are an important component of marine visual ecology by mediating agonistic male-male interactions. © Inter-Research 2014.