Plasticity of male mating behaviour in a marine bioluminescent ostracod in both time and space

Spectacular and abundant light displays consisting of highly complex and repeated vertical trains of secreted bioluminescent pulses are ejected into the water column above shallow grass beds in the western Caribbean about an hour after the sun sets if there is no moon present. These are male courtship displays produced by upwardly swimming male Photeros (formerly Vargula) annecohenae, small (<2 mm) myodocopid ostracod crustaceans, attempting to attract females, which approach males while remaining photically quiescent. Observations in both the laboratory and the field revealed different behaviours by males during the courtship period. Using infrared videography in the laboratory to track individuals, we observed distinct male mating behaviours from multiple males in a single tank. Each participating male is capable of (1) ‘initiating’ a luminescent display train (∼leaders), (2) ‘entraining’ on another displaying male in loose luminescent synchrony (∼followers), and (3) ‘sneaking’ silently on a luminescing male. Males can switch among these three tactics even during a single, 10–19 pulse display train (ca. 12 s). The alternative mating tactic chosen by a male is highly predicted by the orientation and distance of the responding male to the initial courtship display at the start of that tactic. Thus, the complex interplay of these different tactics among a group of males even during a single display train is highly choreographed in both time and space. The mating tactics of P. annecohenae are an extreme example of plastic, neuronally controlled courtship behaviour and provide rich new avenues for investigations into understanding communal sexual displays and sexual selection.