Fast, bioluminescent blinks attract group members of the nocturnal flashlight fish Anomalops katoptron (Bleeker,...

During their nighttime shoaling, the flashlight fish Anomalops katoptron produce fascinating, bioluminescent blink patterns, which have been related to the localization of food, determination of nearest neighbor distance, and initiation of the shoal's movement direction. Information transfer e.g., via alarm signals is an important aspect in group living species especially when being under threat. In dark environments, bioluminescence has the potential to accurately transfer such information. Under threat A. katoptron show increased swimming speeds and a higher group cohesion accompanied by fast blink frequencies.

In this study we used a two-choice paradigm to test the preferences for typical blink characteristics e.g., frequency and duration. Our data show that individuals decided within short periods (< 4 s) for faster blink frequencies of artificial light organs and the preference for the higher blink frequencies became more pronounced as the difference between the presented frequencies increased. The preference correlated with the frequency rather than the duration.

Our study suggests that fast, bioluminescent blinks of light organs lead to aggregations of A. katoptron.