Data from: The flashlight fish Anomalops katoptron uses bioluminescent light to detect prey in the dark

Bioluminescence is a fascinating phenomenon occurring in numerous animal
taxa in the ocean. The reef dwelling splitfin flashlight fish (Anomalops
katoptron) can be found in large schools during moonless nights in the
shallow water of coral reefs and in the open surrounding water. Anomalops
katoptron produce striking blink patterns with symbiotic bacteria in their
sub-ocular light organs. We examined the blink frequency in A. katoptron
under various laboratory conditions. During the night A. katoptron swims
in schools roughly parallel to their conspecifics and display high blink
frequencies of approximately 90 blinks/minute with equal on and off times.
However, when planktonic prey was detected in the experimental tank, the
open time increased compared to open times in the absence of prey and the
frequency decreased to 20% compared to blink frequency at night in the
absence of planktonic prey. During the day when the school is in a cave in
the reef tank the blink frequency decreases to approximately 9
blinks/minute with increasing off-times of the light organ. Surprisingly
the non-luminescent A. katoptron with non-functional light organs
displayed the same blink frequencies and light organ open/closed times
during the night and day as their luminescent conspecifics. In the
presence of plankton non-luminescent specimens showed no change in the
blink frequency and open/closed times compared to luminescent A.
katoptron. Our experiments performed in a coral reef tank show that A.
katoptron use bioluminescent illumination to detect planktonic prey and
that the blink frequency of A. katoptron light organs follow an exogenous
control by the ambient light.