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Message:

> Schooling fish with lights around eyes:
> 
> https://cosmosmagazine.com/biology/fish-flashing-below?utm_source=Cosmos+-+Master+Mailing+List&utm_campaign=c41ecef7a0-RSS_EMAIL_CAMPAIGN&utm_medium=email&utm_term=0_3f5c04479a-c41ecef7a0-180344213
> 
> "the aptly named flashlight fish (Anomalops katoptron), and this how it goes about its nocturnal business.
> 
> "Researchers from the City University of New York, US, have discovered that they use their own light to allow them to school at night, and only a few need to be actively flashing to maintain the group.
> 
> "They generate the light via bioluminescent bacteria in specialised organs under their eyes.
> 
> "Over 25% of fish species exhibit collective schooling behaviour, but schooling based on bioluminescent signalling has not previously been demonstrated," says research leader David Gruber. 
> 
> "'Being in the middle of one of these bioluminescing schools was one of the most magical things I've ever experienced as a marine biologist. It was like an Avatar moment as we watched rivers of bioluminescing fish merge like a blue-brick road and flow down the reef."
> 
> "During two research expeditions to the Solomon Islands, Gruber and colleagues used low-light video to film large assemblages – hundreds to thousands of individuals – of the fish at night. 
> 
> "The recording showed that once fish velocity increased past a certain level, a loose group would transition to a closely-knit school, even with relatively-few flashing fish present.
>  
> "After tracking each flashing fish in the analysed video clips and localising the fish in every frame, the authors created a model to simulate the movement of flashlight fish schools based on individual fish actions (cohesion, separation, and alignment) as well as water friction as a resistant force.
> 
> "The model showed that less than 5% of the schooling flashlight fish needed to be flashing in order for schooling to be maintained in dark conditions. 
> 
> "Since fish reveal their location when they flash, the authors suggest that this may be a predator-avoidance strategy. They speculate that in order to confuse predators, some fish might flash, then rapidly change direction before flashing again.:
> 
> Comment: Many animals use bioluminescent bacteria by symbiosis.  And  not just fish. Think of fireflies