When bioluminescent ostracods or ‘sea fireflies’ mate, they perform a courtship dance complete with glowing blue mucus. The males sway together in sync while basking in the light of the shiny slime. This mating ritual is detailed for the first time in a study published November 29 in the journal Proceedings of the Royal Society B.
[Related: Surprise! These sea cucumbers glow.]
Ostracods are tiny crustaceans that are about the size of a sesame seed. They are found in a variety of fresh and saltwater environments, from deep ocean depths to shallow seas to rivers, lakes, and estuaries. The dancing, shrimplike species in the study is called the entraining grassbed downer and was observed in the Caribbean Sea near Panama.
During this dance routine, male EGDs create their distinct patterns of bioluminescence to attract females. They secrete packets of protein from a specialized gland. The females respond by angling themselves to these bright blue luminous displays and swimming towards the males. According to study co-author Nicholai Hensley, a Cornell University evolutionary biologist who specializes in animal behavior, the other males will then join in a synchronous light display and repeat the same pattern in the water during each dance.
The study found that this very coordinated swim also doesn’t happen randomly. The mating dance sequence only occurs after sunset at nautical twilight, when the moon isn’t bright in the night sky. The team found their level of precision and coordination very surprising.
“This precise timing leads to the unexpected phenomena of huge waves of light that cascade across the grass bed, with hundreds of males displaying at the same time,” Hensley tells PopSci. “Amazingly, this is very similar in appearance to the fireflies most people are familiar with, where some…
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