The sparkling enope squid (Watasenia scintillans), also known as the firefly squid, at Toyama Bay, Japan.
These amazing squids are about 15cm long and die after only a year of life. Found in the depths of the Western Pacific ocean, they come up to the surface at night to hunt for food. The bioluminescence which lights up the photo is produced by organs called photophores, which are located at the end of each tentacle. The squids use this light to lure in prey and attract a mate.
The squid spends the day at depths of several hundred metres, returning to the surface when night falls. The combination of light-sensing and light-producing organs enable it to match its underside to the brightness and colour coming from the surface (counter-illumination), making it hard for predators from below to detect it.
Firefly Squids