The firefly squid (Watasenia scintillans), also known as the sparkling enope squid, is a species of squid in the family Enoploteuthidae. It is the sole species in the monotypic genus Watasenia.
The firefly squid is found in the Western Pacific Ocean at depths of 183 to 366 metres (600–1200 feet) and is bioluminescent. The mantle, head, arms and tentacles are dotted with tiny, light-producing organs called photophores. When flashed, the light attracts small fish, which the squid can feed upon.
This squid has three visual pigments located in different parts of the retina which likely allows color discrimination, each having distinct spectral sensitivities.
The firefly squid measures about 3 inches (7.6 cm) long at maturity and dies after one year of life. It has the standard eight arms and two tentacles, with one pair each having three, bright light-emitting organs at the tips.
The squid spends the day at depths of several hundred metres, returning to the surface when night falls. It uses its abilities to sense and to produce light for counter-illumination camouflage: it matches the brightness and colour of its underside to the light coming from the surface, making it difficult for predators to detect it from below.
The firefly squid can also light up its whole body to attract a mate. Once the squid's eggs have been fertilized and laid, it dies, having reached the end of its one-year lifespan. Spawning, which involves large aggregations of the squid, takes place between February and July.
This squid is commercially fished in Japan, accounting for an annual catch of 4,804 to 6,822 tons from 1990 to 1999.
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Patel, K. and D. Pee 2011. "Watasenia scintillans" (On-line), Animal Diversity Web. Accessed October 9, 2016 at http://animaldiversity.org/accounts/Watasenia_scintillans/