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Introduction
- The firefly squids (Watasenia scintillans), which are also known as sparkling enope squids, are significantly small creatures that are bioluminescent and typically found off the coast of Japan at depths anywhere between 200 and 400 meters (600- 1200 feet). In Japan, they are considered a delicacy and referred to as "hotaru-ika," which literally translates to "firefly like firefly." Every year, millions of firefly squids gather to spawn in Toyama Bay in Japan and illuminate the dark waters with an illustrious cobalt blue glow. This event attracts large crowds to the area and has led Japan to designate the bay as a "Special Natural Monument." The firefly squid is the only species in their genus
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Taxonomic Classification Kingdom: Animalia
Phylum: Mollusca
Class: Cephalopoda
Order: Oegopsida
Family: Enoploteuthidae
Genus: Watasenia
Species: Watasenia scintillans (The Firefly Squid)
Physical Description and Behavior
- An adult firefly squid is typically 1.5-3 inches (4-8 cm) long and weighs close to 0.31 oz (9g). They range anywhere in color from yellow to blue or white, but all emit a robust blue radiance with light producing cells known as photophores. These cells appear as small dots and are distributed across the animal's body. Larger photophores are found around the eyes and on the tips of its' tentacles. The squid is able to control these lights and flash them in unison or in various alternated patterns. This creature also has been discovered to have highly developed vision, possessing three different kinds of visual pigments and a double-layered retina. This information has led scientists to believe that this is the only species of squid that possesses color vision. This adaptation allows the animal to differentiate between bioluminescence and ambient light, as well as decipher the light patterns of other squids. Although the firefly squid spends most of the day at great depths, at night, it returns to the surface to hunt for prey. They usually only live up to one year.
Distribution and Habitat
- The firefly squid is found primarily in the Western Pacific Ocean off of the coast of Japan and is found at depths between 200 and 400 meters (600- 1200 feet).
Diet and Common Predators
- The firefly squid is known to be an active predator of small fish, crab, shrimp, and planktonic crustaceans. They flash their photophores located on the tips of the tentacles on and off in order to attract prey. Once a squid lures something close enough, they use their powerful tentacles to attack and consume their prey. They are usually preyed upon by sperm whales and killer whales.
Mating and Reproduction
- The spawning season for firefly squids is usually from March until May. During this time, millions of adult squids gather and light up their entire bodies in order to attract a mate. They discharge eggs, which are then fertilized, and the adult firefly squid die, completing their one year life cycle. The eggs hatch approximately 6-14 days after fertilization.
Bioluminescence and Adaptations
- As mentioned earlier, firefly squids have more than 800 photophores distributed across their body, which emit a deep blue light. According to Frederick I. Tsuji, the luminescence of this animal is produced from an ATP- dependent reaction. The squid are able to flash lights in unison or in a particular pattern. Firefly squids use their photophores to make themselves appear larger than they actually are to ward off predators. They light up their entire body in an attempt to counter- illuminate themselves and escape from danger. Firefly squids use their photophores to attract prey and a mate. Also, as mentioned earlier, the firefly squid is able to differentiate ambient and bioluminescent light because they have a double layered retina and three different visual pigments, allowing them the ability to see color.
Works Cited
Patel, K. and D. Pee 2011. "Watasenia scintillans" (On-line), Animal Diversity Web. Accessed November 21, 2018 at https://animaldiversity.org/accounts/Watasenia_scintillans/.
Seidou, M., Sugahara, M., Uchiyama, H. et al. J Comp Physiol A (1990) 166: 769. https://doi.org/10.1007/BF00187321.
Tsuji, F I. “ATP-dependent bioluminescence in the firefly squid, Watasenia scintillans” Proceedings of the National Academy of Sciences of the United States of America vol. 82,14 (1985): 4629-32.
CRITTERFACTS. “Critter Of The Week # 16: Firefly Squid.” CRITTERFACTS, www.critterfacts.com/pages/critter-of-the-week-17-firefly-squid.
Preston, Elizabeth, and Solvin Zankl. “Inside the Frenzy for Japan's Mysteriously Glowing Firefly Squid.” Oceans, News Deeply, 12 July 2018, www.newsdeeply.com/oceans/articles/2018/07/13/inside-the-frenzy-for-japans-mysteriously-glowing-firefly-squid.
“Watasenia Scintillans (Berry 1911).” Encyclopedia of Life, National Museum of Natural History, eol.org/pages/399186/details.
Images
-https://newsdeeply.imgix.net/20180712041025/nd_squid_7.png
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-https://cdn.shopify.com/s/files/1/1070/1064/files/glowing_1024x1024.jpg?v=1477247752
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