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Watasenia Scintillans Classification Essay

Geographic Range

The geographic range of Watasenia scintillans is the Western Pacific ocean around Japan. (BBC, 2005)


Watasenia scintillans is a marine animal found in depths of 200 to 400 meters. (BBC, 2005)

Physical Description

Watasenia scintillans is a small cephalopod, growing to 7-8 cm. The firefly squid is equipped with special light producing organs called photophores. Photophores are found in many parts of the body but large ones are usually found on the tips of the tentacles as well as around the eyes. These lights can be flashed in unison or alternated in patterns. This squid has arms with hooks and tentacles with hooks and one series of suckers. The mouth cavity has dark pigmentation. (Tsuchiya, 2007)


Fertilized eggs hatch in 6-14 days depending on the water temperature, which varies from six to 16 degrees Celsius. Higher temperatures encourage quicker hatching.

At 15 degrees Celsius, one hour after fertilization, polar bodies appear, followed in five hours with first cleaveage. By 10 hours, 100 or more cells have been formed, and around 16 hours the embryonic lobe has been developed. The embryonic lobe covers about half of the egg in a day and a half. In four days, primordial eyes are present and oral depression starts. A day later, primordial arms, mantle, and funnel appear and then chromatophores appear on the mantle and the eyes are developed. Final organ and chromatophore formation and hatching occurs in 8-8.5 days. (Tsuchiya, 2007)


Bioluminescent photophores can attract mates and be used for communication with other squids. (BBC, 2005)

The spawning season runs from March to May. During this time, firefly squids can be seen gathering in large numbers to lay their eggs. Once the eggs have been released into the water and fertilized, the adult squid die. This completes the one-year life cycle of the squid. ("Firefly Squid", 2010)

Adult firefly squids die after eggs have been released into the water and fertilized. ("Firefly Squid", 2010)


The firefly squid lives for about one year. (BBC, 2005)


Watasenia scintillans are generally deep sea dwellers. They spend their days at depths of 200-400 m but swim up to the surface at night to capture prey. Watasenia scintillans also rise up to the surface during their period of spawning, appearing in huge schools along the shoreline. (Animal Planet, 2011; BBC, 2005; Dahlgren, 1922)

Communication and Perception

The photophores along the body and tentacles of the Watasenia scintillans are used to attract prey, provide camouflage, frighten predators, and to attract a mate. The firefly squid also has highly developed vision. Its eyes contain three different types of light-sensitive cells and are believed to be capable of distinguishing different colors. (BBC, 2005)

Food Habits

Watasenia scintillans consumes a diet consisting of shrimp, crabs, fish, and planktonic crustaceans. The photophores on the tips of its tentacles are used in a flashing pattern to attract prey, especially fish. (Hayashi and Hirakawa, 1997; Hooper, 2003)

  • fish
  • aquatic crustaceans
  • other marine invertebrates
  • zooplankton


The photophores along the body of the squid can be used against predators in either a warning form or as counter-illumination camouflage. The northern fur seal, Callorhinus ursinus, is a known predator. (BBC, 2005; Mori, et al., 2001)

Ecosystem Roles

Watasenia scintillans are prey for northern fur seals, Callorhinus ursinus and is a predator of shrimp, fish, and planktonic crustaceans. This squid is also a host to nematode larvae. (Aoyama, et al., 1996; Hooper, 2003; Mori, et al., 2001; Smyth, 1994)

Commensal/Parasitic Species

Economic Importance for Humans: Positive

Watasenia scintillans can be eaten raw, known as Hotaruika in Japan, or cooked. These species of squid also draw large crowds during their spawning season at Toyama Bay in Japan. The large schools that swim up to the shallow waters light up the dark water along the shore, giving tourists a nighttime show. This spectacle has led to the bay being named a Special Natural Monument and construction of a museum devoted to the species. ("Travel Guide Toyama", 2009; Aoyama, et al., 1996; Hooper, 2003)

Economic Importance for Humans: Negative

Eating raw Watasenia scintillans, known in Japan as Hotaruika, that is infected with spirurina type X larvae, belonging to the phylum Nematoda, can cause abdominal pain, nausea and vomiting, diarrhea, creeping eruption, and ileus (bowel obstruction). (; Aoyama, et al., 1996; Smyth, 1994)

Conservation Status

Watasenia scintillans is not protected under any conservation program.


Krupa Patel (author), Rutgers University, Dorothy Pee (author), Rutgers University, David V. Howe (editor), Rutgers University, Renee Mulcrone (editor), Special Projects.


Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.


having coloration that serves a protective function for the animal, usually used to refer to animals with colors that warn predators of their toxicity. For example: animals with bright red or yellow coloration are often toxic or distasteful.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


an animal that mainly eats meat

causes disease in humans

an animal which directly causes disease in humans. For example, diseases caused by infection of filarial nematodes (elephantiasis and river blindness).


having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.


humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.


animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature


A substance that provides both nutrients and energy to a living thing.


having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.


A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.


having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.


reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.


generates and uses light to communicate


an animal that mainly eats fish

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

seasonal breeding

breeding is confined to a particular season


that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).


the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.


uses sight to communicate


animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)


Sea and Sky. 2010. "Firefly Squid" (On-line). Deep sea creatures. Accessed June 20, 2011 at .

Toyama Prefectural Tourism Association. 2009. "Travel Guide Toyama" (On-line). Accessed June 21, 2011 at .

Animal Planet, 2011. "Squid" (On-line). Animal Planet. Accessed June 19, 2011 at .

Aoyama, S., Y. Hinoue, H. Takahashi, Y. Yoshimitsu, Y. Kusajima, T. Hirono, N. Takayanagi, N. Akao, K. Kondou. 1996. Clinical study of ten cases with acute abdomen after eating raw firefly squid (Watasenia scintillans, Hotaruika), which are probably due to type X larvae of the suborder spirurina. Nippon Shokakibyo Gakkai Zasshi, 93: 312-321.

BBC, 2005. "Animal fact files: firefly squid" (On-line). Accessed June 19, 2011 at .

Dahlgren, U. 1922. Phosphorescent plants and animals. Natural History, 22: 19.

Hayashi, S., K. Hirakawa. 1997. Diet composition of the firefly squid, Watasenia scintillans, from Toyama Bay, Southern Japan Sea. Bulletin of the Japan Sea National Fisheries Research Institute, 47: 57-66.

Hooper, R. 2003. "The Japan Times Online" (On-line). Accessed June 20, 2011 at .

Mori, J., T. Kubodera, N. Baba. 2001. Squid in the diet of northern fur seals, Callorhinus ursinus, caught in the western and central North Pacific Ocean. Fisheries Research, 52: 91-97.

Shimomura, O. 2006. Bioluminescence: Chemical Principles and Methods. Singapore: World Scientific Publishing Co. Pte. Ltd..

Smyth, J. 1994. Introduction to Animal Parasitology. Cambridge: Cambridge University Press.

Tsuchiya, K. 2007. "Watasenia scintillans" (On-line). Accessed June 20, 2011 at .

This is a mesopelagic-boundary species associated with the shelf waters around Japan occurring from the surface to mid-ocean depths (typically 200 to 600 m in depth) (Young et al. 1998, Norman 2003). Individuals form large near-surface aggregations at night during the spawning season (Roper et al. 1984). Eggs are spawned in shallow water between the surface and 80 m in depth (Tsuchiya 2007). The spawning season extends between February to July (Norman 2003). In Toyama Bay, eggs occur in the plankton between February and July, and November and December (Tsuchiya 2007). In the western Sea of Japan, eggs were present throughout the year except December to January, peaking April to late May (Tsuchiya 2007). Mature females have between a few hundred and 20,000 mature eggs (1.5 mm in length) in their oviducts (Tsuchiya 2007). The eggs are spawned into a narrow gelatinous string of more than 1 m in length (Tsuchiya 2007). Eggs hatch in 14 days at 10 ºC, and in 6 days at 16 ºC (Tsuchiya 2007). Post spawning mortality is high (Roper et al. 1984). They are preyed upon by marine mammals (e.g. Northern Pacific Fur Seals, Callorhinus ursinus) and are an important food for a variety of finfishes including salmonids (Tsuchiya 2007).

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