Range: Western Pacific Ocean; Concentrated around Japan Habitat: Seafloor Size: About 2.4 inches (3cm) long Diet: Fish, copepods, and more Threats: Fish and seals Life span: About one year

Transcript:

Today on Animal Fact Files we’re discussing the firefly squid. These little cephalopods have been known for quite awhile in the areas to which they are natives, but they’re not as well known outside of their native range. Firefly squids live in the western Pacific Ocean mostly in the waters around Japan. These little squids, which only average about 2.4 inches (3cm) in mantle length, live near the seafloor during the day at depths of more than 656 feet (200m). At night, they migrate towards the surface and remain at depths of around 164 to 328 feet (50-100m). We’ve talked about the nightly migrations many of the marine animals around the world make including the nautilus and even megamouth sharks - be sure to check out those videos to learn more about this phenomenon known as Diel migration.

Even at night, when firefly squid are closer to the water’s surface, they’re still quite deep below the waves, so what makes these squids so well known? It’s their appearance near shore during the breeding season that brings about their popularity. Specially it’s the female firefly squid who, during the months of March to May, move inland and fill the shore waters. Toyama Bay is especially a hot spot for catching these glowing visitors. Yes, glowing.

Firefly squid, like the animals from which they get their common name, are bioluminescent. It’s estimated that upwards of 90% of animals living in the Mesopelagic (or Twilight) Zone of the ocean are able to produce light. Firefly squids are no exception to this belief! Originally, scientists predicted that firefly squids produced light via a symbiotic relationship with light emitting bacteria, but it’s now known that the little cephalopods create their own light.

There are three main centers for light production on a firefly squid. The ventral, or underside, of their mantle, around their eyes, and on the tips of some of their arms. The first two are a weak type of light and described as similar to distant stars in the nighttime sky, but the light produced from this squid’s arms is so bright it can be seen in a lit room! Plus, they create pulsating patterns with their light emission, hence the common name firefly squid - though in Japan they’re known as hotaru-ika.

Firefly squid are especially important in Japan because they’re captured in droves during the breeding season. Upwards of 4,000 tons of firefly squids may be taken in a single year and used as food! Firefly squids make their way inland during this time to release their fertilized eggs. 99% of those caught throughout this season are actually females, and, in fact, the male life cycle of the firefly squid is unknown. A female firefly squid will travel towards the shore laden with several hundred to more than ten thousand fertilized eggs. She’ll release these eggs in gelatinous strings reaching over three feet (1m) in length. The eggs will hatch within one to two weeks depending on the temperature of the surrounding water, and, like other cephalopods, the mother will die shortly after; so really the squids that are captured for consumption are already on their way out. Firefly squid larvae and adults are predated by fish such as salmon as well as northern fur seals, but those that survive will make the same journey the following year - well, the females will anyway, who knows what the males do!

Some cephalopods, like cuttlefish, are colorblind even though they produce brilliant arrays of colors, but firefly squid are believed to be able to see color. They have more receptors in their eyes for seeing color than other cephalopods, so they are likely able to appreciate the blue toned light they produce. Firefly squid also lack a cornea meaning their meaning their irises are in direct contact with the surrounding sea water. And here I thought it hurt to open my eyes underwater in the ocean.

For more facts on the firefly squid, check out the link in the description. Thank you to icaro lobo for today’s request! Give a thumbs up if you learned something new today, and thank you for watching Animal Fact Files!