• Before: Did I just walk into a fantasy world?
  • After: Fancy lights, invisibility, and magic crystals. I’d say yes.

I’ve always thought squids looked like a fully-bearded man in a bishop’s hat. The teeny firefly squid is no exception, but it brings an entirely different level of strange to the table. Sometimes literally, if you live in Japan.

A magical night

With up to 90% of mid-level ocean creatures flaunting it, bioluminescence is shrug-worthy in the sea. But the firefly squid is covered in light organs or “photophores”, and because of the resulting sea of galaxies when spawning, it’s spectacularly visible to humans at night, to the point it’s considered a “Special Natural Monument” with its own museum at Toyama Bay.

Of course, you need several things to make the magic happen, such as a perfect alignment of tides, weather, and moonlight. We’re not the only ones that can miss it, either.

Secrets of the squid

Being tiny and defenceless isn’t great 200-600m (656-1968ft) down in the Pacific’s mesopelagic or “twilight” zone. So during the day, the firefly squid uses “counter-illumination” to make itself invisible amongst the falling sunlight. At night, it squiggles (“squiddles”?) to the surface to munch small fish and crustaceans, flashing to attract them or ward off predators. We’re still not 100% sure how it does it, but it may involve magic crystals.

Hamanaka et al.’s 2011 study found the arm photophores contained microcrystals full of light-emitting enzymes and a mystery protein. What’s more, it may have its own secret code.

Blue light is most common at these depths due to how water absorbs wavelengths of light, but the firefly squid has green photophores as well. Few marine species bother detecting this colour, so it’s possible the squid uses this for its own exclusive “channel”! It’s ideal for attracting mates too, bringing us to another element needed to “make the magic happen”.

So much magic, it makes the background disappear.

Love at first light

How about this steamy description: after an impressive flash or few (fnar), the male squid places his hectocotylus in the female’s mantle cavity, and she will collect several “packets” from different males. After delivery, the male disappears and presumably dies. When the eggs are fertilised, the females rise to the surface en masse and fling them out in a one-metre (3-foot) string of jelly. Shortly afterwards, they’ll join the males in the big squid sanctuary in the sky, either before or after eggs-haustion (sorry). Why? Well they’re not exactly inconspicuous.

Flashy food

Between being picked off by larger fish and fur seals, the firefly squid is hauled up by many a Japanese fishing boat. Although eaten fried as tempura, or even candied (?!), firefly squid are recommended raw from the sea, (hotaruika), and like other mythical-looking sea-life, apparently taste like magic.

Despite the Toyama Bay crowds and the seemingly endless haul of starry squid, for now at least, the fishing seems to be sustainable and consistent. Another magic trick of nature?

Maybe, but while it enthralls us, the firefly squid’s magic does seem to backfire: its counter-illumination creates the opposite effect once it gathers in large numbers. You have to wonder if it realises, or, with a one-year lifespan, it just wants to go out in a blaze of glory.


Latin: Watasenia scintillans

What? Bioluminescent squid that spawns in large numbers, lighting up the waters.

Where? Waters around Japan, from 200-600 metres  / 656-1968 feet deep. The most famous spawn location is Toyama Bay.

How big? Teeny! Only 7-8 cm / 2.8-3.1 inches long.

Endangered? Currently Least Concern due to large numbers, although we should probably take stock (pun not intended) of how sustainable the fishing is.

Probable motto: I guess there isn’t safety in numbers? Never mind, it’s my kids’ problem now.

They look strangely beautiful. Do they need my help at all?

Nope, Least Concern, and at the moment their fishing seems both consistent and sustainable.

Just to prove I’m not fibbing:

Barratt, I. & Allcock, L. 2014. “Watasenia scintillansThe IUCN Red List of Threatened Species 2014: e.T163146A977074“.

Graham, Adam H. 2015. “Japan’s mysterious glowing squid“. BBC Travel.

Hamanaka, Toshiaki et al. 2011. “Luciferase activity of the intracellular microcrystal of the firefly squid, Watasenia scintillans”. FEBS Letters. 585(17):2735-2738.

Hooper, Rowan. 2003. “Firefly squid“. The Japan Times.

Kawahara, M. et al. 1998. “A note on the fibre-optic light-guides in the eye photophores of Watasenia scintillans“. South African Journal of Marine Science 20:123-127.

Patel, Krupa, and Pee, Dorothy. No date. “Watasenia scintillans“. Animal Diversity Web.

Preston, Elizabeth. 2018. “Flashes of brilliance“. Biographic.

Watasenia scintillans“. No date. Sealife Base.

What is firefly squid?“. No date. Hotaruika Museum.

Featured image credit: Phil and Monica Halper