When they light up, it’s as if someone has flicked on a switch — the sea suddenly fills with tiny blue orbs.
These glowing lifeforms are umi-hotaru (sea fireflies). But though they’re called “fireflies” they’re unlike their terrestrial cousins. These are ostracods — a kind of micro-crustacean known as “seed shrimp” that emit light using the organic compound luciferase.
In the daylight, umi-hotaru look like plankton or minute chia seeds floating in the water, but at night you can see the luminescent chemicals activating in their light organ. The glow is strong enough that Japan collected umi-hotaru during World War II and ground them into a light-emitting powder to help soldiers check maps at night.
Locals in Okayama Prefecture gave us many tips for finding umi-hotaru and we spent hours driving along bumpy coastal roads of Okayama looking for the right spot. We eventually found a perfect location: a small beach near Ushimado on the Seto Inland Sea. Locals also told us many stories about the creatures’ secretive behavior — but umi-hotaru aren’t as shy as the old wives’ tales suggest.
The key to finding them is visiting a sandy beach. They dig down into the sand along the foreshore during the day, and come out to feed at night. Relatively common on beaches in the Seto Inland Sea throughout summer, their habitat stretches all along this coastline, from Kyushu to Awajishima.
If you’re lucky, you may be able to catch one of them in the water. When it eventually escapes, there is a sudden burst of light rushing from your hands — a stream of blue energy. It’s like having a temporary superpower.
Sometimes you may see them in the distance, lighting up the whitewash of breaking waves, at other times they may only glow for an instant as you walk along the shore. But, if you want them to really put on a light show, you will need to catch them in large numbers.
Attracting umi-hotaru wasn’t easy. But after some experimentation we finally found the magic ingredient: bacon.
In order to take these photographs, we lured umi-hotaru into containers with our magic ingredient and gently poured the caught shrimp over exposed rocks to observe them up close. After they took part in our photos, the tide came in and returned them to the sea. We didn’t pay them an hourly rate, but perhaps we should in the future — it’s important for us to treat these locations with respect. We try to leave them just as we found them.
Japan is full of bioluminescent organisms, from Hato-no-hi “pigeon fire” mushrooms that sprout after rainy season in Kyushu, Wakayama and Hachijojima, to bugs and larvae with rhythmically pulsing tails in the Okinawan island chain — there are even glowing squid in Toyama Prefecture.
But the most-observed bioluminescent creature in Japan is the hotaru (firefly), with festivals and gatherings celebrating their arrival after the rainy season. Though there are many cultural events related Japan’s fluttering lights, we’ve never heard of any that celebrate umi-hotaru. Perhaps that is because they seem so elusive and alien, despite swimming — and glowing — right under our noses.
For a chance to see umi-hotaru, visit the beaches near Okayama during summer. Okayama is roughly a one-hour train ride from Kyoto. For more information about the light photography of Trevor Williams and Jonathan Galione, visit www.tdubphoto.com. For more information about photographer Tim Cleminson, visit www.chapinthehat.com.