October 19


How to See Creatures That Live in the Dark by Julia Kuo

As an illustrator, I rely on existing imagery to learn about subjects I haven’t seen with my own eyes, especially when most of these creatures live in the deep sea. When I started to work on my picture book Luminous: Living Things That Light Up the Night, my first question was: what do bioluminescent creatures even look like? I’ve had the privilege of witnessing the light they produce in some extraordinary settings: kayaking among dinoflagellates in Northern California, discovering the dim glow of foxfire in a forest in Taiwan, and drifting under a shining constellation of glowworms in a cave in New Zealand. Each encounter felt so precious and so hard to come by that I wanted to share this phenomenon in a book, so that others might learn about bioluminescence and eventually see it for themselves!

But it is one thing to see bioluminescent light and another to see the creature itself. I noticed that in photos, a fair amount of the glowing deep sea creatures had a pinkish gray hue to them. Thanks to Dr. Steven Haddock, the marine biologist advising on Luminous, I learned that these pink-gray creatures were all specimens, or deceased creatures that changed from their natural colors when they were preserved for study. Luminous was meant to portray bioluminescent creatures interacting and glowing, so I steered far away from the dead creatures. Dr. Haddock saved me from more than a few such bioluminescence blunders, but others have not been so fortunate! I was astonished to learn that the fearsome (but gray) anglerfish in Finding Nemo also referenced a dead specimen. I even found a pink-gray stuffed animal squid for sale online, which I purchased out of amusement. This bit of research seemed like a modest hurdle in the larger process of writing and illustrating a picture book, but it turns out that quality footage of these creatures living and glowing in their natural habitat has been long awaited and hard-earned.

It was once largely accepted that the deep seas were like a vast desert, devoid of inhabitants. Researchers have since realized that the depths are teeming with life, especially those that have evolved to glow. It’s actually exceedingly common for marine creatures to make their own light, and bioluminescent creatures are estimated in the trillions, perhaps even quadrillions! But creatures that live deep down in the ocean are hard to study, and it took years before scientists had the ability to observe and record them lighting up in their natural habitat. Early bioluminescence researchers studied deep sea creatures brought up in trawl nets. Unable to cope with the tremendous change in temperature from the icy depths to the warm surface, the creatures were often reduced to a lifeless, gelatinous puddle by the time human eyes were on them. Marine biologist Edith Widder, stunned by what she could see from the depths in a submersible, spent much of her career developing specialized instruments to record creatures living and lighting up in their natural habitat. It’s thanks to researchers like Dr. Widder and Dr. Haddock that I had enough source material to create Luminous. It turns out that most deep sea bioluminescent creatures are actually transparent, black, or sometimes a deep red. In Luminous and in real life, this coloring helps them to blend into dark backgrounds, and for their bright blue glow to pop even more. Illustrating Luminous felt straightforward once I had the right references; I couldn’t have dreamed up more otherworldly creatures, or wished for a more striking contrast in colors.

Public access to the mysterious world of bioluminescence is something these researchers often think about, too. The ocean makes up 70% of Earth’s surface area and 99% of the habitable space on this planet is in the ocean. But despite our close proximity to this vast and unknown territory, public interest in our “last frontiers” has pushed space exploration far ahead of deep sea exploration. It is understandably difficult to be excited about what we don’t know, and the majority of these marine creatures have stayed out of human view until the greater part of this past century. But now that we are aware of these fantastic creatures, the race is on to discover and understand them before global warming changes their environment past the point of no return.

From the light-expelling vampire squid to the camouflaged bristlemouth lightfish, each glowing creature adds to the richness of this planet. I’m happy to share Luminous so that I can spread this wonder and curiosity with the next generation of scientists. Luminous has just a few examples of these incredible creatures, and there is so much more to discover outside its pages. I can’t help but pass on these questions: what else is out there, deep in the sea, and why is it glowing? And don’t forget to take some photos!


Julia Kuo is a Taiwanese–American author–illustrator who has worked with The New York TimesThe Wall Street Journal, and Science Friday. She’s illustrated I Dream of PopoI Am an American: The Wong Kim Ark Story, and The Sound of Silence, among others. She lives in Seattle, Washington.