Jellyfish are enigmatic creatures, drifting along with the sea’s currents, occasionally pulsing their bells as if driven by some unseen purpose. Despite lacking a brain, they’ve survived for over 500 million years—far longer than humans are likely to manage.
Reading Ed Yong’s An Immense World taught me not to underestimate creatures with minimal or no brains. It made me wonder: Could intelligence sometimes be a hindrance to survival? How, then, does the brainless jellyfish manage to thrive in such diverse environments?
Jellyfish use surprisingly complex eyes to perceive their surroundings. Though they lack a brain to integrate sensory data into a unified picture, their distributed nerve networks guide their movements and help them find food. Their bodies are simple yet efficient, consisting of three layers: an outer layer (epidermis), a gelatinous middle layer (mesoglea) that provides shape and buoyancy, and an inner layer (gastrodermis) that encases the digestive system. Unlike us, jellyfish have a single opening that serves both as a mouth and an exit for waste. Prey caught by their stinging tentacles is brought in, and waste is expelled through the same opening.
One of the unexpected joys of my recent visit to Gwaii Haanas was observing these fascinating creatures. Each morning, standing on the deck of the 82-foot Island Solitude sailboat, I relished the mirror-like water and cool breeze. Most days, I could spot jellyfish drifting by, but it was during kayaking trips that I got an even closer look.
Paddling near shore one day, I came upon what appeared to be a jellyfish nursery. The water was thick with tiny white dots, which turned out to be “baby jellyfish.” These small forms were likely jellyfish in one of their early lifecycle stages—either planula larvae or polyps.
All jellyfish have stingers that they use to capture food, such as plankton, small fish, or crustaceans. The potency of their stings ranges from deadly (as in the case of the box jellyfish) to mildly irritating. Fortunately, Gwaii Haanas is free of the dangerous box jellyfish (you’d need to go to Australia for those), but I did spot several other species, including lion’s mane, fried egg, moon, and hydromedusa jellyfish.
Despite their stingers, jellyfish are not without predators. Sea turtles, large fish, and seabirds all feed on them. Interestingly, some small fish and crabs seek shelter among a jellyfish’s tentacles, particularly with the fried egg jellyfish, finding protection from predators.
Many jellyfish exhibit some degree of bioluminescence. Had I known this while sailing in Haida Gwaii, I might have stayed up late to witness the ethereal glow beneath the surface. But with early starts each day, and by the time dinner and our daily briefings were over, I was ready for bed.
About the images: A few of the images were taken by immersing an iPhone 15 Pro Max underwater. I'd never done that before, but it worked. If you try it, just make sure to rinse the phone afterwards and place it somewhere to dry. It will dry on its own, so don't immerse it into rice or stick anything into its connection. You will know the phone is dry when you can plug in a connector without the phone complaining. Make sure your phone is fully charged before its water adventure because it will take several hours to dry. You may want to use the phone while it is drying. Click an image to see a larger version and access the slideshow version that allows you to step through all the photos.
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