Amidst Nature’s seemingly infinite collection of wonders, even harsh battles for survival can sometimes be breathtakingly beautiful. Take this electric-blue encounter, for example. What may at first appear to be a storybook character suspended in a dream is, in fact, a real-life predator grappling with its prey. Granted, it’s a slow-motion grapple, but considering the size disadvantage of the feathery blue dragon sea slug (Glaucus atlanticus) on the left and the deadly weaponry of the Portuguese man o’ war (Physalia physalis) in the opposite corner, it’s not short on drama or stakes. Indeed, for the blue dragon—predator in this particular case but itself a potential target for other hungry mouths—the battle is a matter of life or death. Without the stinging cells it harvests from this man o’ war meal, the slow-moving sea slug would be utterly defenseless and easy to catch.
Both the blue dragon and the man o’ war spend their lives adrift on the surface of the open ocean, traveling at the mercy of winds and currents. It’s a dangerous place for a squishy organism to find itself, with hungry predators lurking both above and below the waves.
The ocean-blue coloration of both species is their first line of protection, and is of course no accident. Shared by an eclectic assortment of other invertebrates—collectively known by scientists as “the blue fleet”—which make their living adrift on the sea surface, it’s not hard to imagine how this hue might enable an animal to effectively disappear when viewed from above. Yet, as helpful as it can be to go unnoticed, it doesn’t hurt to have a potent back-up strategy.
Few back-ups are more potent or infamous than the Portuguese man o’ war’s. Brushing up against any one of its dozens of tentacles, which can stretch 30 meters (100 feet) beneath a gas-filled chamber at the surface, unleashes hellfire for would-be predators, prey, and unsuspecting beachgoers alike, as barbed tubes fired from the tentacles’ stinging cells inject a powerful neurotoxin. Avoiding contact with the man o’ war is therefore always advisable—unless you’re a blue dragon.
Not only are these beautiful mollusks immune to the cnidarian’s stings, they have evolved the ability to coopt its defense for their own. Taking enormous bites with their tough, chitinous jaws, blue dragons use their slug slime to keep the stinging cells from firing, then transport the cells, intact, through their digestive tracts and out into their feathery extremities. There, they concentrate them, such that a sting from the elegant blue dragon can be significantly more potent than that of the dreaded man o’ war—real-life inspiration for the beautiful-but-deadly storybook archetype.
Doug Perrine is a photojournalist specializing in marine wildlife.His photographs have been published in thousands of magazines, books, and calendars, and have won numerous awards, including the grand prize in the Wildlife Photographer of the Year competition. He is the author of seven books and numerous magazine articles about marine life.