Tommy Knowles peers into an illuminated column of seawater and gestures at what looks like the dangliest of dangly earrings, except it’s made of clear, gelatinous goo. When this improbable accumulation starts propelling itself through the water in graceful loops, he beams. “This is one of my favorites,” says the senior aquarist at the Monterey Bay Aquarium in California. “Something I really wanted to be able to pull off was exhibiting a siphonophore.” These predatory marine invertebrates—actually a colony of specialized creatures that form a single organism—spend their days at…
