Funky Filter Feeders

Any diver will tell you that the ocean is full of surprises. From immortal jellyfish to deadly snails, there’s always something new and fascinating behind every clump of coral or drift of seaweed. But even the most seasoned diver would be forgiven for doing a double-take when encountering a disco beneath the waves.

Thankfully, the light show isn’t a hallucination brought on by an attack of Nitrogen narcosis, but rather due to a remarkable species of clam. Ctenoides ales, otherwise known as the Electric Clam or Disco Clam, is widespread throughout the tropical waters of the Indo-Pacific from Australia to Indonesia. Nestled in cracks and crevices in the coral, this striking mollusc has a dazzling talent for generating flashes of light that at look like flickers of neon or ripples of bright electricity.

The clam’s impressive display was long thought to be “just” another example of bioluminescence, but recent research has shown that it’s actually made possible by the unique structure of the clam’s mantle which is lined with microscopic spheres of silica - the primary element in glass and quartz. Only one side of the mantle is covered in highly reflective silica, while the other side is very good at absorbing light. By rapidly rolling and unrolling their mantles and alternately exposing the dark and reflective sides, the funky filter feeders generate bright flashes at a rate of about 2 times per second.

Despite this illuminating new revelation, however, scientists are still in the dark about the reasons behind the pulses. But whether it’s designed to lure in mates, attract prey, or ward off predators, the dazzling underwater disco remains an amazing example of nature at its most surprising.