Glow Worms

Tomopteris are segmented worms that are cousins to earthworms, but belong to a separate group called polychaetes, meaning many (poly) bristles (chaetes). Despite being related to earthworms, they look completely different due to the challenges that come with living in the midwater. They are usually transparent, except when they take on the color of the prey they’ve just eaten (like the one shown here with a red gut). Their bodies are mostly water, which means damage to their outer surface causes the immediate loss of water pressure inside resulting in a dramatic decrease in size. Their appendages produce yellow bioluminescence, a unusual color among midwater animals, nearly all of which make some sort of light. See more images of mid-water creatures in our slideshow.