Railroad Worms, Comb Jellies, and Other Living Fireworks

Most Americans will see some fireworks on
July 4, but some animals produce light shows with their bodies all
year. These living fireworks light up the night. But how, and
why?

These beetles are named for the lights
that run down the female’s larva-like body, said to look like
lights from train windows at night.

The female’s juvenile-looking form may
let her “maintain a bigger store of eggs in a more stable
ecosystem, where wings to disperse to another location are not
needed,” says Paul Marek^[1], an entomologist at the
University of Virginia. Males look more like beetles with fancy
“moth antennae and fly wings.”

Only adult female railroad
worms^[2] and larvae glow. Like
many bioluminescent animals their light is created by a reaction
between the light-emitting molecule luciferin and the enzyme
luciferase.

The greenish-yellow lights on her body,
which she can control, warn predators that she’s toxic.

Some Brazilian species also have a red
“headlamp.” Insects typically can’t see red, Marek says, but it’s
thought that the railroad worm can. A red headlamp allows her to
see and surprise prey insects who can’t see her.

Blue ghost fireflies also have females
that resemble larvae, Marek says, only in these insects the light
is about mating.

These insects are native to the
Appalachian forests of the U.S. and range as far west as Texas.
emit a greenish glow. To find females, males fly slowly through the
forest broadcasting their light, while females also glow and may
emit pheromones.

These tiny sharks leave deep underwater
in total or near-darkness, but they supply their own
illumination.

At just six inches long the and the are
the world’s smallest shark species, found on the northern coasts of
Venezuela and Colombia.

George
Burgess^[3] of the Florida Museum of
Natural History, who described both species, says their
photophores, light-producing organs, are mainly located around
their reproductive organs.

Males and females are “strutting their
stuff, showing where their stuff is,” Burgess says. Each species
has a specific light pattern, “like a name tag,” so they can find
mates in the dark ocean depths.

Hawaiian
bobtail squid^[4]
sleep under the sand all day, coming out to forage at night. The
light camouflages them against moonlight on the surface and
eliminates their shadow, obscuring them from predators.

Some species like the Leidys comb jelly^[5] have photophores inside
the bell, or main body, Burgess says. All are propelled through the
water by columns of cilia which refract light, producing a
shimmering rainbow to rival any fireworks display.