They have compared the activity of these genes in vertebrates like us with their activity in a distantly related invertebrate – a marine worm called Platynereis dumerilii.
As 2-day old larvae, these worms float near the ocean surface at night, feeding on algae and other bits of food. Then they spend the day at lower depths, where they can hide from predators and the sun’s ultraviolet rays.
Scientists discovered that cells on the top of the larvae make light catching protein – the same ones we make in our eyes to switch melatonin production on and off. These same cells also switch on genes required to produce melatonin.
They wondered if the worms were using this network of melatonin genes the way we do. To find out, Dr. Maria Antonietta Tosches and her colleagues tracked the activity of the genes over 24-hour periods.
They found that the worms didn’t produce melatonin all the time. Instead, they made it only at night, just like we do. In addition, the scientists found that this nightly surge of melatonin allowed the worms to move up and down in the ocean each day.
The worms travel by beating tiny hairs back and forth. During the day, they rise toward the surface of the ocean. By the time they get there, t he sun has gotten so faint that the worms start making melatonin.
The hormone latches onto the neurons that control the beating hairs and cause them to produce a steady rhythm of electrical bursts. The bursts override the beating, causing the hairs to freeze and the worm to sink. When dawn comes, the worms lose their melatonin and start to swim upward again.
