Scientists at the European Molecular Biology Laboratory (EMBL) in Germany found that a hormone that influences the sleeping patterns and jet lag in humans is also responsible for the daily migration of plankton.
Melatonin is a hormone that controls the body's sleep and wake cycles. Earlier studies showed that taking melatonin can help reduce the symptoms of jet lag or the disruption of the sleep and wake cycle due to traveling across time zones. The researchers initiated the new study to determine if melatonin also affects other species and their sleeping patterns.
The research team observed the Platyneris dumerili, a type of oceanic worm. As a larva, this worm was observed to perform the largest migration in the sea as it travels from the depths of the ocean to the surface of the water every day. It uses its flippers, called cilia, to push itself above the surface during daytime and returns to the deeper parts of the ocean come night time.
"We found that a group of multitasking cells in the brains of these larvae that sense light also run an internal clock and make melatonin at night," lead author Detlev Arendt said in a press release. "So we think that melatonin is the message these cells produce at night to regulate the activity of other neurons that ultimately drive day-night rhythmic behavior."
The amount of melatonin during the night causes the cilia to pause from its continuous beating. These pauses reduce the speed of the plankton's movement and eventually, allow it to gradually sink deeper into the ocean. Melatonin levels during the day, on the other hand, are higher, causing the cilia to move faster and propel the plankton to the surface.
"When we exposed the larvae to melatonin during the day, they switched towards nighttime behavior," said co-researcher Maria Antonietta Tosches. "It's as if they were jet lagged."
The results of the study implied that the mechanisms that govern the human's sleeping patterns started evolving in the first oceanic species, millions of years ago. It also showed how other species evolved to move away from the light.
Further details of the study published in the Sept.29 issue of Cell.
