{"id":1885,"date":"2014-09-25T21:00:47","date_gmt":"2014-09-25T19:00:47","guid":{"rendered":"http:\/\/news.embl.de\/?p=1885"},"modified":"2024-11-14T16:31:43","modified_gmt":"2024-11-14T15:31:43","slug":"1409_plankton-jetlag","status":"publish","type":"post","link":"https:\/\/www.embl.org\/news\/science\/1409_plankton-jetlag\/","title":{"rendered":"How plankton gets jet lagged"},"content":{"rendered":"\n

A hormone that governs sleep and jet lag in humans may also drive the mass migration of plankton in the ocean, scientists at the European Molecular Biology Laboratory (EMBL) in Heidelberg, Germany, have found. The molecule in question, melatonin, is essential to maintain our daily rhythm, and the European scientists have now discovered that it governs the nightly migration of a plankton species from the surface to deeper waters. The findings, published online today in Cell<\/em>, indicate that melatonin\u2019s role in controlling daily rhythms probably evolved early in the history of animals, and hold hints to how our sleep patterns may have evolved.<\/p>\n\n\n\n

In vertebrates, melatonin is known to play a key role in controlling daily activity patterns \u2013 patterns which get thrown out of synch when we fly across time zones, leading to jet lag. But virtually all animals have melatonin. What is its role in other species, and how did it evolve the task of promoting sleep? To find out, Detlev Arendt\u2019s lab at EMBL turned to the marine ragworm Platynereis dumerilii<\/em>. This worm\u2019s larvae take part in what has been described as the planet\u2019s biggest migration, in terms of biomass: the daily vertical movement of plankton in the ocean. By beating a set of microscopic \u2018flippers\u2019 \u2013 cilia \u2013 arranged in a belt around its midline, the worm larvae are able to migrate toward the sea\u2019s surface every day. They reach the surface at dusk, and then throughout the night they settle back down to deeper waters, where they are sheltered from damaging UV rays at the height of day.<\/p>\n\n\n\n

\"Multitasking
Multi-tasking neurons sense light, run an internal clock, and produce melatonin. Credit: EMBL\/M.A.Tosches<\/figcaption><\/figure>\n\n\n\n

\u201cWe 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.\u201d says Arendt. \u201cSo 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 behaviour.\u201d<\/p>\n\n\n\n

Maria Antonietta Tosches, a postdoc in Arendt\u2019s lab, discovered a group of specialised motor neurons that respond to melatonin. Using modern molecular sensors, she was able to visualise the activity of these neurons in the larva\u2019s brain, and found that it changes radically from day to night. The night-time production of melatonin drives changes in these neurons\u2019 activity, which in turn cause the larva\u2019s cilia to take long pauses from beating. Thanks to these extended pauses, the larva slowly sinks down. During the day, no melatonin is produced, the cilia pause less, and the larva swims upwards.<\/p>\n\n\n