Power down to rest up: light-emitting tablets disrupt sleep and melatonin levels

One of my favourite parts of the day is when I get to change into my pajamas and bury myself in blankets and a good book. After a long and busy day, I look forward to my quiet time when I can decompress and read about Cheryl Strayed’s long hike or why Gwyneth Paltrow is wrong about everything (review coming soon!). My husband, on the other hand, prefers to spend this time driving racecars on his phone or reading about new gadgets on our iPad. According to new findings from Harvard Medical School and Brigham and Women’s Hospital in Boston, these differences in our bedtime routines could be the reason why I generally sleep much better than my husband.

In a study published in the Proceedings of the National Academy of Sciences, Anne-Marie Chang and her colleagues found that reading on light-emitting eReaders before bed negatively affected sleep by altering levels of melatonin. The researchers recruited 12 participants and randomly assigned them to one of two groups: one group read printed books for four hours before bed every day for five consecutive days while the other group used eReaders. After five days, the participants switched to reading on the other device. This study design allowed researchers to compare sleep-related metrics from the same individual when they were reading a printed book to when they were reading an eReader. The eReaders used in this study were iPads set to maximum brightness.

There is nobody else I'd rather lie in bed and look at my tablet next to. (Source)
There is nobody else I’d rather lie in bed and look at my tablet next to. (Source)

Melatonin is a hormone that helps to controls your sleep cycles. If your eyes get progressively droopier as the clock ticks towards your 11:00 pm bedtime, that’s because your melatonin levels are rising and telling your body it needs to sleep. When participants read from an iPad, they had lower levels of melatonin and rated themselves as less sleepy an hour before bedtime. The timing of melatonin release was also affected. Melatonin release was delayed by more than one and a half hours when participants used an iPad compared to when they read a printed book, essentially shifting the sleep cycle to a later time. Continue reading

A case of magnetic attraction: sea turtles use magnetic coordinates to navigate to their nesting sites

What do salmon, sea turtles and songbirds have in common? They are all excellent navigators capable of finding their way home after a long journey. These animals use a process called natal homing to make their way back to their birthplace to reproduce. Every two or three years, female sea turtles return to nest on the same beach where they first emerged as hatchlings. New research has shown that these turtles use the Earth’s magnetic field to guide them back home.

On a map of the world, you can pinpoint the exact location of any place using its unique latitude and longitude coordinates. Replace those latitude and longitude lines with intensity and inclination and you’ll have a new map of the world based on the Earth’s magnetic field. Inclination, the angle at which the magnetic field hits the Earth’s surface, and intensity are two important descriptors of the Earth’s magnetic field. Together, they can be used as a magnetic coordinate system, giving each place a unique magnetic signature.

Since the 1990s, biologists have known that sea turtles use the Earth’s magnetic field as a navigation system. One hypothesis in the field is that baby turtles imprint on the unique magnetic coordinates of their “home beach” as a way of guiding them back when they, themselves, are ready to nest. For the first time, researchers at the University of North Carolina, Chapel Hill have found evidence to support this idea of geomagnetic imprinting in sea turtles. Continue reading

Animals can adapt, but not enough to stay ahead of climate change

On Friday, NASA issued a news release stating that 2014 was the warmest year on record. Two groups of scientists at NASA and the National Oceanic and Atmospheric Administration (NOAA) independently arrived at this conclusion after analyzing surface temperature measurements from over 6,300 sites all over the world collected over the past year. Since 1880, the average surface temperature on Earth has risen by roughly 0.8°C or 1.4°F. As temperatures continue to climb, ecosystems and animals are forced to adapt or risk becoming endangered.

This map shows how temperatures have changed between 1950 and 2014 in different parts of the world. Orange indicates a rise in temperature. Blue indicates a drop in temperature. (Source)
This map shows how temperatures have changed between 1950 and 2014 in different parts of the world. Orange indicates a rise in temperature. Blue indicates a drop in temperature. (Source)

Cold-blooded animals, or ectotherms, rely on environmental heat sources to help their bodies reach an optimal temperature. Because their bodily functions are directly linked to and influenced by external temperatures, rises and fluctuations in temperature pose a serious challenge to ectotherms.

To better predict how resilient cold-blooded animals are to climate change, Australian researchers at the University of Sydney and the University of Queensland combed through over 4,000 papers looking for data on how ectotherms change their physiology in response to changes in external temperature. They used data from 205 studies published between 1968 and 2012 to generate the largest database on physiological adaptability in cold-blooded animals. Continue reading