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Comparison of Astyanax mexicanus surface fish and Pachón cavefish

Mexican cavefish (right) lack eyes and sleep little, whereas their relatives (left) that live on the surface have eyes and sleep a lot. Credit: J. B. Jaggard et al./eLife/CC BY 4.0

Animal behaviour

Fish forgo sleep thanks to a molecule in the brain

Chemical helps blind cavefish to survive on catnaps.

Even the most sleep-deprived human has nothing on a Mexican cavefish. These blind creatures have long been scientific curiosities because of their habit of sleeping just 1.5 hours a day on average — about four times less than related, sighted populations of the species (Astyanax mexicanus) that live at the surface.

A new investigation might have found an explanation for the unusual behaviour: the fish’s brain produces excessive amounts of a molecule called hypocretin/orexin (HCRT), which regulates wakefulness and appetite. Alex Keene at Florida Atlantic University in Jupiter and his colleagues discovered that the brain of the Mexican cavefish contains almost twice as many HCRT-packed neurons as that of the surface-dwelling variety.

When the team gave the fish drugs that reduced the effects of HCRT on the brain, the cavefish slept up to three times longer than untreated fish. The finding suggests that high levels of HCRT help to keep them awake.

More Research Highlights...

Camera-trap image of Dendrohyrax interfluvialis

Some tree hyraxes scream in the night, but the newly identified Dendrohyrax interfluvialis (above, camera-trap image) utters a complex series of squawks, rattles and barks. Credit: J. F. Oates et al./Zool. J. Linn. Soc.


A bark in the dark reveals a hidden hyrax

Its neighbours scream, but a new species of tree hyrax — a cousin of the elephant — unleashes a rattling bark.
Plastic and other debris floats underwater in blue water

Plastic detritus from snacks and meals floats in the Red Sea. Marine sampling shows that food waste accounts for nearly 90% of plastic pollution at some locales. Credit: Andrey Nekrasov/Barcroft Media/Getty

Ocean sciences

Humanity’s fast-food habit is filling the ocean with plastic

Food bags, drink bottles and similar items account for the biggest share of plastic waste near the shore.
Conceptual artwork of a pair of entangled quantum particles.

An artist’s impression of ‘entangled’ particles, which share properties even at a distance. Entangled photons can be used to help secure a multi-party video meeting. Credit: Mark Garlick/Science Photo Library

Quantum information

Quantum keys dial up tamper-proof conference calls

A new experiment efficiently distributes the highly secure keys to four parties instead of the typical two.
Farmers harvest pineapples in a field.

Workers harvest pineapples in Lingao County, China. Less than one-third of the money spent on food eaten at home reaches farmers. Credit: Yuan Chen/VCG/Getty


Poor harvest: farmers earn a pitiful fraction of the money spent on food

The bulk of consumer food spending around the world ends up in the coffers of distributors, processors and other parties beyond the farm gate.
A woman wearing a protective face mask splashes her hands in a jet of water

A pedestrian seeks relief from searing temperatures in Spain, where a high proportion of heat-related deaths have been linked to climate change. Credit: SALAS/EPA-EFE/Shutterstock

Climate change

More than one-third of heat deaths blamed on climate change

Warming resulting from human activities accounts for a high percentage of heat-related deaths, especially in southern Asia and South America.
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