NewsWhen many eyes twitch in the night

When many eyes twitch in the night

Created: 08/09/2022, 16:56

Diese Augen! Evarcha arcuata, auf einem Blatt sitzend. imago images
These eyes! Evarcha arcuata, sitting on a leaf. imago images © imago images

Jumping spiders also dream quite vividly

Most people are only vaguely familiar with Evarcha arcuata. Because either the little jumping spider runs away in the event of an unexpected encounter – or the human takes his legs in hand. After all, spiders are still – even if their nature is rather timid and their contribution to biological balance is not to be underestimated – the feared enemies par excellence for most people. A nightmare on eight legs!

Not so Daniela Roessler. She is one of those people who study jumping spiders intensively, even sitting by their beds at night and watching them sleep in the service of science. And the biologist, who conducts research at the University of Konstanz, and her team made an amazing discovery: Evarcha arcuata dreams at night!

observed while sleeping

As has now been published in the scientific journal PNAS, Rößler’s team discovered a state similar to REM sleep in jumping spiders. This “rapid eye movement” phase has been studied in detail in mammals and birds, and it has also been documented in reptiles and cephalopods. But since many animals do not have moving eyes, a comprehensive comparison of active, sleep-like states is difficult, according to the university’s statement. For example, jumping spiders are unable to move the lenses in their eyes, but can move their retinal tubes to adjust their vision.

Whatever the case, the behavioral and evolutionary ecologist from Konstanz and her team examined nocturnal infrared images of 34 young jumping spiders. And recognized “phases of clear retinal movements that occurred at very regular intervals and increased over the course of the night”.

It is not known whether the spiders snored. But – and this is somehow touching – the retinal movements were “accompanied by uncontrolled body movements, such as the legs curling up or the twitching of individual limbs”.

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