On the edge of the twilight zone. New spider species go blind in Israeli caves

Researchers immediately discovered 7 new species of funnel spiders that have partially or completely lost their sight, living in the darkest corners of the caves.

In the new study, scientists sought to understand the evolutionary relationship between normal-eyed funnel-web spiders that settled and live at the entrance to caves, with those that live in the darkest corners of the caves and seem to have completely or partially lost their sight, Science Alert writes .

According to study co-author Shlomi Aharon, an ecologist at the Hebrew University of Jerusalem (HUJI), she and her colleagues walked around three dozen Israeli caves. They found 26 cave-preferring species that all relied on external conditions, namely light (troglophiles), and lived at cave entrances or in their twilight zones. However, 14 species turned out to be inhabitants of the darkest zones (troglobites).

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Curiously, half of the 14 were completely unfamiliar to scientists – 5 of them with reduced eyes and 2 completely blind. According to the ecologist, they found that five species were unique to different caves, and two other species were found at once in several caves in the Galilee and in caves located in the Ofra karst field.

Next, the scientists analyzed the DNA of the spiders and tried to trace their history. It turned out that the spiders that had adapted to the unique cave twilight zones, alas, could no longer thrive outside them. Ecologists say the data indicate that the new species are evolutionarily closer to species from caves in Mediterranean areas in southern Europe than to species living in their immediate vicinity at cave entrances in Israel.

The researchers note that the process of vision loss occurred independently in different cave systems, causing the spiders to lose their ability to see. Thereafter, the original species became locally extinct outside the caves before other related species succeeded in repopulating them outside.

One of the recently discovered species, Tegenaria ornit, is completely blind

Photo: Shlomi Aharon

It is assumed that the extinction occurred about 5 million years ago, and irreversible climate change was to blame. According to the ecologist, this study shows the impact of climate change on many of the world’s habitats that are in danger. Therefore, scientists note that we need to do everything to preserve the unique nature of the planet, including underground systems, in order to understand exactly what processes they were created by.

Focus has previously written about jumping spiders having unique vertebrate skills .


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