New Scientist – Flexible Spiders, Electric Fish and the Deepest Microbes Ever Found

A Water Web (Photo by Darko Cotoras)

Dear Readers, there are some amazing articles in New Scientist this week. First up, scientist Darko Cotoras of the California Institute of Sciences in San Francisco has found that a tiny spider found only on Cocos Island, off the coast of Central America, can make three different types of web according to the circumstances in which it finds itself.

Wendilgarda galapagagensis makes ‘aerial’ webs high above ground, attached to nearby stems and leaves. Near to the ground it makes ‘land’ webs, with long horizontal strands attached to branches, and with vertical strands anchored to the ground. Over pools it makes ‘water’ webs, like the ones in the photo, with the vertical strands attached to the water surface itself.

Cotoras wondered if this meant that the spider was actually turning into three separate species. However, when the spiders were relocated, they often started to build webs in the style that was most suited to their new home. In other words, these tiny invertebrates are not limited to just one web (which seems to be the case with many spiders) but can adapt according to circumstances. This seems to me to contradict one theory, which is that island animals adapt to occupy a very specific niche and are hence threatened if things change.

You can read the whole article here.

Juvenile Brown Ghost Knifefish (Apteronatus leptorhynchus) (Photo by Guy L’Hereux)

Brown Ghost Knifefish are found in the rivers of Colombia, and have a surprisingly complicated social structure. They use electric discharges to find food in the silty water, and to communicate with one another, and until 2016 little was known about them. Then scientist Till Raab and his colleagues at the University of Tübingen in Germany found a group of more than 30 fish in an area only 9 metres square. However, Raab noticed that there was little fighting between the fish, and wanted to examine what was going on.

In captivity, it was found that when a fish was denied access to a shelter by a competitor, the fish responded by targeting the other fish with electric pulses, which gradually increased in discharge before falling back to normal. The subordinate fish seemed to be deliberately provoking the fish who had control of the shelter into chasing and biting it. Although this didn’t result in a change of ownership, it did seem to improve the social standing of the subordinate fish, and over time seems to have ‘evened out’ the relationships between the fish. One fish that made repeated ‘attacks’ on the dominant fish eventually ended up with control of the shelter (one imagines a weary fish deciding that control of a piece of tubing wasn’t worth all this aggro).

Of course, the mere fact of being in captivity will have an influence on behaviour in any animal. However, what this does seem to illustrate is that fish are as capable of weighing up the delicate nuances of social relationships as any mammal.

You can read the whole article here.

The Chinese Continental Scientific Drilling Project (Image by Qin Wang et al)

And finally, here is something truly incredible. Scientists Hailiang Dong at the China University of Geosciences and Li Huang at the Chinese Academy of Sciences have discovered bacterial cells from a 5.1 kilometre-deep borehole in Eastern China (the Chinese Continental Scientific Drilling Project or CCSD). Previously, the deepest known microbes on land were nematodes found 3.6 kilometres deep in a South African gold mine.

At this depth, temperatures are a staggering 137 degrees Centigrade, far above the accepted threshold of 122 degrees Centigrade. Scientists now believe that temperature might not be the only factor involved – the pressure, the physical nature of the rocks and the availability of water might also play a role.

Proving that the cells are alive will be another problem – organisms living at this depth often have an extremely low rate of metabolism because of the poor availability of nutrients. However, experiments with deep sea organisms have revealed that, if fed, they often ‘wake up’ with surprising enthusiasm. It will be interesting to see what approach is taken with these new microbes.

One reason that finds like these are so exciting is that it greatly increases the range of habitats on other planets where life might be possible. But for me, a second reason is that it demonstrates the extraordinary versatility of life. It gives me hope that, even if we screw things up irredeemably on the surface, we might not wipe out life completely. Of course, we won’t be here to see it if things go that wrong but maybe, in millions of year time, the next inhabitants of earth won’t be quite so feckless with the planet that they inherit.

You can read the whole article here.

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