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Critically endangered spider that dives and hides from predators  

Not only is the spider's habitat highly restricted, it is also under several threats. Chaklewadi has one of the largest wind farms and if construction on top of the plateau alters the course of the streams, the population would be disturbed.

Credit:  Ananya Dutta,TNN | The Times of India | May 18, 2015 | timesofindia.indiatimes.com ~~

PUNE: If it’s a choice between the devil and deep waters, this particular spider found in the Western Ghats, will dive underwater. To escape from its predator, the spider can remain under water for as long as 14 minutes before resurfacing for air.

How long can you hold your breath underwater if your life was at stake? On spotting a predator, a spider found in the Western Ghats is able to dive under water and stay there for as long as 14 minutes before resurfacing for air.

“Spiders are by and large terrestrial arthropods that do not have any mechanism for breathing underwater. The behaviour of this species of spider (Tylorida sataraensis) isn’t seen in any of the others of its genus,” said Siddharth Kulkarni, country coordinator for the World Spider Catalogue.

The spider’s body is covered in setae – dense hair-like structures. As the spider dives in, its body swells up creating pockets to trap air before it hits the water. This air is what will sustain it for the entire duration it spends inside the water. Once underwater, it clings to the first boulder it can find so that it isn’t washed away in the water current, Kulkarni added.

Not only does the spider have a good escape plan, it also has an excellent exit strategy.

“As the spider plunges into the water, it secretes a silk thread (similar to the one used to create its web). This waterproof thread called a ‘dragline,’ is attached to its web and allows the spider to return to safety once it resurfaces,” he said.

Kulkarni has found only one record – made as far back as 1915 – of a spider in India demonstrating similar behaviour. Arachnologist Gravely had reported that Orsinome marmorea “drops into the water beneath when disturbed, clinging to the first rock against which it is swept by the current an inch or two below the surface till its alarm has subsided.”

“The behaviour described by Gravely is exactly what we observe in Tylorida sataraensis. However, in field surveys, we haven’t seen Orsinome marmorea dive underwater raising questions about their identification. Both species need to be studied more closely,” he said.

Tylorida sataraensis is a critically endangered spider is found only on two laterite plateaus in Satara – Kaas and Chaklewadi. It was found in orb webs constructed in its preferred habitat of boulders by the streams on the slopes of the plateau under a dense canopy of trees, Kulkarni said.

Not only is the spider’s habitat highly restricted, it is also under several threats. Chaklewadi has one of the largest wind farms and if construction on top of the plateau alters the course of the streams, the population would be disturbed. The diversion of water from the streams for agricultural purposes could also reduce the flow of water. This may cause a fragmentation of the habitat and the population, he said.

The removal of the boulders for construction work is also likely to be a direct threat to these spiders, he added.

Another spider species that Tylorida sataraensis closely resembles is Tylorida ventralis, which is also found in the Western Ghats and beyond. However, the two species are distinct in their anatomy. Moreover, the latter does not demonstrate the “dive and retreat” behaviour that makes this spider so fascinating.

Source:  Ananya Dutta,TNN | The Times of India | May 18, 2015 | timesofindia.indiatimes.com

This article is the work of the source indicated. Any opinions expressed in it are not necessarily those of National Wind Watch.

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