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Published on Sunday, 17 March 2013 08:27

Poecilotheria 360px 17-03-1(Mirror) – While conducting a survey on Theraphosidae Spider fauna, a group of Sri Lankan scientists made a special discovery– a discovery of a new species of tiger spider in Northern Sri Lanka.

The tiger spider (Poecilotheria rajaei) belongs to the genus poecilotheria and is endemic to Sri Lanka.

 The species was discovered by principal investigator and scientist, Ranil Nanayakkara and his team which includes Peter Kirk, Salindra Dayananda, G.A.S.M.Ganehiarachchi, Nilantha Vishvanath and T.G.Tharaka Kusuminda in 2009. 

 “The first specimen of this new species, which was brought to the attention of the researchers, was a dead specimen of a male spider. The spider had been killed by the villagers. Upon close inspection, it was noticed that it did not conform to the descriptions of any of the species of Poecilotheria so far discovered from the island, as it differed in possession of a ventral abdominal band, among other significant differences,” Nanayakkara said.

According to him, the only other species of Poecilotheria which possesses such a band is the Poecilotheria regalis, found in mainland India. “The researchers carried out intensive and extensive surveys in Northern Sri Lanka to establish the distribution and ecology of this new species, but what went lacking was a female or any other specimen of the same species.

 “Days of extensive searching in every tree hole and bark peel were rewarded with a female and to researchers’ also discovered several juveniles too. “With the help from Sub Inspector of Police, Michael Rajakumar Purajah, we were able to secure and study more specimen of the same type in their natural habitat. Research in the Northern Province also became possible due to the end of the 27- year- long war that had affected the area,” Nanayakkara said.

All specimens of the new species were gathered from Mankulam in the Northern Province and deposited in the National Museum of Sri Lanka and the Wildlife Training Centre Museum in Giritale.

 “The new tiger spider species can readily be differentiated from all other species of Poecilotheria recorded from Sri Lanka by the ventral abdominal band (pinkish- grey in colour) which passes right across the abdomen from side to side,” Nanayakkara explained.

The Poecilotheria rajaei falls in to the group of Poecilotheria and is named after Purajah, in recognition of his support and tireless hours in the field, while the work was being conducted on this new species.

“Most Theraphosidae are found in tropical areas but some representatives live in subtropical and temperate regions. They are mainly terrestrial in habit, living in burrows and other natural cavities or under rocks and fallen logs. Arboreal forms are found mainly in the tropical new world, Africa and Asia. So far, 15 species of Poecilotheria have been recorded, eight from India and seven from Sri Lanka (Platnick, 2012),” Nanayakkara explained.

According to him, spiders of the genus Poecilotheria are known for their large size, colourful markings, their lightning-fast speed and their potent venom (Nanayakkara & Vishvanath, 2011). “Most of the spiders in the genus are marked cryptically with colours of brown, black and grey, with a few exceptions which are metallic blue, green, yellow and black in colour. The ventral aspect of these spiders is marked with intense yellow, white, lilac and black depending on the species,” he further said.

The principal researcher further said, when compared to other theraphosid spiders, the genus Poecilotheria has some of the most colourful species in the world. “Poecilotheria are arboreal spiders that inhabit bark peels, naturally occurring in tree hollows and, at times, found under rocks, decaying trees and in cracks in brick walls. However during the monsoonal period, they display a tendency to enter human dwellings that border forested areas and appear to be more prevalent amongst the males, according to “British Tarantula Society Journal”.

“The main threat to this species is not the loss of habitat but the villagers who kill them out of fear. Villagers believe that tiger spiders are poisonous and that if they bite people would die. At times colonies of these spiders are wiped out when the trees they are found on are burnt- out of fear. These spiders play a major role in the eco system as they control the pests like locusts and should not be killed,” Nanayakkara said.

 According to him, research is yet to be carried out on the venom of the tiger spider and it is possible that its venom could be used for medicinal purposes in the future.

 Naturalist, Sameera Suranjan Karunaratne said, villagers tend to believe that when they are bitten by these spiders, their bodies would shrink just like the spider before they die.

 “However, these spiders don’t just bite a person. We are presently conducting awareness programmes for the villagers and among school children to save these spiders from being killed,” Karunaratne said.( Courtesy Ceylon Today)

Last Updated on Sunday, 17 March 2013 08:27

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