Animals

Shimmery blue tarantula discovered

The new species of arachnid, native to Sri Lankan rainforests, is big enough to comfortably hug a doughnut.Sunday, 25 August 2019

By Nadia Drake
Females of the newfound species have bright blue legs, while males are a mossy brown.

Sri Lanka is home to a new species of tarantula—and its females are fuzzy, turquoise-tinged, and big enough to comfortably hug a doughnut.

Scientists found the arachnids within an isolated patch of southwestern rainforest, ringed by tea and rubber plantations. Living in tubular, silk-lined burrows, they are fast and aggressive, seizing unlucky insects that wander too close to their underground lairs. Measuring roughly five inches from tip to tip, these spiders are not exactly small, nor are their brilliant blue patches particularly subtle.

In fact, it’s these snazzy blue colours that first caught biologist Ranil Nanayakkara’s attention, and flagged the creatures—now named Chilobrachys jonitriantisvansicklei—as potentially new to science. 

“When we first spotted them I was in awe, lost for words,” Nanayakkara says of the decked-out females. “The males,” he notes, “are smaller and are mossy brown in colour.”

C. jonitriantisvansicklei is only the second species within the Chilobrachys genus to be found in Sri Lanka; the first, a drab brown arachnid called C. nitelus, was identified 126 years ago. Neighbouring India is home to more than two dozen closely related Chilobrachys species, and while many are mostly unremarkably brown, several are similarly adorned.

Nanayakkara, a prolific spider-hunter from Sri Lanka’s University of Kelaniya, collected some of the shimmery arachnids on an expedition in 2015, then spent two years making detailed physical comparisons between them and known Chilobrachys species. He eventually concluded that the spider was unique, as he and colleagues reported in the British Tarantula Society Journal, and named the species after donor Joni Triantis Van Sickle.

The discovery highlights the rich diversity of Sri Lankan wildlife, and how many spider species are yet to be found.

Sprucing up the family tree

Though the spiders are clearly new to Sri Lanka, experts say more genetic research is needed to clarify C. jonitriantisvansicklei’s position on the family tree.

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“I accept the species as a good new species,” says Robert Raven, principal curator of arachnids at Australia’s Queensland Museum. “But given that some species, like C. andersoni, are widespread, the possibility that the new one is one of the named Indian species will eventually need to be addressed.” 

Genetic sequencing can confirm that the spiders are unique; the analysis is also crucial for understanding the spiders’ evolution and for planning conservation strategies. Raven notes that in areas like Sri Lanka, high levels of biodiversity are often coupled with small populations—“and even smaller scientist numbers.”

At the moment, scientists don’t know whether C. jonitriantisvansicklei is particularly rare or threatened, but other Sri Lankan spiders are listed as endangered.

A treasure trove of spiders

This is not the first time Nanayakkara has identified a scene-stealing Sri Lankan tarantula.

In 2013, he described a new species of massive, tree-dwelling tarantula called Poecilotheria rajaei. Ornately decorated with interlocking geometric patterns, and with a legspan that could comfortably reach around your face, this so-called tiger spider ended up being a media sensation.

That such large spiders could hide in plain sight, even now, is not particularly astonishing in Sri Lanka, says Suresh Benjamin of Sri Lanka’s National Institute of Fundamental Studies, who was not involved in the new research.

Though the country is a treasure trove of biodiversity, only a fraction of its riches have been closely studied since independence in 1948, Benjamin says.

For instance, of the 593 spider species currently identified on the island, 108 were described within the last two decades. The only guide to Sri Lankan spiders was published more than a century ago, he adds.

Given that, get ready for more newly described spiders to crawl into the news.

“Fieldwork conducted by us during the last few years,” Benjamin says, “has shown the presence of an abundant, largely unexplored spider fauna living in the remaining forest patches of the island.”

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