Researchers in India have discovered a new species of the happy-face spider – the Himalayan happy-face spider (Theridion himalayana).
The scientists were originally studying ants when they came across this smiley species. They identified 32 different colour varieties from locations across Uttarakhand: Makku, Tala and Mandal.
Through DNA analysis, they concluded that the spider differs from the Hawaiian happy-face spider by approximately 8.5 per cent, which confirms that this species evolved independently.
“I had seen the Hawaiian spider during my master’s programme itself, and I knew instantly we had a jackpot because of its striking resemblance,” said Dr. Devi Priyadarshini, co-author of the study published in the journal Evolutionary Systematics.
The Himalayan happy-face spider resembles the Hawaiian species the most when it comes to general morphology and colour pattern – but it can be distinguished by the structure of its genitalia.
Interestingly, researchers also found insects in the same habitat which had similar patterns in hues of red, green, yellow and black – although it isn’t known why this has occurred.
The spider favoured ginger plants, also something in common with the Hawaiian cousin.
However, ginger is an invasive species in Hawaii – which makes the connection unusual. Scientists are also not sure of the purpose of the patterns on the spider’s back. They are in some way crucial to the species survival, but the specifics are yet to be uncovered.
“This is definitely indicative of a deeper genetic mystery,” added Dr. Priyadarshini.
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The Hawaiian happy-face spider
While scientists wrestle with that mystery, we actually know much more about this new species’ cousin, the Hawaiian happy-face spider (Theridion grallator). Discovered in 1900, it was a milestone for evolutionary biology as the first polymorphic spider.
Polymorphism is the occurrence of two or more different physical characteristics (such as colour patterns or body shapes) within one species. To be classified as such, these characteristics must occupy one habitat at the same time.
Some morphs of the happy-face spider sport the smiley face imprint on their abdomen, although the patterns differ across the Hawaiian Islands. Some of those spiders even lack the markings altogether.
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This species not only comes in many variations of patterns, but they also change colour depending on the spider’s diet – a behaviour quite rare among other spider species.
Measuring only up to 4.5mm, the Hawaiian happy-face spider mostly inhabits the underside of leaves in the upper-elevation Hawaiian wet forests of Maui, Hawai’i Island, Moloka’i and O’ahu. Its base colour is pale, translucent yellow and can contain a variety of red, white and/or black patterns.
Its varying appearance and colouring is thought to be a survival tactic to avoid predators like birds, who will use a particularly abundant colour to identify possible prey. This is not confirmed, however – scientists have a lot of different theories as to why these spiders evolved to exhibit this pattern.
Top image: Hawaiian happy-face spider (Theridion grallator) on a leaf. Credit: Nate Yuen, CC BY 3.0, via Wikimedia Commons
