We Thought Only Females Of This Stick Insect Existed, Until Now

Acanthoxyla inermis originally from New Zealand but populations have been known to exist in south England. Martin/Flickr CC BY-NC 2.0

Meet Acanthoxya linermis, a stick insect native to New Zealand, and a particularly strange creature at that as it only exists in female form. Well, that’s what scientists thought until the first known example of a male was found over 18,000 kilometers (11,180 miles) away from their homeland in the UK.

“No males of any Acanthoxya species have ever been recorded until now,” Professor Mary Morgan-Richards, of Massey University in New Zealand, said in a statement.

“It seems a puzzle why the first male Acanthoxyla should turn up in a small offshoot population on the other side of the world from their native land. It may be that males are to be found in New Zealand, but their rarity means they have yet to come to the notice of researchers in this field.”

Acanthoxya linermis, sometimes known as the unarmed stick insect, is a truly parthenogenetic species, meaning the females can reproduce themselves by laying eggs without the need for fertilization by a male. As such, scientists have never documented a male of this species before.

In October 2016, insect enthusiast David Fenwick came across a stick insect on his partner’s car in Cornwell, in the southwest of England. After noticing there was something strange about this specimen, the insect was eventually passed on to Professor Steve Trewick, an evolutionary ecologist at Massey University in New Zealand who knows a thing or two about stick insects.

Researchers carried out DNA sequencing on genetic material they obtained from the leg of the stick insect. To their surprise, their results showed that this was almost certainly the very first known example of a male Acanthoxya

The “missing stickman” is the focus of a new study published in the journal Atropos. The researchers at Massey Unversity are hoping to use this individual to understand if sexuality can re-emerge in a species with asexual lineages, like the unarmed stick insect. And if so, how do they do this? 

“The male is likely a mutant, and therefore unlikely to father offspring,” explained Professor Morgan-Richards.

“A mother has two X-chromosomes, so the production of a son can occur from a mistake during egg formation, when an X-chromosome is lost. The chance of this happening in Acanthoxyla is reduced because many are triploid, with three X-chromosomes.”

Lastly, we regret to inform you that the stick insect died a few days after capture. He now lives in a jar of ethanol at the Natural History Museum in London. Gone but not forgotten. 

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