CLOSE
ZooKeys
ZooKeys

Why Won’t These Bugs Cross This Line?

ZooKeys
ZooKeys

One of the most tightly-controlled borders in the world is a strip of forest in northwest Tasmania. It runs almost 125 miles and separates two areas by as little as 330 feet in some places. Those that live on one side of the border rarely, if ever, cross to the other. The border isn’t a geographical barrier or a wall, and it doesn’t separate political entities or ethnic groups. Rather, it’s an invisible line where two related species of millipedes meet, but don’t mix—and no one knows why. 

On the western side of the border lives Tasmaniosoma compitale, a 15 millimeter long, yellow-brown millipede. On the eastern side is T. hickmanorum, a similarly sized red-brown millipede in the same genus. Both species were named and scientifically described in 2010 by Bob Mesibov, a millipede specialist and research associate at the Queen Victoria Museum and Art Gallery in Launceston, Tasmania. He describes them and related species as a “head + 19 rings” (the head + 17 segments with limbs + 1 segment without legs + the telson, or end segment). Mesibov spent two years mapping the species’ ranges as preparation for further field studies. When all was said and done, he had an image of a very clear division that he could not explain.

Biogeographers, the scientists that study the spatial distribution of species, have a name for these cases where species meet, but overlap very little or not at all: parapatry. It’s very common with millipedes, and occurs with other invertebrates, some plants, and some vertebrates, like birds. Normally, parapatric boundaries follow some other natural boundary like a river or the edge of a climate zone. This millipede border, though, is the longest and narrowest of any that Mesibov has seen in Australian millipedes, and doesn’t have any apparent environmental or ecological cause. It rises from sea level at Tasmania’s north coast to some 700 meters in elevation and then drops back down to sea level. It crosses many of the island’s western coastal rivers and the headstreams of two major inland river systems in the area. It runs over different geological barriers and covers different soil and vegetation types and local climates. The border seemingly ignores the vast differences in topography, geology, climate, and vegetation that it covers, and maintains its sharpness for its whole length. 

Breach!

Strong as the border is, Mesibov did find places where each species had managed to cross over into the other’s territory. There’s an “island” of T. hickmanorum surrounded by T. compitale range that’s at least 15 square miles and maybe bigger—Mesibov hasn’t found its outer edge yet. There’s also a group of T. hickmanorum living several miles into T. compitale territory, where they might have been accidentally dropped by a cattle truck.

For now, Mesibov can only speculate that the border is the result of some biological arrangement between the two species, and its origin and the way it’s maintained are a mystery. It’s one that he’ll leave to other biologists to solve as he continues his regular research finding, naming, and describing millipedes new to science (he’s got 100+ under his belt, so far). 

Whoever takes up the border question will have their work cut out for them. Further mapping and investigation is hindered by the fact that parts of the border cross through pastures, farms and other private property, as well as unroaded and inaccessible wilderness. 

nextArticle.image_alt|e
Martin Wittfooth
arrow
Art
The Cat Art Show Is Coming Back to Los Angeles in June
Martin Wittfooth
Martin Wittfooth

After dazzling cat and art lovers alike in 2014 and again in 2016, the Cat Art Show is ready to land in Los Angeles for a third time. The June exhibition, dubbed Cat Art Show 3: The Sequel Returns Again, will feature feline-centric works from such artists as Mark Ryden, Ellen von Unwerth, and Marion Peck.

Like past shows, this one will explore cats through a variety of themes and media. “The enigmatic feline has been a source of artistic inspiration for thousands of years,” the show's creator and curator Susan Michals said in a press release. “One moment they can be a best friend, the next, an antagonist. They are the perfect subject matter, and works of art, all by themselves.”

While some artists have chosen straightforward interpretations of the starring subject, others are using cats as a springboard into topics like gender, politics, and social media. The sculpture, paintings, and photographs on display will be available to purchase, with prices ranging from $300 to $150,000.

Over 9000 visitors are expected to stop into the Think Tank Gallery in Los Angeles during the show's run from June 14 to June 24. Tickets to the show normally cost $5, with a portion of the proceeds benefiting a cat charity, and admission will be free for everyone on Wednesday, June 20. Check out a few of the works below.

Man in Garfield mask holding cat.
Tiffany Sage

Painting of kitten.
Brandi Milne

Art work of cat in tree.
Kathy Taselitz

Painting of white cat.
Rose Freymuth-Frazier

A cat with no eyes.
Rich Hardcastle

Painting of a cat on a stool.
Vanessa Stockard

Sculpture of pink cat.
Scott Hove

Painting of cat.
Yael Hoenig
nextArticle.image_alt|e
Tony Karumba, AFP/Getty Images
arrow
Animals
How a Pregnant Rhino Named Victoria Could Save an Entire Subspecies
Sudan, the last male member of the northern white rhino subspecies, while being shipped to Kenya in 2009
Sudan, the last male member of the northern white rhino subspecies, while being shipped to Kenya in 2009
Tony Karumba, AFP/Getty Images

The last male northern white rhino died at a conservancy in Kenya earlier this year, prompting fears that the subspecies was finally done for after decades of heavy poaching. Scientists say there's still hope, though, and they're banking on a pregnant rhino named Victoria at the San Diego Zoo, according to the Associated Press.

Victoria is actually a southern white rhino, but the two subspecies are related. Only two northern white rhinos survive, but neither of the females in Kenya are able to reproduce. Victoria was successfully impregnated through artificial insemination, and if she successfully carries her calf to term in 16 to 18 months, scientists say she might be able to serve as a surrogate mother and propagate the northern white rhino species.

But how would that work if no male northern rhinos survive? As the AP explains, scientists are working to recreate northern white rhino embryos using genetic technology. The San Diego Zoo Institute for Conservation Research has the frozen cell lines of 12 different northern white rhinos, which can be transformed into stem cells—and ultimately, sperm and eggs. The sperm of the last northern white male rhino, Sudan, was also saved before he died.

Scientists have been monitoring six female southern white rhinos at the San Diego Zoo to see if any emerge as likely candidates for surrogacy. However, it's not easy to artificially inseminate a rhino, and there have been few successful births in the past. There's still a fighting chance, though, and scientists ultimately hope they'll be able to build up a herd of five to 15 northern white rhinos over the next few decades.

[h/t Time Magazine]

SECTIONS

arrow
LIVE SMARTER
More from mental floss studios