Antarctica is the only continent that doesn't have any indigenous tarantulas. Generally speaking, these critters tend to avoid frigid areas. Most of the 900 or so recognized tarantula species live in desert, tropical or subtropical environments. Those native to places that get chilly in the winter, such as Utah or southern Australia, must often retreat to their burrows and become inactive during the coldest stretch of the year.
So the fact that not one, not two, but seven new tarantula species have just been discovered high in the Andes Mountains — where nighttime temperatures are liable to dip below the freezing point — is rather unusual. What's more, one of them lives at a higher elevation than any other tarantula known to science.
The Mountain Spiders
All seven spiders belong to the genus Hapaloptremus. Roughly translated from Greek, that name means "of the soft hole," which may refer to the way the animals build their lodgings. Hapaloptremus tarantulas roam high-altitude parts of the Andean region. To date, they've been observed in Peru, Bolivia and Argentina. For shelter, the arachnids dig shallow burrows in the ground — sometimes under piles of rocks or fallen branches.
Columbia University's Tracie Seimon discovered the first of these new spiders in 2006. At the time, she was flipping rocks in the Cordillera Vilcanota mountain range, a Peruvian section of the Andes. Seimon had been on the hunt for local frogs, but as the biologist told National Geographic, she noticed several tiny burrows beneath the upturned stones. Many holes were occupied by diminutive tarantulas; the biggest were around 2 inches (5 centimeters) long.
With some help from a fellow scientist, Seimon dutifully photographed several of the creepy-crawlies and sent the pictures to arachnologist Rick West, one of the world's foremost tarantula experts. She also presented field specimens she'd collected to Nelson Ferretti of the Argentinian National Scientific and Technical Research Council. Minute details in the spider's reproductive anatomy revealed that it was a previously unknown species. The scientists named it Hapaloptremus vilcanota.
Ferretti, West, Seimon, and three colleagues describe the little tarantula in a paper that was published in the Journal of Natural History on Aug. 23, 2018. The document also introduces six other new species from the Andean region that their team has identified.
Reaching New Heights
Before this paper came along, only three species of Hapaloptremus were known to science. These seven newcomers will no doubt force arachnid specialists to reevaluate the entire genus. In the past, experts thought that one of the distinguishing characteristics shared by all Hapaloptremus tarantulas was the low number of cuspules (tooth-like ridges) on a mouth segment called the labium. Yet some of the new species boast many cuspules there. Such anatomical findings might seem mundane, but they help improve our understanding of the genus itself. That in turn might enable us to figure out where Hapaloptremus belongs on the tarantula family tree.
Ferretti and company made behavior-related insights as well. There are just two seasons up in the Andes: dry and rainy. Judging by when their male tarantulas were captured, they deduced that most Hapaloptremus spiders mate in November, near the beginning of the annual rainy season, which lasts until April. Females hypothetically lay their eggs in the dry months.
Another finding earned one species a place in the record books. Seimon encountered some Hapaloptremus vilcanota in southern Peru at an altitude of 14,842 feet (4,524 meters) above sea level. Wild tarantulas have never been documented at such a high elevation before — though the paper does acknowledge that an unrelated Peruvian species from a different genus was once found lurking 14,429 feet (4,398 meters) above sea level. Close but no cigar.
Opportunities in a Changing World
Let's revisit Seimon's frogs for a moment. The slopes of Peru's Cordillera Vilcanota are rapidly losing their glaciers. Between 1975 and 2016, 48 percent of the glacial ice that once covered these mountains disappeared. And during that period, elevations below 16,400 feet (5,000 meters) lost 81 percent of their former ice deposits.
Local animals are adjusting to this new environmental status quo. In 2006, Seimon was the lead author of a study about high-alpine amphibians in the Peruvian Andes. Her group's research found that as the mountain ice melted, indigenous frogs expanded their range vertically. They ascended the slopes and started turning up at high elevations where they'd never been seen before. Future studies may be able to determine if the Hapaloptremus tarantulas are following suit and scaling the mountains to exploit newly-available, ice-free habitats.