Lined up head to rear-end in their tunnels, the way they spend much of their lives, naked mole rats look like a string of pale, buck-toothed, wrinkled sausage links that have sat a few months too long in the dark recesses of a refrigerator.
Though certainly not pretty, the 3-inch-long creatures can't see each other anyway. They're blind.
But when Thomas Park looks upon his 120 naked mole rats, he sees something beautiful -- a species that is guiding researchers on unexplored paths toward what they hope are new medical marvels, such as treatments for chronic pain, cures for cancer, and help for stroke and heart attack victims.
The world's only known cold-blooded mammals, they live in insect-like underground societies, incapable of feeling certain kinds of pain and never suffering cancer. And, perhaps because they smell so bad, they have learned to live on very little oxygen.
"They look like they came from another planet," said Park, a research biologist at the University of Illinois at Chicago who established several colonies of the subterranean African rodents in his lab in 1998.
Since then he has studied the way they communicate, their obliviousness to pain and -- in a scientific article published this month with colleague John Larson -- their ability to live packed together in dark tunnels breathing each other's exhaled breath.
"They're the sweetest animals I've ever worked with," Park said.
That's saying something for a guy who grew up in Baltimore with understanding parents who allowed him and his brother to keep every imaginable kind of pet, including dogs, cats, turtles, snakes and ducks.
"When I was 7, I trained our guinea pigs to jump up the stairs in our house," Park said. "I was always interested in finding out how animals learned to do what they do."
In college, he began studying how songbirds learn their songs, and worked with all manner of animals in his graduate and post-doctoral studies. He encountered naked mole rats on a fellowship in Germany in 1995, the same year he joined the UIC faculty.
Researchers first took note of the rodent's strange, insect-like social organization about 30 years ago. In nature, they live in tunnel systems reaching 6 feet below the arid plains of northern Kenya and southern Somalia and Ethiopia. With a life expectancy of up to 30 years, they live far longer than any other rodent.
Like colonies of ants, termites, wasps and bees, naked mole rats live in tightly packed colonies of as many as 300 animals ruled by a ruthless queen, the only female in the colony allowed to reproduce, sired by one to three kings of her choosing. All others in the colony are divided into two castes, housekeepers and soldiers.
When he got to UIC, Park said he took note of naked mole rat colonies at the Brookfield and Lincoln Park zoos. Before starting his own colonies, he took students to see fertility studies in the Brookfield colony done by University of Chicago researcher Sue Margulis.
"It may be of benefit that naked mole rats are so goofy-looking," he said. "They attract students considering science as a career."
The animals' odd lifestyle and remarkable traits have attracted intense interest worldwide in the last 20 years from scientists looking to solve some of medicine's most vexing problems.
Park started his UIC colonies to compare low-frequency naked mole rat vocalization with high-frequency bat vocalization.
He uses transparent PVC tubing to mimic their underground tunnels, connecting them to clear plastic boxes used as a food storage and eating area, a gathering area and a toilet chamber.
Each of his colonies -- some with just a few animals, others with a couple dozen -- is kept in a separate habitat stacked on wire shelving in two sealed storage rooms not much bigger than large walk-in closets. The mole rats live in extreme humidity at temperatures hovering in the 90s.
"The air is so foul down there that it would kill any other mammal that had to breathe it," Park said.
Realizing the air they breathe is highly acidic from high carbon dioxide content, he discovered naked mole rats lack a common mammalian neurotransmitter called "Substance P."
In other mammals, Substance P telegraphs chemically induced pain, such as from acid, but naked mole rats feel nothing -- a revelation that has researchers looking at them for clues to therapies for human chronic pain syndrome, which is chemically based.
More recently, he and Larson, who studies brain and memory function, have been investigating how naked mole rats manage to live in their carbon-dioxide-rich, oxygen-poor tunnels.
They measure how long sectioned brain tissue maintains electrical activity as oxygen supplies are cut back, comparing it with those of mice. Larson said the rats' neurons function more than six times longer after they begin to experience oxygen deprivation.
"We're trying to find a way to use what they use in these hypoxic [low-oxygen] conditions to alleviate the damage done to brains of human stroke, heart attack and brain-injury victims."
Mullen writes for the Chicago Tribune.