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Glider ants of the Amazon, a 4-million rpm champ spinner

Recent Discovery: Rainforest ants that glide

Clutching a skinny tree trunk while collecting mosquitoes 100 feet (30 m) above the Amazon rainforest floor in Peru — ecologist Stephen P. Yanoviak brushed 30 or so ants off a branch "and watched in amazement as they glided back to the trunk" in an ant cascade homeward bound.

A glider ant. Click to watch the ant glide, control her flight, and land back on the trunk. [Stephen P. Yanoviak, University of Texas Medical Branch at Galveston, copyright © 2003-2005, used with permission]

He expected the ants to plummet in tight spirals, become vanishingly small, and disappear into the distant understory as respectable ants would. Instead, these creatures fell a little bit, slowed down, twisted for a backward approach, swooped to the tree trunk (like a kid on a rope swing), hit on the back of their armor-plated abdomen, and plunked their feet on the trunk — only about 30 feet (10 m) from where they started.

Sometimes they slid down the trunk before getting a good grip and occasionally bounced off. No problem, they simply glided some more, turned, and made another landing.

"It is the first documented example of directed aerial descent in a living wingless insect and the first record of intentional backwards aerial gliding in any animal," says Yanoviak.

Yanoviak of the University of Texas Medical Branch and the University of Florida is certain that the ants, as they fall, locate the trunk with visual cues. He and his colleagues (Robert Dudley of the University of California at Berkeley and Mike Kaspari of the University of Oklahoma) suspect the ants wave their hind legs, abdomen, and head to both direct the glide and align backwards with the tree. The researchers are now investigating exactly how the ants do it.

Why they do it is easier: so they don’t fall into water teeming with hungry fish and die. So they don’t fall into leaf litter and get lost struggling through dim strange vegetation on the ground far below. After all, these are small animals "adapted for following chemical trails along sunlit branches," says Yanoviak. If they can’t find their tree-nest home, a hungry lizard or bird will find them.

The glider ants (called Cephalotes atratus) typically clamber back to their nest in 10 minutes. Natural selection to the rescue!

Further Reading:

University of Texas Medical Branch at Galveston: Gliding ants by Stephen P. Yanoviak

Yanoviak, S.P., Dudley R., Kaspari M. "Directed aerial descent in canopy ants," Nature 2005 Feb 10; 433(7026):624-6.

Q: (Earlier question) What is the fastest spinning man-made object and what is the speed? I am writing a book and that is an important fact in the story. (David, Woodland, California)

A: (Better answer) Reader Joseph Ford has come up with an even faster spinning artifact than the 400,000-rpm carver drill that I described in a previous column — one that spins 10 times faster.

The devices that Ford mentions are small ceramic rotors (2 to 2.5 mm in diameter and 15 to 20 mm long — about the size of a straightened raw macaroni) used inside superconducting magnets to spin up samples in a NMR (nuclear magnetic resonance) spectrometer.

The tilted white cylinder (indicated by the green arrow) — tilted by the “magic angle” of 54.7° — is the stationary part of the high-speed spinner. The rotor and its sample sit inside the white cylinder. An experimenter puts the whole assembly (i.e., the probe) inside a superconducting magnet to investigate nuclear magnetic resonance. [Doty Scientific, Inc.]

Ford, a biochemist who has worked with NMR for 30 years, has "personally spun samples at 20 kHz" — which is 1.2 million rpm. Faster still are some rotors that may, indeed, be the fastest spinning artifact. They whirl at least at 4 million rpm. Ago Samoson makes these remarkable rotors in his small University-based company in Tallinn, Estonia. Beat Meier, professor of physical chemistry at the ETH technical university in Zurich, Switzerland, uses Samoson’s rotors in his NMR lab.

"We spin routinely at 40 to 50 kHz [2.4 to 3 million rpm] and have taken spectra at 69 kHz [4.1 million rpm]," reports Meier.

Any of us who has ever gone in for a MRI scan of an injured knee, for example, to examine tissue structure — has experienced nuclear magnetic resonance. It’s a nice noninvasive procedure that excites atoms (mostly hydrogen) in our body with a small varying magnetic field superimposed on a strong magnetic field. Our body’s atoms experience resonance at certain frequencies that depend on the atom and its molecular environment. The image captures these resonances, which rise like isolated peaks above a steady line, and thereby pictures our tissue structures.

But we — the sample — don’t spin. I asked Ford why he spins his samples at such incredible rates. Well, the clean resonance peaks that an MRI gives for tissue are not at all distinct for a solid material like carbon, silicone, or aluminum. In fact, the resonance spectra are a "mess." So, experimenters spin the sample to average out factors that create the mishmash. A nonhomogeneous magnetic field is the primary culprit. The field must be the same, within one part in 100 million, over the sample. A cute trick. Spinning the sample a million or more revolutions per minute does the job.

I also asked David Doty, physicist and president of Doty Scientific in Columbia, South Carolina, this question. Please click here for his answer that elucidates everything from the "magic" spin angle to the tussling fields of neighboring atoms. Breifly:

"Solid (rigid) samples must be spun at the magic angle at incredible speeds in NMR so that all the molecules in the sample sing in the same key. Not the same note – it’s still an incredibly complex mix of closely spaced resonances, but at least it can be analyzed. This allows us to get precise 3D pictures of the most complex biological macromolecules."

NMR has become one of the most prized tools in organic chemistry and biochemistry. With it we can not only identify unknown substances but "also get detailed structural information about molecules, proteins, and solids that are otherwise difficult or impossible to obtain," says Ford.

Further Reading:

Doty Scientific, Inc: Magic Angle Spinning (MAS) and Nuclear Magnetic Resonance (NMR) made simple (almost) by F. David Doty

Doty Scientific, Inc: MAS (Magic Angle Spinning) spinning modules

ETH: Nuclear Magnetic Resonance

National Laboratory of Chemical Physics and Biophysics: Sampling spinning NMR by Ago Samoson

Ernst, M., A. Samoson, and B.H. Meier. 2003 Aug Low-power XiX decoupling in MAS NMR experiments. J Magnetic Resonance. 163(2):332-9

Wikipedia, the free encyclopedia: Nuclear Magnetic Resonance (NMR)

(Answered March 11, 2005)