Galleries / Frankenhuman! 9 Lab Animals That Add Up to 1 Person

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Andrew Moseman; published January 5, 2010

Enter the Frankenhuman!

Fruit Flies

Moths

Frogs

Naked Mole Rats

Prairie Voles & Meadow Voles

Rabbits

Beagles

Pigs

Monkeys

<p>Ever since <a href="http://en.wikipedia.org/wiki/C._C._Little" target="blank">Clarence Cook Little</a> started his landmark genetic experiments on mice more than a century ago, the mouse has been the go-to animal model for medical research. </p><p>But a wide variety of other animals can be found in medical labs around the world. Taken (or stitched) together, they form a kind of laboratory doppelganger for humans: similar biology, fewer moral qualms--though certainly not none.</p><p>Click through the gallery to see some of the animals that stand in for humans in medical research.</p>

<p>It's not just that <i>Drosophila melanogaster</i> live, breed, and die fast. That helps. But these insects boast other features that make them ubiquitous test subjects in labs around the world. </p><p>They have thickly banded chromosomes that helped researchers figure out that <a href="http://discovermagazine.com/2002/apr/featworks/" target="blank">chromosomes contain DNA</a>. That also allows scientists to watch deletions and rearrangements of the genetic code under their microscopes. And the flies' simple brains allow a less complicated way to unlock the neurological effects of <a href="http://www.eurekalert.org/pub_releases/2009-12/acs-tbo120209.php" target="blank">drug addiction</a> than studying mice or monkeys.</p>

<p>We try all kinds of crazy thing on mice: breeding them <a href="http://blogs.discovermagazine.com/80beats/2009/12/02/study-biotech-mice-with-two-moms-and-no-dad-live-longer/" target="blank">without fathers</a>, <a href="http://blogs.discovermagazine.com/80beats/2008/07/11/stem-cells-treat-muscular-dystrophy-in-mice-can-humans-be-next/" target="blank">stem cell testing</a>, and experiments with <a href="http://blogs.discovermagazine.com/80beats/2009/06/15/stress-the-genetic-kind-really-can-make-hair-go-gray/" target="blank">stress and hair color</a>, just to name a few. One problem, though: Those little rodents are actually rather expensive. They cost $80 to $130 per experiment, <a href="http://blogs.discovermagazine.com/discoblog/2009/09/08/are-moths-the-new-lab-mice/" target="blank">some researchers argue</a>, while caterpillars are cheap guests, costing only 16 to 32 cents. </p><p>Because humans and insects have such similar immune systems--90 percent identical, by some measures--those researchers argue that employing more moths and other insects could reduce lab mouse demand by 80 percent. But bugs can't always get the job done; for that stress and gray hair experiment we might have to stick with mammals.</p>

<p>We know today that electrical signals are part of our central nervous system. How did scientists figure it out? Frogs. <a href="http://scienceworld.wolfram.com/biography/Galvani.html" target="blank">Luigi Gavlani</a>, in 1771, sparked a dead frog's muscles and saw it twitch. His interpretation of this turned out to be wrong in the details, but led to the modern understanding of bioelectricity. </p><p><a href="http://www.pnas.org/site/misc/classics4.shtml" target="blank">Robert Briggs and Thomas King</a> achieved the first cellular nuclear transfer in 1952 using a frog. Frogs remain a popular test subject, especially in reproductive studies because their developing embryos are easily <a href="http://www.google.com/url?sa=t&source=web&ct=res&cd=2&ved=0CBEQFjAB&url=http%3A%2F%2Fwww.lamer.lsu.edu%2Fprojects%2Fnativefish%2Fpdfs%2FLP10_Embryos.pdf&ei=Su0WS9-bOI-0tgeGorDnBA&usg=AFQjCNGgFi3yrucwQLftWoAHJi7hc_KuUw&sig2=3sLgvdheOOrUjgguZYtjHw">observable (pdf)</a> inside their jelly-like eggs.</p>

<p>You've got to be tough to get through life looking like this.</p><p>Naked mole rats are. While other creatures on this list are popular with researchers due to their short life cycles, naked mole rats can live for up to 30 years. You can pour lemon juice on their cuts and they won't feel it because they lack a neurotransmitter (ominously called <a href="http://pubs.acs.org/cen/critter/8202molerats.html" target="blank">substance P</a>), which allows scientists to perform unusual pain research. Their brain tissue can withstand oxygen deprivation for close to half an hour. Most importantly, <a href="http://blogs.discovermagazine.com/80beats/2009/10/27/what-can-we-learn-from-the-naked-mole-rats-immunity-to-cancer/" target="blank">they never get cancer</a>. </p><p>Bizarre animals often make for interesting research subjects, so expect naked mole rats to become more popular with scientists. Plus, they're kind of adorable, in a so-ugly-it's-cute way.</p>

<p>Mice and rats may dominate medical research, but if you want to study social behavior, it helps to have a hyper-social animal. Enter the prairie vole, which is particularly interesting to study <a href="http://discovermagazine.com/2005/jan/rakish-rodents-reformed/" target="blank">in comparison to</a> its cousin the meadow vole, pictured here. </p><p>Prairie voles are particularly interesting because they form long-term <a href="http://blogs.discovermagazine.com/80beats/2008/10/16/monogomous-rodents-lose-their-mojo-when-their-mates-are-gone/" target="blank">monogamous pair bonds</a>. Meadow voles, on the other hand, <a href="http://www.esf.edu/aec/adks/mammals/meadow_vole.htm" target="blank">are promiscuous</a> and try the "mate and move on" strategy, giving scientists the chance to study two closely related species with totally different mating habits. By studying the hormones at play in their brains and bodies, researchers hope to understand the roots of human monogamy--and monogamy failures.</p>

<p>Prototype contact lenses--be they <a href="http://blogs.discovermagazine.com/80beats/2009/11/10/who-needs-sunglasses-new-contact-lenses-respond-to-light/" target="blank">UV-sensitive</a>, <a href="http://www.wired.com/dangerroom/2009/11/could-self-assembling-contact-lenses-become-head-up-displays/" target="blank">self-assembling</a> or <a href="http://blogs.discovermagazine.com/sciencenotfiction/2008/11/11/seeing-the-future-literally/" target="blank">containing an integrated circuit</a>--are always tested on rabbits, it seems. Why? Because we've tested rabbit eyes for years. </p><p>The Draize test, created in the 1940s, requires products that could be damaging to human eyes or skin be tested on animals for four hours to measure the irritation; researchers most frequently use rabbits. However, more and more <a href="http://www.google.com/url?sa=t&source=web&ct=res&cd=1&ved=0CAcQFjAA&url=http%3A%2F%2Fwww.iivs.org%2Fdocuments%2F49.pdf&ei=5jsYS8KyK8qztgeJoannAw&usg=AFQjCNFVl9zRtBGv8fvGWfI4Dw6CmxIWtg&sig2=1BENATPQf0OQTYW7G1dcUg">scientists have questioned (pdf)</a> both the validity of the test: it might not be especially useful, given the differences between rabbit and human eyes.</p>

<p>The same things that make beagles great pets--their even temperament, a lack of inherited disease--make them ideal test subjects. Many pharmaceuticals and food additives have been tested on beagles as a prelude to human testing. </p><p>Much to the delight of tenderhearted canine lovers, dog testing is on the decline. In Britain, dog testing dropped to <a href="http://www.official-documents.gov.uk/document/cm68/6877/6877.pdf" target="blank">0.26 percent (pdf)</a> of all animals used in 2005, though almost 97 percent of the dogs in that reduced population were beagles. British lab Huntingdon Life Sciences <a href="http://news.bbc.co.uk/2/hi/uk_news/1123837.stm" target="blank">endured years of protests</a> after a 1997 videotape caught workers hitting beagles.</p>

<p>Pigs have always been one of the best animals for doing organ research. The size of their organs roughly corresponds to ours. They reproduce faster than our nearest relatives, apes, and raise fewer ethical controversies. We've also figured out how to create <a href="http://blogs.discovermagazine.com/80beats/2009/06/03/making-pig-stem-cells-raises-the-possibility-animal-organ-donors/" target="blank">pig stem cells</a>. </p><p>But dreams of transplanting pig organs into humans have run up against the last big barrier: the fact that putting a pig organ in a person causes hyperacute rejection. There's also the fear of <a href="http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/T/Transplants.html" target="blank">spreading pig retroviruses</a> into humans.</p>

<p>In November we reported on the Puerto Rican area that's <a href="http://blogs.discovermagazine.com/discoblog/2009/11/30/puerto-ricans-are-tired-of-escaped-belligerent-research-monkeys/" target="blank">sick to death of patas monkeys</a>, as these descendants of escaped lab monkeys continue to terrorize the town. Now a biotech company wants to host a new generation of lab monkeys there.</p><p>Few labs use patas monkeys anymore, but other monkeys still abound in research. Their biological processes are fairly similar to those of humans, but they have a shorter life cycle than apes and are easier to control. (Try telling that to the Puerto Ricans.) A 2004 census of U.S. testing found that monkeys, especially rhesus macaques, made up the majority of non-humans primates that scientists test.</p>

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