Yogurt-eating mice have larger testicles and "mouse swagger"

A study at MIT involving mice fed a diet of vanilla yogurt with probiotics yielded interesting and unanticipated results:

First, the scientists noticed that the yogurt-eating mice were incredibly shiny. Using both traditional histology techniques and cosmetic rating scales, the researchers showed that these animals had 10 times the active follicle density of other mice, resulting in luxuriantly silky fur.

Then the researchers spotted some­thing particular about the males: they projected their testes outward, which endowed them with a certain “mouse swagger,” Erdman says. On measuring the males, they found that the testicles of the yogurt consumers were about 5 percent heavier than those of mice fed typical diets alone and around 15 percent heavier than those of junk-eating males.

More in SciAm. The fact that these manly-mouse-man results were achieved from girly-vanilla-yogurt is not lost on me.

But I want to know is, how exactly does one go about weighing the mice's testicles? Your thoughts in the comments. (via Ed Yong)


    1. They kill the mouse and cut the testicles off, then they weigh them with a scale.

      1.  Yes, but the blindingly obvious isn’t nearly as entertaining of a thought as a mouse sighing and going “Not this shit again.”

  1. To weigh mice testicles you remove them from the mouse and place them on a scale.

  2. Hmmmm. Would this mean that, say, the males of pretty much all Mediterranean countries have larger dangly bits?

  3. Actually, they sacrifice the mouse, cut out the testes, and weigh them. Usually volume measurements are taken for testicles, but weight works, too.

    1.  Yep. Grip head in large forceps. Use tail to give the body a sharp snap from side to side. Broken neck, severed spinal column, quick and — presumably — fairly painless death. Dissect and assay effects of the experiment.

      Obviously this presumes this particular mouse will not be continuing the experiment.  Lab mice are pretty close to being genetically identical, so it’s presumed that other mice can provide the later samples.

      NOTE: The old-fashioned spring mousetraps are actually more humane than glue traps and the like — they kill the same way. Yes, they require that you look at the dead mouse, so maybe they’re less humane to squeamish humans… but the alternative really is worse.

      (In case you’re wondering why I know this: “The Effects of Cys-Dichloro-Diaminio-Platinum-II on Ehrlich’s Ascites Tumor”, a study we reproduced in high school as part of a summer science program.)

      1. The old-fashioned spring mousetraps are actually more humane than glue traps and the like

        They’re still not all that humane. The humane part requires that the mouse place the correct body part in the correct place. Those can snap down on a snout or a leg.

      2.  I once had to shoot a mouse with a bb gun after it tried to run through a spring mousetrap and nearly got cut in two parts. A mouse screaming in pain while dragging the trap around the floor sure ain’t no fun to hear. Gave me a lesson about where Not to place a trap. The rest of the traps worked fine, though…

  4. OR:

    1) Carefully weigh mouse.
    2) Remove mouse balls.
    3) Weigh mouse again.
    4) Subtract weight from 3 from weight from 1.

    I’m buying yogurt on the way home. I was planning on doing this anyway, mind you. But now I’m buying more.

    If y’all hear that I’ve been arrested for shtupping female mice, you know what happened.

    1.  It’s not often I hear “y’all” and “shtupping” in the same sentence.

  5. It’s true, testicle weights were probably terminal, but there’s another way to do it!  

    Long term measures of rodent testicular development rely on a little anesthesia and a pair of calipers.  Multiply width^2 * length and you get the so called “estimated testicular volume” which is linearly related to testis weight.   

    Not that I spent too much time my first year in grad school squeezing rodent nuts…

  6. they weigh the junk food dead mouse against the weight of a yogurt mouse and assume the difference is in the enlarged vis atrophied scrotum sac. Hence the balance of the balls.

  7. This is all fake!  No manly, ball dragging, yogurt eating, swaggering mouse would allow anyone near his junk!

  8. With balls that big, the mice just walk up and plop them on the scale for bragging rites.

    1.  Bragging rites?  I’m pretty sure I’ve witnessed that.  Maybe participated.

  9. SURGEON GENERAL’S WARNING: Eating yogurt may lead to unexpected testicular growth and advanced swag.

  10. I know I’ve always wanted bigger, heavier balls that affect the way I walk.  Girls tell me that constantly.

  11. Next Thanksgiving when these researchers are trying to explain to their relatives yet again exactly what they do in the lab, they can say, “I castrate mice and weigh their balls. Things like that.” No need to explain it again next year.

  12. “In mating experiments, yogurt-eating males inseminated their partners faster…”

    So, males who don’t eat yogurt inseminate the partners slower and longer.  Okaaayyy!

  13. Once the mouse balls are removed for weighing, the opportunity should be taken to clean the accumulated crud from the little rollers they nestle in. Cotton wool bud usually does the trick.

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