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This Is Why A Mouse's Sperm Is Longer Than An Elephant's Sperm

A mouse’s sperm is much, much larger than an elephant’s sperm. A fruit fly produces the longest sperm known to science. Why do tiny animals make big swimmers, but large animals make small ones?

The Last-Ditch Fertilization Method For Infertile Men Just Got More Reliable

For the past 25 years, men whose sperm can’t manage the arduous swim across a Petri dish have had the option of injecting a single sperm cell directly into an egg. But that method still left some sterile men out in the cold.

Women Aren't The Only Ones With A 'Biological Clock' -- Men Lose Fertility As They Age, Too

Women know that menopause can put a “sell by” date on getting pregnant, but common wisdom says that men retain much of their fertility well into old age. That common wisdom is wrong.

Here's How Ejaculation Actually Works 

Ejaculation may feel like a glorious mess, as uncontrollable as an avalanche or a runaway train. In reality, it’s a tightly choreographed court dance: integrating three different branches of the nervous system, triggering cascades of contractions in smooth and striated muscles, all accompanied by the electrical storm of orgasm. Here’s how it works.

This Video Proves That Penguin Sex Can Get Kind Of Messy

Video: Two penguins at the Monterey Bay Aquarium decided to make baby penguins in front of their viewing window. In the process, they showed off a fascinating aspect of bird reproductive biology.

Watching These Sperm Cooperate Is Oddly Fascinating

Get your Sunday started right by watching how sperm sometimes form power-swimming blocks to get ahead. And learn why these particular sperm get together.

There Are Special Neurons That Tell The Brain It's Time To Make Babies

Biologists already knew that one set of neurons play a big role in triggering puberty. A new study shows that these neurons don’t stop working once puberty ends, but keep running through adulthood, serving as a sort of reproductive timer.

How Sperm Cells Get Stripped Down And Ready To Race

Lots of human cells are specialised, but I can’t think of any that are as stripped down to a single purpose as spermatozoa. Sperm have just one job, and they will die doing it.

Chemically Freezing Sperm Tails Could Be The Key To A Reversible Male Contraceptive

As sperm swim they transform chemical energy into motion, the way a car’s engine uses gas to propel you down the road. Like that engine, the process is complicated — if just one part stops working, the whole system can grind to a halt. This idea might lead to a contraceptive for men that’s reversible.

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