Everything You Never Wanted to Know About Snail Sex | Deep Look

Besides being hermaphrodites — all snails have both boy and girl parts — they stab each other with “love darts” as a kind of foreplay.


SUBSCRIBE to Deep Look!

DEEP LOOK: a new ultra-HD (4K) short video series created by KQED San Francisco and presented by PBS Digital Studios. See the unseen at the very edge of our visible world. Get a new perspective on our place in the universe and meet extraordinary new friends. Explore big scientific mysteries by going incredibly small.

The sex life of the common snail is anything but ordinary.

First, they’re hermaphrodites, fitted with both male and female reproductive plumbing, and can mate with any member of their species they want.

Sounds easy, but the battle of the sexes is alive and well in gastropods.

In nature, fatherhood is easier. It’s the quickest, cheapest way to pass on your genes. Motherhood requires a much greater investment of time, energy, and resources.

During courtship, the snails will decide who gets to be more father than mother. But their idea of courtship is to stab each other with a tiny spike called a love dart.

The love dart is the snails’ tool for maximizing their male side. It injects hormones to prevent the other snail’s body from killing newly introduced sperm once copulation begins.

When snails copulate, two penises enter two vaginal tracts. Both snails in the pairing transfer sperm, but whichever snail got in the best shot with the dart has a better chance of ultimately fertilizing eggs.

In some species, only one snail fires a love dart, but in others, like the garden snail, both do.

You can spot love darts sticking out of snails in mid-courtship, and even find them abandoned in slime puddles where mating has been happening.

Scale it up to human size and the love dart would be the equivalent of a 15-inch knife.

— How common is hermaphroditism?

Less than one percent of animal species are hermaphrodites. They’re most common among arthropods, the phylum of life that includes snails.

— How do hermaphrodites decide who’s going to the male and female?

In most cases, both individuals will be both male and female, to some extent. Sometimes, like with garden snails, it’s a question of degree.

— Can a love dart kill the snail?

In theory yes, but not very often. One researcher told us that in the thousands of matings he’s observed, he’s seen only one snail die that way.

—+ Read the entire article on KQED Science:

—+ For more information:

Visit Joris Koene’s site. He’s one of the world’s foremost snail and slug researchers:

—+ More Great Deep Look episodes:

Banana Slugs: Secret of the Slime

The Ladybug Love-In: A Valentine’s Special

—+ See some great videos and documentaries from the PBS Digital Studios!

Gross Science: Help a Snail Find True Love!

4 Valentine’s Day Tips From the Animal World!

—+ Follow KQED Science:

KQED Science:

—+ About KQED

KQED, an NPR and PBS affiliate in San Francisco, CA, serves Northern California and beyond with a public-supported alternative to commercial TV, Radio and web media.

Funding for Deep Look is provided in part by PBS Digital Studios and the John S. and James L. Knight Foundation. Deep Look is a project of KQED Science, which is also supported by HopeLab, the S. D. Bechtel, Jr. Foundation, the Dirk and Charlene Kabcenell Foundation, the Vadasz Family Foundation, the Gordon and Betty Moore Foundation, the Smart Family Foundation and the members of KQED. education