She's a Crustacean. She's a Mom. She's a Roly Poly.

Added: 2026-05-12

[00:00:00]What does this roly pololy have in common with a kangaroo?

[00:00:04]Here's a hint. It's all about her parenting style. Unlike mammals, most insects take a hands-off approach. They find a good spot, lay their eggs, and move on.

[00:00:18]Good luck, little one.

[00:00:21]But roly pololies, also called pill bugs or doodlebugs, aren't like most insects.

[00:00:28]Actually, they aren't insects at all.

[00:00:31]They're crustaceians like shrimp and lobsters.

[00:00:37]Roly polies belong to a group of crustations called isopods which originated in the sea.

[00:00:44]About half of isopod species still live there. But Roly Poli's ancestors ventured out onto dry land, and they brought with them a maternal adaptation from their aquatic past.

[00:00:59]After mating, a female roly pololy transfers her eggs into a fluid-filled pouch on her underside called a marupium.

[00:01:10]At first, the marsupium just looks yellow. But it doesn't take long, just a few days, till you can spot the eggs, about 40 to 60 of them. Keeping them close is a good strategy. If she were to lay her eggs on land, they'd dry out.

[00:01:28]They don't have the protective outer barrier of an insect egg to keep moisture in.

[00:01:34]But inside their mom's marsupium, the eggs have their own tiny ocean.

[00:01:40]Roly polies are clad in overlapping armored plates called perionites.

[00:01:47]If she gets spooked, she can curl up in a perfect little ball to shield herself and her babies.

[00:01:56]The marsupium is protected by more plates called oastagites, but they're thinner, almost clear, like a window into her nursery.

[00:02:08]After 3 to 4 weeks, the babies, now called Mankey, emerge from the eggs.

[00:02:13]They look like miniature yellow versions of their mom. But they aren't ready to face the world yet. They keep developing inside their mama's pouch for another week or so. As they mature, they start getting restless.

[00:02:29]60 squirming babies in one crowded pouch, a feeling only a mother could love.

[00:02:37]The mankey eventually wrigle out from between the plates covering their mom's pouch.

[00:02:44]Then after about a month of being little pouch potatoes, they're on their own.

[00:02:51]They'll go on to do the good work of detrites, eating rotting wood and leaves, recycling the nutrients back into the soil. And one day, the females will get to host their own pouch parties.

[00:03:07]Marsupials and isopods tell a story of convergent evolution. Two wildly different animals who come up with a similar solution. But unlike a kangaroo, a roly pololy mom doesn't invite her babies back in for a ride. She gave them a nice cozy upbringing. Now it's time for them to venture out and let the good times roll.

[00:03:31]If you like this video, please consider supporting KQED, the PBS station that produces Deep Look. Donations from viewers like you allow us to continue making our awardwinning series. Click the link on screen or in the description below. Now, check out the Six Raid Sea Star, another very overprotective mom.