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One of the weirdest things about pea aphids is their reproductive cycle. Most animals reproduce in one of two ways: asexually or sexually. But the pea aphid does not stick to just one type of reproduction...and it gives birth to pregnant clones.

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When people find out that you make a YouTube show about weird animals, it's pretty common for them to suggest what you should cover next.

Sometimes they're gonna suggest their favorite critter, because they want everyone to know that it exists. Other times they suggest something super rare or something that just looks really weird.

But those people don't know what they are talking about. Cause they never suggest animals that are incredibly common. That are not what one might call ‘charismatic.’ But they should.

Because, if I’ve learned anything from this channel, it’s that even animals I can find in my backyard are bizarre. Why didn’t anyone tell me that pea aphids were keeping a secret?! [ ♪♪ INTRO ♪♪ ] Before we get into this episode, the Bizarre Beasts pin club is open for subscriptions again from today through November 13th! Sign up now and the first pin you get will be one of these Bizarre Beasts!

Aphids are tiny, soft-bodied, sap-sucking insects. There are around 5100 species of them and they can be found almost everywhere in the world, except places that are very cold. And unlike a lot of other groups, they're actually more diverse in the temperate parts of the Northern Hemisphere than they are in the tropics or the Southern Hemisphere.

Around 250 species of aphids are considered pests because of what they do to plants that we care about, like crops, or houseplants, or my cherry tree! And they suck up a lot more of the nutritious kind of plant sap, called phloem sap, than you’d think they need, because it has a lot of sugars, but not a lot of nitrogen. And so they excrete those extra sugars and the liquid as a sticky fluid called honeydew, which sooty molds can grow on, which is part of what makes us think of aphids as pests.

Now pea aphids are mostly pests of legumes, as you might expect from the name. They can transmit yellow bean mosaic virus, which kills pea plants, but they also can damage lentils and alfalfa. Pea aphids probably originated in Europe or Asia, but have since spread to a lot of places with temperate climates, including here in Montana.

And one of the weirdest things about pea aphids is their reproductive cycle, which they share with some other aphids. So, most animals reproduce in one of two different ways: asexually or sexually. And there's a bunch of different kinds of asexual reproduction.

There's fission, where an animal basically rips itself in half and then each half regenerates any parts it needs to be its own animal. Or fragmentation, which is like fission, except the animal doesn’t need an entire half to regenerate from. Or budding, where a small individual grows, or buds, off of a larger one, and they eventually separate into two animals.

And then there’s parthenogenesis, where an unfertilized egg develops into a new individual. If you’re a long-time Bizarre Beasts fan, and why wouldn't you be, you may remember us talking about parthenogenesis before, in our seagrass-eating shark episode, but that was kind of a one-off for the shark. It can happen, but mostly they reproduce sexually.

Which is the other option that animals have. In sexual reproduction, one sex brings the sperm to the party and the other sex brings the eggs. And what happens from there is actually more complicated than it might seem.

There are essentially four options. You either get eggs fertilized outside of the body, eggs fertilized inside the body and then laid, eggs fertilized that then hatch inside the body or are laid just before hatching, or live birth. But the pea aphid does not stick to just one type of reproduction.

The pea aphid reproduces both asexually and sexually, and not just as a one-off. Their life cycle goes like this: pea aphid eggs are laid in the fall and they just hang out in a period of suspended development during the winter. This is probably an adaptation to food being scarce in the winter in cold climates.

In warmer climates, some species of aphids don’t lay eggs at all. In the spring, those eggs hatch into a generation of wingless females, which then give live birth in the summer to even more pea aphid females via parthenogenesis. Pea aphids only have hot girl summers.

And those females can be born with wings or without wings, depending on a bunch of factors. Including how crowded their mothers were, the quality of the host-plant they lived on, and the presence of predators. Crowding, food stress, and predators produce females with wings by subjecting their mothers to chemical and tactile cues that signal to the developing daughters that they’re more likely to reproduce successfully if they can leave.

Which on its own is very weird! Then, in the fall, as the days get shorter, this change in the amount of light the aphids experience triggers the birth of a single generation of sexually-reproducing aphids, both males and females. The males can have wings or no wings, but the females are all wingless.

For the males, having wings means they can disperse to better food sources and avoid inbreeding. For the wingless females, it probably comes down to an energy trade-off: not using energy to build wings means they can use it to maximize egg production, instead. So this one generation mates, exchanging genetic information, the females lay their eggs, they overwinter, and the cycle begins again in the spring when the parthenogenetic females hatch, already pregnant with their clone daughters.

While the pea aphid might be among the most common and widespread of the creatures we’ve covered on this show, it reminds us that it’s always worth taking a second look at the animals that seem most familiar to us. We are so excited to announce that Bizarre Beasts calendars are BACK. We picked 13 of our favorite past beasts and worked with artist Greer Stothers to create backgrounds that highlight each gorgeous original illustration.

Every beast also comes with a blurb full of bizarre facts! Get your limited edition 2024 calendar now at [ ♪♪ OUTRO ♪♪ ]