Short Wave - New Discoveries In Underwater Plant Sex

Episode Date: October 24, 2022

Plants living underwater can't count on pollinating insects to get it on. The prevailing theory has been that pollen moves underwater simply by floating around in water currents. But a team of researchers co-led by Dr. Vivianne Solís-Weiss, have discovered a helper organism pitching in to pollinate seagrasses: marine worms. In today's episode, Vivianne tells Short Wave Scientist in Residence Regina G. Barber how she happened to catch these worms, called polychaetes, in the act of pollinating seagrass flowers underwater, and how the discovery is shedding new light on evolution in the oceans. See pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences.NPR Privacy Policy

You're listening to Shortwave from NPR. Hey, short wavers. Today we're starting out with the story of the birds and the bees. No, like the actual birds and the bees. We're talking pollination. Okay, quick plant sex ed talk. Plants reproduce when pollen from a male flowering plant ends up in the female part of a plant. That fertilization leads to seeds, the embryos of the plant world.

And though a flower can pollinate itself, cross-pollination between plants give them the advantage of increased genetic diversity. Dr. Vivian Solis-Fice says, for the garden variety land plant, there are two main ways cross-pollination can happen. One is airborne, taken by the wind, and they eventually end up in the female flower and pollinated. The second is by insects. In general, it's bees or butterflies that are, attracted to the male flower. Vivian studies pollination, but not in any of the plants we grow in our gardens. So in the ocean, no one ever imagined that there was an animal that could influence this sexual reproduction. So it was accepted that it went only through water currents.

And it's exactly like with the wind, except it's water. Viviann and our team discovered pollinators in the ocean for the first time ever. Today on the show, how Vivian and her team made their landmark discovery, what underwater plant sex looks like, and why the research is currently on hold. I'm Regina Barber, and you're listening to Shortwave, the Daily Science podcast from NPR. Vivian Solis-Vice is an oceanographer at the Institute of Marine Sciences. Puerto Morelos, Quintanaro, in Mexico, close to Cancun. She specializes in a kind of marine invertebrate called polychaetes. They're also known as marine worms, although they can get fancy-looking.

Even though some look like worms, there are others that they call the Christmas tree worms. They are beautiful. When you see corals, at some point, you will see like tentacles or like a little Christmas tree, which can be orange or red or whatever. These are polykids, and others look like flowers. And they look like whatever, because there are 14,000 known species. So they come out at night to feed. They stay during the day embedded in the sediment

so as to avoid the predators that would eat them. Vivian had studied these worms for years, discovering dozens of new species. And then, one day, she got a call from a colleague who worked with ocean seagrasses. Seagrasses are underwater plants, unlike, say, seawoids, most of which are types of algae. And seagrass beds happen to be where the marine worms she studies live. A well-known botanist called Brigitte Van Tuthenbrook. She approached me as a zoologist to know what did I think of finding there these invertebrates in the flowers. It was an intriguing question, because these plants are unique.

About 100 million years ago, some plants, some grasses, which are called now sea grasses, they went back to the sea, the sea grasses will stay in the sea forever. They cannot go back because the DNA changes were too big. Changes like surviving in salt water and losing those little pores they use to absorb air. But these grasses kept their flowers. which had something in common with Vivian's marine worms. Coincidentally, we discovered that the flowers open up at night. The female flowers can open any time, but the male flowers only open up at night,

and they release pollen just after night has set on. Vivian and Brigita had a feeling they were on to something, but they didn't know exactly what. Brigitte herself asked, do you think they do something? to pollinate? Well, I said, I don't know. Remember, underwater plants were thought to reproduce

just from pollen drifting in the currents. Having a helper organism in there was a totally new idea. So they made a plan to figure it out. So we would go before the sunsets and we would put cameras there. Close to the flowers. The flowers, by the way, are very hard to locate

because they are very small. and they are very close to the ground, like one or two centimeters to the seafloor. When the team went back and reviewed the videos, they saw marine worms and other small animals visiting flowers and getting pollen stuck to their bodies. They hypothesized that this could be evidence of animal pollination in the ocean. I must say that when we first wanted to publish those results, we met strong opposition, especially the journals are in the United States,

And they wouldn't believe us. So they said, this is only an hypothesis that you invented, and it's not possible, especially because we are Mexicans. But anyway, finally, we could get through. And so they published it. The next step was to show that this pollination could happen without any water currents. So the team recreated the experiment. They put seagrass in aquaria with different polychaids and crustaceans.

What we saw is some species of polygates that can swim. It makes movements directed to the flower. You can see them foraging, which is looking for food inside. And that's how they get all the pollen grains attached to their body parts. And we found them also with pollen grains in the body, not only around the body, which means they are also eating it. They publish their results from the aquarium studies in a big name journal in 2016. So now nobody can deny it.

And now it's a fact. Vivian says these findings change the way people who study life in the ocean think about its evolution. And it gave her the chance to revel in the feeling of discovery. I feel real, real great because it's something nobody has seen before, nobody had imagined before. This is evolution that we are witnessing. We know they came back to the sea about 100 million years ago, but we didn't know how similar can the situations be between inland life for those grasses and what is happening now under sea, you see?

So it was such a joy to be there, you know, in the scuba diamond. and I felt immediately that it was very important in our knowledge of how evolution develops. But the pollination research had hit a serious ecological roadblock. In fact, the work had basically ground to a halt while they deal with an interloper. Deadly blooms of algae called sargassum. It's kilometers and kilometers of that sea of sargassum. It's 60 centimeters deep. However, with the climate change, with the warming of the seas, they began to grow out of control

and they began to drift with the Gulf Stream and then to Africa and then they crossed the Atlantic to get to Brazil and then the current takes them down to here, down to Florida, Carolinas and it will eventually get to New York. So we are trying to save the ecosystem that are beneath. And once we save them, we can return to the basics. But right now is a problem of survival that we are enduring. Now Vivian is working on what to do with the sargassum that washes up on the beaches and rots. It begins to be like a corpse who is rotting in front of you because there are tons and tons and tons that accumulate every day.

And they will make you sick. and eventually you will die if you stay there. If the seaweeds are there, the algae, the sargassum, it will kill everything which is underneath. Our group is focused from the detection with satellites from NASA to the final disposal. First, to avoid having it come to the beach and then when it is in the beach, because it will get there, some part of it, what do you do with it? So this is, everyone is focused on that. Scientists can figure out how to eradicate all this toxic algae, Vivian can get back to the business of studying underwater plant love again. I think it's very romantic to know that, you know, you have plants there that are pollinized exactly the way we see the bees and the butterflies in land.

Although maybe because it happens at night, we should think more of the bats and moths, but I think it's more. romantic to think of them as butterfly zombies. Vivian Solis Weiss is an oceanographer at the Institute of Marine Sciences in Mexico. This episode was produced by Burley McCoy, edited by Gabriel Spitzer and fact-checked by Margaret Serino and Albi Levine. The audio engineer was Valentina Rodriguez Sanchez. Giselle Grayson is our senior supervising editor. Brendan Crump is our podcast coordinator. Our senior director of programming is Beth Donovan and the Senior Vice President.

president of programming is Anya Grinman. I'm Regina Barber. Thanks for listening to Shortwave from NPR.