Interview Interlude Playlist, Part 8: Marah Hardt

Christian Seger. And that may have sounded like the Dr. Seuss version of Coral Sex, but actually it was a bit from mar j Hart Sex in the Sea, which we've talked about on the show before and we're gonna do again this episode. Yeah, it's a great book. We talked about it in our previous episode that was devoted to the weird sexual ways of the Asso Docks, the bone Worm, the bone eating worm of Ocean, And in that episode, Corals came up and we said, hey, there's

a lot of stuff to discuss here. Why don't we just have you back on in the summer, We'll do a whole episode on corals, and we wanted to time it for this summer because we're in corals spawning season

right now, as mar will discuss with us. So the way this episode is going to be set up is we're gonna give you just like a brief primer on corals and their reproduction, and then we're gonna talk tomorrow because she's the expert on this, and we really get into all the details, especially because Mara just got back a week ago from the what sounds like the world's biggest conference on coral ecology, so she had a lot

of like groundbreaking news for us. Yeah, some of some of it rather sobering, but some of it very exciting as well. You know, I think one of the big tay comes here that I got out of the research that I hope that that that listeners get to is this idea that and I feel like this sometimes lost in our media absorption of the information, is that coral

reefs corals are not just like a background organism. They are the bedrock of these ecological systems, making life possible in areas that would otherwise just be barren and lifeless. I think for a lot of people, the way that they think about them is almost as if that they're like plant life and I have to admit, even for myself, until we sat down and really did the research for this episode, I didn't quite understand their anatomy. And so maybe that we can sort of help set that up

for the audience for you out there. And uh, then when we talk tomorrow about just how dire the consequences are right now for coral ecology, that'll, you know, drive home the importance of trying to help these critters out. Yeah. I feel like at times we almost have an amateur aquarium um view of it, where we think, oh, I'm the fish is what I'm excited about. Anything else is just like a plant that we throw in, or maybe like a ceramic Buddha that flows to the bottom right.

And then in looking at the coral reefs to we we see the finished picture. We see the corals, we see all the fish and all the creatures. I feel that it's kind of like looking at Las Vegas and seeing all this life, all the light and the fountains and saying, look at that life is just splendid there. It's just going just going splendidly without realizing that without Hoover, damn, without the with the necessary um um, you know, water

system in place, there would be no life there at all. Yep, yeah, exactly. Corals are a hugely important ecosystem for and this is a stat a quarter of all marine fish species, so they're very important. They're not just pretty structures that happen to be underwater. They also benefit us, and by us, I mean human beings by buffeting coastal regions from strong waves. And I'll get into it a little bit further. Uh, they promote our economy and huge way is too. So Uh,

these are super important. And they have totally weird, bizarre orgy sex too, which is fun to talk about. So let's get into it. Let's talk about coral reefs and coral polyps and what's the story here. So they're actually made of two things. Now, when we think about corals, or at least the way I did, I always thought of just the limestone skeletons, right, these these formations. But corals themselves are actually tiny little polyps. Uh, and they

excrete the limestone that creates these skeletons. Now, I said earlier, we talk a lot about sort of the dire threats that they're facing. They're actually being destroyed at a rate that will see seventy of them gone in less than forty years. That was one stat that I read when we just talked tomorrow. She said ten percent of all reefs are already permanently lost are expected to be lost in the next few decades. So that's that's the lot um. And why is that? Well, we talked to her about

that as well. But real quick primer, if you even shift one degree of temperature in the water that they're in, it can damage them, causing them to expel the algae that's within them, which they have a symbiotic relationship with this and this is the key to their ability to colonize these these rather hostile regions. Absolutely, yeah uh. And they're also facing external threats from hurricanes, predators, pollution, over fishing,

and from us. Just talking tomorrow, she did a great job of explaining what a bleaching event is, which is the actual impact of these temperature changes causing the algae to separate from the coral polyps and basically either killing them or making it so that they don't have enough energy to reproduce. So why should you care? Here's why. If you want just a purely selfish reason, If all you care about is your own well being. It's import

to our economy. Actually, uh, they provide jobs for fishing, construction, and believe it or not, pharmaceuticals. There's an estimated three hundred and seventy five billion dollars a year that come out of coral reefs, So that's pretty huge. We don't want to lose these, even on just like a purely selfish monetary level, outside of any kind of like altruistic ecological level. Okay, alright, let's roll into the basic biology of corals. Okay, So corals were originally thought to be planted,

so I wasn't alone in that. And if you're out there and you thought the same thing, scientists thought that too. But they're actually tiny, little soft bodied creatures and their carnivores too. They're fixed to one spot as a polyp, and it's they basically have these barbed stinging cells that are called nematocysts, and these are what they used to capture food, like little tiny fish or zoo plankton. They're only about three millimeters long, and they grow to become

reefs that stretched from miles. When they combine together with their limestone and their huge colonies, the polyps themselves are basically and and Mara says this as well. They're basically just a gut with a mouth that's surrounded by tentacles. So it's like a teeny tiny little Lovecraft monster. Yeah, the thing that you discredited as a mere plant turned out to be closer to your heart exactly. Now, we

talked about the symbiosis that they have with algae. Well, the algae that they live together with are called zoos in Theelli and uh Um I believe Mara says that it's okay to refer to them as zooks. That's that's kind of like the the in crowd nickname that they have. But they're an algae that lives inside the cell walls of corals, and the algae provides them with byproducts of

photosynthesis that then feeds the polyp. The polyps subsequently shelters the algae and provides them with the chemicals that they need for photosynthesis. So up to of the algaees energy is transferred into the polyps. So you can see now why if that algae is forced to flee because of coral bleaching, why the polyp would be weakened significantly. Okay, so this energy helps them to do things like produce the limestone that they are covered in, and that's made

of calcium carbonate. They secrete it from their base and it creates a protective skeleton that they basically hide in from predators. And because they rarely exist alone, they also joined together with other polyps as a colony and act basically like a single organism colonies. Now I just told you one polyp is like three millimeters. Colonies can weigh tons. These things are huge, uh, and they have many branches

that form out, and this is what we call reefs. Okay, so let's get to the nitty gritty of what this is about, all right. That today's episode is about coral sex re production. And they reproduce in two ways, or they grow in two ways. The first is they just keep adding limestone to their base and they secrete upward and outward, right, so the reef gets bigger that way.

The main way what we end up talking to Ma about primarily is reproduction, and they produce a sexually and sexually a sexual reproduction is where they divide and create identical clones of themselves. And we're gonna talk tomorrow about why that's not always such a good thing. But they can basically make fragments of themselves and then reattached to different parts of a reef and then continue to grow.

Sexual reproduction this is the weird stuff, and this is what we spend a lot of time talking with Mara about. This is basically when they send out their eggs and sperm, and it works like this. Their sexual reproduction only occurs once a year, shortly after a full moon. It's called broadcast spawning, and this is where the colonies release a cloud of rightly colored eggs and sperm into the ocean.

And these bundles are not only buoyant, but they are also attached to their parental polyps by like umbilical strings of mucus. Mara describes it as being like this pink cloud of snow flakes floating upward. It it sounds kind of beautiful, actually, if if you get the opportunity to see it. Shrimp and worms that are around there part of the ecology of the coral reef. They're gonna eat this stuff as it floats upward. But but basically the

polyps turn pink right before they release it. One of the articles that I read for research on this described it as milky, pink waters. The eggs are then ejected, they float upward to the surface and they wait to get fertilized. But they have nothing to protect them, so the first twelve hours that they're out there in development, they're real fragile. Mara actually describes these globules. She says this in her book and in our interview with her,

and I like it. She says they look like pink orange nerd candies, which is pretty fun um and gave me like a really good picture because I, I don't know about you, Robert, but I've never been to a beach area that has coral reefs, and I grew up on the ocean. Um. I had not really experienced it until earlier this year when I went to Jamaica and got to Snarling h with the with my wife and see some of it in action, and I was just

really blown away by it. Because there's one thing to see, like the super HD footage and it's beautiful, but it seems like another world. It's like watching Avatar, but totally to actually poke around there and see it in real life, it's it's quite amazing. So one of the things we talked tomorrow about that no one quite has the exact answer to is how these corals are timing it so that they all spawn at the exact same time every year.

And there's a theory that the solar they're they're taking solar cues or wind cues to figure out the month that they should spawn in, and then they're taking nooner cues somehow to figure out which day they should spawn in. Us Alian scientists have recently found out, however, that when they're exposed to even tiny little waves, that coral can break into identical pieces that can each develop their own larvae. So this is the clone process. It's similar their stem

cells then reassemble and continue to develop. So there are a lot of identical twin coral polyps out there. But as we talk about with Mara, that's not very that's not exactly a good thing if you need diversity to sort of protect you from ecological problems. So, but we have billions of naked embryos on the surface of the ocean during these spawnings, there's a potential to create even

more clones. When they conducted this first experiment that I was speaking of in Australia, fifty of the embryos that they exposed, fragmented and then reorganized so they could develop larvae. So the cloning thing is is fairly prevalent. Now. Sent of the zooks algae corals, those are hermaphrodites, and they're basically both male and fee male. They can release sperm and eggs, but some are only male and some are only female. Uh. Some even fertilize their own eggs internally

if they can snatch up the sperm. This is called brooding. They also release fully developed larvae. Now, the sexuality of these uh particular polyps tends to be consistent across the different species of corals that we're talking about here. Another number seventy of the zooks corals also spawn eggs and sperm for external fertilization. So the broadcast spawning we're talking about is their majority of their reproductive process. So this is this is contrary to the brooding that I was

speaking about earlier. Now, when species brewed like I'm talking about this is when they're fertilizing their eggs internally, they can store the unfertilized ova for weeks at a time, whereas spawning species requires this very specific time frame of hours that we talked about with Mara, sometimes colonies of different species spawned simultaneously. This is when hybridization occurs. We know that it happens, we just don't really know the extent.

And as we'll talk about with Mara, most hybrids are sterile, but it's hopefully avoided when most species of polyps spend their time spawning at different intervals. Um we talk about that as well with particular kinds of species the boulder coral and what was the other one, lobe star coral and and indeed there are also some some interesting twists and turns with hybridization that I think everyone will will be rather delighted by. Yeah, and we were totally surprised

by two because it's a brand new research. Another thing that's super fascinating about this broadcast spawning. It can happen over vast distances. Corals can basically take extended sea voyages once they float to the top, and they can survive for months before they fully integrate and sink back down to the bottom. Now, when an egg does get fertilized after the embryo forms, it's it actually swims, so so sinking isn't really the right term I should have used there.

It swims to the bottom to anchor itself. And scientists thought until four that all coral reproduction was internal like this brooding method. But then in Science magazine somebody published a description of the mass spawning event at the Great Barrier reef. And here we are now, you know, spending an entire episode talking about it. So this is relatively

new science to humans. A study in a Smithsonian article that I read for this that's called watching Coral sex indicated that if corals spawn just fifteen minutes out of sync with their majority of the rest of their species, it greatly reduces their chance of reproductive success. So you know, this is why it's so important that it happens all at the same time and that the area is protected. Just a lot of factors that go into the ecology

of keeping these reefs safe. Uh. And then to go along with Mara's nerd candy example, one of the other scientists described it as being a little bit like tapioca. That like, you're basically floating in a sea of I think tapioca. It's like swimming and bubble tea essentially. Yeah, that's a good one. I like that bubble tea. All right, Well, we're gonna take a quick break and when we come back,

we're gonna call up Mara and discuss coral sex. Hi, Mara, thanks so much for coming on the show again for a summertime discussion of corals. So we had such a great time chatting with you before on the the Oppidas episode that we recorded, so it's nice to have you back on to discuss corals. Thank you so much for having me. I'm I'm really excited to be here and to be able to chat with you guys about definitely one of my favorite animals, which are corals somorrow. I

didn't realize this until like almost five minutes ago. I've read through the book, We've talked to you before, but you have a background as a coral reef ecologist, right, that's right. Yeah, They're where I really um got started in my career doing me in science. So they hold a very special place in my heart. Quarrels and sharks. Okay, awesome, Well good, because we got a lot of questions because because quarrels have a very strange reproductive practice. This is true,

they do. They're they're pretty amazing, especially given that they can't move, and they are pretty simple animals that I don't like to use the word simple, but you know, basically they're they're sort of this jelly like blob that sits with extending little tentacles out of a little hard

cup that they manufacture themselves. So for folks out there who are familiar with finding Demo um and know that he lives in an anemone, which is uh, I don't want my it up, and then with me, uh, they're they're close cousins of those animals, and so they fit in these little cups all day long with their tentacles outstretched into into the environment, sort of taking little particles out of the water to feed on. But they have some other cool tricks up there. The sexual reproduction and

corals is pretty amazing. Yeah, you you presented so well in the book. I almost almost hate to ask you described to describe it here, you know, I'd almost rather encourage the readers to read it. But can you take just a few minutes to describe for us the synchronized hotel orgy of the corals? Sure, i'd be to So again, corals can't move right, so they're stuck. They're cemented to the sea floor. This means they can't go out in

date to find their mates there. They have to allow their gammets, which are their eggs and their sperm, to do the dating and meeting for them. And I should say there's two types of coral in the when I'm about to describe it does this big synchronized orgy. These are called broadcast spawners. So they release both their sperm

and their eggs into the water column. And the best way to ensure that their sperm and eggs are going to mix the sperm and eggs of other corals and be able to make the next generation is to time

that release with their neighbors. So if you imagine that corals are sort of sitting in their little cups, and their cups sort of form these big colonies, and then there's multiple colonies along the reefs, it's kind of like thinking that, um, the sperm and eggs are are getting together in a hotel room, right, and these corals have to make sure that they're going to synchronize their mate

their release. But then it's also like that couple in that hotel room that synchronizing their release is also coordinating with their neighbors maybe in the two rooms on either side, and then those neighbors are also synchronizing with their neighbors, and so the whole floor of the hotel are all coming together and being able to synchronize their climax exactly

the same time. And then actually, because there's miles and miles of reef and millions and millions of corals, you've actually got to blow it out to imagine that every single hotel room across say, the entire city of New York is full of couples that are all climax thing exactly the same time. So it's pretty phenomenal when you think about the scale at which this synchronization is occurring.

And you know, given uh sort of bar pop culture, and again I talked about you know, if you look at any cover of Cosmo, it's all about how to you know, connect better with your partner. We we seem to struggle to do this on a one on one basis. Meanwhile, corals are doing that's across millions of individuals, no problem, year after year, down to you know, really really fine timing.

So we're talking within you know, within moments uh of of their their sort of buddy colonies up and down the reef, and this is a once a year occurrence, it is. So what happens is coral sort of spend the entire year celibates, building up the energy and storing the energy to make these staddy balls of sperm and eggs.

So it's called a bundle. And the bundle looks like, for those of you who know nerd candies, kind of a small pinkish orange colored spear, and it takes a lot of energies to pack all these eggs and sperms together, so they wait and again. Um, it's a once a year event and it normally happens um for different species. It'll happen within a two to three day window around the full moon, and it normally happens in the summertime, so there's likely some water temperature cues. There's definitely cues

from from the sunset. It often happens at night after sunset and moon phase also coordinated around that that full moon time, so there's a whole bunch of virominal cues that they're using to kind of start to align and then and then let it all go. But it's yeah, so each coral will only go once they've got one

little sperm egg bundle to release and that's it. Uh So, within a colony you might have one or two days of different polyps going off, but in general there's one peak night where the vast majority of of all these animals are releasing at the same time. Now, of course there's a reason for all of this. So what what

are the core advantages to this once a year sexual blowout. Yeah, so again, um, it's really expensive to manufacture these, especially the eggs um and all the sperm, and you really want to make sure that in the environment like an ocean where there's lots of currents and lots of predators, so that you are getting your your sperm and eggs to mix with other sperm and eggs from your fellow

species so that you can make next generation. And by coordinating the timing really precisely, you up the odds that your sperm and eggs are going to bump into another coral sperm and eggs and be able to fertilize and make make that viable a little larvae. But it also helps to release all these millions and millions of gammets all at once because it's sort of swamps out the

predators as well, and the sex facts of coral. That sort of starts really peacefully, and it's just really it's really quite a miraculous event to witness, and and folks can see this because it happens on shaller wreaths. You can take a flashlight and even just snorkel um down in the Caribbean or off the Great Day or reef

and be able to actually watch this happen um. But it starts off really beautifully where these little bundles form and then it's sort of this slow release and the sperm and eggs are buoyant that they slowed up, and it creates sort of like the snow storm underwater, but the snowflakes are bright pink and float to the surface, and it's really quite magical. And then all of a

sudden it turns into this like crazy. I think I refer to it as like a rave where shrimp are coming in and worms are coming in, and fish are coming in, and then bigger fish are coming eat the little fish that are eating the corals. You know, it's it's chaos. And if you're if you are diving down there, you stop is hitting your mask. It's going in your face.

It's like bumping your regulator out of your mouth. I mean, it's like it's a wild all you can eat, say, And so for the corals, it's helpful to know that everybody else is releasing their stuff too, so that it's not just your sperm and eggs that are going to get sort of focused on. But hopefully you'll satiate all the mouths out there and a couple will make it to the surface where they can break apart and and sort of mix and and and form that next generation.

So doing it all at once has its benefits for a couple of reasons. So, Mara, I got a question, just for clarification, can you explain for our audience what we mean when we're talking about gam meats. Are we talking about the sperm the eggs both? Is this the bundle we're referring to, right? Yeah, So gam meat is the scientific term for a sex cell, and it's either a sperm or an egg, so it counts for both. Yep.

So the bundles are there gam meats because it's the sperm and eggs um sort of tightly wrapped around each other in these in these little balls. And when they get to the surface, they actually break open and the sperm and multiple eggs. Do you have lots and lots of sperm and lots and lots of eggs inside each bundle, and when they break open at the surface, that's when the sperm and eggs can actually bump and mix with the sperm and eggs of other coral individual to make

a new a new offspring. And one thing that I think we should quickly clarify here too is you mentioned this already, but we're spece typically talking about broadcast spawning coral reefs. There's other forms of reproduction for coral reefs, right right, Yeah, So corals are They're really cool animals.

There's hundreds and hundreds of species of coral thousands, I think, and um, the ones that build the big reefs, the ones that we think of when we think about coral reefs, tend to be these broadcast spawners that do these mass

um spawning events, these big orgies. There are others, however, that are brooders, which mean that they release their sperm into the environment, but they actually hold eggs so that the sperm will have to come into the coral colony and fertilized there's also some corals that are so again the broadcast spawners are hermaphrodite. They're producing both um sex cells right spur and eggs. But there are some corals

that the colony is either female or male. They have separate sexes, in which case they'll release um into the environment the sperm, and then the females again hold the eggs,

and there's tons of varieties sort of in between. UM. I just came back from a coral conference, the Big Coral Conference happens once every four years and it was just last week in Hawaii, and I thought this great presentation by Dr Kristen Marhavior who works out of Karmabi in Curse Out, and they're finding some corals that seem to be doing this weird kind of in between where they don't really brood, but they're sort of holding the eggs up in the tentacles but not really letting them go.

So it's like the funky yeah in between. So one thing with corals is that they do it all, and they seem to do it in lots of different ways that we're still learning about. Uh, this seems like a good opportunity for us to hone in on two particular species you bring up in the book. Yeah, indeed you make a special mention of the lob star coral and

the boulder star coral. Which I found this particularly interesting because we're talking about this sort of this broadcast orgy of reproduction here, but it seems like it doesn't pay to bump into just anybody in a broadcast orgy. That's right, This is definitely true, um. And it's again it's not something that we mammals tend to have to worry about because we are pretty certain of who it is that we're mating with, who are gammetes are sperm and eggs

are mixing with at the time of sects. But for corals, um, they don't have that control. Right, they release their sperm and eggs into the water column, and they're hoping that they do it in the right time period so that it bumps into other sperm and eggs of not only fit healthy other corals, but corals of the right species. So coral. There are corals that are very closely related, and the low as a boulder star are examples of that.

And it is possible that if the sperm from say below star coral bumps into the egg of a boulder star coral. Uh, you know, they could they could fertilize that egg and a barbacaus form. That's a hybrid. And hybrids are not always the best outcome for four species

for a couple of reasons. And and folks may be most familiar with, um sort of the cross between a horse and a donkey that creates a mule, right, mules for sterile, Like a mule can't go on to reproduce, And so that sort of idea that hybrids of these genetic dead ends, Um, it kind of defeats the whole purpose of having sex in the first place, right, which is to create future offspring and hopefully that those offspring will be fit and create the next generation, the next generation.

So hybrid sort of um squelched that in many cases. And UM, I don't know if you guys want me to go into it, but there is actually some really cool work that has been done since the book came out about some coral hybrid stuff. So we could we could talk about that if you want. Yeah, yes, certainly, especially because like one of the things that I'd like to clarify just from the book itself is like getting back to the Lobes star and the Boulder star coral.

There's very specific ways in which they are compatible, right, but it's not always so easy for one to fertilize the other. Right. So, because of this risk of forming hybrids, corals have come up with a couple of tactics and there is a level of screening that happens at the level of the eggs um. Some eggs um some species are very prude and they won't let sperm in from

other species or they make it very difficult. But other eggs are are much more promiscuous if you will and are if sperm from another species is around, it can fertilize. So to help kind of create more barriers to hybrids and really separate the species corals, the timing of these uh orgies is very very specific. So again the load star coral and the Boulder star coral are a great example of this because they spawn on the same night.

You know, they use the same environmental cues the warming temperature, the moon phase and then the timing of sunset. But what happens is with the low star coral there was no start with the Boulder star coral. The Boulder star are the early birds, so they will start to release um it's about two hours after sunset, so if you're down in the Caribbean, sunsets may be around seven. So the Boulders first start to release their eggs around nine o'clock.

And it really is that precise. You're on year, it's within two to three minutes of the year before that, the same colony will spawn at the same time. I mean, it's you absolutely could think you're nice your watches to

it's it's pretty awesome. And then the Lowe Star coral is about an hour and a half de lad from the Boulder Star, so they would be you know, maybe ten thirty leaven ish And that separation and time turns out to be just about the time it takes for the Boulder Star sperm fizzle out after about an hour

and a half. So the fact that they go first at around you know, say nine o'clock, by the time the Lobes Star go off and they release their eggs, there's not a lot of the Boulder Star sperm left that has a lot of you know, much energy you know,

to get out there and find their eggs. UM. So that hour and a half spacing seems to be just enough time to allow the first coral in this case, the Boulder star, for its eggs to be fertilized by its own sperm, and then by the time the next species goes off, there's there's really not too many of their eggs left to be fertilized by any new sperm coming into the picture from another species, and any of the first sperm that are around sort of are a little wizard at that point and unlikely to go and

fertilize the new eggs that are released by the second species. So I know it's a little a little complicated, but that's why I asked, Yeah, so tell us about this new hybrid research that you said that's come out, because maybe it answers a question that I was going to ask you anyways, which is how frequently are coral hybrids actually sterile? Yeah, so it's a it's a really important question.

And Dr Nicole fogerty Um is studying this extensively and and this is her work at all I'll summarize here, and she again just presented sort of a new component of it just last week at this big coral conference, and she has been setting this question in two species of endangered corals in the Caribbean called elkhorn and staghorn, and these are the beautiful, big branching species that used to dominate some of the shallow reef crest environments and

have been really quite wiped out. They were the first um invertebrates to ever go on to the endangered Species list, I believe, or one of the few um so they've really been hammered and we're trying to figure out why and try to figure out what this means for their reproduction. And what Dr Bobodies found is if you look at the fossil record, which is for corals, really um pretty

robusts because they create these these hard skeletons. They actually are captured really well and represented very well in the fossil record. If you go back, you see that hybrids between elkhorn and staghorn are very rare. And they can look at this by epe colony shape in different um aspects of their morphology sort of the shape and the way that um polyps are arranged, and hybrids, yeah, they're

just they're just not around very much. But if you come now into and we also know from early surveys in the seventies and eighties on coral reefs, there's not all the hybrids, but recently there are. We see a lot of hybrids going on, and they've done some genetic tests and they're actually finding that these hybrids, so this is a cross between an elk horn and the staghorn, makes a hybrid. These hybrids are actually able to breathe with other hybrids and make a second desperation that seems

to be viable. So that's a really neat kind of twist on the whole Hybrids are always bad thing. Now the catches we don't know if that second generation of hybrids is viable, so we're still sort of aiding to see. You know this, this can happen where the first generation of hybrids is viable and seems really um fit and actually does very well, but then it's kids peter out. It is it's like a it is, and it's in.

What happens also is that these these these vigorous hybrids can often compete with their parents, right, So they're competing with the elk horns and the stag horns that maybe aren't doing as well, and if they start to take over those environments, but they don't have the ability to reproduce successfully for multiple generation. Then you wind up with

hybrids actually being another threat to the parent. Now, to put another spin on it, which is what corals love to do, these hybrids can also meet back with the elk horn or with stag horns, so you get what's called a back cross, which gets even you know, you, guys, your guys show is stuff to blow your minds and get really so wait, I'm trying to envision this, given that the elk horns and the stag horns release at different times on the same night, do the hybrids release

like somewhere in the middle there, You know, that's a really good question, and I I don't know the answer to that. They are going to be spotting the full moon this month. July is a big month for elk horns and stag horns July in August, so I can I will send you guys an update or maybe we can throw it in the comments, but I will ask down there doing the study right now. But that's a really good question. I'm not sure whose timing they take

or if it's a combination. There their shape is definitely um a range of in between the two parents between the elk horn and stag horn, that there's sort of a whole variety of shapes that these hybrids seem to be taking. And when the hybrid back crosses, so when the um the combo coral of of elk horn and stag horns, then fertilizes or mixes with an elk horn or a pure you know, stag horn and make this sort of back cross species um, they tend to have

slightly different shapes and sizes as well. So the good news on this is if there's not too much competition with the parents and there's not too much back crossing, the little bit of gene mixing and the little bit of hybridization that's happening could actually really help the species and could be a way that this species, the two species, the elk horn and the stag horn, are trying to adapt to these changing environments and are actually dealing with

some of the impacts. It's one way that species may be evolving, and we do see some you know, Dr Brogan is starting to see some very preliminary evidence of higher disease resistance, higher heat tolerance to you know, with some of the global warming issues and mass teaching issues.

This is a positive um and and that we will be able to see new forms of these branching corals based on this hybridization, or it could go the other way, where again these hybrids actually wind up to be not viable multigeneration and multiple generations down the line, and they wind up contributing to the decline of the two parents species. So it's UM, it's something that she's studying really intently and watching and it's a fascinating um sort of I

don't know who. I don't know who to root for, really, but it's important for us to keep an eye on, especially given the threats to coral ecology that are going on. So I've there's a lot of biologicals sort of hypothetical question for you, because you say in the book the same question that immediately popped into my head as I was reading it, which is, if corals don't have brains or eyes, how is it that they're seeing light, how

is it that they're uh sensing lunar patterns things like that? Um, And my question was we just did a piece here recently about new research that came out about two months ago on underwater slime and algae and that they're able to on a cellular level sense light and move toward it. That like each cell on its own can quote see light and then like subsequently sort of crawls forward. And I'm wondering if you think that maybe is something like

that possible with corals. That's fascinating. I will have to go and listen to your story because I don't know much about the the how that kind of a a slime can do that. That sounds really cool. With corals, they definitely have light sensors, Um, I'm not up to speed on like the the detailed physiology there for whether it's at a cellular level, whether it's um sort of a very primitive kind of organ nolle that that we see in some worms that can you know, tell if

a shadow moves across, you know, light and dark. But they definitely definitely have a way of sensing the light. But I'm not sure exactly how it works, to be honest, Um, I can I can dig into that a little further. But the reason why we know it's cued by light though, and pretty specifically is not only because the timing happens after sunset year on year so precisely, but it's also

that we've done some experiments, um, and these were initially started. Yeah, the garbage bags, right, so simple as best in science. And Dr Nancy Knowlton, who's now runs the the Marine Science Hall over at the Smithsonian. So when she was studying some of these systems, she was like, all right, well, if we wanted to see whether or not these corals can actually fertilize one another, and what's going on between

these different species. She looked at the Lobes and the Boulder Star corals and was like, okay, well they're delayed about an hour and a half apart, so what would happen if we tricked the Lobes Star coral, which is the later spawner in the thinking sunset happened sooner. So they took colonies and they put black garbage bags over them about an hour and a half before sunset, so they sort of faked the corals out into thinking that sunset had happened at day six o'clock rather than seven thirty.

So low and behold it right. An hour and a half later, when they were que to go off, they went off. And what they were able to do by by kind of sort of shifting the time of sunset earlier, they were able to actually get the Load Star coral and the Boulder Star coral colonies to spawn at the same time, and then they were able to check and see sort of what happened if if that were to occur.

So we know that the light queue is key because if you, if you sort of could unquote mess with when sunset happens, it literally shifts exactly the timing of the release of the sperm and eggs. So it was pretty cool. Indeed, Now in discussing these elaborate reproductive methods that the coral use, Um, there's a weakness in all of this, right now, how does this reproductive strategy make corals so vulnerable to pollution, climate change, and these other

influences that are are making so many of them threatened. Yeah, so there's a lot of reasons why corals are vulnerable to to these threats and why they're being threatened. Um,

but when it comes to their sexual strategy. So this idea of the broadcast spotting these mass orgies, the real issue is that it all depends on everybody releasing their egg and sperm at the same time, and that all these neighbors are coordinated across the reefs, so we know that it's not only are there their cues from the moon phase and the sunset, but as the actual release is happening, there's likely some some level of chemical communication

to really get that timing very very tight and very exact. And what happens is corals are starting to decline due to threats such as overfishing um which is creating more algae on the reefs, and there's climate change which is warming the waters and acidifying the waters, and all of these things um pollution and runoff that they're wiping out corals. So coral colonies that are still left are spaced farther

and farther apart. This means that their ability to really sink up and their ability to get their spermag bundles to meet and mix at the surface is it's harder

and harder to do that the farther apart their space. Again, if you think about the hotel example, it's easier to coordinate with your partner when you're right there with them, and it's definitely if you were to try to coordinate with your neighbors, you know it would help to be able to see where they were in the process, and and and no kind of what that timing was like, so you could adjust. And the farther and farther apart these these species are the coral colonies are spaced, the

harder it is to do. And this is this is known as density dependence. So the the amount of corals in in proximity to each other actually affect how successful their fertilization rates are. And the farther apart there's space, that level of fertilization goes down. So it's sort of a double whammy. Not only are you not only are we wiping out coral colonies, you know, putting less less adults.

Less adults are out there able to spawn because they're dying, but the ones that are left or space farther apart, and so there are odds of having successful sex go down. So it just winds up being a double whammy. Now, some listeners might be wondering, well, if the if the corals can reproduce a sexually, then that's their backup plan, right, Why doesn't cloning solve the problem? Yeah, And it's a really good question, because coral colonies grow through a sexual reproduction.

So you start with this one little larvae that settles down on the sea surface will swim down attached somewhere on a hard up straight on the hard bottom rocky botty um but old reef and creep this one single cup with this one polyp, and then that polyp will divide and divide again and again in ace and that's the a sexual reproduction. It clones itself. But um clones are genetically identical, so there's no diversity in that coral colony.

All those individuals are individuals that they have the exact same genetic identity. So this helps the colony grow, and there's benefits to being a big colony, but it doesn't allow the species as a whole to have variety and genetic diversity. And diversity is nature's insurance policy against all the changes that are are rough against us. So if a new disease develops, you need genetically diverse individuals in the population, some of who may have a natural resistance.

If um there's a big shift in in uh, say predator or prey, say there's there's a different food supply, you need individuals who might have slightly different morphology or slightly different genetic ability to digest a different type of food source so that they can survive. So as these different changes occur in the environment and different threats arise, that genetic diversity is really critical that the species as a whole can survive. And genetic diversity is created through

sexual reproduction, not a sexual reproduction. So it's when the sperm from one individual mixes and meshes with the eggs from another that a whole new DNA blueprint is formed. And that is where the diversity of genetic uh, that is where the diversity that these scis needs comes from.

Without sex, there's no diversity. So given what we learned from you today about what's going new research that's going on with hybridization, I'm starting to wonder now if maybe that's the role of hybridization in some species is to further the diversity. Yeah, and I think it might be.

I think that's that's one of the questions that Dr Folky is really um digging into to say, could it be that under certain circumstances, hybridization does work to help increase that genetic diversity in a way that allows for adaptation, that allows for species to withstand a changing environment or changing threats so that it can then move forward and

maybe it will form a new species eventually. That's you know, collected over time from the genes from the two two parents prior to it, you know, in this case of tag Horn and elk Horn. Yeah, I think it's still it's possible, and that's what makes it a really intriguing space to investing. Eight Um, but we we just don't know yet, but it absolutely is possible. So where are we right now in terms of coral loss? So well, what are we doing and what can we do to

fix them or at least to address the problem. Oh yeah, So you know, this is where I try to find that balance between staying optimistic while also being really honest that the data coming in it's sobering. So last week's conference again, Um, it's really alarming how quickly we are losing coral reefs and they are being hit by every it's sort of a perfect storm. So, um, we're losing them due to over fishing, which has removed a lot of the grazers on the reefs, so the equivalent of

the cows that chomped back the seaweed. So we're getting corals overgrown by seaweed because we've taken out things like parrot fish and sea urchins. Um, we're losing corals extremely quickly now to bleaching events. These are um the result of global warming. It's when waters warm. Corals exist naturally right at their edge of thermal tolerance. Um. You know, they don't have air conditioning or heating systems in their houses, so they live right at that perfect window where they

are just warm enough. And if you crank up the heat of the ocean too much and we're talking one to two degrees celsius, so not a lot of change, coral stress and that stress um disrupts a really unique relationship that they have with a tiny microscopic little algae called those in selly you can calm zoaks, and these zooks are food factories for the coral. They actually live inside the coral tissue and they photosynthaesize just like a

tree eat um, turning sunlight into energy. And the energy and the new in the sort of uh nutrition that those those lly produced are what the coral can then use to have extra energy to build their really massive and impressive skeletons. Because the truth is the water environment where corals exist. The reason why that water is like that amazing clear, beautiful tropical turquoise blue that we all love to swim, swim through and see for hundreds of

feet because there's nothing in it. It's a desert, which makes it ideal for the right, right, which makes it perfect for that this coral algae relationship, because they can make their own nutrients and be able to build build these reefs and have really clean clear waters. And when we throw pollution in there, it disrupts that that relationship, and when we heat the water, it especially disrupts that relationship. And the bleaching is literally the coral kicking out the

zoaks and it turns the coral white. They get their color from having these symbiotics algae in there, and so when they bleach, they don't necessarily die. The coral does not necessarily die right away. Sometimes they can recover, but oftentimes they will die. And even if they do recover, it can take them several years to regain those symbionts and regain enough energy to them be able to reproduce, because again, producing those sperm egg bundles takes a long

a lot of energy. And you know, it's just like us if we're sick and we're not healthy, We're not going to do the the extra things, you know, we're gonna every all the energy we have goes through just esic survival and sex is not basic survival, so production of sperm and eggs drops or the number of sperm you know, sperm and eggs that are produced will go down. So all of these things, and climate change, especially UM is really really threatening the reefs. The Great Beery Reefs

off Australia, the largest restructure in the world. UM. We just had the worst bleaching on record UM. So it was their summer right in February in March, and we're seeing rates of severe bleaching that are just off the charts. We've never seen it like this before. I mean we're talking well over half the reef UM and that's really

really alarming. You know, some of these colonies are hundreds of years old and if they go, it's going to be a long time before that, you know, before a new coral colony can can take over that role and perform all of the benefits that that type of structure can provide. Clarify for our listeners, and my understanding is even at their growth rate when they're they're broadcast spawning something like that would take thousands of years to regrow

a reef. Oh absolutely, I mean coral colonies are slow. These are slow growing. Think of an old growth forest, you know, where where your tallest trees are hundreds and hundreds of years old. UM. To get that level of perplexity takes for for centuries and centuries. And to build something as big as a gray faery reef, absolutely, a thousands You can drill down and scientists will core down to see, you know, colonies that have built and staffed up on top of each other over over time, and

it's thousands and thousands of years. So it's um a slow, long process that has worked really really well and has allowed them to withstand quite big changes, you know in the environment. I mean we we've had big changes in

the past, but those changes haven't happened so quickly. And so the problem with you know, climate change caused by humans, caused by us, is that it's happening very very quickly, and so the ability for these corals to adapt, um seems to be pretty compromised, and we're seeing some pretty pretty sad state of affairs. UM. I think there's over six hundred species of coral now that are being considered for threatened or endangered status UM because of the losses.

So that's that's a bummer, But there is some good news, um, you know, it's I definitely and we can talk about that UM for sure, because it's it's not the kind of situation where we should throw our hands up and say, oh, well, um, it's the bummer that my kids won't get to dive on a cool reef, because that's that's not necessarily the case. You know, the door is not closed UM with coral restoration uh in places where they're actually it's sort of

like I VS. For corals. They go out when they when the corals spawn at night, and they they're collecting some of the sperm and eggs and they're bringing them back to labs um and and going through a whole process that actually increases the fertilization rate. And then they're rearing the larvae and then the juvenile corals up to sort of a bigger size so that they'll they'll have a better chance to survive on the reef and not get overgrown by algae or not get eaten by a predator.

And then they outplant these corals and they're finding that they're really successful and some of the ones that they've done over the past two to three years, those corals now are spawning in the wild, which is great. So there's some really neat um examples of coral farming for for restoration that are are helping to sort of repopulate areas that have been hit hard by by some of these events. There's also um a lot more work in

attention now and fishering management to protect herbivores. So like then these are the grazers the cows of the reefs. And you know, for the listeners out there who do like to eat fish, do not eat parrot fish. That's one great thing you can do to help corals is encourage folks to leave parrot fish um on the reefs where they can be doing their job to eat back this algae. And you know, we can talk more extensively.

There's some great resources out there, but you know, using tourism dollars if you want to go to the Caribbean or go to the Great Theoryes, support those countries that have good management and plates that do abide by certain fisheries policies, that do have protected areas that do enforce their their pollution and clean water rules so that the reefs there are given the best chance they can and

we have seen that. While we've seen that local management can make a difference, it's absolute be a way to help corals resist and get through some of these these challenges. That said, without addressing climate change, there's no way. So we have to deal with climate change. We have to support you know, legislators and policies that are really progressive at this stage, and there's fantastic proposals out there, there's

great clean energy technologies. Really its political will at this point, and that actually can be a very hopeful thing because that means all of us we get together kind of like the corals do and synchronize our actions. We can actually turn turn down feet and try to change the tide on this um. And it's really important that we do so. So that I'm trying to think of I

like that that's a nice boat to put on. It isn't like for us to be able to help them out so that we can continue to have this ecosystem together. We need to sort of learn and how to behave like them. Yeah, sink sink up a bit for bigger impact. Another, I know, you know, it's always nice to give very

practical things. Um. Another really important, uh, especially coming into summer here in the Northern Hemisphere, that folks can do is when you go to the beach, if you are swimming or diving in areas around coral reefs, don't use sunscreen with oxybenzonate benzonate. Excuse me, oxybenzonate is um oxybenzone. I think it's also called They're finding more and more that the impacts of sunscreen, especially very sort of shallow

bays with lots of tourists is significant. And again that's a local impact we can all be much more conscious of. And if you just google you know, coral safe sunscreen, you'll there's you know, tons that come up. Um, this is new work that's been done. We just didn't realize how sensitive again that that coral's works of these chemical inputs. So just be smart about your sun screen choice. That's a really simple way, um, to try to be more conscious and give give corals a bit of a leg up.

Cool And is here a particular organization Coral Advocacy group that that that that one should follow or even you know, contribute to monetarily that can also help. Well, those are great, that's a really great question. There there are several really excellent groups out there that are doing wonderful work. UM. There's a group called REEF which is the Reef Environmental and Education Foundation. They do a lot of science but also volunteer work, so folks can go check out reef

dot org. UM there's coral monitoring monitoring networks and groups like the Nature Conservancy and others, especially in the field of Nature Conservancy in the US Virgin Islands and the Nature Conservancy of or to Are do call on on volunteers to help UM monitor for bleaching. So if you're someone who goes diving or snorkeling or wants to take a trip, you can go and report what you've seen so that we can help keep track of where bleachings

occurring and and try to understand those patterns better. So I think it's called Coral Reef Watch, and I believe it's run UM by Noah, which is the you know, the US government's federal arm that studies oceans. But again, folks like the Nature Conservancy I know, help train volunteers to execute on that program. So those are those are some that come to mind that are doing you know, direct work with corals. UM. There's other great work by UM groups like Moat Marine Lab in Florida that are

doing some of these UM farming and restoration techniques. So if you if you're sort of more towards wanting to support UH some of the science behind how we're studying and learning, there, they're a great a great place to look. There's a lot, but I would say that UM that those are the ones that kind of immediately pops pop

into my head. UM. Oh, there's another there's a wonderful initiative by um UH the Weight Foundation called the Blue Halo Initiative, and this was initially started by a woman named doctor Ayana Johnson and they it's island wide Marine policy um in marine sort of management for Caribbean countries.

At this point, it's in the Caribbean, but it's really great because it's it combines education and outreach, it combines fisheries management, and it combines sort of typical conservation all into one so that these island governments are actually implementing a very holistic policy that works to protect their waters. But all so you know, support fisher livelihood, but make

sure that they're they're taking all interest into account. So that's another really neat initiative to look into or again see where the blue Halo projects are and support going to those countries, um for you know, for your vacation, because they're ones that you know, um, your your tax, your tourism tax is going to two governments that are

really trying to do the right thing. Um. Trying to think if anything else comes to mind, Um, well, if any additional ones come up, you can always you shoot them to us via email and will include them, uh you know on the landing picks for the episode. Yeah, there's I think there's. Um. The last thing I'd say is there is the Coral Restoration Foundation, which is I

think just Coral Restoration dot org. And they do some really great work as well, um in terms of trying to against farm out corald and I think they might also have volunteer opportunities, which is it's fun. I mean, they're it's neat to get to go and spend your vacation helping to grow baby corals or outplant them honor reef or ten to ones that are out there. It's it's a nice nice way to really feel like you're just like going and doing um, you know, tree plantings.

On Earth Day you can go do coral plantings and and help reef to recover cool well. Um, is there anything else you want to get out there before we close it up here? Um? Um, I don't think so. Just for folks to know that, unlike so much sex and to see coral spawning is something we can actually see pretty easily. Again, it happens in the shallows. You just need a mask, you don't even need thin go

right offshore. There's lots of places in the world that are you know, face and easy to get to and and you can just swim out with a flashlight water waterproof flashlight. Um. And you can watch this. It happens right after sunset and it's starting now, I mean from now through October and the Caribbean there will be different mass spawning events. And if you go online and google them, there there are schedules and you can go and and

watch this happen. And it really is. Um. Not only is it magical and sort of mystical and ethereal and just how it looks visually, but there's something that I find incredibly uplifting and inspiring. And knowing that despite all the threats, despite all the negative impacts that we are having on these animals, every year, they continue to soldier on.

These mass spawnings still are happening, and that rhythm of nature that has been established for thousands and thousands of years continues to hold strong so that the next generation can be possible. And you can witness that, and you can see all that potential and all that hope floating up right before your eyes. And it's um to me, It's it's what it keeps me going cool. Well, Sex and the Cy is the book. It is currently out

on hardcover, e book, audio book, and UM. As we've stressed a several different times on the podcast on past podcast episodes, it's just a delightful, insightful read full of just some mind blowing but also entertaining content. We've recommended it as as just a perfect bit of summer reading for our listeners. Yeah. In fact, we just did our summer reading episode a couple of weeks ago, and uh

we recommended this book Maraw to our listeners. And and also I just want to say that I really appreciate the work that you put into your prose in this book. And just the analogies and similes and metaphors, the kind of work that you do there make it so much more readable than the hundreds of articles that we read on similar topics and really kind of picturesque too. Yeah, oh,

thank you. I appreciate that, and appreciate so much the support you guys have have given for it, and I'm I'm just hopeful that your listeners will find it entertaining and inspiring and hopefully some really good cocktail party fodder.

So definitely unfacts around the barbecue, all right. So there you have it, a whole lot of coral biology, a whole lot of coral sex, if you will, and some some sobering but indeed hopefully optimistic information about where we are in terms of coral loss and um readjusting pivoting if you will, to try and um and and and say these species that that do so much for our ecology.

And one of the things that I really loved about this interview is that while we had done research ahead of time and prepton, we'd read her book, and we were we were ready to have this conversation. You know, Mara in just the last week could already looking new stuff because the science is moving so fast. So you heard it here first, folks, or maybe maybe there are some articles that came out of that conference she was mentioning.

But you know, I'm glad that we were able to talk about all these changes with hybridization that scientists are realizing about. Indeed, yeah, some some really cool data from the book and and and some stuff that has just come out in the last couple of weeks. So Okay, you out there, maybe you have an experience like Robert where he went to Jamaica. Have you been up closing personal with coral reefs? Tell us about it based sent us your pictures, let us know what you think about

the coloral bleaching effects that are going on. You can do that on social media. We are all over the place on social media. Were lousy with social media, as Josh Clark likes to say. We're on Facebook, Twitter, Tumbler, and Instagram as Blow the Mind. And you can always visit us at our home base at stuff to Blow your Mind dot com. And I want to throw into you know with Facebook, the algorithm is always changing. Uh, if you would visit us Blow the Mind on Facebook,

visit us there. Make sure that you're subscribed, but also make sure that you've hit the adjustment so that we show up in your fee, because that's going to ensure that no matter what changes in the Facebook algorithm, we can still get our content to you. Yeah, And basically this is so that you can be updated whenever a new podcast episode comes out, or we can let you know when Robert or I or Joe have recorded a video about something related to the show or published an article.

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