Hunters of the Dark Ocean, Part 3

and so forth. And to be sure, the majority of marine fauna do live relatively close to the surface of the water, where sunlight can reach the phytoplankton and the other photo autotrophs that form the base of the food chain. Up there, they photosynthesize things, eat them, things eat those things, and so on. Now, in centuries past, there were thinkers such as the naturalist Edward Forbes, who observed that you know, the deeper you trawl or plunge into the water looking

for life, the less you find. And from that he extrapolated that you know, below a certain depth there will be no fauna at all. Within the sea. This was the so called azoic hypothesis. We of course now know

that that is not true. And while conditions are harsher and life forms may be less dense and less diverse in the depths than they are near the surface, there is nevertheless a fascinating world of animal interactions taking place in the deeper, darker zones of the ocean, even going all the way down to the very bottom, down to the abyssle ocean floor, and even into the sort of

inverted island communities of the deep ocean trenches. Now, when you look at the animals within the environments, some of them are grazers, you know, grazing on microbial mats. Some of them are scavengers. But some are also predators and even top predators. And that's what we've been looking at in this series, Hunters in the Dark Parts of the Ocean. Now, in part one, we started by talking about a couple

of specific organisms. One was a type of predatory amphipod crustacean called Dulcabella common chaka the sweet, Sweet, Sweet, Beautiful Darkness, newly discovered and documented in a paper by Weston at All from November twenty twenty four This was a crustacean predator found in the Hadel zone at a depth of almost eight thousand meters in the Atacama Trench, and this led us down a tangent of looking at bizarre amphipod

body forms that was very fun. But we also in that episode talked about predatory sciphonophores, which can have unbelievably weird body forms as well. There's the one we talked about that's long as a waial thin rail, and we discussed a specific sighting documented in twenty twenty one of

a large unidentified predatory cephonophore in Hadl waters. Now in Part two, I started off by talking about an abyssle predatory fish found more than four thousand meters deep in the Pacific, known as the gridi fish, which was notable, at least to me, for having these absolutely bizarre bean shaped neon yellow plate like depressions in the top of its head that apparently function as light sensitive spots for

hunting bioluminescent prey. And then after that, Rob talked about a couple of deep swimming cephalopods, the strawberry squid, which inhabits a sort of boundary zone in the midwater with a little bit of twilight above and dark water below, which requires an interesting adaptation of two different kinds of eyes on opposite sides of its body, one for seeing shadows moving against the faint sunlight above and one for

seeing glowing self illuminated organisms from below. After that, we also talked about the dumbo octopus, a very very cute, interesting little critter that seems to have forsaken many of the defense mechanisms of its cephalopod kin because it lives deep where predators are less of a concern. And we're back today to talk about more. Yeah.

fish as a those kind of treasures of introspection and meditation. I don't know if anyone out there familiar with this book and to understand it's kind of an autobiography but also a self help guide and gets into some of the meditative concepts that David Lynch gravitated towards. I'm going to read a quick quote here from it. Quote ideas are like fish. If you want to catch little fish, you can stay in the shallow water. But if you want to catch the big fish, you've got to go deeper,

down deep. The fish are more powerful and more pure. They're huge and abstract, and they're beautiful. Everything, anything that is a thing, comes up from the deepest level. Modern physics calls that level the unified field. The more your consciousness, your awareness is expanded, the deeper you go toward this source, and the bigger fish you can catch. So I think

that's pretty cool. We can quibble about deep sea gigantism and the relative small size of some of the deep sea organisms been discussing here, but in general I will say, yes, these are the waters where you find organisms as deeply weird as a David Lynch film.

the space deeper than six thousand meters from the surface. Now, while the Hadele zone is almost half of the ocean's maximum depth, it takes up less than one percent of the ocean's horizontal seafloor area because it's limited to these deep sea trenches and trench systems. So just in terms of depth, these regions are going way beyond even the abysstal depth of most of the world's ocean floor, but in terms of space taken up on the surface of

the Earth, very limited they're little, tiny islands. So what this study wanted to examine was what happens when a large dead animal, in effect a huge cache of food, hits the floor of an ocean trench. This obviously happens naturally all the time, but we're not around to observe it from the beginning when it does happen, And so they staged these They staged these events where a dolphin carcass would fall down into hadel waters and then they

would monitor what happens. One of the findings was of a kind of dynamic interaction pattern where first scavenger like impipod crustaceans would show up to eat the soft tissue of the dolphin's body. But how fast the crustaceans were able to consume that soft tissue was in part controlled by the presence of secondary predators who showed up to eat the amphipod scavengers who were eating the carcass. And one group of secondary predators mentioned in that research was

the snailfish. So I wanted to explore more about these creatures, figure out what they are and what's special about them.

some are in much deeper waters. In general, snailfish tend to be good at adapting to extreme environments, so a lot of snailfish species gravitate toward cold waters, such as in the Arctic and the Antarctic. A snailfish is often shaped sort of like a tadpole, so you can think of a big, bulbous head and a narrowing tail, and the deep dwelling varieties are often pale or translucent pink

in color. So to picture a deep sea snailfish, imagine a fish in the form of a fat, pale, pink tadpole without scales on its body and instead a kind of loose, milky sea through skin, which is usually covered in a gelatinous slime, and occasionally that skin will be prickly or spiny.

my own like weird sensibilities. Like a lot of people seem to think that snailfish are kind of cute.

directly observed by humans. And I do have to put an asterisk on there, because I was reading in one article there are claimed observations of fish that have been cited lower but like, not directly imaged or documented, And for various theoretical reasons we'll get into those other claims seem unlikely to be true. But so yeah, I guess we'll put a question mark on this the best confirmed sighting of the deepest diving fish ever.

right up in Scientific American by Tom metcalf. So the location of this record breaking discovery was within the izu Ogasawara Trench, which is south of Japan, at a depth of eighty three hundred and thirty six meters. The previous record before this for the deepest confirmed sighting of a fish was held by a Mariana snail fish more on that species and a bit at eighty one hundred and seventy eight meters depth, and that was within the Mariana

Trench back in twenty seventeen. This new find, which was deeper, was in this other trench south of Japan, izu Ugasawara. This new record holding fish in twenty twenty three beat the previous record by one hundred and fifty eight meters and as far as I can tell, the observation still has not been surpassed. This sighting took place during an exploration of several trench environments in the Pacific around Japan

in twenty twenty two. The expedition was conducted by a research ship called the DSSV Pressure Drop, so the research team used baited cameras plunked down into the deepest parts of several trenches, and at one of these baited cameras, at this kind of unlikely depth of again eighty three hundred and thirty six meters, a fish appeared. Interestingly, this solitary deep diver was a relatively small juvenile snail fish, which seems to be able to venture a bit deeper

than the normal adult range for its species. More on that in a moment. The fish in question was idd as the genus Pseudoliparus, but the exact species couldn't be verified. Also, just two days after the deep fish was caught on camera, two more snail fish were actually caught like trapped in baited traps at a depth of eighty twenty two meters

and brought up and rapidly preserved. In this case, the fish were identified down to the species level, and these were pseudo lyperis at Belle Yavy and rob I attached a picture from the s expedition for you to look at, with several of these snail fishes crowding around a baited trap. I'm not sure quite what that is on the trap. It might be might be a mackerel or something, but yeah,

some kind of bait they've got there. And I think the idea is that the dead fish attracts the crustaceans probably amphipods that come to eat the dead fish, and then the snail fish show up to eat the scavengers. Yeah.

want to see the deepest fish ever. You're like, yeah, I'm in for a horror show, and then you look at it and you're like, well, you know, oh, quite quite cute when I take into account expectations.

crustaceans and other types of an animals even deeper. But fish, they're saying, you're probably not going to find one much deeper than this, and that's because there appear to be biochemical circumstances that place a pretty rigid theoretical maximum depth on how far you can go if you are a fish. Now,

why would that be? How would that work? Well? Fish that live under extremely high pressure are only able to do so because of compounds in their cells called osmolites, such as the molecule you might have read about this before, trimethylamine in oxide or TMAO. Osmolites like TMAO act as protein stabilizers. So within an animal's cells, you can think of proteins as sort of the machine parts that make

most cellular functions possible. Proteins need to maintain their particular folded structure in order to do what they do, much the same way that the parts in a machine need to maintain their shape and the way they move, or the machine will stop working. But physical stresses like heat and pressure can denature and deform proteins or prevent them from folding correctly. And this is one of the difficulties of life in the high pressure conditions of the deep sea.

Hydrostatic pressure does violence to the proteins in your cells, and so high osmolite concentrations are an adaptation deep sea animals use to get around this problem to stabilize their proteins against the high pressure environment and basically keep the machine parts stable and working the way they're supposed to.

And one interesting side note that I was reading about dig you know that osmolites, these compounds that stabilize proteins, are the main cause of the fishy smell of decomposing seafood. So as a dead marine organism, you know, like a fish that's not frozen, it starts to rot in the sun, begins to decay. Bacteria break down the trimethylamine inoxide or TMAO into volatile trimethylamine, which smells fishy. That is the main part of what the fishy smell is interesting. Come

back to that in the second. So marine biologists have found that as you go deeper and deeper in the ocean and the pressure gets greater, the fish species that live at each depth zone have higher concentrations of osmolites. Makes sense, right, That trend continues until you reach the maximum possible concentration of osmolites in the body tissues, which according to theoretical models, would be the concentration that would

allow fish to survive at about eighty four hundred meters. So, according to this model, the fish that was observed in this expedition like eighty three hundred and something meters. It was within about seventy meters of the theoretical limit of fish biology. You basically can't get enough osmolytes into the cells to stabilize proteins any deeper than this, which is why researchers don't expect to find a fish much deeper than this one.

and on the other site they were not. I'm going to have to go back and look at the depths that they were discussing there and see, because it makes me wonder, well, did maybe the snailfish didn't arrive at one of the drop sites because it was too deep for them? And to be clear, this would this would not be out of keeping with the general inclusions that were made in that paper, which were that the exact like shape of the whale fall site is going to depend on the depth and on the you know, the

the organisms that are in its vicinity. So again I'm gonna have to go back and look.

we associate with decaying seafood. Pairing that fact with the increasing osmolite concentrations that go up with depth, the depth of a fish's natural habitat. If you put those two facts together, that made me wonder, do abystle or hatel fish smell the worst? Like, would the deeper fish be the most foul smelling of all the fishiest of all fishy smells. I was looking to see if there was any any research into this. I don't know if there's direct research into this exact question, but I did find

a marine biologist commenting on it. So I found a twenty twenty four ap article by Nick Perry about research on hal snailfish, and this article cites a marine biologist named Paul Yancey of Whitman College in Washington State, who directly says, yes, indeed, the deeper the fish lives, the worse it will stink. So hatel snailfish quite likely have like the ultimate fish smell. They've got to be a contender.

I don't know if anybody's tested this directly, but it seems a priori that would be the assumption that they are the kings of stink. I also have to mention this article was the source of that comparison of trench snailfish to guts wrapped in cellophane. And there was another good one in here, not directly from the author, but it quotes a New Zealand marine ecologist and named Ashley Rodin, who caught a number of hadel snailfish from more than

seven thousand meters depth in twenty twenty three. And Rodin describes holding on to one of these fish after bringing it up from I think a mackerel bated trap, and Rodin says, quote, it was like a water filled condom, a sloppy, gelatinous mass that moves between your hands. It was very cool and very strange to see its organs and everything. But anyway, back to the discovery of the

deepest fish ever from the trench south of Japan. According to Professor Alan Jamison, the chief scientist of the expedition, quote, the real take home message for me is not necessarily that they are living at eighty three hundred and thirty six meters, but rather we have enough information on this environment to have predicted that these trenches would be where the deepest fish would be. In fact, until this expedition, no one had ever seen nor collected a single fish

from this entire trench. Now, next, I want to look at a particular species of hadel snailfish. This is the Marianna snailfish or pseudo Lyparis sweary i SwRI. It's one of these deep adapted species. It's believed to grow about a foot long. And I'm going to say this one looks even more tadpoley than most of them do. I've got a picture for you to look at here, rob of one specimen, just like a like a pale wad of chewing gum with eye spots and a tail.

the apex of the food chain. The species was actually discovered fairly recently announced in a publication in the journal Zoa Taxa in twenty seventeen by Garringer at All and the article was called Pseudo la Peris suirie, a newly

discovered hatl snail fish from the Mariana Trench. The authors of the study described the new species on the basis of thirty seven individuals collected from the Mariana Trench between depths of six eight hundred ninety eight meters and seven nine hundred and sixty six meters, so going almost up to the eight kilometer mark. And one thing that was interesting is despite the resource challenges we've talked about, reports are that these fish tend to be well fed and

their natural range. The ones that have been caught tended to have full stomachs. And they conclude that this fish is likely endemic to the Mariana Trench. And this is in keeping with the observation that since trench ecosystems tend to be somewhat isolated again kind of like inverted islands, when a snailfish species becomes locally trench adapted, it's kind of stuck there. It's kind of stuck in the specific trench environment or system it's evolved for and the author's

rite quote. The discovery of another hatele liperid species, apparently abundant at depths where other fish species are few and only found in low numbers, provides further evidence for the dominance of this family among the hatelfish fauna. So again, snailfishes are the kings and queens of Hades. So in the years following this initial discovery, researchers continued to look

into what made the Mariana snailfish special. And I wanted to refer to a paper from twenty nine teen in the journal Nature, Ecology and Evolution by Kunwang at All called Morphology and Genome of a snailfish from the Mariana Trench provide insights into deep sea adaptation. So the authors of this study begin by explaining, you know, it is largely unknown how animals, especially vertebrates, survive in the Hatel

zone given the extremity of the physical environment. So to better understand the vertebrates of the Hatel zone, the authors look at the specific morphology and genome of pseudo leiperisuirii. I'm not going to cover everything they explore in the paper, just wanted to mention a few interesting things that stood out to me. Of course, as we already discussed, fish use osmolites such as TMAO to stabilize proteins, and these fish are no exception. In fact, they are they are

prodigious osmolite factories on the Mariana Trench snailfish. The eyes are if you see pictures of them, it looks kind of like they have eyes, like they have little dark spots. The eyes are non functioning. The fish did not react to lights from the lander vehicle, and genomic analysis also found that these fish were missing gene variants that are

associated with photoreceptor tissues. They have an inflated stomach, so the stomach of the snailfish is larger and takes up more space in the body cavity than in other snail fishes. Why would that be I believe the thinking is in extreme environments where prey density is lower, you need to have space to eat more when you get the opportunity. So I think maybe you just don't ever want to be like, oh, sorry, there's food right here, but I am too full to eat it right right.

They also have a non closed skull, like there's a gap in their skull structure, and this may be an adaptation to the pressure environment to help balance pressure inside and outside the skull.

we've talked about on the show before. So you know, apologies old time listeners for coming back to familiar territory. But I couldn't help but think how so many of the body forms that we see as scary are a result of the kind of environment in which we live

and the predators you find there, you know. So like when we try to think of what a scary monster would look like, often we think of the kinds of animals you could easily imagine eating a human being, So you know, it's going to be something with sharp teeth and big claws, that sort of thing. And so I'm wondering which types of adaptations and body forms you would come to see as those defining you know, a frightening

anatomy or monsterhood. If you were a prey organism in one of these deep sea trenches, would it be you know, it's like the hole in the skull, or the thin bones of the thin skin that you can see through, the gelatinous coating of slime on the body, the broad pectoral fins, like what would be the scary things to the organisms down there? Because it's got to be something that looks like these these critters.

was a kid. I had a poster out of it like a national geographic that had a bunch of these illustrations, and I was always captivated by several of like the needle toothed a variety of deep sea fish, and the angler fish is definitely one of the more alarming looking. You know, it has that frog like face, sharp teeth, and then of course this bizarre bioluminescent lure that hangs in front of its face and encourage it's prey to move in and check out the light, only to be sucked into this fierce maw.

of the water. All told, when we're talking about anglerfish, we have sea toads, we have brightly colored frog fishes, and we have batfishes, we have goose fishes and more. They're all ambush predators of one sort or another. They'll also all do a little bit of scavenging. They're not too proud. Some hunt on the seafloor, others in midwater or again even near the surface. Now, why all the like frog and toad. Why aren't we invoking these terrestrial

organisms in particular. Well, they tend to have frog like heads due to their broad mouths, which they use in suction feeding, which is something you see in a lot of sea organisms. In order to swallow something. What do you do? You just suck it in. You just you know, create that vacuum and just take in a portion of water that has an organism in it and you consume it.

fish of the sea. Some seafloor anglers have a frilly but non bioluminescent lure, sometimes said to resemble a worm, and then batfishes actually release a bait chemical from their lures in order to bring in prey, but the deep sea anglerfish are best known for their glow. Morphologically, the lure or even lures can vary greatly, so what we're talking about here is generally the first dorsal fin spine

has modified. It's evolved into a long, wiggling rod an elysium, and again they can wiggle it so they can actively move it to help bring in the prey. And then there's a lure at the end of the elysium called the esca, and in bioluminescent anglerfish, the esca is a sack of glowing bacteria chef's kiss. Yes, so these are

symbiotic photobacteria. Embiotic relationship here is that, of course, the angler fish uses the light to draw and prey, and in return, the photobacteria get to live in a little fleshy knob at the end of this protrusion on the fish's head, which I know doesn't sound very attractive to most of us. But if you're a if you are a photobacterium, this is advantageous because you get to live with a whole bunch of your fellow photobacteriums by the millions,

inside of this lure. And you get to see the world. Baby, maybe not all the world, but you get to travel around. It takes you places.

or in some way like it's passed on parent to offspring. Now, most of the recent research I was looking at does seem to point more towards the idea that they acquire

the photobacteria in the open ocean. And it's also worth noting that the anglerfish do have specific species of bacteria that they pair with and when when you get into some of the other details, you can see how you could potentially lean one way or another and trying to figure out where they get this stuff, because on one hand, young female anglerfish apparently don't seem to yet have room for the bacteria in that little knob in the escap Also,

as Baker at All reported in twenty nineteen's Diverse Deep Sea anglerfishes share a genetically reduced luminous symbiate that is acquired from the environ. This was published in Ecology Evolutionary Biology. They point out that if the bacteria were transferred parent to young then we would then we would be able to observe it in the bacteria DNA. There would be this sort of lineage of coevolution, and we don't see the telltale markers of that with the angler fish and their specific bacteria.

ability to exist without the angler fish. Well, then maybe it's something that's passed on initially from parent to offspring, because otherwise how could it live free out there in the water. However, the other studies have added different wrinkles to this by pointing out, well, okay, maybe there are examples, and it seems like there are examples of free floating symbiants of the angler's photobacteria, at least in some cases.

So based on what I've read here and elsewhere, it sounds like the current wisdom on the topic drifts somewhat towards the acquired in the wild argument, but with some possible shades of the parent transfer theory as well, like perhaps they pick up the bacteria from an environmental population

that is supplied by symbiants ejected from adult anglerfish. Now I'm not sure if they're ejected at some point during the fish's life or a death, but the idea here would be that perhaps the bacteria live the majority of their life within the anglerfish, within that fleshy knob at the in the esca. But then at some point they're going to escape or they're going to be released, and it's when they're free living that's when they're picked up

by other anglerfish. Okay, the esca, by the way, does have a pore on it that seems to be the likely exit entry point in question, so it's not, you know, completely sealed. There does seem to be like a hatch to go in and out of. I should also add that the exact findings on all this it may depend on which specific anglerfish species and corresponding bacteria species you're looking at, but again, things in general do seem to

tip toward the acquired and the wild model. However they get their glow, they definitely use it, drawing in hungry or perhaps mate seeking prey that the anglers then suck and gobble into their large mouths. We already mentioned that you know, it's good to have a large belly in addition to a large mouth in the deep, because again, you don't know when you're gonna get your next meal, and in the case of the anglerfish, specifically, this means

they can also kind of take in oversized prey. They've got the big mouth and they've got the big belly, so they're really here for it. They're gonna clean house anytime there's an all you can eat buffet. Also, those teeth, those noticeable teeth of the anglerfish. They can depress the teeth at will to allow unobstructed travel down their throat, and they can likewise raise them again like the bars of a cage, to prevent engulfed prey from escaping.

doesn't even feed as an adult. In other species, the male is small and parasitic nature, so what it does is and in general the males again, they're small, they often have like oversized sense organs, and they are basically like heat seeking little missiles. Their one goal in life is to find the female, which you know, this matches up with with other modes of reproduction sexual reproduction we

see in the animal kingdom. But when they get there, some of them, particularly like these black sea devils, they will attach to the female's body. They will latch on and they will fuse with her.

it is extreme. The female here looks like she just has You could mistake this for just like a little flourish on the creature's back, but that is a male that is fused with her. It would be like, I don't think a mole. Yeah, yeah, it would be like you have a male if the male human being was the size of a squirrel, you know, compared to the female. Like that's how small he is.

They're small, and they also require comparably little nourishment, so they're not too much of a drain, and they're just they're ready to provide sperm whenever she is ready to reproduce again. This comes down to the idea that in these deep waters you may have trouble running in to prey, and when you do, you need to be able to be ready to eat them entirely, eat as much as you can. And likewise it's going to be hard to

find a mate. So when you find one, you better be ready to fuse with her body, and or if you're the female, you need to go ahead and attach them to you and carry them with you so you can use them later.

start imagining like human versions of this. But one of the crazy things about the merging here is that we're dealing with genetically disparate male and female counterparts, and yet they're able to fuse together without invoking a strong anti graft immune rejection response, let's say on the part of

the female. This is you know, this is the what you generally see in cases of parabiosis, particularly of the surgical variety, in pretty much all other vertebrates, any kind of grafting like this, you know, limb transplant, organ transplant,

tissue transplant, depending on exactly on what you're transplanting. You know, when you get down into bones, it's a little different, but generally you're going to generate an immune system response resulting in the rejection of the grafted tissue, unless immunosuppressant medications are employed, or i know, in the case of some organ transplants, you'll have bone marrow transplants that are sometimes employed to reduce rejection.

for scientists. I was reading an article from twenty twenty two that gets into some of this, titled Histocompatibility and Reproduction Lessons from the Anglerfish by Noah Issakoff in the journal Life, and they point out that it's thought that anglerfish evolved to quote tolerate the history incompatible tissue antigens of their mate and prevent the occurrence of reciprocal graph rejection responses, and so they likely this is where it

gets interesting. This doesn't mean that they just like flipped off all defenses and they're like, well, we don't care about infections now because we need to breed. It's likely The author points out that they evolved other immune strategies to protect against, to protect against the sorts of infections and threats that those very defense systems would otherwise be

in place for. So they're arguing, there's obviously there's so much we could learn, you know, from these fish to better you know, to better understand how, for instance, on one hand, how we might just protect against infections, like what sort of strategies are they using that are different from what we see in other organisms. And then of course, the the obvious ramification here is what if we could learn from them to improve human too, is shoe limb

and organ transplants. Those are the potential quote lessons from the anglerfish. Now, Joe, I only shared like one, maybe two pictures of anglerfish in our document, but I do I recommend that everyone out there just do a few image searches. Look around there. Anglerfish vary so much in their appearance and their morphology. You know, it's really wild

and wonderful. And once you see, especially when you get out of deep sea angler fish and you start looking at like all of these like colorful examples you find in shallower waters. Yeah, there's some amazing diversity here.

Interesting question looking either way at the at the anglerfish sexes.

a little open. High likelihood that you're going to get another episode on deep sea predators and it will also be gross and amazing and weird. But if not, you know, we'll come back with something else. In the meantime, we'd like to remind everyone that Stuff to Blow Your Mind is primarily a science and culture podcast, with core episodes on Tuesdays and Thursdays, short form episodes on Wednesdays and on Fridays. We set aside most serious concerns to just

talk about a weird film on Weird House Cinema. Follow us wherever you get your podcasts. Follow us on various social media accounts. I can't keep track of what's going on social media these days, but we're on some of them and you can follow us. I know we're on Instagram where we are stb Yan.