#1 - Anglerfish

Hello, and welcome to the first of what I hope  will be many podcasts making up a series of stories documenting the strange and unusual creatures we share our world with. It’s going to be a science podcast packed full of interesting facts which will be revealed as the stories unfold. We’ll be focus on my personal interest which is the biology of animals on the very periphery of what we are familiar with – animals which exist against all odds and live their lives in the most unusual ways.

I’m going to dive straight in and introduce our first tale.

·        This is a tale of nightmarish romance, where the grotesque meets the monstrous.

·        It is a tale of temptation and sacrifice, fraught with unexpected dangers.

·        But ultimately, it is a tale of survival in an alien world of extremities

Welcome to “Tales of the Wild”

We’re going deep for this one. 1500 meters down into the ocean. The light from our sun can’t penetrate beyond depths of 1000 meters and so the ocean becomes a world of desperate, cold blackness and unknown secrets. The water is eerily still in the absence of any wave energy from above and if one were to shine a light into the darkness at this depth, the cold stillness would only be broken by the gentle falling of marine snow – drifting flakes of decaying organic matter from the upper levels. The pressure at these depths is immense. Our species can only survive down to around 350 meters without our bodies collapsing in themselves. How any creature can survive at such depths is extraordinary and indeed there is nothing ordinary about the creatures that dwell in this darkness. Our creature for today is no different.

An egg has hatched and a creature emerges. It is almost blind, but must feed. It swims slowly out into the blackness in search of food, but at these depths, nutritious meals are difficult, almost impossible to find. To make matters worse, he is small and defenceless. He has a face that only a mother could love, and a body that seems barely able to function – survival out here is going to be tough. The one thing he has going for him is an immensely powerful sense of smell with highly specialised olfactory tastes – he is searching desperately for a very particular kind of meal. If he could only see himself – he would ask himself how on earth he would eat his meal, for his mouth was pathetically formed with teeth that would strike fear into only the most microbial creatures. It was almost entirely functionless. Almost entirely. Furthermore if he were able to turn his eyes inwards and gaze upon his innards, he would be shocked at the appearance of his stunted gastrointestinal tract and he would surely give up immediately in his hungry quest for nourishment. Even if he could find food, how would he possibly digest it? But still, nature does not make mistakes, and he follows his natural impulse without question, moving slowly to stave off his hunger and conserve what little energy he inherited at birth.

Days go by and he floats out in the blackness, like a comet drifting in endless space, with no hope of colliding with any other entities by chance alone. At this point he is ravenous, and in pure desperation for a meal. He notices an occasional dull flash of grey light around him as he moves about in the darkness, but with his terrible eyesight he can barely tell if it is real or just his imagination and he ignores it. He knows that any chance he has in this world is entirely dependent on his sense of smell, which so far has not helped at all. He is weak and starving, and starts to float aimlessly more than he swims with intention.

He feels a current moving towards him and he freezes, motionless. He has no chance to fight with whatever blind horrors lurk at these depths and he can only hope that he has not been noticed. The current becomes much stronger, and he can feel from it that this creature is much, much larger than he is, perhaps too large to be interested in him, although food down here is scarce enough not to rely on that fact. Without the gift of sight he can only imagine the form of this shadowy terror. He waits motionless, as the creature, to his relief, moves slowly above him. The current generated by this unknown leviathan sends him spiraling out of the way and for a moment he thinks he is safe. Then in a split second the dark terror makes an instant and violent U-turn snapping at the water with unseen teeth to his right, but narrowly missing him, and then it swims off silently and slowly into back into the darkness from which it came. Our lucky creature drifts in the residual currents, shocked, and waits a little to be sure that it is safe, before slowly continuing on his journey.

He could never know that 1500 meters directly above him, the sun beamed down onto the glistening wings of cormorants as they dried themselves after a successful morning of fishing. They had joined the gulls in picking off fish from a living ball or sardines sculpted by hunting bottle nosed dolphins at the sea surface. It was a warm and breezy day and the sea was full of colour and motion. It could not have been more different to the world our creature was born into.

He was now starving, and close to death. This was not uncommon for his species. Most of his siblings would suffer this fate, or be snapped up by unseen monsters from the depths. As he waited for his fate something happened that changed his world. Was this starvation playing tricks on his mind? An overpowering smell had flooded into his senses. It was a glorious smell, and seemed to fill his entire body with a kind of primal energy he would not have thought possible given his near-starved condition. This is what he had been searching for his whole life and the scent consumed his entire being. As he moved, the smell became stronger and even more overpowering, and he swam faster in response. It did not matter to him if he used all of his energy in this endeavour, for he knew this was his one chance. He was getting closer and now swam as fast as his deformed little body would allow. A dull grey light was blinking a few meters in front of him, like an air traffic control tower guiding in a plane to land. He rushed forward in a feeding frenzy, with his underdeveloped eyes starting to make out some details of what lied ahead. Then he froze. He could not believe what he saw before him . He was face to face, with two rows of giant and ferociously sharp teeth. The teeth were longer than his entire body, and right above them, embedded into a pale fleshy face, were two tiny beady eyes, glistening in the light of a strange ethereal orb which hovered and blinked brightly above the face. She was absolutely beautiful.   The glowing orb which dangled above her head glistened like mistletoe in the darkness, and he could no longer hold back. His urges were a confused mix of hunger and sexual desire, and they were so overwhelming, he could no longer contain himself. What must she think of him? He was a wretched creature by comparison. Had she even noticed him? He became consumed with a cold fear that she had not, and that she would surely leave him for a superior suitor as soon as she did. No, he would not let that happen. He did not know how he would hold onto such a powerful beauty, but instinct took over and he gladly surrendered himself to it. He swam rapidly below her and buried his teeth into her flesh so hard that his jaw locked shut and he knew in that moment that he would never be alone again. He felt immense relief that his quest was over, and felt strangely like he was exactly where he was supposed to be.

However, as he desperately gripped her scaly flesh in his jaw, something strange started to happen. It was a horrifying and unexpected thing, which made him question whether or not he had made a terrible mistake. His lips began to dissolve. He kept his grip, fearing nothing more than to fall away and float back into the cold desolate darkness of the deep ocean, but the burning in his mouth was becoming much greater, and difficult to bear. Not only did his lips dissolve, but so did his teeth, and the skin and flesh around the bite wound he had inflicted on his ginormous princess. He could not have known that his saliva was full of flesh eating enzymes, specifically designed for this task.

As the pain became too great, he changed his mind, this would not be his fate, he pulled away but found that he could not. A fusion had occurred around his mouth to the body of this beauty. Where his skin had dissolved, new skin had grown and bonded to that of his partner. Slowly the pain began to subside. He hung from her body as though lifeless, like a piece of seaweed, moving only in response to the currents as she swam through the blackness. He was still starving. Biting into the flesh of his princess had not fixed his underdeveloped anatomy and despite his urges, he had no means to consume, nor digest flesh. For several hours he hung there, still starving, when suddenly a nutritious energy flooded into his cold body. Finally his blood had fused with hers. He would never have his freedom again, but he would never be hungry nor alone – she would be his protector.

She was an Anglerfish of course. She had been sending         out pheromones to attract a mate, when a starving and pathetic individual not much larger than her eyeball had approached her at an insultingly slow velocity. She briefly considered eating him, but she had recently gulped up an squid twice her size and this visitor would hardly suffice as an appropriate dessert for such an exquisite meal. No, she decided she would allow him to mate with her. Not out of pity, pitiful though he was, but because males were hard to come by in this place, in fact, he was the first suitor she had received in months, and she needed him to fertilise her eggs. She twitched her esca – the light emitting organ at the top of her head, to draw him in and barely noticed when he bound to her but for a small pinch on her abdomen. Truly pathetic, she thought, and began to fall asleep, drifting in blackness in body and mind.

As she slept, open eyed, as all fish do, she began to dream about her recent squid encounter. It had been crawling along the ocean floor looking for deep sea crabs, when she noticed it. She did not have the ability nor the will to carry her bulky body at speed through the water under these enormous pressures, but she could manage short bursts – a few feet at most. She was after all an ambush predator by nature, and preferred luring her prey to her rather than any of that unsophisticated chasing stuff. The squid was moving away from her, kicking up plumes of sand as he went rummaging around for unsuspecting crabs. She had to catch his attention. If she moved her whole body, she might spook him, or because of his size, might even become prey herself, but she had a highly sophisticated tool to deal with situations like this. It was in fact the same tool she had used to draw in her suitor, this light emitting esca, was located at the top of one of her dorsal spines. She began to flick it back and forth, and the squid, a visual hunter, with his far superior vision immediately noticed this enticing glowing orb and his prey drive was triggered. He shot towards her using his jet propulsion and landed almost within her strike zone. She waited for a moment, eying him up in the light of her esca. He was huge, and for a moment she wondered if she actually could eat him. Her jaw was designed to swallow prey whole, and she did not have the ability to tear up the flesh into smaller chunks. Fortunately she could distend her jaw and her belly, and her beady eyes glimmered with greed as she anticipated consuming this supersized meal.

She saw the squid creeping slowly, trying not to scare this strange glowing orb…but then something terrible occurred. Her esca went out and darkness filled the space. The squid froze, and then locked its huge eyes directly with hers. She was terrified. She shook her esca around desperately but it was too late. The squid had directed his interests towards a far greater opportunity. The squid’s 8 arms sprawled outwards like an umbrella and it fired out its two feeder tentacles towards her. Pain surged through her body as she was drawn quickly towards its extraterrestrial-like beaked mouth and then just  before the end came…she woke up suddenly from her dream.

That was not how her encounter had gone. Her esca contained a loyal colony of bioluminescent bacteria, and she had complete faith that they would not let her down in moments like that – as long as she continued to provide them with nutrients, they would continue to do their job. That was the deal. The squid had in fact, like so many before him, been totally enthralled by her flickering esca and as it approached she had promptly gulped him up filling her expandable stomach and doubling her size in the process – a strategy which has helped many species of Anglerfish survive in the absence of a reliable provision of more reasonably sized meals. This meal would provide plenty of nutrients for herself, her bacterial colony, her eggs and her pathetic parasitic partner who hung limply from her abdomen. She felt totally stuffed. It was not just the squid she had devoured, but she was also full of a million eggs, and now that she had accepted a mate, again without indulging in any unsophisticated chasing, she was in the perfect situation to spawn.

Before continuing this tale there is a mystery here of great scientific interest that I would like to talk about briefly. I’m talking about the bacteria that live inside the esca of our female Anglerfish. Firstly, bioluminescence is the production of light using a chemical reaction involving an enzyme called luciferase. You might be wondering, how organisms evolved the ability to use this enzyme to generate light. Much like heat, a tiny amount of light can be emitted as a sort of by-product of many biological reactions. In fact with a sensitive enough camera, you would see that the entire surface of your skin is glowing with the light emission of biological reactions at all times. Organic life really does glow in the dark but in nearly all cases, the darkness required to see it, and the sensitivity of the eyes required to detect it do not exist in nature. When you live pure darkness, even a tiny amount of light can result in large increases in your chances of survival, and so this places a huge evolutionary selection pressure favouring this phenomenon. In other words, those individuals which can detect minute quantities of light, will out compete those who cannot. Such a great advantage has resulted in bioluminescence evolving independently on at least 40 separate occasions in marine animals, many of which are totally unrelated.

Just to clarify how these evolutionary leaps might occur in nature, imagine for a second that you are a fish and your diet consists of eating difficult to find decomposing fish at the bottom of the ocean in the absence of any light. You’ve evolved from fish at the higher levels of the ocean where light can still penetrate, so you have some kind of vestigial but still slightly functioning eyesight, although with enough time without use, evolution will of course start to eradicate this unnecessary sense. Just look up blind cave fish for an excellent example of this. So down at the bottom of the ocean, the more of these delicious fish carcasses you can find, the more you can eat and the greater your chance of survival in a world of limited resources.

Now the fish carcasses you are eating, are also the food of choice of many species of bacteria. Some of these do emit tiny undetectable amounts of light as a by-product of natural biochemical reactions as they digest the nutrients they are consuming. If by chance there is a very high density of these bacteria in one location, you might even detect the tiniest amount of light emitted and you can go and eat the fish carcass that you previously would not have seen. Evolution now selects for better eyesight, and as we have just said, this is an easy adaption because your ancestors, who had lived at the surface levels, had excellent eyesight, and much of the hardware is already in place for these minor genetic adjustments to take place. Now that evolution has restored your vision and continues to enhance it over the generations, you are better at finding these glowing fish carcasses more easily. You might be thinking the bacteria would start to evolve to become darker, so as not to be eaten by fish like you, but actually the bacteria are very happy with this arrangement. They find conditions inside your gut, with all that partially broken down food, much more favourable than being out in the open ocean, so evolution instead strengthens their light emitting reaction as they digest nutrients, and they are more likely to be found. In the end, you have a sort of symbiosis, where the fish is being directed to good meals, and the bacteria are being collected to exist in a better environment inside the body of the fish.

Now this part is just speculation, but it could be that some of this light emitting bacteria begins to glow strongly enough in your gut, that it attracts a mate. They might have swum over to investigate a possible meal signposted by the light of bacteria, but they have found a partner instead. Now you have a situation where it is even more in your benefit to glow from time to time, and you may start to undergo some genetically driven physiological adjustments, such as developing thinner skin or clear scales around the location of the bacteria so that they transmit light out of your body more effectively. Perhaps it will go a step further and create special organs to house the bacteria and ensure that they are given everything they need to survive. Perhaps it is not only potential mates that these glowing lights behind thin skin and clear scales are attracting, but some smaller fish are attracted to what they think is a small moving meal, and you no longer need to rely on the carcasses of fish for sustenance but you can use your light to entice unsuspecting prey right into your waiting jaws. You can conserve energy by not swimming around anymore because your meal will come right to your door. One problem you have now is that to move these fish attracting lights you must move your whole body, and that can either spook the fish you would like to eat or make larger predators aware of you. Evolution creates a solution for that and you find that over time, your bacteria housing organ migrates to the top of one of your dorsal spines, which you can now move back and forth like a lure on a fishing line, and this of course gives the anglerfish its name.

Now as I said, this is just speculation, nobody is sure exactly how this symbiotic relationship has developed, but it gives an idea of how evolution might have shaped such an incredible light emitting organ in anglerfish.

The esca, this bacterial housing organ, is not a closed container. The fish has not imprisoned this colony, but rather it is a mutual agreement with symbiotic benefits for both parties. There is a small opening in the esca which leads out into the surrounding ocean, and so the bacteria can come and go as they please, however nobody has ever found these bacteria outside of the body of the fish and it is unlikely that they would leave voluntarily because of their dependence on the fish. They are unable to produce light outside of the Anglerfish and recent research has shown that they have lost a large portion of their genome compared to their free swimming relatives suggesting that the anglerfish itself is providing nutrition for the bacteria. In addition, each species of Anglerfish has its own species of bacteria, and it remains a complete mystery as to how the bacteria are transferred from mother to offspring. It has been proposed that the Anglerfish may transfer some of their bacterial colony to the eggs during spawning but nobody really knows.

Back into the black cold still water of the deep and our male angler fish is in trouble. He’s hanging from the female by the skin of his face. He wanted to form an endless bond with this female, but had no idea about this nightmarish situation he would find himself in.

 While he initially enjoyed the security and nourishment provided by his beautiful host, he could not help but feel like he was losing himself. He was, in fact, literally losing parts of himself. His fins had withered away into nothingness. His eyes had completely deteriorated and much of his internal anatomy felt no longer present. As if by some kind of curse, he had been rendered little more than a small bag of flesh, hanging from a far superior being. The only part of his body which seemed unaffected was his gonads, which if anything, felt more developed than ever before. If only he could have resisted the attraction of those potent pheromones. He cursed his ancestors being so pathetically successful in their bizarre parasitic mating attempts and passing on these strange genes to him. As he hung there he felt like more like an appendage rather than a being within his own right. Must he wait this out until his host finally dies? Can there be a more miserable existence then this?

Then something peculiar happened…he had become used to the steady nutrient flow of his partner’s blood stream, but now it felt different. Hormones were surging through the blood. A long stream of eggs was evacuating the body of his partner forming a thin gelatinous ribbon, which floated out into the open ocean. With a bit of luck, even if it were discovered in this darkness, it’s total 1 million egg length and gelatinous coating should keep it safe from most predators. His last role in this world was to fertilise those eggs, and he did so without question. Not that he had any choice. For he had bitten into the apple of temptation and sacrificed any notion of independence and free will. Even though his existence now resembled little more than a sperm donating appendage, he did finally find some peace of mind – what little mind he had left that is. His peace of mind came with the following conclusion:

“Though he was a mere part of something greater than he

without him, that greatness would not exist in the sea”

And that ends our first tale. 

I decided to start us off with the angler fish I think because I find them such an unusual and interesting species. It is difficult to match the menacing look of the species, and there are so many weird and interesting facts about it from the way it emits light in the darkness to catch its prey, the extreme sexual dimorphism (with the female being so much larger than the male) and the fact that the skin of the male’s mouth fuses to her permanently as she floats around at the bottom of the ocean. I think of all of the species I am familiar with, a male angler fish really got quite unlucky during the history of evolution.

So I hope you all enjoyed this first tale as much as I enjoyed making it and if you would like to connect with Tales of the Wild, please do so on our website or the usual social media routes which I’ve linked in the description to this episode.

Next week we have something very exciting in store. This time we are travelling to China, to explore a completely different species struggling to survive in a very different habitat. It is once again full of information about the unusual lives of some species, and a balance of real science and storytelling. Please subscribe to make sure you don’t miss it.

Thank you all once again for joining me on this zoological journey and if you are in a position to do so please consider supporting the podcast - it will really help me to get this project going.

Thanks a lot and see you next week!