Sharks You Might Never Have Heard Of
SHOW NOTES
Kristian has been fascinated by sharks since childhood [07.33]. He saw his first shark in the wild at age 13 while scuba diving off the coast of Mozambique. It was an oceanic whitetip shark, and the experience changed everything for Kristian: “That for me was a life-changing moment. I just went on then to be absolutely obsessed…I think something just ignited in me at that point, and it hasn’t gone away.” Kristian then went on to complete a master’s degree at the University of Exeter, and now works as a research associate there and freelance shark scientist, studying a variety of topics. He is also an accomplished science communicator, with a successful YouTube channel dedicated to sharks called ‘Shark BYTES’.
A shark Kristian knows very well – and the first he wanted to discuss on this episode – is the spiny dogfish [14.30]. There are two species, Pacific and Atlantic, which look identical but are genetically distinct. They are small sharks, growing between two to three feet long, but as Kristian says, “just because they’re small doesn’t mean they can’t pack a punch.” He wanted to talk about them on this episode because of their unusual defensive strategy, which, he believes, is one many people will be surprised by. “These guys have a sort of not-so-secret weapon up their sleeve, a pair of dorsal spines.” He explains. “They’re pretty sharp, but not only are they sharp, they’re also jam-packed with venom.” Yes – the spiny dogfish is one of the very few species of venomous shark! The spines are located at the base of the first and second dorsal fins so that anything attacking them from above will get a nasty surprise.
But how venomous is the spiny dogfish [18.21]? Well, Kristian has experienced the spines first-hand and has lived to tell the tale. “I was working with these Atlantic spiny dogfish as part of my master’s research…as part of that research, I was tasked to go and pick up some of these sharks that I (was) using for dissection from fishermen who had caught them as by-catch. I was cutting them open and seeing if they’d ingested microplastics. And I accidentally skewered myself on one of the dorsal spines as I was putting the sharks into like a big plastic bin in the car. Do you know what? It was throbbing the entire way home. I was not a happy bunny at all. It didn’t hurt as much as I thought it was going to, but I wondered whether maybe because they’d been dead and frozen for a little while, some of that venom had kind of faded away, but it was still incredibly painful. I think that some fishermen or people working in the fishing industry have said before that it’s similar to that of a bee sting, but some of them have described it as excruciatingly painful. I would say it was painful, maybe not excruciating, but that’s probably because I didn’t get a big old whack of venom. That was quite an experience for me!” So, not pleasant for humans, but definitely not fatal. As for predators of the spiny dogfish, the venom may be just enough to startle it, so that the dogfish can make a quick getaway.
But that’s not the only interesting fact about them [22.13]. They also have one of the longest gestation periods of any vertebrate, lasting anywhere between 18 and 24 months – that’s two years! And, the pups are born with the venomous spines, but to protect the mother during birth, they are covered in a kind of cartilaginous sheath which dissolves once they are safely out in the world.
So, the spiny dogfish is a shark that definitely deserves to be talked about more – but how about a shark so rare that only two specimens of its kind have ever been found [24.02]? Enter Mollisquama, a genus of extremely small sharks known as the pocket sharks. Host Isla explains the story of their discovery: “Back in 1979, one of these tiny little sharks was found in the deep waters off Chile, in the southeastern Pacific Ocean…and it was only 16 inches (40 centimetres)!” Undoubtedly one of the smallest sharks to have ever existed, it was named Mollisquama parini and remained the only specimen of its kind for 40 years, until 2010, when a team of scientists from the National Oceanic and Atmospheric Administration (NOAA) discovered a similar shark while on an expedition in the Gulf of Mexico. This one was even smaller – just 5.5 inches (14cm). And, although it looked similar to M. parini, closer inspection revealed it to be a completely different species, Mollisquama mississippiensis or the American pocket shark. “The part of this story I really love is that the NOAA team were actually looking for sperm whales.” Says Isla. “And this little shark that they found instead actually looks like a miniature sperm whale…they’ve got this really blunt snout, and small little eyes.”
Like the spiny dogfish, the pocket sharks have a very cool defensive mechanism up their sleeve [26.12]. They were found in deep-sea trawls, at depths of around 1,900 feet (560m). Here, there is very little light, but many species have evolved ways to produce their own. Like other deep-sea sharks, the pocket shark have special cells on their skin, known as photophores, which effectively glow in the dark. This process is known as ‘bioluminescence’. In the pocket shark, and many other species found in the deep sea, these photophores are located on their underside. It is thought that this helps to conceal them from anything looking up at them from below, as it mimics the faint light coming from above. However, the pocket shark has an additional glowing mechanism. Located just behind the pectoral fin is something called a “pit organ”. This specialised organ produces a sort of bioluminescent goo, that the shark can eject out into the surrounding seawater! While scientists aren’t exactly sure how it is used, the most popular theory is that it can be utilised to startle or even blind predators temporarily, allowing the pocket shark to escape.
From sharks with unusual ways of protecting themselves, we then move on to discussing a shark with a different hunting method from what you might expect: the wobbegong [35.00]. This group of sharks defies all the classic sharky tropes. For one, they are unusually shaped. They have a flattened body with a very large, wide mouth, and a number of adornments around the head known as barbels, which are whisker-like sensory organs. In the wobbegong, the latter are highly branched, designed to help the shark blend into its surroundings – but they also give the impression of a beard! As Kristian explains, wobbegongs may look quite unassuming, but they are actually masters of the ambush. Rather than chase after fish, the wobbegong lies in wait on the seabed. Each species has a colouration and pattern that enables it to be perfectly camouflaged with its environment, so that it seamlessly blends in with the seafloor. “They’re basically invisible.” Says Kristian. “And the tassels – those barbels – help break up their outline because they’re so webbed and branched and come out at weird little angles. They just disappear into the seafloor, it’s just incredible.” Once hidden, the wobbegong lies in wait for an unsuspecting fish to drift into its path, perfectly still and silent. Then, once the prey wanders close enough, the wobbegong opens its mouth at lightning speed and snaps it up. “It’s actually so fast that, as they open their mouths, it causes a sudden pressure change in the water, which basically means that anything at the business end of the wobbegong gets sucked closer.” Adds Kristian.
But that’s not all. Waiting for a fish to come close enough might take some time, so the wobbegong has another tactic to employ. “Wagging their tails.” Smiles Kristian. “Their tail is also incredibly patterned and shaped really weirdly, and they use it as a lure.” The wobbegong will slowly waft their tail back and forth, which mimics a fish in distress, encouraging other fish to come and check out the scene. And, once they’re close enough, there is no escape…
Another species that defies the stereotype is the nervous shark, Carcharhinus cautus [40.01]. Named after its timid nature, the nervous shark is known to be skittish around divers. It is a reef associated shark found in northern and western Australia, the Solomon Islands and New Guinea.
While there are lesser-known species that may not be talked about all that often, we are also finding out new and exciting facts about all sharks, including those that have been in the spotlight for some time [45.15]. Kristian rounds off the episode by telling the story of how America’s space agency, NASA, are connected to the largest shark on planet earth – the whale shark. “So people might have heard before that whale sharks have spot patterns all around their bodies and each spot pattern is unique to an individual whale shark. It’s kind of like a thumbprint. And for a long time, what we would do as scientists is we just take a picture of the left-hand side of the shark and sometimes the right-hand side and we’d be able to compare them visually and see, okay, this whale shark is different because its spot pattern is different. But at some point, I think the scientists realized they were like, you know what, this is taking too long. We got to try and figure out a better way to do this. And what they did was they repurposed a piece of software that was originally designed by NASA for mapping stars, to then map the spot patterns on the sides of whale sharks. So that piece of software was originally designed by NASA and it was used to help them map.
And I just think, that that is one of the most beautiful things you can kind of think of. Is that now this piece of software that was looking, you know, up into the sky, is now looking at stars on whale sharks.”
ABOUT OUR GUEST
KRISTIAN PARTON
Kristian is a freelance shark scientist and science communicator, working out of Cornwall in England. He completed his undergraduate degree in Zoology and then a masters by research in biological sciences at the University of Exeter, specialising in shark science. Specifically, he studied the impact of plastic pollution on sharks and rays globally and locally in the UK, via entanglement in marine debris and ingestion of microplastics. Kristian has worked closely with a number of shark NGO’s around the world including LAMAVE (Philippines), Beneath The Waves, The Shark Trust, and soon to be MARECO.
Kristian began his journey into science communication a few years ago by creating the YouTube channel Shark Bytes, talking all things shark – from creature features, new research, movie commentaries, and some of the harder hitting topics like shark attacks.
You can find the Shark Bytes channel on YouTube here, and Instagram here, or follow Kristian on Instagram and X.
