Hello and welcome back Shark. Here is to another episode of
Deep Dives with Sharks. My name is Alex and I'm the host
of this thing. And if you're new to the
podcast, welcome in. We like to talk about everything
sharks and oceanic things, as well as shark week and movie
reviews, which that sentence is getting rather long, but it's
OK. We'll see if we can't even add
more to it eventually. But we do have a movie review
coming sometime soon, so stay tuned.
But thank you so much for your continued support.
Follow along on Instagram at Deep Dives with Sharks and don't
forget to turn on the post notifications so that you know
when the next episode is released and they will get more
on time. I promise.
That is my fault. So working on it.
I did get a little bit busy once again with work and everything
like that, but I feel like I add that in every episode and I just
need to to get good. It's a skill issue at this
point, so you know we're going to work on it.
But we also have our merch. We've got shirts and hats that
are perfect for the warm weather coming up.
And if you're going to be going to the beach or anything like
that, it's a great way to let the sharks know that you love
them and also keep that sun from burning up.
Because if you're like me, you burn every time you go to the
beach and it's great. But we're doing something a
little bit different today. So today's episode is all about
sharks. It's going to be kind of the
same as the others, except for we're going to be talking about
sharks, and that's the only thing that's the same about
them. We're not actually focusing on a
specific species today or safety or news.
We're actually looking at what makes a shark a shark, which is
a very broad category. And I will be referencing many
sharks during this episode as I try to give examples of what I
am talking about. But to start with the basics,
we're going to be going into shark anatomy.
Before we can really appreciate sharks, we need to understand
what makes them some of the most efficient predators ever to
evolve in the ocean. That, of course, means that
we're going to start with one of the things people associate with
sharks the most, which is usually teeth.
And I paused to kind of give you a little bit of a guess there.
I would also accept fins. We will get to those, but for
right now we're starting with teeth.
Now shark teeth are made of enamel just like human teeth, so
we got the same thing there, but they're far more durable and
designed for constant replacement.
Sharks are born fully equipped and a merely capable of
surviving on their own. No parenting manuals, no
learning phase, just instant survival mode.
And a lot of times this is out of necessity because some shark
parents like the great white, will have the baby and then just
leave. And it's probably for the best
because others like the hammer heads tend to try to eat their
young sometimes. So, you know, give and take.
Now they have multiple rows of teeth and those teeth are
constantly rotating forward as they fall out, which is usually
every one to two weeks. Over a lifetime, some sharks can
lose and replace 30,000 teeth, which is quite a lot of teeth
because humans only lose about 32, if that.
I don't even know if we lose all of our our baby teeth if we have
32 baby teeth to start. Clearly, I'm not a dentist, but
when it comes to sharks, they're going to lose teeth and they're
going to replace them. So while humans get one set of
adult teeth and just kind of hope for the best, sharks are
out here running a tooth replacement business and that
really bites the competition and everyone.
I'd like to to give Bree some claps here.
That is a solid pun and I am very proud of it.
Very proud of it indeed. Now what's really interesting is
that shark teeth aren't random at all.
They're highly specialized tools.
Marine researchers working at the Smithsonian Ocean, which is
part of the Smithsonian Institution's Ocean Research
Division, say that five times fast explain that shark teeth
are closely tied to diet and ecological role.
In their work. They note that shark teeth
function as highly specialized structures reflecting feeding
strategy and habitat. So essentially you can look at a
shark's mouth and figure out its entire, entire job description.
Now this goes into different species as well.
So flat teeth mean crushing shellfish.
Pointed teeth mean gripping fish.
Serrated teeth means slicing through larger prey like seals.
Every design has a purpose with that.
Great whites got those large triangular teeth.
They eat big animals. Sea lion, seals, big fish, tuna,
things like that. Meanwhile, Mako use more speed
base. They've got the more pointy and
serrated teeth, so they can get both smaller fish and they can
get larger fish as well, which is really cool there.
Now, of course, as mentioned earlier, some people think of
fins when talking about sharks, and that's what we're going to
talk about now. Fins are, of course, just as
important. Sharks have several fins working
together like a perfectly coordinated system.
The dorsal fin, which is the one you see breaking the surface,
helps stabilize the shark. Many species also have a second
dorsal fin farther back that assists with balance.
Of course, you'll see this kind of very much like a Skag that
you would see on a surfboard, paddle board, kayak, that little
thing that goes underneath. If you don't have those, you
tend to spin around in the water and it's really hard to control.
So this year offers that stability.
Their pectoral fins, located on either side of the body behind
the gills, act like wings. They provide lift and steering
control, almost like underwater aviation, which is now making a
lot of sense why I also find planes very cool.
They're just giant metal sky sharks.
It works out. And then there is the tail or
caudal fin. That's the engine, that's what
drives a shark forward through the water.
Different sharks have different tail designs depending on
lifestyle. Fast open open ocean hunters
like the short fin Mako have Crescent shaped tails built for
speed. Slower deep water sharks tend to
have longer more flexible tails. Steady for cruising.
One thing to note as well as many bottom dwelling sharks such
as nurse sharks, I believe wobegongs have similarly built
tails as well. Will tend to have a longer tail
on the top than the bottom. For a while I was just taking
guesses as to why that was until finally I came across it in
research that it's quite literally just because if they
had a thing on the bottom, they'd hit the the bottom of the
ocean a lot. So it just makes it easier that
they're not bumping into coral and everything with their tail.
So they evolved to have a longer one on top and that's pretty
cool honestly. Moving to muscle, sharks have
two types of muscle, red muscle and white muscle.
Red muscle is designed for endurance swimming and is rich
in oxygen, allowing sharks to travel long distances without
fatigue. White muscle is used for short
bursts of speed, like chasing prey or escaping danger.
A marine biologist at the Carl Meyer, who studies shark
locomotion and energetics, has explained that his research that
sharks are uniquely adapted for both sustained cruising and
rapid acceleration, making them exceptionally efficient long
distance predators. And I think once again, great
whites and Makos are great examples of this because they
can travel hundreds of thousands of miles throughout the years
and they can go ahead. And when they migrate thousands
of miles up coasts and everything like that, they still
get their food. They're not starving.
They're able to get there and get back and barely even break a
sweat, which that could be me. Shark movement itself is kind of
full body wave long muscle fibers running from head to tail
contract in sequence, producing that smooth side to side motion
we associate with sharks. Here is the efficiency hack.
They don't always swim at full effort.
They accelerate then glide, conserving energy over long
distance. Basically sharks are the ocean
oceans definition of work smarter, not harder.
A great example of that one as well is the Greenland shark,
massive shark that hunts deep in the ocean.
Great way that they hunt their prey, goblin sharks as well is
that they'll get a push going and they'll just glide.
And then of course things can't seem coming in the dark.
And what's crazy is how big Greenland sharks are, but
they'll just go up behind them and just get them.
It's nice and easy. It's how they've gotten, I
believe it was the Pacific Sleeper shark eats moose that
way too. But they just kind of come up
with the animals not knowing that they're there.
And that's really cool to see. I do think it's the goblin
shark. I'm going to think about it and
like, we're going to get a few things down.
Also, I'm going to be like, that's not the goblin, you goof.
It's a different one. But the goblin also has that jaw
that lunges out. I love them, They're really
cool. Now let's talk about something
people don't think about enough the skin.
Shark skin is covered in microscopic structures called
dermal denticles, which literally translates to skin
teeth, which is one of my favorite facts.
These act like tiny armor plates that reduce drag and increase
swimming efficiency. Scientists at the National
Oceanic and Atmospheric Administration, commonly known
as NOAA, described dermal denticles as structures that
reduce drag and turbulence, allowing sharks to move more
efficiently through the water than most marine animals.
The efficiency is so extreme, it has inspired engineered
engineering designs, including high performance swimsuits used
in competitive swimming, which I do remember they had those in
the Olympics. I think the ones in like 2008
end up getting banned or something like that because they
were too efficient, which is crazy, but humans are literally
trying to copy shark skin to win races and it worked.
Now let's briefly touch on temperature regulation as well,
because this is where sharks break another stereotype.
Most fish are cold blooded being their body temperature matches
the surrounding water. But certain sharks, especially
members of the mackerel shark group like great whites Makos,
can particularly regulate their internal temperature.
Doctor Barbara Block, a marine biologist at Stanford University
Hopkins Marine Station who has spent decades studying shark
Physiology, describes this system as a biological heat
exchange network that allows certain sharks to maintain
elevated muscle temperatures for improved hunting performance and
cold waters. So in other words, some sharks
are really built like internally heated athletes.
Very well put. Very well put indeed.
I will say the poor Beagle is another great example of this
one, especially up around New England.
They are usually one of the last ones to leave the waters around
Maine and Massachusetts, along with the great whites as their
food source will hang out for a little bit longer until it gets
too cold for it and it will head out.
But they'll be able to spend time in that water and then hunt
those seals and similar things. So rather neat to see.
One thing I do want to talk about with the dermal denticles
as well is that with different sharks, you will see how they
can kind of appear differently. What I mean by that is if you
look at a great white, they get their color and everything
because of that's just the way their skin is.
That's what their dermal denticles do.
But when it comes to a nurse shark, you'll notice that they
usually look Gray or brown and then unless you get right up
next to them, you tend to not see too much of A purple hue.
But you can unless you when you get right next to them, this is
really good to see you at many aquariums.
And that is because the way that the light hits their denticles,
the way that they're facing, the way that they're, they're on
that skin, it creates that that lighting effect, which is really
neat to see. So it can affect the way a shark
looks away, a shark moves and of course, the way a shark feels,
because not every shark has the same kind of dermal denticles.
Now a question that we get asked all the time, why there's a wide
variety of sharks. Now that we understand how
sharks are built, let's talk about why there are so many
different kinds of them. There are over 500 known species
of sharks, ranging from tiny deep sea species just a couple
feet long to massive filter feeders like the whale shark,
which can reach lengths of over 40 feet.
And how do we end up with all this variety?
A lot of time, a lot of it. Sharks have been around for
roughly 450 million years. That means they've existed
before trees, before dinosaurs, and long before humans were even
a concept of their evolutionary timeline.
Modern shark lineages, the ones that we recognize today, emerged
around 200 million years ago and survived mass extinction and
wiped out the dinosaurs. So sharks are not the extinction
did. Just to be clear, I kind of said
that. Weird paleontologist Doctor John
Long, a researcher known for his work on ancient vertebrae and
shark evolution, has described sharks as one of the most
resilient vertebrae lineages in Earth's history due to their
ability to repeatedly survive mass extinction events and adapt
to new ecosystems. That resilience is key to their
diversity. Over time, sharks went through
multiple extinction events, including one in the Devonian
period where roughly 75% of species disappeared.
But instead of dying out, sharks adapted and diversified.
Every time the ecosystem reset, new ecological roles open up,
and sharks filled them. That's where you get hundreds of
species Today. Sharks now live in nearly every
aquatic environment on Earth, deep ocean trenches, coral
reefs, open ocean systems, polar waters, and even freshwater
rivers. Each of those environments comes
with completely different challenges, pressure,
temperature, prey availability, and visibility.
So sharks evolve different body shapes, feeding strategies and
behaviors to match those environments.
Marine conservation scientist Doctor David Shiffman, who
studies shark ecology and human impacts on shark populations,
has explained that shark diversity reflects an
extraordinary ability to occupy nearly every marine niche on the
planet. Diet is a major driver of that
diversity. Some sharks filter plankton like
basking sharks. Others actively hunt fish.
The others specialize in ambush predation.
Predate predation. I don't know why I can't say
that word. Or deep sea scavenging
predation. There we go.
That's why you see such unique adaptations like hammer heads
with wide set heads that improve sensory detection or cookie
cutter sharks that specialize in taking small bites from such
larger animals. Around 50 million years ago,
coral reef expansion created create even more ecological
opportunities which further accelerated shark
diversification. Reproduction also plays a role.
Sharks are used multiple reproductive strategies from egg
laying, live birth, even immediate forms, intermediate
forms depending on species and environment.
That flexibility increases survival in changing conditions.
So when you combine evolutionarily, time,
evolutionary time, environmental change, dietary specialization,
and reproductive flexibility, you get one of the most diverse
predator groups on the planet, which is why they cast such a
huge net. And of course, Speaking of Nets
and fish and everything like that, why are sharks different
from fish? Another great question there.
Now let's clear up something that surprised a lot of people.
Sharks are fish, but they're fundamentally different from
most fish. The biggest difference is
skeletal structure. Unlike Bony fish, sharks have
skeletons made entirely of cartilage.
This is the same flexible connective tissue found in human
noses, ears, and joints. Cartilage is lighter than bone,
which gives sharks a huge advantage in movement
efficiency. Researchers at Florida Museum of
Natural History explain that their marine biology
publications that cartilage provide sharks with a
lightweight but durable skeletal structure that enhances agility
and swimming efficiency. Which real quick, just this
popped in my head here. We already talked about how
heavy some sharks are and all of them are made out of cartilage.
Could you imagine how much heavier a shark would be if they
had bones? Like a great white is already a
couple £1000. It would be so much heavier if
it had bones. That's just a crazy thought to
have. But anyway, sharks are part of a
broader group called cartilaginous fish, which I
like. How I can say that, but I
couldn't say evolutionary earlier.
My God. Which also includes Ray's skates
and shamaras. Even though they share cartilage
based skeletons, their body shapes differ dramatically.
Rays have flattened bodies adapted for bottom dwelling,
while sharks have streamlined forms built for active swimming.
Most Bony fish have one gill opening on each side, protected
by a flap. Sharks however, have 5 to 7
exposed gill slits. And contrary to a very common
myth, not all sharks must keep swimming to breathe.
Some sharks use their ram ventilation, swimming forward to
push water through their gills. Whale sharks and basking sharks
love that. Others, especially bottom
dwelling species, use sphericals, small openings
behind the eyes to draw water in wall resting or in Sharks do
that for one shark. Biologist Dr. R Aiden Martin,
who has studied shark behavior extensively in field
environments, has explained that many species are fully capable
of resting on the sea floor while maintaining normal
respiration though these specialized structures.
So no, sharks are not constantly in motion.
Another major difference is buoyancy.
Most fish use swim bladders filled with gas to stay afloat.
Sharks don't have this adaption. Instead they rely on a large oil
filled liver which can make up as much as 25% of their body
weight. The oil provides buoyancy and
interestingly, sharks are that are well fed float more easily
than lean sharks because fat accumulation increases lift.
Now let's return briefly to the skin, because it plays a huge
role in how sharks move. Dermal denticles reduce drag and
make sharks extremely efficient swimmers.
They also help to reduce noise and turbulence, allowing sharks
to move almost silently through the water.
The efficiency is one of the reasons species like the short
fin Mako can reach speeds exceeding 30 miles an hour.
And finally, that's their evolutionary timeline.
Sharks have existed for about 450 million years and have
survived multiple mass extinction events.
That alone sets them apart from most fish lineages, which are
far more recent in evolutionary history.
So while most fish are relatively adaptive in the short
term, sharks are evolutionary veterans.
I will say I did learn really recently as well that there is
some things in Yosemite National Park that are older than sharks,
which I was kind of disappointed because I used to jokingly go
with my friends to different national parks and go sharks
older than that, sharks older than that.
And I think it was Half Dome that we learned that it is not
in fact younger than sharks. I think that I think Half Dome
does in fact out last sharks. But getting into why sharks are
important, this of course, is going to be the most important
part of the entire episode. Now, why sharks matters?
Because sharks are not just predators, they are keystone
species, meaning their presence supports the structure of the
entire ecosystem. Remove them and the system
destabilizes. Marine ecologist Dr. Boris Worm,
I love that name, who has published extensively on ocean
ecosystem collapse and predator loss, has stated that the
removal of large predatory sharks can trigger trigger
cascading effects throughout marine food webs, altering
ecosystem stability at multiple levels.
In similar terms, sharks keep everything in balance.
It's kind of like a lot of you've learned in school about
the deer populations. You often will have some sort of
debate on oh, should we hunt deer?
Should we not? And usually 9 times out of 10,
people come to the conclusion that we should because humans
are one of the apex predators that help to control population
density, especially when it comes to animals that don't have
quite as many predators, which is also why we're messing up
sharks a lot. But we'll touch on that a little
bit too now. They function as natural
regulators, targeting sick, injured or weaker animals.
This reduces disease spread and maintains healthier populations
overall. This also creates evolutionary
pressure, ensuring only the strongest individuals will
reproduce. Sharks also regulate mezzo
predator populations, mid level predators that sit between apex
predators and smaller species. Without sharks, those
populations can explode, leading to collapse further down the
food chain. For example, if herbivorous fish
decline, algae can overgrow coral reefs, eventually
suffocating them. And coral reefs are not just
beautiful ecosystems, they are essential infrastructure for the
ocean. They support biodiversity,
protect coastlines from storms, and provide food and income for
millions of people. That is very true as well.
Sharks also play a surprising role in climate regulation.
A marine scientist named Doctor Federico Mariani pronounce his
name fine, too. I don't know what in the world
is wrong with me pronouncing some words, but others I cannot.
co-authored a major 2020 study on shark ecology.
Function found that shark declines over the past 50 years
have prevented the storage of over 2 million tons of carbon in
ocean systems. Instead, that carbon is released
into the atmosphere as CO2. Sharks also influence seagrass
ecosystems by controlling grazing behavior in species like
sea turtles and duagongs. Without sharks, these grazers
can over consume seagrass beds. And that's not great.
Seagrass is one of the Ocean's most important carbon sinks and
contributes significantly to oxygen production.
And Speaking of oxygen, phytoplankton in the ocean
produced roughly 70% of the Earth's oxygen supply.
Sharks indirectly support this ecosystem through their
influence on nutrient cycling and food web balance.
Sharks are literally connected to the air you breathe.
They also support global economies through ecotourism and
providing income for coastal communities worldwide.
And despite all this ecological importance, humans kill millions
of shark every year. Meanwhile, global statistics
consistently show that fewer than 10 human fatalities
annually from shark related incidents.
So you know, like we say, humans be messing stuff up.
We do sometimes, but that's why we always talk about how you can
help sharks. Even if you're someone who lives
in Kansas, which is not very close to the ocean.
There are many things that people can do in their daily
life looking at different ways to essentially not use products
that have been overfished, not support businesses that are
selling sharks. I myself have boycotted quite a
few. I'm not going to suddenly set
out a slam list here, but I will say I do know of a specific
restaurant near where I grew up that was selling Mako shark
during shark week. I have not gone to them since.
So there are things that you can do in your own life to make a
little bit of a difference. And of course, you can do things
to learn more, to let your friends know.
And just getting that word out does tend to help.
So of course, there is always hope.
We're not just doom and gloom up in here.
This is exactly why we're doing this.
We're not trying to make you bummed out.
We're trying to let you know what we're all doing to help
make things a little bit better, but we do have a few questions
going on in the question slash comment corner to make things a
little bit easier for folks. We're going to start going over
these a little bit more as well. And Leah asked if we could talk
about Go Sharks because they are so cool.
And I agree with you because I did that in episode 14, which
helps a lot. Now Go Sharks are really cool.
They are also known as Shamaras and they were one of my favorite
sharks for a while. They did get bumped out of my
top five, unfortunately, but I do love them quite a bit.
They move so majestically. They're one of the few that
actually don't use their tail to help propel themselves a lot.
They actually use their fins more, which is rather neat.
So definitely check that one out.
If you want me to revisit that one please let me know because I
do know some of the earlier browser earlier episodes might
need some work and possibly the late ones too.
So we'll see what we can do there.
Harry Zeo said. Hey Alex, just wondering if you
could help me with something. Recently I went to a restaurant
that served skate. I was having some angry feeling
about them having it on their menu so I told my family my
annoyance and they said they had it before.
I didn't know how to react to this as I'm a very big shark
enthusiast. Could you put some tips on how
people can react or do to help? So this one we did have to look
into a little bit. And eating skate is actually
very common in Europe, mostly France.
It's quite niche in the United States.
Not sure on where it would be there.
It depends on the area, but it is one of those things that some
people like it and some people don't.
Some skate species are overfished or vulnerable and
they grow slower and don't reproduce as often.
But also not all skates are endangered.
And in some regions they're managed sustainably.
So it just kind of depends on how this restaurant was getting
their their food. And I'm not quite sure how they
were, so I can't speak to that. But there are sustainable
practices, which is why we also don't advocate for completely
getting rid of the fishing industry altogether, because I
myself love seafood and I'd be very sad if I couldn't get it.
But at the same time, I also try to make sure I'm not going to
get something that's going to just absolutely wipe it out
Futurama style, You know, eating the last can of sardines that's
been extinct for years because Zoidberg's people came and ate
them all. Sorry if that spoiled a small
joke in that show for you guys, But you know, we're going to try
to not be be that way. We're we're going to try to find
the sustainable thing. So I do think it's acceptable
just depending on how they get their their things at Izzy said
I love this podcast so much. I listen to it every night.
I was wondering if there were sharks around the England UK
area. Well, I love you for listening
to this podcast every night. Thank you so much.
Yes, this surprises people, but there are actually a lot of
sharks around the UK. There are about 40 species that
live or visit UK waters and about 20 plus species live there
year round. We did an episode on the poor
Beagle shark, which you might find around England.
They're mostly found in the southwest England shores during
the summer. But yeah, the has a ton of
species. They're more low key and non
dangerous compared to the shark species you find in places like
Florida, which is the shark bite capital of the world, or
Australia. I will say one of the sharks
that was suggested by a shark, Hira, was the angular rough
shark. They're also around the UK
there, so check them out, but that's what I have for this
episode. I wanted to thank you for
listening all once again. Please comment or DM your shark
encounter experiences and I may share some at the start or end
of the next episode wherever they feel they fit the best.
Follow along on Instagram at deep dives with sharks or on
Twitch where I run polls and stuff throughout the week to see
what you would like to hear. Of course, send any questions,
comments, anything of the sort. Turn on the notifications so you
know when the next episode is out and give us a rating on
Apple, Spotify, anywhere you're allowed to and tell your
friends. Spread us all around.
We're going to keep doing this thing for a while and I promise
I will let you all know if I'm actually going to end this
thing, but we are not planning on doing that anytime soon.
So take care of yourselves, take care of each other, and I will
see you in the next one. Oh, also forgot to shout out my
other podcast. I do a podcast called Hot Takes
from the Bleachers with a few of my friends.
I had Bailey on to help with the The Meg episode.
So yeah, check that out. I appreciate you guys.
I'll link it in the description. You all have a great one.