Sharks (we're gonna need a bigger podcast)

This week, we discuss sharks!!! Need we say more?

Episode Transcript

Speaker 1 (00:00):
Welcome to an hour of our time, the podcast where
we pick a topic, study it, and come back to
tell you what we've learned. Today, we're talking about sharks.
We're gonna go over the evolutionary history of sharks, talk
about the diversity of living sharks, and tell you why
sharks are special and maybe why we should protect them.

Speaker 2 (00:19):
I'm Joe and I'm Dave talking to some sharks man, but.

Speaker 1 (00:36):
My kids became Anna need.

Speaker 2 (00:39):
A bigger podcast.

Speaker 1 (00:42):
Should both be like smoking cigarettes that are just like
barely dangling out of our mouths. We're watching it recording.

Speaker 2 (00:48):
Did you ever see the Whitest Kids you know skit
or they parody that scene when the guy like scratches
the chalkboard my gout.

Speaker 1 (00:55):
Yeah, I love those guys so much.

Speaker 2 (00:57):
Do you know you know the skin on what I'm
talking about? Yeah, where they just keep zooming in and
it's an upskirt shot, so dumb there, gosh.

Speaker 1 (01:07):
There's a reason why, like I think their stuff still
is like popping up on clips on various social media
platforms with like no context because it was like like
kind of like. However, when became familiar with that British
show The Mighty boosh because of old Greg because like

(01:28):
someone just discovered that that clip and it got all
over than it. But it's just because, Yeah, they're so funny.

Speaker 2 (01:36):
I was bummed out when Trevor Moore died a few
years ago.

Speaker 1 (01:39):
Yeah, bummer We my wife and I all the time
when someone like basically they she says something where like
she's right, she'll be like listen to the woman John
from the The a of Lincoln Skitch.

Speaker 2 (02:01):
Had too much a drink and piss.

Speaker 1 (02:04):
Don't beat my butt. Oh he is beating my butt. Folks,
if you're this is this is brilliant podcasting. By the way, David. Folks,
if you don't know what we're talking about, you need
to go actually stop listening to this unless you're in
your car. Don't don't try to watch videos in the car.
Pull over to the side of the road, type into

(02:27):
your search bar, the lightest kids, you know, Abraham Lincoln,
and just enjoy. We're not here to talk about sketch
comedy from No probably twenty years.

Speaker 2 (02:38):
Ago, speaking of things that are sometimes white sharks.

Speaker 1 (02:42):
Okay, it's a bit of a stretch.

Speaker 2 (02:45):
Oh it wasn't my best one, but I'm such.

Speaker 1 (02:48):
A nerd that I was n't thinking about the white shark.
I was thinking of like countershading. Usually sharks are yeah,
lighter colored on the bottom and darker colored on the top,
which makes it difficult for their prey to see them
from below.

Speaker 2 (03:07):
That's just like people, because you know, we wear pants
and so our undercarriags are getting the less sun.

Speaker 1 (03:14):
I think it's a little different than that.

Speaker 2 (03:17):
I mean, I'm not saying it's for the same reason,
but you could describe me that way.

Speaker 1 (03:22):
They've called me a nerd about about this topic, and folks,
I gotta be straight with you. We gotta, we gotta,
I gotta give you the real ship here. Dave and
I were quite busy m hmm. And the point of
this podcast typically is we ramble on about a topic

(03:44):
that we didn't know very much about until we decided
to do it as a podcast topic. Then we go
and we learn as much as we possibly can about it,
and then we try to organize our notes into an
hour conversation. And if if that is familiar to you,
welcome to an hour of our time podcast. We're really

(04:04):
happy to have you. But that's usually what we have.
What we do for this one, though, because we've been
kind of very busy with work and our shared a
place of business, we decided to do a topic that
I already knew quite a lot about. In fact, we

(04:27):
have an exhibit about sharks at our museum right now.
So I've been ya, you know, thinking a lot about sharks,
and so we decided, you know, actually, sharks are incredibly interesting.
I knew, though I knew quite a lot, there's still
less to learn. So that's why we're doing sharks. But Dave,
how much do you know about sharks before we started this?

Speaker 2 (04:49):
Uh? Not much. I knew that they can't swim backwards.
I knew that they are a fish, and I knew
that supposedly, if a shark atta, actually you punch it
in the nose, and the batman may or may not
have a can of repellent on him.

Speaker 1 (05:04):
Yeah.

Speaker 2 (05:05):
Uh, the so you could say I know a thing
or two, Joe.

Speaker 1 (05:09):
You know, the shark repellent thing is really interesting because
the Office of the OSS, the Office of Special Services,
the precursor to the CIA, did try to develop a
shark repellent.

Speaker 2 (05:27):
Yes, they did for.

Speaker 1 (05:28):
The UH for the Navy in the Pacific Theater, and
one of the people who worked on that project was
Juliet child Ship.

Speaker 2 (05:39):
I know I did read this once. Yeah, now it.

Speaker 1 (05:42):
Was Julia child Or the shark will try to buy
a jewel, but it will it will't want to just
spins too bad.

Speaker 2 (05:52):
You feel good about this.

Speaker 1 (05:53):
I feel good about that. That's by Juliet.

Speaker 2 (05:55):
You glad this?

Speaker 1 (05:56):
But I say well, love, say well love?

Speaker 2 (05:59):
But didn't he oss? Also weren't they the ones that
were in charge of mk ultra.

Speaker 1 (06:08):
Well that they became the ci C I but.

Speaker 2 (06:11):
Wasn't that Yeah, or maybe it was the CIA that
was doing mk ultra.

Speaker 1 (06:16):
I mean, ultimately it's the same it's the same group,
so it is all right. So as I, as I
alluded to, I I know quite a lot about sharks,
as I am by training. We've often mentioned in this
podcast that I referred to myself as a paleontologist or
an evolutionary biologist. I sort of prefer evolutionary biologists because

(06:37):
it's a it's a more like broader, inclusive term. And
I studied the evolution of sharks and uh and like
living organisms quite a lot in in school because I
came to paleontology from the world of like studying living animals,

(07:00):
which is why I don't know as much as I
would like to about like geology, and a lot of
people come from geology, and then still other people come
from like anatomy anyway, right, But yeah, so because I
I know too goddamn much about this. But also by
the same token, sometimes these topics are challenging. As Dave

(07:21):
and I were talking off Mike, it's kind of like
the Dunning Krueger effect. Once you start to learn enough
about a topic, you get to a point where you realize, oh, actually,
I don't know shit about this, because you become aware
of how much there is to know. Right, So I

(07:43):
would say, I know like a little bit about sharks,
but I guess I probably know more than most people.
So Dave's gonna help direct our conversation a little bit
so that I'm not just rambling like I just have
then for five minutes.

Speaker 2 (07:55):
Sure, and let me directed ver second bat to Julia
Child because I was looking up looking up what you
had said, and I just read here that the reason
they were developing shark repellent was to make sure that
sharks were not going to get in the way of
weapons they were trying to use against German u boats.

Speaker 1 (08:13):
Oh it was Oh, I thought it was the specific theater.

Speaker 2 (08:15):
Okay, and her trying to mix different cooking concoctions to
develop shark repellent was the first thing she did in
the culinary world. Yeah, that was like her introduction into it.
So super fucking weird.

Speaker 1 (08:30):
Yeah, I learned this by I had like ten minutes
to get through a museum exhibit about Julia Child and
I was in my family wanted to look at it,
but I have I basically like skimmed it. So I
saw the part about the shark repellent, but obviously didn't

(08:52):
get all of the context. Okay, So let's talk about sharks.
So the first thing I wanted to talk about is
what is a shark? Because it can get a little
bit confusing, and when you start talking about shark evolution,
it gets really confusing because, like Dave, when you think
of a shark, what do you think.

Speaker 2 (09:12):
Of you know, I think of the great white shark,
I think of you know, jaws. You know, I'm not
thinking of whale sharks and things like that right off
the top of my head, but I know that they exist.

Speaker 1 (09:25):
Yeah, that's a good point on the most people's conception
of sharks. So there's a lot of species of shirks,
and I'm going to talk about like the diversity of
living sharks. I'm not going to spend the entire time
talking about fossil sharks, although I would absolutely love to
do that. Possibly that's another episode, but most people are

(09:45):
probably thinking of a white shark. For the record, apparently
shark biologists get really irked by this when people call
it a great white shark. Is apparently the name is
a white shark. I can't get that upset of that,
because I think that common names are not useful, period,
and so that's why scientific names are more useful. I

(10:11):
know that people are like think that they're intimidating and
that they're just jargon me. But the thing is, there's
rules for scientific names, sure, and each species only has one,
whereas they may have multiple common names. And often these
common names kind of like get you confused as to

(10:34):
like what the animal actually is. But apparently it is
white shark. But car carroton carcracles is the the species name,
genus the species name.

Speaker 2 (10:47):
But we're trying to ask where where did the great
come from?

Speaker 1 (10:50):
I have no idea.

Speaker 2 (10:53):
Cool, it's just a last and answered.

Speaker 1 (10:56):
Well, that's the thing is, you'd also like the etymology
of these common names is like hard to track, So
who knows. I'm sure there's a story there, I just
don't know it.

Speaker 2 (11:07):
Sure.

Speaker 1 (11:07):
One of the things that like I hope that people
understand that when we don't know the answer to something
on this show, we just are like perfectly happy to
say that we don't know. Just don't just like make
shit up.

Speaker 2 (11:22):
True.

Speaker 1 (11:23):
I feel like we would be doing you a great disservice.

Speaker 2 (11:26):
That we're not. We're not RFK or the president over here,
you know.

Speaker 1 (11:32):
Anyway, So when people are thinking about a shark, thinking
about like, yeah, like a white shark kind of shape,
or you know, like a tiger shark or something like that,
kind of what you call fusiform, like a like kind
of a long shape with a two tectoral fins, which

(11:52):
are the you know, the ones on the front or
like the sides, usually quite large. Yeah, usually uh, you know,
because of because of jaws, right, They're they're thinking of
that dorsal fin, the singular one that that sticks up
from the top, and then there are actually several other

(12:14):
sets of fins that modern sharks have but uh, but
we like pelvic fins and anal fins, which are obviously
the name is justin near the anus. But the one
that is most important would be the caudal fin, the
tail fin, as modern sharks do have a really distinctive

(12:36):
caudal fin that kind of is is different from other fish.
But what's interesting and kind of confusing for their evolution
is that relative now, living sharks have all different shapes
and sizes, so that's kind of like the general shark shape. Yeah,
but they have they have taken many different forms, which

(12:59):
will can get into a little bit. But the thing
is that general shape of sharks has actually evolved multiple times,
and so there are fossil sharks are fossil animals that
if you looked at one, you would say, yeah, it's
a shark, but they actually might not be that closely

(13:23):
related to the living sharks. So roughly and then in
fact they were quite sure that they're not. There's roughly
three main radiations of sharks, and it does seem that
they keep going back to that sort of body shape

(13:47):
because it's probably very good for doing what they need
to do for swimming, you know, kind of usually sort
of long distances catching their prey, you know, being pretty fast,
things like that. At the first major radiation of shark
like animals happened during the Palaeozoic, which would be the

(14:12):
first like major section of the history of complex life.
Then there was a radiation of shark like animals in
the Mesozoic, which is the typically like the Triassic, Jurassic,
and Cretaceous many people call the Age of reptiles, is

(14:34):
when dinosaurs were dominant on land. So you have shark
like creatures in the oceans at that time. In fact,
there were some of the major predators.

Speaker 2 (14:47):
Sure.

Speaker 1 (14:48):
And then lastly you get the modern radiation of sharks,
which doesn't happen until the gre Classic period, So we're
talking like somewhere between two hundred and one hundred and
fifty million years ago. So now, if you're the kind

(15:09):
of person who's like sort of interested in this stuff,
you might be saying, well, wait a minute, Joe, or
if you'll watch some of the videos that we make
for work, maybe saying, I put a minute, Joe, I
heard I saw a video that said something like sharks
are older than trees, right, So how does that fit
with what I just said that the Joe that sharks

(15:32):
are you know, relatively recent from like you know, geologic scale. Well,
that's because there's kind of two ways that people were
talking about sharks. Shark and then there's shark in you
know aar quotes. So shark can refer to the living

(15:54):
sharks and their last common ancestor. So that would put
that that you know, you traced that line on the
family tree. Like I said, that gets you back to
about the Jurassic period one hundred and fifty two hundred
million years ago, where we have things that like look

(16:15):
structurally just like living sharks. But then shark can also
refer to all of the group that we call the Kondrichthians,
which are the fish with a cartilage skeleton. Now, there
are a lot of groups of extinct fishes, but that
would roughly contrast them with the other major group of

(16:38):
fishes the ostiak These so chondriac these is carlage skeleton chondros. Yeah,
and ick these is fish ostiach these osteos is bone
ich these fish so carlistfish, bonefish. We are bony fish, okay,

(17:05):
because we've all from bonyfish ancestor. Okay, So Kandriacthians would
be sharks, skates, and rays, so things like sting rays,
manta rays, the other things like sawfish and other some
sort of weird creatures, uh, which we're not going to
talk about very much after this. And then also these

(17:27):
weird creatures called kinras or ratfish, which is like a
really like who did they piss off to get that name?
They are alive today, but they they're not, you know,
super common, and they live often like kind of in
out of the way places like the deep ocean.

Speaker 2 (17:46):
Okay, gotcha, all.

Speaker 1 (17:47):
Right, So Dave, how how how do you feel about that?
So far?

Speaker 2 (17:51):
Good?

Speaker 1 (17:51):
So those those three major living groups and then grabbing
like collecting them and finding if you found their earliest
common ancestor, that would get you all the way back
to maybe as old as four hundred and fifty million

(18:12):
years ago. So when we say that sharks are older
than trees, this is what we mean because land plants
haven't appeared. Not only tree not trees, but land plants
have not evolved at this point. Sure, so this puts
you way back into the Ordovisian. Now, the thing is,

(18:33):
what's interesting about the late Ordovisian period. These fossils that
we find are we find shark like scales but no teeth. Okay,
so does that mean that these animals were toothless? That

(18:55):
seems weird, but that actually would not be super bizarre
because fish evolved from the earliest Fish do not have jaws. Yeah,
they just have like a like a cheerio, you know,
like just a oh shape, like a if you know,

(19:16):
an O face and an O face. If you are
familiar with modern the modern day lamprey or hag fish,
I don't know, if I am, you can look them up.
They're gross as hell. They're problem in Lake Erie. Those
are Jallis fish. So we do have some jollish fish
in their life today.

Speaker 2 (19:36):
So how do they what?

Speaker 1 (19:38):
They They just stick on to a fish and like
start sucking.

Speaker 2 (19:44):
Hot mm hmm.

Speaker 1 (19:47):
So they you'll see, you'll find fish in Lake Erie
they have these like circular wounds on their.

Speaker 2 (19:52):
Sides like a leech basically kind of that's.

Speaker 1 (19:56):
From lamprey, but it's it's a very it's a vertebrate
like you and I. Okay, so maybe the Ordovisian We're
not sure, but for sure we have by looking at
fossils as well as DNA. We we know that these chimeras,
these ratfish split off from the main condrict the in

(20:20):
line four and twenty million years ago, sure, and the
oldest shark teeth. So the thing about sharks is, like
I mentioned, they have a cartilage skeleton. It's not made
out of bone and this, and I think people assume
that that came first, and because we have a bony skeleton,

(20:40):
that that's the bony skeleton is the more derived condition,
and that a cartilage skeleton is quote unquote primitive. It's not.
It's actually the other way around. Bony skeletons appear first,
and later on this group evolves a cartilage skeleton, which

(21:02):
allows them to be more flexible, gives them some benefits.
It is not true that living sharks have that. The
cartilage is just like what's on your nose, your ear lobes.
It's actually coated. Parts of it are coated in these
hard plates called tessaly, So it's not like completely mine
out of rubber. But they are very flexible. So anyway,

(21:27):
you get these cartilaginous fish four and ten millionaires ago,
you get the first shark teeth what as I was saying,
because they have that cartilage skeleton. It isn't fossilized too well.
But the teeth are extremely hard. Teeth are the hardest,
about the hardest thing that animals make. They're pulp cavity,

(21:52):
which has like the blood supply and everything. That's what
they drill out. If you have a root canal.

Speaker 2 (21:59):
Oh, I have, yes, I have too. It's fucking terrible,
it's very unpleasant.

Speaker 1 (22:04):
Around that you have dneine, which is pretty hard, and
then around that you have enamel, which is almost it. Actually,
once you grow enamel, you can't like repair it because
it's a rock at that point. Well sure, so it's
extremely hot and that's why you have to get your
teeth drilled if you don't take care of them, because

(22:24):
they won't. They can't la necessarily repair themselves very well.
But what's interesting is they have teeth in their mouth.
The sharks also have teeth on their skin. They're called denticles.
And again this is where evolution has worked maybe backwards
from what people think it was. Actually those Remember I
said that the first verdets didn't have jaws. I do

(22:45):
remember the mouth teeth come from the skin teeth. I'm okay,
wrap your head, try to wrap your head around that.

Speaker 2 (22:55):
I don't think I understand.

Speaker 1 (22:57):
Okay, what I want you to do. So they have
these teeth, these denticals on their outside, on their skin.
Now imagine take your lips and like kind of suck
your your lips like in your mouth like this over
your teeth. Like do that at home listening. You look
really cool in your car.

Speaker 2 (23:19):
Yep.

Speaker 1 (23:19):
Okay. Now that skin that's on the outside is now
on inside of your mouth.

Speaker 2 (23:26):
Yes.

Speaker 1 (23:26):
So by unfolding that skin with the teeth on it,
now the teeth are inside the mouth. And that's the
first step. And then you evolve a jaw that has
a hinge. And then later the group of animals that
we belong to lost the teeth on the outside, and

(23:47):
now we only have teeth in our mouth.

Speaker 2 (23:49):
Wow, huh, very strange. Seems like an inefficient process.

Speaker 1 (23:56):
Uh well, it was not efficient.

Speaker 2 (23:58):
I know, That's what I'm saying.

Speaker 1 (24:00):
Okay. So anyway, what we have, like I said in
the Silari and like four and a ten million years ago,
we have these like shark like animals called acanthodians are
spiny fish or spiny sharks. They're notable because they have
these sharp spines associated with the fins, so they kind
of like they don't they have some features that are

(24:24):
kind of shark like, some features that are not very
shark like, but we do think that sharks evolved from
this group of animals. An example of these would be
an animal called Doliotis problematicus, which was given the name
because people were like, what the fuck is this? Where

(24:48):
does it fit into the family tree?

Speaker 2 (24:50):
Sure?

Speaker 1 (24:51):
By the Devonian period, which are the rocks that we
have right underneath our feet here in Ohio, you have,
so we're talking like three hundred and eighty, three hundred
and seventy million years ago, you get animals like Claudo Slackie.
And if you looked at this happy little guy, that's
a C L A d O s E l A

(25:14):
c H Claudo Silacki. I was pronounced this as Claydo Salachi,
but it's it's from Cleveland, and I feel like Clauda Slackie.
I feel like it's pronounced with like a northern Ohio accent.

Speaker 2 (25:28):
You know what I mean?

Speaker 1 (25:30):
Yeah, I know what you mean, but that's the apparently
the proper scientific pronunciation. If you saw this thing, you
know what you would say, like, yeah, that's a shark.
They look just like pretty much like a shark, with
some key differences. Their their pectoral fins are kind of
weird and stiff. Monern sharks have are able to move
their their fins quite a lot to change the angle

(25:54):
that they cut into the water. They still have these
spines by some of their fins. And then most importantly,
the mouth is right at the front of the face.

Speaker 2 (26:09):
Now, I know that seems like I was say, isn't
that normal?

Speaker 1 (26:12):
Where else would it be? But when you look at
modern sharks, I think of your white shark. They've got
that rostrum, that nose part that sticks out in front,
and the mouth is actually below and behind that. Okay,
so they have like a little bit more specialized kind
of jaw which they can actually like if you've seen
footage of sharks like attacking things, how the mouth can

(26:37):
kind of swing out right, they don't like the kind
of it looks very like the zenomorph actually, Okay, these
ancient shark ancestors couldn't do that yet. That's called the
highest higho stylic jaw. So anyway, we've got kletyslaki and

(26:58):
these other like kind of shark like things and I
always want to again shout out like Ohio. If we
don't have fossils from this area, then we could not
understand the evolution of sharks. People come from all over
the world that are experts on the subject to study
fossils from like northern Ohio because that's where you find

(27:20):
this stuff. Then you get to like the Carboniferous periods
about three hundred and fifty three and sixty million years ago,
there was a extinction at the end of the Devonian period,
the previous period, which wiped out like maybe like seventy
five percent of life on the planet, and it also
wiped out a lot of fish groups, but it did

(27:44):
not kill sharks or the shark ancestors, and then they
kind of like radiated into filling all kinds of different niches.
In fact, there was a lot of weird fish like Stephacanthus,
which they and they did like freshwater habitats. Most living
sharks don't, except for a few exceptions, live in saltwater only,

(28:07):
not fresh water. But there was a lot of different
freshwater sharks. There's If you're familiar with fossil sharks who've
been to a museum, you might have seen a fossil
of helicoprion, which is this shark that's got this like
weird tooth whirl that people didn't know what they were

(28:32):
at first. And then by the Permian period there's another
mass extinction that we've talked about on the show before
two hundred and fifty two million years ago, which wiped
out like ninety six percent of marine life and only

(28:54):
a few sharks, our shark ancestors make it through. And
then in like I said, the Jurassic period, maybe about
like two hundred million years ago, you get the oldest
group of sharks, the six skill sharks, which are still

(29:14):
around today. Okay, so the Jurassic that's when you get
the modern groups of sharks appear. By the Cretaceous period,
sharks were quite common predators in the oceans. But then

(29:35):
they also went through that mass extinction at the end
of the Cretaceous which we have also talked about on
this show, and wiped up many of them, but not
all of them, and then they radiate again into kind
of like the modern lineages that you see today. One
last thing about fossil sharks. Most people are probably familiar

(29:56):
with O. Totis megalodon. Yes, involved about twenty three million
years ago, and it was the largest predatory fish that's
ever lived. This thing ain't whales. What's interesting is you

(30:19):
usually see it drawn or depicted as like a big
giant white shark.

Speaker 2 (30:24):
Okay, yeah, but they're not in.

Speaker 1 (30:28):
The same group as white sharks, so there's not necessarily
a reason to think that they looked exactly the same
as a white shark. What else. The last thing I'll
say about them is that it is not the case
that we only have their teeth. Those are fairly common,

(30:48):
but we do sometimes get other parts of their skeleton
as fossils, like their vertebrae. So when people are like, oh,
well we just got we have no idea what they
look like because we just have the teeth, that's not
totally true, but it is still an active area scientific
debate exactly what their body shape was, and like, for instance,

(31:09):
how long they got. But these are some badass whale
eating sharks, and that's cool, huh.

Speaker 2 (31:19):
Can I ask you know, clearly sharks or you know,
some of the precursors to modern sharks, some that still
exists now have been through these mass extinction events. What
has made them so hardy or hardy enough to make

(31:40):
it through those.

Speaker 1 (31:41):
Let me say one real quick thing. I think I
think I accidentally said that Ototis Megaladon appeared twenty three
million years ago. It was the genus Ototis that it
belongs to Ototis Megladon's closer to like four five million
years ago. Okay, and then it's sorry, Jason Stath, and

(32:05):
it's not still around. It died out about maybe like
two and a half million years ago.

Speaker 2 (32:09):
Gotcha?

Speaker 1 (32:10):
How well? So the thing is like these different groups
of like shark relatives or shark ancestors did suffer through
these mass extinctions, but some of them made it through,
and then they were able to adapt and rediate into
these now unoccupied positions in the ecosystem would call a niche.

Speaker 2 (32:31):
Huh.

Speaker 1 (32:32):
But what happens is, and the reason why it's been
so complicated to try to tease apart their evolution, is
that when they like evolve, they sort of keep going
back to this shark like shape, even though like some
of those fossil sharks like Ladislaki that I talked about,

(32:55):
it's probably more closely related to the chimeras and not
to things like you know, white sharks and hammer head
sharks and things like that. Okay, we'll talked a little
bit about uh shark diversity.

Speaker 2 (33:18):
Yeah, absolutely, like you said, we well, no, I was
gonna I was gonna ask about that because again, like
you said, and we started, we tend to think of
sharks kind of in one way, and there are a
lot of different kinds of sharks, different different species of shark.

Speaker 1 (33:35):
Oh, I'm gonna tell my cool story about uh shark
teeth and geology at the end of the episode. We'll
save it. Oh, sure, a little treat. Well, we got
to take a break from talking about fossils, you know,
because no one cares. No one cares for me. I

(33:59):
don't think that's true, but it could be wrong.

Speaker 2 (34:02):
Well, let us know an hour of our time podcast
at gmail dot com.

Speaker 1 (34:08):
Joe Qui, Yeah, about fossils. I can't help it. So
I mentioned that the uh the condrict these the cartilaginous fishes,
has three living groups. So you've got your camera, which
they split off like four hundred million years ago. I

(34:29):
should say we know that from DNA evidence. They actually don't.
They they represent something called a ghost lineage because they'll
like there are large gaps in their fossil record where
they don't we don't find them for periods of time,
which is really interesting. Obviously knew that they had to

(34:51):
have been there, but yeah, they're fossil records botty. But anyway,
you've got the rat fishes or the camera, you have
the batoids, which are the skates and rays. Now it's
really interesting, Dave Is. I was going to go back
and looking through my old textbooks from when I was

(35:12):
in graduate school, and I remember like what skates and
rays were being like an active area of scientific debate
at that point. Okay, basically like are they just weird sharks?
Has the skates or the ray like flattened shape evolved

(35:35):
like multiple times independently. My understanding now is that we
don't think that they're what we call on monophyletic groups,
So they're like all actually one group that you can
trace back to a single common ancestor. Sure, so they
split off and then you get the Sileka morpha or

(35:56):
the Sileaki, which are the shark sharks.

Speaker 2 (36:00):
Mm hmm.

Speaker 1 (36:00):
And that's the only ones we're gonna talk about. There's
over five hundred species living today.

Speaker 2 (36:07):
Damn, you've got two.

Speaker 1 (36:10):
Main groups the gallio morphs and the squala morphs. Okay,
but I'm just want to give you, like we're not
going to get into like the whole like taxonomy. If
you're interested, like you can look it up. But you
have the the car karinaformes, which would be like tiger sharks,

(36:36):
black tip and white tip reef sharks, which you're probably
familiar with, right Dave from.

Speaker 2 (36:45):
Yeah, reef sharks.

Speaker 1 (36:46):
I'm aware of, yeah, because if you if you go
to like the aquarium of the Zoo, you've seen those.

Speaker 2 (36:50):
Oh yeah, yeah, and I see here that dog fish
that's the most common shark species in the world. On
there are quite a lot of those, So, yeah, the
car there are hundred and nineteen different species of dog
fishud they fit in this category as well.

Speaker 1 (37:04):
No, they don't. The other main group of sharks that
you would recognize would be the hammerhead sharks are in
the carcoon forms, the heterodonta formes. Those are some of
these are like you may have heard of them less,
but a good example of the heterodont form shark would
be the port Jackson shark, which are these really interesting sharks.

(37:28):
They eat hard shelled animals and so they have really
weird teeth. They do not have like the sharp teeth
that you think of a shark to have. They have
like these flat plates for crushing shellfish. Oh.

Speaker 2 (37:42):
Interesting, a great example of a creature that has evolved
specifically to eat what it eats.

Speaker 1 (37:48):
Yeah. Well, there's this idea that, like sharks are living fossils,
they haven't changed for like, no, it's not true. Like
just because you could go back in time for hundred
million years ago and see a thing that like it
looks shark ish doesn't mean that they haven't evolved. I
obviously I went through the whole discussion of them, and
they're all different shapes and sizes than things that they eat.

(38:10):
There are even some sharks that are partly herbivorous.

Speaker 2 (38:15):
Really yep.

Speaker 1 (38:17):
The heck sankafore Me's would be.

Speaker 2 (38:19):
When you say partially herbivorous, you mean that they're they're omnivores.

Speaker 1 (38:25):
Yes, Like they'll eat fruit that falls into the water
and things like that.

Speaker 2 (38:30):
Oh so they're just kind of like opportunistic eaters.

Speaker 1 (38:34):
Yeah, but they're just you know, it's definitely a more
diverse diet that you might expect.

Speaker 2 (38:40):
Yeah, I mean I'm kind of that way, Like I
opened the cabinet and it's like, huh, I don't really
eat a lot of oatmeal, but there's a pack of
oatmeal here. I could. You know, I'm an opportunistic oatmeal eater,
you know what I'm saying.

Speaker 1 (38:56):
I like oatmeal. I thought it was something that you
would probably eat. The Other day I had some oatmeal
and I had some like fancy yogurt, what fruit on
the bottom. When I was like, hmm, what if I
mixed these two together? And I mixed them together and
it was really good.

Speaker 2 (39:13):
Yeah, left it in the fridge overnight.

Speaker 1 (39:15):
No, I didn't do that, but yeah, I didn't make
glorp as you called it.

Speaker 2 (39:20):
Yeah, okay, how you breakfast? It seems like you could.
You could spackle a wall with it.

Speaker 1 (39:28):
Yes, yeah, well you know it serves a dual purpose,
it does, Okay. So I said the car koariniformis, which
would be things like reef sharks, bull sharks, hammerhead sharks,
the heterodontiformies those are the like the weird bullhead sharks,
like the Port Jackson shark. The hexankafor mes, which would

(39:51):
be things like the the seven gill shark, which I
think I said earlier that hexankerformies are the most the
earliest group of sharks to evolve in the modern groupings,
but that may or may not be true. There are

(40:11):
still a lot of debates amongst scientists that study sharks
as to the exact like inter relationships with these groups.
So I'm giving you just a broad survey the land informes.
These are the way people call the mackerel sharks, So
there's a lot of different There's a lot of diversity here,
everything from the white shark and the mako shark, which

(40:36):
is the fastest shark, one of the fastest fish. Two
things like the megamouth shark and the basking shark right,
which are filter feeding sharks, and then the shark that
my son may wanted to make sure that I told
everyone about, the goblin shark, which which is.

Speaker 2 (41:00):
That's kind of fun name is it look like it
would be called the goblin sho.

Speaker 1 (41:05):
They look ugly, all holy fuck, they have a very
long fossil record. Good lord. Then you get the the
a rector lobe before me is, which would be things
like nurse sharks, the zebra shark, which zebra sharks are

(41:28):
interesting because they don't have stripes. They have spots.

Speaker 2 (41:33):
Did you say nurse shark.

Speaker 1 (41:35):
Nurse sharks.

Speaker 2 (41:36):
Yes, Oh that's a friendly looking guy.

Speaker 1 (41:40):
They're you know, they look friends shaped, helpful, but also
those and then in that group is also the whale shark,
which is the largest living fish. They are the largest shark,
but they are filter feeders, so they eat some of
the smallest creatures. I have.

Speaker 2 (41:56):
I have a whale shark fact here. Yeah, like you said,
biggest fish in the ocean. Their spot pattern is unique,
like a fingerprint, although we also know that the fingerprints
being completely unique is a fallacy. Right, Yeah, we're gonna
talk get the idea more like a snowflake. Is this

(42:17):
the pattern on a whale shark?

Speaker 1 (42:19):
There you go. I was so I mentioned that we've
got this shark exhibit. I was talking to our our
mutual coworker, Brendan, and he was saying like he had
never heard of a whale shark before. He was like,
I didn't like know that that was like an animal
that existed. And I was like, this is how I

(42:39):
can tell that you weren't like a quote unquote animal. Kid.

Speaker 2 (42:44):
Yeah, because like I'm going to guess that your kids
know that a whale shark exists.

Speaker 1 (42:47):
Yeah, oh, they they know exactly what a whale shark is,
and they knew like every speeches shark les in that exhibit.
Like my ass was getting zoo books when I was
a kid, Like I knew a whale shark. Yeah, but
not everyone grew up as an animal nerd.

Speaker 2 (43:05):
Yeah, no, I got you.

Speaker 1 (43:07):
Yeah. So the the like the well shark that's a rectolobiform,
the pristia for for mes. These are these saw sharks
which they are kind of flat, so they look sort
of like ray like, and it does seem that while
also the shark shape has evolved multiple times, sometimes sharks

(43:32):
like get flattened, and that seems to be like a
a thing that's evolved several times. Sure, Ultimately, obviously like
one of those times led to the lineage that we call,
you know, the rays, the squale of formes, which would
be things like dogfish like you said, Dave, there commonly

(43:53):
like you know, some like smaller sharks, the squatnaf mes,
which are the angel sharks, which again look real. There
are some flat focks they kind of resemble sting rays
and skates. And then lastly the ekreinaformes, which is the

(44:18):
prickly shark and the bramble sharks. So these are like
some kind of like strange sharks that are unsort of
uncle where they fit. So I hope to give you
like a few examples, and obviously, like you may not
know what those are, but some of them maybe you're
be familiar with, like you know, hammerhead and things like that.
But that way, if you listen to this and you're like, oh,

(44:39):
that sounds weird, you can you know, look it up
to learn more. But they're not all these like hyper
predators like the white sharks.

Speaker 2 (44:52):
Yeah, and you're right about the angel shark, I mean
very ray, like very flat.

Speaker 1 (45:02):
I think it's to the point where there was an
idea that was that had not yet been ruled out
by the time I was like in undergrad that maybe
skates and rays evolved from something like an angel shirk.

Speaker 2 (45:22):
Yeah, I mean that I was going to kind of
ask that it seems like a logical assumption.

Speaker 1 (45:27):
It is, but apparently that that is not the case.
That they the skates and rays split off a lot
longer ago than maybe we thought. Okay, this is an
example what we call conversion evolution or parallel evolution, where
you have. Well, parallel evolution is kind of a separate

(45:50):
or related concept convergent evolution where organisms that are under
similar environmental pressures, maybe like live in a similar environment
or eat the same kinds of things, tend to develop
shapes or structures that look very similar.

Speaker 2 (46:06):
What's parallel evolution.

Speaker 1 (46:10):
It's a related concept where you you maybe have like
groups of organisms that are like evolving sort of along
alongside one another for a long periods of time. That's
a fuzzyo. Is there a good example, there's a fuzzier concept. Well,
an example would be, like I mentioned these different like

(46:32):
radiations of sharks. They sometimes you have like different lineages
of sharks and shark like creatures living at the same time.

Speaker 2 (46:44):
M hmm, okay, I gotcha.

Speaker 1 (46:46):
It's not this like sequence like we we kind of
think tend to try to think of it.

Speaker 2 (46:53):
Like, okay, I got youa.

Speaker 1 (46:57):
Let's talk about some of the interesting so we talk
to diversity. Let's talk with some of the kind of
interesting like adaptations of sharks. They've kind of briefly in
like their biology. So have you've probably heard, like you know,
sharks can smell.

Speaker 2 (47:17):
I've heard that, Yeah, like that that's supposedly a fallacy.

Speaker 1 (47:21):
Right, Well, it's a little bit of a exaggeration, I guess.
M hm. So sharks do have really amazing senses, and
because they have very highly developed senses, they do seem like, uh,

(47:45):
they're they've got to they have to develop. Sorry, they
have to devote a lot of brain capacity to their senses.
So sharks, many sharks, have some of the largest brains
of any fish, and there are many sharks that have
brains sizes that are approaching the same size as land vertebrates.

(48:12):
So sharks are, you know, relatively intelligent compared to other fish.
And they, like I said, they have very acute senses.
So one of the really think, really cool things that
they have are these really cool organs for sensing electrical

(48:33):
currents in the water. Oh yeah, so they have these
pits in there, usually concentrated around their snout area, called
mpulae of Lorenzini. These are structures that are unique to
contract dans and they are named after the protege of
a dude that I'm going to talk about at the

(48:54):
very end here. But yeah, they they actually have they
can sense, they're electro sensors and they're also thermal sensors,
and it seems like some sharks, like hammer head sharks,
had a lot of these, and the idea is that

(49:15):
the hammer shape actually like gives a wider area to
spread those ampuly out onto. Yeah, it would, so they
can like find prey that are buried under the sand
and things like that. They don't have to see them.
They can just sense the electrical signals coming from their
muscle movements. They seem to maybe be able to sense

(49:41):
magnetic fields of the earth to be used for navigation.
Cool as hell, But sharks seem to use their their
amazing senses in sequence. So they start with like those
electro I'm sorry, they start with smell and they have
done stuff bodies where they can sense different chemicals and

(50:05):
concentrations as low as one part in ten billion.

Speaker 2 (50:09):
Damn.

Speaker 1 (50:09):
Okay, So the whole like you know, one drop of
blood kind of thing is like maybe a little bit
of an exaggeration, but.

Speaker 2 (50:15):
Only just sure.

Speaker 1 (50:17):
So, But the thing is, you know, they can detect
smell from really really far away, but they can't necessarily
tell like, it just gives them a general sense of
like over there somewhere might be something to eat, so
that they'll start heading in that direction. Then they sort
of switch to their vision, and they do have very

(50:40):
acute vision, and a lot of sharks are actually quite
good at seeing in low light. Is there are a
lot of sharks that live quite deep in the water.

Speaker 2 (50:48):
I was gonna say, there's a lot of like bottom
dwelling sharks.

Speaker 1 (50:50):
Yes, exactly. So they sort of switch to their vision.
Then they also have like a sense of their lateral
line system, which and also their inner ears which sense vibrations, oh,
in the water. So then they so they're so switching
from like smell to to like these electrical senses to

(51:22):
the like pressure sense to vision. And then lastly, a
lot of sharks actually close like a membrane, a clear
membrane over their eye. If you watch videos of a
white shark biting something, it looks like their eyes close
just before they go in to bite it, so they

(51:43):
actually can't see what they're biting, and they've switched completely
to their electro sensors. And this tends to mess up
like experiments where they're trying to study the sharks because
they'll like go in to bite something and then like
at the last minute, like thrash to the site and
bite like the cage and stuff like that, because they

(52:06):
see they seem to think that it's like messing up
their electro or sense electro receptors.

Speaker 2 (52:11):
Hmm. I can say this seems like the adaptations that
you would find with a with prey more so than
a predator. A lot of it seems like defensive. I mean,
I guess it's good for hunting too, but.

Speaker 1 (52:25):
Well, a lot of fish do have that lateral line
system where they can like sense vibrations in the water.
That's a sense that's completely useless to us in air,
but you live in water, it's extremely useful. So a
lot of things that live in water have that, but
sharks have a particularly sensitive I talked about jaws, their
jaws and their feeding the Dave. One thing you mentioned
was like why are they been so successful? I think

(52:47):
their teeth. A lot of scientists talk about like sharks
have like really specialized teeth, and depending on what they eat,
their teeth look quite different. But one of the great
things about that is that their teeth are very specialized.
And because teeth are usually the only things that we
get from sharks as fossils, not always the case. We

(53:10):
have like full body fossils from klaudysilaki and some of
those other extinct shark relatives that I mentioned. But usually
you only get the teeth. But you can identify a
shark down to the species just from its teeth because
they're so specialized to what they're doing. Sure, and I
mentioned they're cool jaws. Last thing I'll mention is reproduction,
so we think about like I don't, I don't think

(53:31):
people like think about this kind of thing. Well, Dave,
if you had to, if I put you on the spot,
like shark reproduction, like, well, how do you think that happens.
I'm not necessarily talking just about like mating it, but
like when they get paid birth and that kind of stuff.

Speaker 2 (53:50):
I don't know. I imagine they just sort of get belly
to belly and then they sort of spiral as they swim.

Speaker 1 (53:55):
Well, here's here's the diagram some sharks getting freaky.

Speaker 2 (53:59):
Oh that is not It looks like if like a
heavy set person tries to get into an inflatable at
the beach.

Speaker 1 (54:07):
The male sharks of these structures called claspers are they
used to both they used to grab onto the female
and also for insemination. So all sharks have internal fertilization
unlike most other fish where it's all external. So female
deposits the eggs and then the male comes by and

(54:30):
shoots like a cloud of sperm on them, so already
they're like more like that's you know what we think
about with like land vertebrates. Then as far as like
what happens with the young, they have just about every
kind of just about every kind of reproduction you can

(54:51):
think of, all the way from ovi parody where they
lay eggs, all the up through live birth where they
have a placenta that nourishes the developing shark fetus like

(55:13):
similar to what you see in mammals.

Speaker 2 (55:16):
And then I say, I would say very mammal like.

Speaker 1 (55:19):
And then everything in between. There are some sharks like
white sharks, where they the baby sharks are nourished because
what happens is the first ones the mother keeps the
eggs inside her body, the first babies hatch, and then
they eat the babies they haven't hatched yet, and then

(55:44):
also the mother continues to ovulate and they eat the
eggs and so that they're nourished in that way until
they're born. So there's every kind of like strategy all
the way from like one of the spectrum, which is
just like laying an egg with like a yolks act,
and then that's it all the way up to kind

(56:04):
of like almost mammalian kind of reproduction. But what we
do know is that once the sharks are born, they
do not have parental care sure, so that that's you know,
sometimes they are investing a lot of resources into their
offspring that they don't invest any more resources once they're

(56:25):
actually like out of the mother m.

Speaker 2 (56:29):
What about shark hunting. I read that the dogfish is
called the dogfish because it they're they're known to hunt
in packs.

Speaker 1 (56:40):
Yeah, so we used to think that sharks were completely solitary.
I think people like assume that they were like not
very intelligent like things like that. But as you know,
more and more people realize that they're actually quite a
lot more intelligent than you would think, and there are
different kinds of groupings of sharks.

Speaker 2 (57:00):
Now.

Speaker 1 (57:00):
I don't know, I think we talked about like pack hunting,
like that's a really specialized thing that like wolves and
a few other mammals do, so they honestly want to
like call it that, but cooperative hunting living in groups
like a decent amount of the time. Yeah, there are
more complex social structures than people used to think with sharks.

(57:22):
Some sharks many are solitary. But what Dave, what I
mentioned was the often sharks are putting a lot of
effort into reproduce to reproduction, so that means that they're
reproducing very slowly, which is a challenge for conservation.

Speaker 2 (57:48):
What's the probably ranges per shark? But gestation period normally
for shark.

Speaker 1 (57:55):
I actually have that, So it depends on the species.
But just for example, white shark car carrotine carcareous. They
might take a decade to reach sexual maturity. Wow, Okay,
they may live to be you know, and actually like

(58:15):
they don't live that much longer after that, I think
usually like some of the old we're not quite sure though,
because we can't keep white sharks in captivity, they just die.
They only give birth. They give birth biennially, so like
they're only even birth like not that often, and they're

(58:37):
only giving birth to two to ten pups at a time.
They have a twelve month gestation period. Wow, so that's
on like kind of like one end of the scale.
Just for a reference, Atlantic cod might lay two to
eleven million eggs. Damn, they reach sexual maturity and two

(59:00):
years ah, and they give birth every year rather than
like every other year.

Speaker 2 (59:10):
Okay, sure.

Speaker 1 (59:11):
So yeah, for something like a large shark, like a
white shark, they're reproducing extremely slowly. So that is one
of the reasons why many shark species are endangered. And
then so they're hunted for food. They are hunted just
because people have a sort of a fear of sharks. Yeah,

(59:36):
so that the thing is like sharks are actually like, David,
I think, did you I think you had looked at
some information about.

Speaker 2 (59:44):
Attacks a little bit, you know, do you have a
guest as to on average, which country sees the most
shark attacks per year?

Speaker 1 (59:54):
Country? Yeah, this is South Africa. That's the United States,
United States. Okay, well we have a large coast.

Speaker 2 (01:00:01):
It's Florida.

Speaker 1 (01:00:01):
My dude, Wow, it is a large it is a
large coastline.

Speaker 2 (01:00:07):
This is from the University of Florida. There's a museum,
the University of Florida, and they have some statistics and
shark specific files here and when they're talking about shark attacks.
This is a report from twenty twenty four Museum Florida
Museum of Natural Histories, International shark attack file. They investigated

(01:00:30):
eighty eight alleged shark human interactions worldwide in twenty twenty four,
and they confirm that forty seven of those were unprovoked
shark bites on humans and twenty four were provoked. So
let me define those terms. Unprovoked bites defined as incidents
in which a bite on a live human occurs in

(01:00:50):
the shark's natural habitat with no human provocation of the shark.
So that just defined the word unprovoked. Provoked bites her
when a human initiates interaction with the shark in some way.
These include instances when divers are bitten after harassing or
trying to touch a shark, bites on spear fishermen, bites
on people attempting to feed sharks, bites occurring while unhooking

(01:01:14):
or removing a shark from a fishing net, and so forth. Okay,
so I think pretty clear to understand unprovoked versus provoked. There. Yeah,
of the again, the eighty eight that they studied, forty
seven were unprovoked, twenty four were provoked.

Speaker 1 (01:01:29):
Was that?

Speaker 2 (01:01:30):
And then there's some sorry, was that?

Speaker 1 (01:01:31):
How many? What what period of time do those attacks happen?

Speaker 2 (01:01:36):
Twenty twenty four.

Speaker 1 (01:01:37):
Just one year. Okay, that's why I was making sure
just one year.

Speaker 2 (01:01:39):
And obviously you might say, well forty seven and twenty
four does an equal eighty eight. Well, they also have
some things in here, like if there if a shark
bites a boat, sure, if there's you know, there are
some where no assessment of that could be made. They
couldn't figure it. The information was sort of inconclusive. So

(01:02:03):
but again, the United States has the most shark bites,
or had the most in twenty twenty four by a
wide margin. They had twenty eight of the forty seven
that were confirmed unprovoked. That's their twenty eight of them
are in the United States. The next highest was Australia,
and then every thing after that is one one byte Egypt.

Speaker 1 (01:02:25):
That's worldwide, there was forty four shark bites forty seven
seven unvoked. Yeah, so on average.

Speaker 2 (01:02:36):
Yeah, I mean, if you want to look at like
a little bit bigger skill here in twenty twenty four
of the forty seven, twenty eight of them are in
the United States. The year prior was thirty six, so
it was actually down a little bit. But there's obviously

(01:02:57):
not a lot of them. Florida has long, it says
here long topp global charge for number of shark bites.
Florida's cases represented fifty percent of the US total thirty
percent of unprovoked bites worldwide. I would guess that that's
again because there's so much coastline in Florida, and there's

(01:03:21):
so much tourist activity.

Speaker 1 (01:03:24):
Yeah, like I said, I mean, it's like a large
area of coastline just for the uncord.

Speaker 2 (01:03:32):
Let me let me add one thing here. Of the
unprovoked bites, they also tried to categorize the circumstances. Fifty
percent of them were due to swimming and waiting, thirty
four percent surfing and board sports, and then you have
things like snorkeling of free diving is eight percent and
others eight percent. So you know there aren't a lot
of them. When they do happen unprovoked, usually there are

(01:03:55):
people swimming and waiting. I guess that's probably what you
would think. But as such a small number, almost none
of them are fatal, which I mean not there aren't
any that are fatal. Of those forty seven unprovoked ones
last year, four of them were fatal. But I think
when you think about Shark Week. It makes it seem much, much,

(01:04:20):
much different than the actual statistics would suggest.

Speaker 1 (01:04:25):
Well, yeah, people are fascinated by sharks, but also like
very afraid of sharks. But just for reference, in the
United States, on average, more people die, not merely are struck.
More people die from lightning strikes in a year on average.

(01:04:47):
So you're more likely to die by getting struck by
lightning than you are being bitten by a shark. And
you know what, You're way more.

Speaker 2 (01:04:56):
Likely to get bitten by a mosquito.

Speaker 1 (01:04:59):
Well, yes, mosquitoes killed by far the most humans of
any organism among the planet. No, I was talking about
a fucking dog. Oh yeah, dog, You're way more likely
to get bit by a dog. But how many ammuna?
There's like, I know, like Kujo exists in movies like that,

(01:05:19):
But for the most part, we don't live in fear
of dog bites like people live in fear of shark bites.

Speaker 2 (01:05:25):
I think it's because, like shark bites are sort of
like a novelty, right, Like, we're always around dogs and
therefore we're more likely to be bitten by a dog
than a shark because we're constantly around them.

Speaker 1 (01:05:36):
Yeah.

Speaker 2 (01:05:36):
Four Point facilion with the shark.

Speaker 1 (01:05:38):
Four point five million people are bitten by dogs every
year in the United States. I'm sorry, I didn't mean
to talk over you.

Speaker 2 (01:05:47):
No, you're fine. What qualifies a bite for a dog?

Speaker 1 (01:05:55):
Any any bites? They can be minor. Approximately eight hundred
thousand of those require medical treatment at about fifty years
are fatal.

Speaker 2 (01:06:05):
Huh. Does it have to break the skin to be
considered a bite.

Speaker 1 (01:06:11):
I'm not sure. Well, I guess if medical attention is
needed then I guess it's kind of a gray area. Yeah,
but it's still like almost a million where you need
to go to the doctor. So anyway, obviously, I'm not
saying we should demonize dogs. Getting in your car and
driving something drank someplace. That's absolutely the most dangerous thing

(01:06:33):
you do every day.

Speaker 2 (01:06:36):
Oh absolutely.

Speaker 1 (01:06:37):
And as I mentioned with sharks, I mean, humans are
not the prey species of any species of shark. There
are some shark species, like white sharks, which are like
the ones that people are really afraid of because they're big.
They do feed on large marine mammals, and there's some

(01:07:00):
speculation that people like on surfboards and things like that
kind of maybe resemble something like a sea lion from below,
but generally shark most shark bites are not deadly because
they they'll give an exploratory bite right, realize that they're

(01:07:22):
not the prey species that they want, and then go away. Now,
of course, that could still lead to life threatening injury.
I'm not tempting to diminish it, but I think we've
we've established our point that sharks are far more endangered
by humans than humans are endangered by sharks, especially when

(01:07:43):
there are things like sharks being harvested intentionally for things
like sharkfin soup, and also being harvested unintentionally, as we
call bycatch, where they're accidentally caught in nets that are
meant for other fish species. Mhm, Yeah, which they often
die in the process of so uh. And as as

(01:08:06):
I said, they reproduced quite slowly. So this certainly is
a conservation challenge. And so you know, you can ask
a look like why do we care about all the
like evolutionary history stuff that I talked about. You sort
of have to understand a lot of that stuff to
understand things like why do they reproduce so slowly and
some of those things, so that maybe we can learn
more about these creatures too, so that they don't become

(01:08:31):
extinct after having survived every major mass extinction of the
Earth history.

Speaker 2 (01:08:36):
Hm hmm, it's interesting when you put it that way.

Speaker 1 (01:08:44):
Yeah, yeah, they made it this far, God damn it.

Speaker 2 (01:08:51):
Yeah really yeah.

Speaker 1 (01:08:53):
Well, so this sharks up and I think that was
pretty thorough. But Dave, did you have anything else you
wanted to add? No?

Speaker 2 (01:08:59):
Not really. I mean there's all kinds of little facts
you can find. Like, for example, we talked about how
like sharks have to keep swimming. Well that's not every shark.
Oh yeah. Apparently this is because some species of sharks
have to keep swimming because that process is constantly pumping

(01:09:22):
water over their gills. But there are some sharks that
have a spiracle saying that right, it can be pronounced
spiracle or spiracle that allows them to pull water into
their respiratory system while at rest. So just an interesting
evolutionary trait there. So a lot of sharks do have
to keep swimming, but not all apparently. Also, scientists age

(01:09:46):
sharks by do do you know how they do that? Joe?
How do they age a shark?

Speaker 1 (01:09:52):
Uh? I know? Other fish they have earstones called otoliths,
so they use otoliths for sharks.

Speaker 2 (01:09:58):
No, much like a They actually count the rings on
the vertebrate.

Speaker 1 (01:10:03):
Yeah, yeah, okay Jesus, of course I know this because
I I have a shark. I have a megalodon vertebrate
on my vertebra on my desk right now.

Speaker 2 (01:10:12):
M m mm hmmm. Sharks can go into a trance
by flipping them on their backs. They go into something
called tonic immobility. M h. Apparently sawfish are known for this.
A kind of shark. When you know scientists are studying

(01:10:34):
them or we'll have to work on them in the water,
they'll flip them over. They'll go into a trance. Yeah.
And although most sharks skin is very rough, feels like sandpaper,
a nurse shark has very smooth skin, or fairly smooth
skin at least.

Speaker 1 (01:10:54):
Yes, many of them have those. The denticles, as I mentioned,
which are literally teeth are or are another scientific term
for those would be placoid scales. They can be like
quite abrasive. In fact, shark skin was used like sandpaper

(01:11:18):
in various times in history.

Speaker 2 (01:11:22):
How that makes sense. Yeah, yeah, but that's it for me,
just some additional facts that are out there.

Speaker 1 (01:11:30):
Yeah, thanks for going over the the respiration because I
failed to mention that. But yeah, most sharks can actively
pass water over their gills at rest, especially like the
bottom dwelling ones. When they're swimming, they use something called
ram Jesus Christ, I totally like lost my train of thought,

(01:11:56):
ram ventilation. M there's a few of the ones that
like typically like never go to the bottom and like
cover large distances, that have lost the ability to pump
water over their gills and they have what we'll call
obligate ram ventilation. Interesting, there are some bony fish that

(01:12:20):
are like that too, Like they have to continuously move.
It's not just a shark thing. Oh okay, but yeah,
most sharks, it's only a few of them will die
if they stop moving. But yeah, anyway, that's yeah, that's sharks,
the really cool animals. They've been on this planet for
goddamn near five hundred billion years. Yeah, older than dinosaurs,

(01:12:46):
older than trees, older than the rings of Saturn.

Speaker 2 (01:12:50):
Good lord.

Speaker 1 (01:12:51):
Yeah, except there's a study came out last year that
Saturn's rings might be a lot older than we think,
but I'm skeptical. That's neither here nor there.

Speaker 2 (01:13:04):
Yeah, so it's sharks are very old. Yes, I slice it.
They're old.

Speaker 1 (01:13:12):
So all right, Well, hopefully you want to go and
learn some more about those creatures. Look up some of
the species that we talked about.

Speaker 2 (01:13:20):
Yeah for sure.

Speaker 1 (01:13:21):
Embrace your inner animal kid.

Speaker 2 (01:13:24):
Mm hmm. I mean you could pick a lot lamer
animal to study than a shark.

Speaker 1 (01:13:29):
You sure could.

Speaker 2 (01:13:31):
Oh hell yeah. So well anyways, on that note, we
will talk to everyone soon.

Speaker 1 (01:13:38):
Bye.

Speaker 2 (01:13:42):
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Speaker 1 (01:13:44):
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