Human Impacts and Extinction of Freshwater Snails

(upbeat music) – Hi, welcome everyone, thank you so much for joining us for this episode
of Smithsonian Science How. I’m Maggy Benson. We’re really lucky we were joined today by invertebrate zoologist
Dr. Ellen Strong. Ellen, thank you so much for joining us. – Thanks Maggy, it’s great to be here. – So Ellen, you’re an
invertebrate zoologist here at the Smithsonian’s
National Museum of Natural History and you’ve brought an awesome collection of things to talk about today. Can you tell us a little
bit about your job here and the collections you use? – Yes, so my official title
here is Research Zoologist and I’m a specialist who studies snails, and I also, one of the
jobs that I have here also is taking care of our
nation’s snail collection. With 15 million specimens, that’s a pretty big job. – [Maggy] 15 million, that’s huge. – [Ellen] It’s big. – So what made you become a
scientist that studies snails? – So when I was a kid I had no idea that studying and taking care of snails was a job description. I had no idea that this
would be my career. I actually wanted to be an archeologist, and I would take my dolls
and bury them in the mud and carefully excavate
them with my dad’s tools, which he was not very happy about. But all that training went to waste because when I went to college, I wrote my undergraduate thesis on snails, and I was hooked from then on. – Very cool, so I see
a lot of snails here, out on the table. Can you tell us exactly what a snail is? There’s a lot of variation here. Yeah, so the technical term for the class that includes
snails is called Gastropoda, and this means, in Latin, stomach foot. So this refers to some of
the main features of a snail. So you can see there, on your screen, the large foot that snails
use to crawl around on. You can see that they have
some tentacles with eyes attached to the foot. They also have a spirally coiled shell that contains all of the internal organs including the stomach and a trap door that closes behind them when they retract into
their shell for protection. – I see some of these don’t have a shell. Are they still snails? – You’re absolutely right,
not all snails have shells, so that was sort of a trick question. Some snails have lost their shells and this includes slugs that we see in terrestrial habitats, it includes brightly colored nudibranchs that we see in the sea. – Now, what about how they eat? Do they have a similar
way in which they do that? – Yeah, a lot of snails have a structure that we call a radula. This is a flexible ribbon of teeth, and you can see this
here, on your screens, of a snail extruding its
radula through the mouth, and this flexible ribbon of teeth is used to graze algae
and other substances that snails feed on. – [Maggy] Very cool,
you don’t usually think of a snail having teeth. – [Ellen] Nope, you sure don’t, but there are some close-up pictures taken with a scanning electron microscope of what these teeth look like in close-up. – Very cool, so how many
species of snails are there with 15 million collection objects? There must be quite a few? – Yeah, there are a lot of snails. Most of the diversity
of snails are marine, so there are about 36,000 species of marine snails that have been described, but snails, as you probably know, have invaded a lot of different habitats. So they’ve invaded freshwater and terrestrial habitats on all continents except Antarctica, and there are about 25,000
species of terrestrial snails, and about 4,000 species
of freshwater snails that have been described. – So terrestrial meaning living on land? – That’s right. – So these shells over here
look really familiar to me. They look like something
found in the ocean. – Yeah, you’re right. These are some beautiful
examples of marine snails, what people would commonly
recognize as seashells, and you can see that
they are brightly colored and a lot of different shapes and sizes. – Yeah, that variation is really striking. I mean, here there’s
no spiral on the shell, and some of them are even
completely different shapes. – Yes, so some snails
have taken this basic idea of a spirally coiled shell and modified it in ways that are, you can’t even recognize
it’s a snail anymore. So in fact, this is an example of a snail. It’s a group of snails that live together in a colony, and each one of those little tubes hosts a tiny snail. – [Maggy] Wow, that’s incredible. It looks like a piece of coral. – [Ellen] It does. – [Maggy] So what about size of snails? A lot of the specimens
here are really big, but is this the norm? – This, this is not the norm. I like to show seashells because they’re something
that people recognize and they’re beautiful, of course, but they are not really representative of the diversity of snails. So snails can range in
size from a sand grain all the way up to more
than two feet in length. So, and in fact, the large snails are in the minority. Only 10% of the diversity of snails are what we would call macro mollusks, whereas 90% of snails are what
we would call micro mollusks, and are only four
centimeters in size or less. So four centimeters is only
about an inch and a half. So the vast majority of snails
are in fact pretty small, and they are harder to
find and harder to study. – So what about the snails that you study, what group do they fall in? – So, they are not marine snails, but they fall into this group that we call micro snails. So I actually study freshwater snails. The snails that I study are in this group of micro snails that
are in about the inch, inch and a half size range, and as you can see on your screen, they are not as beautiful, not as charismatic as
their marine relatives, not as highly variable. They usually come in shades
of brown or green or yellow. So they are not quite as charismatic as their marine relatives, but some of the features of the animals are really quite beautiful when you look at them close up. – So because they’re part
of this micro mollusk group, this group that’s very large and as you said, a little
bit more understudied, do we have a lot to learn about the freshwater snails? – Yes, there’s a lot to learn. As I mentioned, there’s
about 4,000 species that have been described, but this might just be
the tip of the iceberg. There are new species that are
being discovered every day, and we estimate that 4,000 species might only be half of
the number of species that there are left to
document and describe. So we also don’t really
understand very well their roles in ecosystems, their ecology, their
physiology, their anatomy. There’s lots we don’t know, and in fact, snails are really important in the ecosystems where they occur, and they are understudied relative to their ecological importance. – Interesting, so it sounds like there’s a lot of work to be done. – There is. – That point about their
roles in the systems that they belong actually led me, is leading me to my next question, which is, what are their roles in these freshwater systems? But before you tell us, let’s actually give our viewers a chance to weight in, what do you think? – Sounds great. – Viewers, here’s an opportunity to participate in a live poll with us. You can respond using the window that appears to the right
of your video screen. If you don’t see it, try minimizing your
window to see the poll. Tell us, snails are
important in ecosystems for: making energy from sunlight, they’re not important, preying on other animals, or being eaten by other animals? Take a moment to think about, and put your answer in
the window that appears to the right of your video. So we’re looking at all of
your responses coming in. Ellen, we can see together that 81% of our viewers,
the vast majority, think that their role is
being eaten by other animals. What do you say? – I think that we have some very knowledgeable
viewers here today. I’m really happy to see that nobody chose they are not important, because we know that they are. So I’m very happy to see that nobody picked that answer. That was sort of a trick question. But basically, they’re, all the other answers were right. There are, they are very important in their ecosystems for food, they transform energy from the sun, and they actually do also
prey on other animals, but not many people picked that answer, and in fact, it’s somewhat rare. So I would say that answer is proportional to that, the occurrence in nature. – Now, if they are an
important food source, what are their populations like in these freshwater systems. Are there a lot of them? – Yeah, so snails can occur
in really high abundances in the communities where they occur. So as you can see in this picture, all those little dots there on the rocks are freshwater snails, and in fact, a good indication that
an ecosystem is healthy is that it supports a healthy population of freshwater snails. So they’re playing, they can reach actually incredible densities in freshwater ecosystems. They can reach more than 1500 individuals per a square meter. – [Maggy] Wow. – Yeah, that’s a lot of snails. – [Maggy] That is a lot of snails. – They are, they are, they represent a very important component of the biomass, so they can represent up to 90% of the benthic invertebrate biomass in fresh water ecosystems. – That’s incredible. So what animals are feeding on them if they are present in such huge numbers and represent that huge
niche in that system? – Yeah, so one of the, most of our reviewers responded that snails are functioning
in their ecosystems as food, and that’s, that’s absolutely right. So, and actually one of the other answers was that snails are transforming
energy from the sun. So we can see here in
this simple food chain that snails are very important parts, very important players at the bottom of the food chain, so they are consuming algae, and with a lot of snails,
you eat a lot of algae, and so algae takes energy from the sun through photosynthesis, and snails then convert that energy into a, something that consumers higher up in the food chain can then make use of, and we see that in this food chain, we have fish, and leading all the way up to humans. So, in fact, humans are
directly linked to snails through the food chain. – So what about water quality? Are they having an impact on water quality if they’re in those
systems in such abundance? – Yes, so one of the things, one of the features that I did not mention that many snails have is a gill, and they are using the
gill to extract oxygen that they use to survive from the water, and this filtering action actually has a beneficial impact on those ecosystems. They are filtering out harmful
particles like sediments, bacteria, parasites even, and harmful algae, and keeping those things
in low concentrations in the freshwater
ecosystems where they occur. – So freshwater snails are
keeping our water clean and they’re even feeding
us through the food chain. – Yeah. – So they’re really important
for human wellbeing. – Yeah, they have a major impact on keeping our freshwaters healthy. – Does that go hand in hand with also experiencing some
of the negative impacts that humans have on
our freshwater sources? – Yes, so you can think of snails as being surrounded in this medium in which they occur. So they are in constant
contact with water, and anything that humans do to, that has an impact on those freshwaters will have an impact on the
health of those snails. So they are affected by the fact that we use freshwaters for agriculture, they are affected by the
modifications that we make to natural rivers by damming, they’re affected by pollution, habitat loss, mining. These are all things that are degrading our freshwater habitats and have a direct impact on the health of freshwater
snails populations. – You mentioned that the
snails are surrounded by freshwater all the time and they kind of occur
in these small areas where there is freshwater. Does that impact their vulnerability in instances where we may
have a negative impact on the water source? – Oh yes, absolutely. So you can think of, so freshwater snails are reliant on being in water for their survival, and they can’t just pick up and move when things get bad. So they have to adapt to the changing habitats where they occur, or they, or they’re driven to extinction. – Does that make freshwater
species of snails more susceptible to these changes compared to their marine relatives? – Yes, absolutely. So you can think of the way that freshwater habitats are distributed compared to marine habitats. So the marine oceans are more or less continuous habitats, but freshwaters are not continuous across the landscape, and so freshwater populations are not continuous across the landscape, and in places where we have had an impact on those freshwater populations, those populations have
declined in number and in size, making these less
resilient to human impacts, and we see that in the numbers. The numbers speak for themselves. So 177 species of freshwater snails have gone extinct, whereas only six species of marine snails have been documented as being extinct. – Wow, that’s incredible. So we really need to be paying attention to our freshwater sources and the snails that live in them. – We do. – We have a ton of questions coming in, so we’re gonna learn more about
your research in a moment, but let’s get to some of those questions. – Sounds great. – All right, this question
come from MacGyver. MacGyver asks, why do you study snails? – Oh, I study snails, yeah MacGyver, that’s a great question. I study snails because
there’s so much to learn. Snails are an incredibly diverse group, and as I said, they are understudied
relative to their diversity. So almost everywhere you look, there is something new to learn, every day I come to the office, I find out something new about snails. So it’s sort of like Christmas every day. – Ellen, let’s learn a little
bit about your research. You started telling us a little bit about the negative impacts
that humans are having on freshwaters which is
in turn impacting snails. Can you tell us how the snails you study have been impacted by humans? – Yes, so one of the groups of freshwater snails that I work on are called pleurocerids, and we actually some
examples of pleurocerids here on the table with us today. Pleurocerids are the
second most diverse family of freshwater snails in North America. There are about 160 species of them. But they have been heavily impacted by human activities, so all of the threats
that we talked about, damming, pollution, habitat fragmentation, and here you see a nice picture of a large hydroelectric dam. These have had a major impact on our freshwaters and on the
diversity of pleurocerids. So you take a free-flowing river like this and you put a hydroelectric dam on it, and this has caused, been the source of major
extinctions in the United States. So in the Coosa River in Alabama, this is a river that’s about 230, 280 miles long, and a series of dams that
was constructed on this river basically took a nice free-flowing river in its natural state and transformed it into a series of lakes. – [Maggy] What did that lead to? – [Ellen] That led to
the biggest extinction of freshwater organisms in
the United States history. – [Maggy] Wow. – [Ellen] And this also
led to the extinction of some pleurocerids, so. – [Maggy] Is that what
we’re looking at here, some of the extinct species?
– That’s right. These are some of the extinct
species of pleurocerids, so already 33 species and one
whole genus of pleurocerid has gone extinct, caused by these impacts. – [Maggy] Wow, that’s really jarring considering how important
freshwater resources are for every plant and animal. – [Ellen] Yes. – [Maggy] Here are more of
the snails that are at risk? – Yes, so even the snails that have survived these extinctions are still at risk and heavily imperiled, so out of those 160 species, 80% are experiencing some level of risk. So this ranges everywhere
from slight impacts all the way to being on
the verge of extinction. So around 130 species of pleurocerids are experiencing some level of risk. – So what does studying these snails actually contribute to the
overall understanding of them? But actually before you tell me, let’s again ask our
viewers for their opinion. – Okay. – Viewers, here’s another opportunity to participate in a live poll. Tell us, what does studying snails help us understand? Individual species, snail biodiversity, ecosystems, or food webs? We’re again watching the results come in. Ellen, we can see that
people have responded, given responses for all the answers, but mostly snail biodiversity. What do you think? – Yeah, great. There was no trick
question here this time, so these are all right answers. As I mentioned earlier, there is still so much to learn about freshwater snails that almost every, there are things to learn in almost every area. So learning how individual species interact in their environment, how they contribute to the
food webs where they occur, their ecology, their physiology, these are all things that
we need to learn about, but the most popular answer, which makes me very happy, is understanding the biodiversity, and that’s my job basically. My job is to document and describe the species of freshwater, and to understand their
biogeographic distributions. – That’s really foundational for understanding everything
about these animals and even how to protect and conserve them. – Yes, absolutely. So the, we can’t conserve
and we can’t protect what we don’t know. So my job is to make sure that we document and
describe every species and that each one has a name. This is the basis for communication. Species are really the
currency of biology, and conservation biology, and that’s where I make my impact. – So how are you
documenting this diversity? Are you using a selection of the museum’s 15 million
collection objects, are you going out into the field, do you do both? – I really do both. Museum collections are an
integral part of what I do, and the reason they’re so important is because, and as you can see here, these are just some of those objects that I help to take care of every day. These museum collection help to document the distribution of species, both past and present, and they are repositories for undiscovered biodiversity. But getting out in the field
is also really important so that I can see how species vary across the landscape, where they distributed, what their ecology preferences are. These all help to inform our interpretation of how
many species there are. – Do you need special gear
when you go out into the field? – I don’t really need
too much special gear for the species that I study. They’re mostly in very
accessible habitats. Sometimes, as you see here, I’m working in places where it’s an active mining area, which is why I had that helmet, but mostly I just need a GPS unit and, or a couple of helpful colleagues. – Those are the tools that I think I would like to use collecting them.
– Yeah, you just need a couple of friends with you in the field. – So when you’re out in the
field and you find a species, do you sometimes just know that it is brand new, and nobody’s every described it before? – Every once in a while you will have that amazing aha moment in the field where you have found something that is so unusual, is so far away from everywhere, everything else where you
would expect it to be, that it has to be new, but for the most part, most of our discoveries come in the lab. Really, the reason is because the shells, which is what you have access to when you’re in the field, are not really a very good indicator of species diversity. We have a couple of
specimens here to show you that really shells can be
quite variable within species, and if this is all that you
have access to in the field, this is not going to be
a reliable indicator if, of what you have is new. – So what tool do you use to determine if it is a new species or not? – So we take, we preserve
those specimens in the field, usual in alcohol, or we freeze them, and we bring them back to the lab. We take a small piece of their tissue and we sequence it and we get their DNA sequences, and we compare many DNA sequences from many individuals for those species that we’re studying. – [Maggy] Which we’re seeing here. – [Ellen] That’s right. – [Maggy] So has this DNA analysis helped you discover new species? – Absolutely, but not just new species, whole new families. – [Maggy] Wow. – Yeah, so some of the
species that I work on occur in the Pacific Northwest. These are species that used
to be called pleurocerids. This is in the genus Juga, and we were able to compare
DNA sequences of Juga from Washington, Oregon, and California, and you can see some of the diversity here to other species of pleurocerids, and we found that they weren’t
close relatives at all, that in fact Juga is most closely related to species in Asia, and we united them in their own family, the Semisulcospiri. – That’s quite a mouthful, I’m not gonna repeat that, I think I’m gonna stick with Juga. – I’ll stick, me too. – Were you able to describe new species within this brand new family of Juga? – Yes, we found several new species. One of the species that we found is, are those specimens that you
see there in those vials. Those are individual sequenced specimens of a new species of Juga that we found in eastern central Oregon. This is one of those species that unlike most species of Juga that occurs in rivers and springs, rather rivers and lakes and creeks, this is a species that occurs there at that orange dot
in these isolated springs in meadows like this. There’s my colleague helping me to collect some of those specimens, and we brought them back and we sequenced them and we found that they are a new species. – [Maggy] Do we know
what the name is yet? – So actually these results are so new that we haven’t had time to give it a name yet. We’re still working on that. – So given its isolated location and not finding them anywhere else, and all of the threats that you have been talking about, is this a little bit
of a race to name this, given the threats that
face freshwater snails? – Yes, absolutely. So this is a species, as you said, is highly isolated, and that makes it especially vulnerable to human mediated threats. A single catastrophic event could wipe it out even
before it has a name. So we really are in a race to catalog and describe these species, let alone understand how they function in their environment. – So it’s not all doom and gloom, though. There are some restoration
and recovery efforts underway that your research has helped inform. Can you tell us about those? – Yes, so there are a
lot of efforts underway to help improve the quality
of our freshwater ecosystems, so one of those efforts
includes dam removal. We’ve talked a little bit about the impacts that dams have on freshwater ecosystems and fragmenting natural populations. You can see here that this is has a beneficial impact on restoring rivers to their natural state, and these are some of my colleagues at the Alabama Department of, Alabama Aquatic Biodiversity Center, who propagate freshwater snails and return them to these communities where they used to occur and where freshwater
health has been restored. – Ellen, this is another great example of how your work is really foundational to the future of freshwater snails species and their restoration
and recovery efforts. Thank you so much for
helping us learn more about your freshwater snails and your research here at the Smithsonian. We have so many questions and we’re a little over time, so we’re gonna get to as
many as we can right now. – Sounds great. – All right, this question comes from, oop, I just lost it. There are so many coming in. Addie had asked, let’s see, or Addie, send your question in again so I can see it. But this one is from Emma and Sophia. They wanna ask, are snails threatened? – Yes, snails are highly threatened. So freshwater snails are among the most highly imperiled animals on the planet, and have experienced the
highest numbers of extinctions. So freshwater snails are very important, but they are heavily impacted by degradation of their habitats and human impacts, and have experienced large
numbers of extinctions. – So Bella and Sienna ask, what would happen if all
snail species went extinct? – Oh dear, I don’t even
wanna think about that. That’s a very depressing thought. – I know, our poor freshwater. – Our poor freshwater,
yeah, as we’ve talked about. Their role as ecosystem engineers means that they play vital roles in maintaining our freshwaters and at the base of the food chain. So you can imagine that if there were no
more freshwater snails, our food, some of our food
chains would collapse, and these are food chains that we rely on to provide us food. – This one’s from Jordan and Mariela. I saw snails in my
backyard after rain, why? – Well, that’s also a great question. A lot of snails are, even if they don’t live in water, are reliant on water for their livelihood. So some snails, some terrestrial snails, when conditions are dry, they will retract into their shells, they’ll bury in the ground in order to preserve moisture. Then when it rains, they can come out and crawl around, feed, reproduce, do all the things that snails do. – Ellen, thank you so much for answering all of our questions. Viewers, thank you so much for all of your awesome questions, I’m really sorry that we didn’t have time to get to all of them, we’re really over time. Ellen, can you tell our viewers where they can learn more about your work? I think they’re all really interested. – Sure, viewers can go to
Conservation International or the Fresh Water Mollusk
Conservation Society to learn more about freshwater mollusks and conserving our freshwater resources. – And we have resources
on the Qruis website,, about Ellen’s work and freshwater snails. So Ellen, thank you so
much for being here, it was a really great show, and viewers, thank you
so much for tuning in to this broadcast of
Smithsonian Science How. (upbeat music)

Comments 1

Leave a Reply

Your email address will not be published. Required fields are marked *