by Nicholas Villeneuve, The
Gateway, University of Alberta’s Student Journalism Society, 8/21/19
Utilizing micro-CT scanning
technology, an undergraduate student at the University of Alberta has published
a research study that could help find the evolutionary link between snakes and
reptiles.
This August, undergraduate
student Catie Strong and graduate student Tiago Simões, supervised by Michael
Caldwell and Michael Doschak, published a research
study on the developmental biology of Plains garter snakes in order to
retrace their evolutionary processes and relationships.
This makes them the
first team to ever utilize micro-CT technology to image any snake or reptile
skulls at various stages of their development.
Strong, lead author of the
study and third-year paleontology student at the time of publishing, said this
research was inspired by the absence of scientific knowledge on the
relationship between snakes and reptiles.
“We’re still not really sure
what group of lizards snakes really evolved from and how snakes fit into the
larger lizard-snake evolutionary tree,” Strong said.
The group chose to study
Plains garter snakes because their common and ordinary nature makes them ideal
candidates for further in-depth study and analysis.
“Because they are so common,
it’s really easy to overlook them and that there’s not anything important that
they can tell us,” Strong explained. “Part of that decision was trying to give
[garter snakes] the attention that they haven’t really been given previously by
other researchers.”
The study employed micro-CT
scanning technology in mapping out garter snake skulls. It functions similarly
to a hospital CT scan, using X-rays to create 2D images or virtual “slices” of
the subject, except with much more detail on a finer scale. The slices are then
compiled together to create a 3D model that can be easily manipulated and
studied.
With this technology, Strong
and her fellow researchers were able to accurately identify and analyze
microscopic structures within garter snake skulls at various stages of their
development, and gain insight into their evolutionary path.
“We looked at the braincase
(the upper-back part of the skull) in some aspects and how that develops,”
Strong said. “We also looked at feeding mechanisms, like how the jaws and
related parts of the skull develop, and we looked at some of the unique
developmental pathways that we found present in the garter snake.”
Strong said she’s “really
proud” and “grateful” for her research work on the study while being an
undergraduate student and transitioning towards graduate school.
“It’s pretty rare for an
undergrad to have this really hands-on experience and to get a publication out
of it is amazing for me on a personal level.”
How red-eared invaders are
hurting California’s native turtles
In the summer of 2011,
visitors to the University of California, Davis, Arboretum may have witnessed
an unusual site: small teams of students wielding large nets, leaping into the
arboretum’s waterway to snag basking turtles.
The students weren’t in
search of new pets — quite the opposite, in fact. The teams were part of a
massive project to remove hundreds of invasive red-eared slider turtles from
the arboretum in an effort to observe how California’s native western pond
turtles fair in the absence of competitors.
Red-eared sliders are the
most commonly traded pet turtles in the world, but are often released into the
wild by disgruntled owners when they get too big to handle. Thanks to illegal
dumping, the sliders, which are native to the Central United States and
Northeastern Mexico, can now be found all over the world. Their new stomping
grounds include California, where they vie for food and sunny basking sites
with western pond turtles, whose populations are in rapid decline due to
agriculture and urbanization.
The results of the removal
study, published recently in the
journal PeerJ, showed that western pond turtles get a lot fatter and healthier
without competition from their invasive brethren — and the remaining sliders
likely fair better, too. The study is the first to quantify competition between
these two species in the wild.
“I think, finally, we have
some good evidence in the United States that it’s time to critically think
about not having pet slider turtles, and likely other aquatic turtles, and
mitigating this pet trade because it’s not great for the pets, and it’s not
great for these wild species either,” said Max Lambert, a postdoctoral
researcher at the University of California, Berkeley, and lead author of the
study.
It’s not hard to see why
red-eared sliders are the most popular pet turtle in the United States: As
hatchlings, sliders are small, friendly and sport striking red stripes on
either side of their heads.
But give it a few years, and
the once-cute reptiles grow snappy, smelly and can expand to the size of a dinner
plate.
“They are so cheap, they are
in every single pet store, and they seem like a great pet until they get to be
a few years old, and then they get big, mean, smelly and are a pain to take
care of,” Lambert said. “So, people just take them to a nearby pond and let
them go.”
As an undergraduate studying
ecology and conservation at UC Davis, Lambert was curious to know what effect
these invasive turtles might be having on western pond turtles, which are
currently listed as vulnerable on IUCN’s Red List of Threatened Species. While
experiments in laboratory settings have hinted that sliders will compete for
food with pond turtles, he couldn’t find any data looking at how the two
species interact in the wild.
Lambert and five other UC
Davis undergraduates teamed up with their faculty adviser, H. Bradley Shaffer,
who is a professor of ecology and evolutionary biology at UCLA, and Gregory
Pauly, curator of herpetology at the Natural History Museum of Los Angeles
County and senior author of the study, to design the removal experiment.
With the help of volunteers
and other UC Davis undergraduates, including Jennifer McKenzie and Robyn
Screen, who are co-first authors of the recent publication, the team used
turtle traps, nets and, when necessary, their own hands, to remove and
euthanize 177 red-eared sliders living in the UC Davis Arboretum waterway
during the summer of 2011. Lambert estimates they caught about 90 percent of
the total red-eared slider population in the arboretum.
They also tracked the weight
of the western pond turtles and observed the turtles’ basking habits. Time
spent basking in the sun is critical for cold-blooded turtles; they need the
heat to power digestion and their immune systems, Lambert said.
The researchers found that,
in the year after the slider removal, the pond turtles gained an average of
about 40 grams, representing about 5 to 10% of their body weight — quite a lot
for a turtle. This weight gain is especially important for female turtles,
whose egg clutch size is related to their overall size, Pauly said.
“If these females are much
healthier and much more likely to have larger clutch sizes, that increases the
likelihood that we are then going to get more juvenile turtles cruising around
these urban waterways,” said Pauly, who was a postdoctoral researcher studying
reptile and amphibian conservation at UC Davis at the start of the experiment.
While the slider removal
didn’t have much of an impact on the western pond turtles’ basking behavior,
the researchers did find that the remaining sliders spread out to a few select
basking sites, indicating that they were actually crowding each other out
before the removal.
“The reality is, in many of
these urban ponds, there are so many red-eared sliders that there are high
levels of competition amongst those sliders for basking sites and also probably
for food,” Pauly said. “It’s not just that red-eared sliders are having
negative impacts on the western pond turtles, but the red-eared sliders are
themselves facing this huge series of challenges.”
As a postdoctoral researcher
at UC Berkeley, Lambert says he has plans to study western pond turtles and
red-eared sliders in the Bay Area. He is initiating partnerships with the East
Bay Regional Park District to first observe western pond turtles in ponds and
lakes in the system, and then conduct another intensive removal of red-eared
sliders in and around places like Jewel Lake.
“What we found with our
slider removal at Davis was that it was just so human-intensive and would cost
any agency a ton of money to do what we did at that scale,” Lambert said. “And
so, while it seems that slider removal has an effect, the question is, ‘How
much of an effect is it having, relative to western pond turtles living in an
urban place, where they get run over by cars, eaten by raccoons and coyotes and
dogs and sometimes taken home as pets by people not realizing the negative
impacts they are having?’ We’re hoping to parse out a bit better the degree to
which sliders are having an impact relative to every other challenge we throw
at these turtles.”
Co-authors of the paper
include Jennifer M. McKenzie of the University of Kentucky, Robyn M. Screen of
the University of Hawaii at Manoa, Adam G. Clause of the Natural History Museum
of Los Angeles County, Benjamin B. Johnson of Cornell University and Genevieve
G. Mount of Louisiana State University.
This work was supported by
National Science Foundation DEB grants (1257648 & 1457832), the Natural
History Museum of Los Angeles County and the Northern California Herpetological
Society.
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