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Bats and Rats: A Deeper Look Into Research at the NSRL

Heidi Toth

January 25, 2017


Researchers at Texas Tech use the university's collection to examine diversity, evolution and genetics in some of the world's most successful species.


The Natural Science Research Laboratory (NSRL) is home to more than 5 million animal specimens, ranging from genetic material and tissue to entire creatures perfectly preserved through decade.

The NSRL also is home to researchers who use the collections, which are part of the Museum of Texas Tech University, to solve biological and geological problems of the world today. Last week director Robert Bradley and biology professor David Ray discussed their work into a variety of species. This week, three more biologists talk about the groundbreaking work they're doing with bats and rats, two of the most widespread, successful animal species on Earth today.

Gut check: Defining our relationship with bacteria

One person gets sick and another doesn't. One baby is more prone to ear infections than another. One pregnant woman has terrible morning sickness; another mother-to-be has never felt better.

Caleb Phillips
Caleb Phillips

If all known factors are equal, that leaves the unknown, and in this case, the unseen: bacteria, fungal and viral communities – all the microorganisms that make up the human microbiome, which affects energy, immunity and how the body responds.

"Microbiomes are quite variable," said Caleb Phillips, an assistant professor in the Department of Biological Sciences and curator of the Genetic Resources Collection at the NSRL. "Amongst humans, they're highly variable for reasons that are sometimes hard to tease out."

Phillips studies metagenomics in mice and bats, two mammalian groups that are diverse, mature quickly and have much in common with the human genome, making them excellent test subjects for people. In a nutshell, his research delves into the diverse ecology of the microbial communities – competition among microbes, what's actually present, what they're doing and how and why they're doing it.

"I'm trying to understand why it is that you or me or someone else, why our microbiomes differ, where they're the same and why that is the way it is," he said.

One of his projects is examining how the microbiome of a female bat changes during pregnancy and lactation. This group is interesting because of the bat's unique energetic demands. When flying, bats have a metabolic rate that's 15 times the rate of a resting bat.

On top of that, bats have a digestive tract that is about a third shorter than a comparable land mammal. That helps make it light enough to fly, but gives the less surface area to digest the calories it needs to provide energy to keep it in flight.


Add to that a baby bat, weighing about a third of the mother's weight, and mama bat finds herself in a difficult energy situation. How does she keep flying? The answer – or, rather, the billions of answers – is potentially in her gut's microbiome. The bacteria changes to meet the bat's needs.

"Basically a pregnant bat carries around a pup that's a third of her body weight. She has to fly around and catch bugs and she's spending 15 times her basal metabolic rate to do that, and her intestines are a third shorter than they should be," he said. "We're trying to understand the relationship of all those things and how the bacteria that live inside the intestines help bats pull that off."

He studies the genomic sequences of bats, pulling samples both from the field and from the NSRL, to find the differences in microbiota and isolating which of those genetic differences contributes to allow the bat to fly while pregnant. He's also able to use this research to make educated guesses into the effects of changes on humans and their gut microbiome. It can be difficult to see the connection from bats to humans, but there are actually more similarities than may be obvious.

"The anatomy of a bat, the anatomy of a mouse, the anatomy of a human, the gross morphology of all the intestines is the same," Phillips said. "The basal metabolic processes we use to metabolize sugars and proteins and fats, those are all essentially the same."


Plus, studying non-humans is more effective, at least early in the process. Species like bats and mice have greater variation than do humans, so tracking genetics is easier than it would be among the slow-growing, slow-adapting Homo sapiens.

Another study looks at how bacteria shuffle genes amongst each other so every bacterium has a function. Scientists theorize this process is how a strain of the staph bacteria developed a resistance to methicillin and created MRSA.

Phillips also studies the relationships between the bacteria and the host, which is necessary to understand why bacteria behave the way they do. People tend to talk about bacteria in terms of healthy and not healthy for people, but that misses a basic understanding of bacteria.

"Microbes are not there to support our health, they're there to survive," he said. "Some are helpful, others are pathogenic. Some disorders, like Crohn's disease, are a mistake in the regulation of who's supposed to be there."


He has found the NSRL collections to be particularly useful for tracking adaptation. The only way scientists know a species has adapted is to compare a specimen from today with a specimen from the past and determine what has changed. Tissues preserved in liquid nitrogen go back to the 1970s, so Phillips could track how a species' genes have changed in the last 40 years. They also know more about the species from the 1970s than was known in the 1970s.

"The things we're able to do now with next-generation sequencing and proteomics, 15 years ago people collecting weren't even thinking of those," he said. "Now we can ask some new questions."

Diversity: a biological buzzword

Every 10 years, the U.S. government sends out millions of census forms, to be followed by hundreds of census takers, to get an accurate count of the people who live in a specific area. Through a meticulous, months-long process, every person in every dwelling on every street is accounted for.

It's a little more complicated for ecologists, who are counting creatures that don't live in houses, move around frequently and don't always have the identifying characteristics to indicate to trackers it isn't the same small brown rodent they picked up a half a mile away a few days before.

Richard Stevens

Yet knowing what species, and how many of those species, exist in an area is critical to understanding biodiversity and ecosystems in the natural world and how those are affected by both natural and human-caused changes in the environment, said Richard Stevens, a community ecologist with the Department of Natural Resources Management. Diversity, and how to encourage diversity, is one of the single most important factors for any natural scientist to consider when making observations about the natural world.

For Stevens and other scientists who fall somewhere along the community ecologist/evolutionary biologist spectrum, diversity and its scientific foil, extinction, are not accidental, random occurrences. Rather, they are the natural results of environmental factors.

"The number of species on Earth and the number of different groups of organisms have not been the same through time," he said. "If you look at it over the millennia and over the geologic record, you have times when groups have very few species and times when groups have lots and lots of species. The big questions are how does extinction proceed, how does diversification proceed and how do those two processes interact with each other to give rise to the number of species that occur in any point in time?"

Stevens primarily studies bats and rats, both of which are highly successful groups of mammals, meaning they've achieved both diversity and abundance. He focuses on both because each contributes to the diversity question in a way the other cannot. Bats are "really cool," diverse and abundant but difficult to study, largely because their ability to fly makes keeping them in or out of specific experimental plots to study the effects of the features of those plots next to impossible. Rats also are diverse and abundant and are easier to trap, manipulate and study.


"Understanding diversity, how it's maintained and how it's generated are really important keys to understanding life, how we got here and how all the rest of the organisms in the world got here," he said.

Diversity matters to the non-scientist as well, Stevens said, an argument made in a study he's doing on the kangaroo rat with Bradley and Ray. The native Texas rodent is on a watch list under the Endangered Species Act, meaning it could be the next to receive protected status. This is great if it's endangered. The problem, Stevens said, is the people writing the list often don't actually know if a species is endangered. Often there is not enough information to say that definitively.

This research, which the Texas comptroller's office is funding, will increase understanding of the rats' distribution, abundance and population genetics through the 11 countries to which the species is endemic. That will provide a clearer picture of whether the species actually is in trouble and whether the United States should devote resources to helping it.

Because of the NSRL's collections, Stevens also can compare an animal population of a certain area today to the same animal's population of the same area decades ago, which presents new questions: how are the populations changing and what causes them to change? True biodiversity is not just a snapshot of animal species today.

Robert Bradley

"What that allows us to do is to understand the distribution of many, many species from a static perspective, but also from a dynamic perspective," Stevens said. "We can go back to sites that were collected in the " 60s or " 70s and see if things are still there or if new things are there."

And what that information allows scientists to do is take real action.

"Humans have big impacts on the world, and one of the consequences of many of those impacts is a decrease in diversity," he said. "We as scientists, in terms of conservation, spend a lot of time trying to understand how it is that those things negatively impact diversity so we can try and mitigate those influences, but also understanding what are the things that maintain diversity so we can partition those into things we don't have to worry about and things we do have to worry about."

Bat luck

Liam McGuire knows these three things with as much certainty as the scientific process allows: 1) White-nose syndrome is a fungal infection decimating the bat population of the United States, killing millions of the flying mammals in the last 10 years. 2) The fungus that causes the disease is widespread in Europe. 3) Bats in Europe don't suffer the high mortality rates seen in North America.

From there he drew a conclusion: Europe's bats somehow evolved to co-exist with the fungus that causes white-nose syndrome.

He wants to know how.

Liam McGuire

The assistant professor of biological sciences is part of a team studying the disease, which essentially wakes bats too frequently during their hibernation period. While hibernating, bats use very little energy, but they burn through a huge amount of energy when waking up. Wake up too much and they starve to death before winter is over. The fungus also destroys the animal's wings and causes other problems that make a bat incompatible with life.

The disease popped up in a New England cave about 10 years ago, the first time it was recorded in North America. It's slowly made its way west, killing millions of bats along the way. Some species, like little brown bats, seem more susceptible; the disease has killed more than 90 percent of the population in some sites. Other species, such as big brown bats, while there have been casualties, have not been as hard hit.

This disparity could hold some direction regarding how to stop entire populations from being wiped out.

"What's different between these two species, and why is one so much more affected than the other?" McGuire said.

What will happen as the disease spreads further west remains anybody's guess. There are more species of bats, many of which have yet to be exposed to the fungus. Maybe some species will have natural immunity or become infected but not die. Maybe the bat population and everything affected by it, including Texas' natural ecosystems and the agriculture industry (bats eat the insects that otherwise would feed on farmers' crops), will be destroyed.


His research, which he's doing through a project with the Wildlife Conservation Society, looks at what bats live where and how the disease may affect different populations based on their physiology and the environment. This approach will guide management decisions, including which mitigation strategies are most likely to be effective.

"The more we know about how the disease works, the more we understand how bats work, so that's a big knowledge gap right now," he said. "When we know what's going on with the bats in the absence of the disease, the better we can prepare ourselves to make the best use of resources that we've got."

This research will add to the extensive bat collection at the NSRL, the depth and breadth of which allow scientists to study how species have gotten to where they are. He recently wondered how bats know exactly where they are in space and theorized the hairs that some bats have on their feet may be sensory hairs. Answering that question, or any question, normally would require researchers to capture dozens of different types of bats for study and comparison. With the NSRL, the specimens are already there, and there are more varied types of bats, allowing for a larger sample size, which in research translates into less room for error.

It's an important resource, he said, because the questions scientists are asking are important if people are to understand the natural world and their part in it.

"These animals are out there on the landscape," McGuire said. "As humans we've done so much to affect the landscape and change things. It's our responsibility to take care of the natural resources we've got out there. At the very minimum, we have to go out and do what we can with the issue of making sure we don't make anything worse."

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