A recent study found a considerable difference between the microbial diversity in the intestines of female and male American mink (Neovison mink). The finding suggests that there is an unexpected gender distinction in the gut microbiomes of carnivores, which has ramifications for future wildlife research.
“This finding is surprising because the entrails of carnivores are very short and simple – literally,” says Erin McKenney, study co-author and assistant professor of applied ecology at North Carolina State University. “The intestines of carnivores are much shorter and less convoluted than the intestines of omnivores and herbivores, which have developed more complex intestines in order to break down plant material. The fact that carnivore intestines are so simple means that the immune system – which differs between males and females – has less time to influence microbial diversity, but we’re still seeing substantial gender differences in this species. “
“In practical terms, this finding is key to informing the design of the future study,” says Diana Lafferty, the paper’s first author and assistant professor of wildlife ecology at Northern Michigan University (NMU).
That’s because carnivorous environmentalists often obtain samples using non-invasive techniques, such as collecting droppings – or droppings from wild animals – during fieldwork.
“This means that we generally don’t know whether the animal that produced the fecal sample was a male or a female,” says Lafferty. “This finding tells us that analyzing microbiomes from anonymous samples may not give us an accurate assessment of the population from which they originated. We will need to perform tests on fecal samples to establish the gender of donors in order to put the gut microbiome data into context.
Wildlife researchers are interested in gut microbiomes – the ecosystem of microbial life in an animal’s stomach and intestines – because studying and assessing the diversity of the gut microbiome provides researchers with information in-depth knowledge of animal health and welfare.
“For example, it provides a tool that we can use to better understand how animals respond to changes in their environment,” says Lafferty.
But as wildlife ecologists, and especially carnivore ecologists, often rely on the analysis of faecal samples from wild animals, questions arise about how to take environmental variables into account, especially time and temperature. In other words, does the microbial diversity of wildlife feces change when it’s hot outside? Are the microbes scientists find in poop any different if they pick up the poop right away compared to if they pick it up five days later?
The researchers chose mink as a model carnivorous species to study these questions because minks can be kept in captivity, can be fed a standardized diet, and their intestines are similar to those of other carnivores.
For this study, the researchers worked with 10 captive mink – five males and five females. All of the mink were roughly the same age, were healthy, were housed separately, and received the same diet.
The researchers recovered stool samples from the 10 mink. While a subsample of poo from each mink was taken immediately for microbial DNA extraction, the rest of each sample was split in half so that each mink’s droppings could be subjected to two different heat treatments. . One set of samples was stored at temperatures below freezing while another set of samples was stored at 70 degrees Fahrenheit. The samples were then subjected to microbial DNA extraction every day for five days, ultimately allowing researchers to determine both what types of microbes were in each sample and how many of each type of microbe.
The results included two surprises.
The first surprise was that neither the weather nor the temperature caused significant changes in the fecal microbiomes. This is good news for wildlife biologists.
“Old poo is still pretty accurate in assessing the gut microbiome of carnivores,” McKenney explains.
The second surprise was that the male and female samples were significantly different from each other. Not only were many different bacterial species found in males than in females, the abundance of the species they shared in common were also different. In other words, when a bacterial species was found in both sexes, the overall population of that species often differed greatly between males and females.
“We could speculate on the significance of these differences, but that would only be speculation,” McKenney says. “Suffice it to say, this discovery raises some very interesting research questions that we would like to explore. “
“Much of the existing microbiome work is in omnivores and herbivores – we’re excited to explore the carnivore microbiome,” Lafferty said. “We thought the microbiomes of carnivores might be simple, and we find they are not.”
The paper, “Mink (Neovison mink) fecal microbiomes are influenced by sex, temperature and time after defecation, ”Is published in the Mammalogy Journal. The article was co-authored by Sierra Gillman, a Ph.D. student at the University of Washington who worked on the project while a graduate student at NMU; Lane Jeakle, a former NMU student; and Brian Roell, wildlife biologist in the Michigan Department of Natural Resources and Environment.
Note to editors: The summary of the study follows.
“Mink (Neovison mink) fecal microbiomes are influenced by sex, temperature and time after defecation ‘
Authors: Diana JR Lafferty, Sierra Gillman and Lane Jeakle, Northern Michigan University; Brian Roell, Michigan Department of Natural Resources and Environment; Erin McKenney, North Carolina State University
Posted: January 7 Mammalogy Journal
DO I: 10.1093 / jmammal / gyab140
Summary: The gut microbiomes code for a myriad of metabolic functions essential to the ecology and evolution of mammals. While fresh fecal samples are an efficient and non-invasive method of sampling gut microbiomes, collecting fresh fecal material from elusive species is a logistical challenge. Non-fresh feces, however, may not accurately represent the host’s gut microbiome due to the succession of gut microbial consortia after defecation as well as colonization by microbes from the surrounding environment. Using the American mink (Neovison vison) as a model species, we examined the succession of the post-defecation microbial community to learn how ambient temperature and time-sampling constraints influence the reliability of non-fresh feces to represent microbiomes. intestines of the host. To achieve our goal, we analyzed fresh mink droppings (n = 5 females; n = 5 males) collected at the time of captive mink defecation from a farm in Michigan’s Upper Peninsula and then downsampled each fecal sample to investigate the microbial community. succession over five days, under both hot (21 ° C) and cold (-17 ° C to -1 ° C) treatments. We found that temperature and time influence the composition of the fecal microbiome; and we also detected significant sexual dimorphism in microbial community structures, with female mink microbiomes showing significantly greater variation than male microbiomes when exposed to the hot temperature treatment. Our results demonstrate that feces from unknown individuals can be a powerful tool for examining the gut microbiomes of carnivores, although rigorous study design is needed because gender, ambient temperature, and time since defecation result in significant microbial variation and the sample size requirements necessary to detect statistically significant differences between target populations is an important consideration for future ecologically significant research.