“We found that a combination of physical and chemical defenses in corn plants can disrupt the protective gut barriers of fall armyworms, creating opportunities for gut microbes to invade their body cavities,” said Charles Mason, postdoctoral scholar in entomology. “This can cause septicemia, which can kill the insect, or simply trigger an immune response, which can weaken the insect.”

The researchers reared fall armyworms in the laboratory and inoculated them with one of three types of naturally occurring gut bacteria. They fed the insects on one of three types of maize — one that is known to express enzymes that produce perforations in insect gut linings; one that is characterized by numerous elongated trichomes, or fine hairs that occur on the surface of the plant and help defend against herbivores; and one that has just a few short trichomes. The team used scanning electron microscopy to evaluate the impacts of the various bacteria and maize types on the integrity of the fall armyworms’ gut linings.

The scientists found that the presence of all three types of gut bacteria decreased the ability of fall armyworm larvae to damage maize plants, especially when other defenses — such as elongated trichomes and enzymes, both of which can perforate gut linings — were present. However, the species of gut bacteria varied in the extent to which they weakened the insects. The results will appear in the July 22 issue of Proceedings of the National Academy of Sciences.

“Our results reveal a mechanism by which some plants use insects’ gut microbiota against them in collaboration with their own defenses,” said Mason.

Gary Felton, professor and head of the Department of Entomology, noted that the results should have broad significance towards understanding the ecological function of plant defenses.

“In the context of our study, disparate plant defenses, such as leaf trichomes and plant enzymes, all require certain gut microbes for their optimal defense against herbivores,” he said. “Our results predict that the variation in the effectiveness of plant defenses in nature may be, in significant part, due to the variability observed in the microbial communities of insect guts.”

The team said the results could help to inform the development of insect-resistant crops.

“It may be advantageous to ‘stack’ plant defenses that target the insect gut in order to create a ‘leaky gut’ that exposes the insect to microbial assaults on their immune system,” said Mason.

The U.S. Department of Agriculture and National Science Foundation supported this research.

Journal Reference:

Charles J. Mason, Swayamjit Ray, Ikkei Shikano, Michelle Peiffer, Asher G. Jones, Dawn S. Luthe, Kelli Hoover, Gary W. Felton. Plant defenses interact with insect enteric bacteria by initiating a leaky gut syndrome. Proceedings of the National Academy of Sciences, 2019; 201908748 DOI: 10.1073/pnas.1908748116

The study involved 13 participants, seven males and six females, who underwent a week-long fasting protocol. Over this period, participants lost an average of 5.8 kilograms in body weight, with significant reductions in lean mass (4.6 kilograms) and fat mass (1.4 kilograms). Despite this substantial loss, maximal isometric and isokinetic strength in the leg muscles remained remarkably intact. These results suggest that humans have evolved mechanisms to preserve critical physical capabilities necessary for survival during periods of starvation.

The participants’ metabolic profiles underwent dramatic shifts during the fasting period. Continuous glucose monitoring revealed a steady decline in blood glucose levels during the first three days, followed by stabilization. Resting metabolic rate (RMR) remained consistent throughout the fasting period, yet the body’s energy substrate utilization shifted markedly. Fat oxidation increased from 37% to 73% of total energy turnover, accompanied by a decline in carbohydrate contribution from 53% to 19%. This metabolic shift underscores the body’s reliance on fat reserves to sustain energy needs in the absence of dietary intake.

Interestingly, muscle glycogen stores, a key substrate for high-intensity exercise, were halved during the fasting period. This reduction aligns with the observed decline in peak oxygen consumption (VO2peak), which dropped by 13% in absolute terms and 7% relative to body weight. Participants’ peak power output during aerobic exercise decreased by 16%, reflecting diminished endurance capacity. The preservation of muscle glycogen and oxidative enzyme expression in skeletal muscle, despite these changes, highlights the body’s ability to conserve essential energy reserves while prioritizing survival.

One of the most striking findings of the study was the 13-fold increase in pyruvate dehydrogenase kinase 4 (PDK4) expression in skeletal muscle. PDK4 plays a crucial role in regulating carbohydrate metabolism by inhibiting pyruvate dehydrogenase (PDH) activity, effectively reducing carbohydrate oxidation during exercise. This adaptive mechanism likely prevents hypoglycemia during prolonged fasting but comes at the cost of reduced aerobic capacity. Elevated phosphorylation of PDH at inhibitory sites further corroborated this metabolic shift, illustrating the body’s prioritization of glucose conservation.

The study also explored the effects of fasting on other metabolic markers. Plasma free fatty acids (FFA) quadrupled, and the maximal rate of fat oxidation nearly doubled during exercise. Ketone bodies, particularly β-hydroxybutyrate, rose significantly, serving as a key energy substrate for skeletal muscle and the brain. Notably, ketone levels decreased during exercise in the fasting state, suggesting their utilization as a critical energy source during physical activity.

While muscle strength was preserved, the study revealed a decline in high-intensity endurance capacity. Respiratory exchange ratio (RER) values, indicative of substrate utilization during exercise, fell from 1.12 pre-fasting to 0.93 post-fasting. This shift reflects a reduced reliance on carbohydrate oxidation and an increased dependency on fat metabolism. The decrease in lactate production during exercise further supports the notion of diminished anaerobic capacity, a trade-off for enhanced fat utilization.

From an evolutionary perspective, these findings underscore the human body’s remarkable ability to adapt to periods of caloric deprivation. The preservation of muscle strength, particularly in the legs, would have been essential for mobility and survival during times of food scarcity. The observed decline in endurance capacity, while notable, may have been less critical in the context of intermittent physical exertion typical of early human foraging and hunting activities.

The study’s comprehensive methodology, including advanced metabolic analyses and muscle biopsies, provides valuable insights into the molecular mechanisms underlying fasting-induced adaptations. The authors highlight the role of PDK4 as a key regulator of carbohydrate metabolism during prolonged fasting. By inhibiting PDH activity, PDK4 ensures glucose conservation while promoting reliance on fat and ketone bodies as alternative energy sources.

Despite the significant metabolic shifts observed, participants reported minimal adverse effects, and no serious complications were recorded. This finding demonstrates the feasibility of prolonged fasting in healthy individuals under controlled conditions. However, the authors caution against generalizing these results to broader populations, particularly those with underlying health conditions or limited fat reserves.

This study paves the way for future research exploring the therapeutic potential of fasting in various contexts, including weight management, metabolic disorders, and physical performance optimization. The authors emphasize the need for further investigations into the long-term effects of fasting, particularly its impact on muscle protein turnover and mitochondrial function. Additionally, the integration of fasting protocols with exercise interventions may offer novel strategies for enhancing metabolic health and physical performance.

In conclusion, this landmark study reveals the human body’s extraordinary resilience and adaptability during periods of prolonged caloric deprivation. By preserving muscle strength and oxidative capacity while prioritizing fat and ketone metabolism, the body demonstrates a finely tuned balance between survival and physical performance. These findings not only deepen our understanding of human physiology but also offer intriguing possibilities for harnessing fasting-induced adaptations in health and performance contexts.

Subject of Research: Human physiology and metabolic adaptation during prolonged fasting

Article Title: Effects of seven days’ fasting on physical performance and metabolic adaptation during exercise in humans

News Publication Date: 02 January 2025

Article Doi References: 10.1038/s41467-025-00122-0

Image Credits: Scienmag

Keywords: fasting, physical performance, metabolic adaptation, muscle strength, endurance capacity, fat oxidation, PDK4, skeletal muscle, human physiology, ketone metabolism

The study, conducted by Kazunori Yoshizawa, Rodrigo L. Ferreira, Yoshitaka Kamimura, and Charles Lienhard, provides compelling evidence of correlated evolution between the female gynosome and the simplified male genitalia. This correlation appears to be driven by reversed sexual selection, where females compete for nutritious seminal gifts provided by males during copulation. These seminal gifts are a valuable resource in the nutrient-scarce cave environments where Neotrogla species thrive, feeding primarily on bat guano and carcasses.

Detailed observations reveal that the female gynosome is a highly specialized structure. It features a sclerotized distal part that deeply penetrates the male’s genital chamber, anchoring the female during copulation. Remarkably, these couplings can last for extended durations, ranging from 40 to 70 hours. The gynosome’s species-specific spines and pouches facilitate a firm grip, allowing females to secure and receive the voluminous spermatophores produced by males. This prolonged copulation is hypothesized to maximize the transfer and utilization of these seminal gifts, which serve not only for fertilization but also as a nutritional resource for the females.

The findings also reveal intriguing patterns of polyandry within these species, with females acquiring multiple spermatophores over their lifetime. In some cases, females were observed consuming the contents of spermatophores post-copulation to support egg production, further emphasizing the critical role of seminal gifts in their reproductive strategy.

This extraordinary sexual role reversal and genital adaptation offer a rare opportunity to study the broader implications of sexual selection, evolutionary novelty, and sexual conflict. The study provides valuable insights into how environmental pressures and resource scarcity can drive significant evolutionary changes, challenging traditional notions of sexual dimorphism and reproductive behavior.

Neotrogla species, inhabiting harsh cave ecosystems, represent an exceptional model for understanding the interplay of morphology, behavior, and environmental constraints. This discovery not only enhances our understanding of sexual selection but also highlights the profound adaptability of life in extreme environments.

Subject of Research: Evolutionary biology of sexual role reversal and genital morphology in cave-dwelling insects.

Article Title: Female Penis, Male Vagina, and Their Correlated Evolution in a Cave Insect

News Publication Date: May 5, 2014

Article Doi References: https://doi.org/10.1016/j.cub.2014.03.022

Image Credits:

Keywords: Neotrogla, reversed sexual selection, gynosome, seminal gifts, cave insects, genital evolution, sexual role reversal, evolutionary biology.

A new study led by Michigan State University researcher Peter Williams sheds light on the profound influence of deep geographic isolation on the evolution of mammals. Published in Nature Communications on March 28, the research reveals how long-lasting separation between continents has shaped distinct mammal communities around the globe.

“Today’s ecology was not inevitable. If there were different isolating factors long ago, we might have vastly different ecosystems today,” said Peter Williams, the lead author of the study. Williams is a research associate in the Integrative Biology department and a postdoctoral researcher in MSU’s Ecology, Evolution and Behavior program, or EEB.

While environmental factors like climate and vegetation are well-known drivers of biodiversity, the new study highlights the crucial role that isolation played for mammals.

“Think tree-dwelling mammals,” Williams said. “Despite similar climates, you’ll find koalas in Australia and squirrels in Spain.”

What you won’t find, however, are koalas native to Spain or squirrels native to Australia.

“That distinction stems from deep-seated geographic isolation and diverging evolutionary paths long ago,” Williams said.

With this new perspective, the findings of this research don’t just satisfy curiosity about that natural world. The report holds significant implications for conservation efforts and modern ecological issues.

“By understanding how historical isolation has shaped biodiversity, we can gain valuable insights into the delicate balance of ecosystems and develop strategies for protecting biodiversity in regions with unique evolutionary histories,” Williams said.

“In ecology, even hyperlocal problems need to incorporate regional, continental or even global processes — weather patterns, ocean currents or, in this case, deep-seated geographic barriers,” said Elise Zipkin, co-author of the study and associate professor of integrative biology. She’s also the leader of the Zipkin Quantitative Ecology Lab and director of EEB. “They all impact today’s natural world.”

Deep isolation shapes mammal evolution

Supported by the National Science Foundation, the study uses a novel approach to analyze biogeographic isolation, incorporating a continuous measure called “phylobetadiversity,” which quantifies shared evolutionary history, Williams said.

For instance, phylobetadiversity would be low when comparing Michigan with somewhere in Europe that’s also home to deer, rabbits, squirrels and the like, he said.

“Even if they aren’t the same species, there is a lot of shared evolutionary history at the community level,” Williams said.

Michigan and Australia would be at the opposite end of the phylobetadiversity spectrum.

“Australia has mostly marsupials, while in Michigan we don’t have any marsupials except the opossum,” he continued. “There is very little shared evolutionary history at the community level.”

Using phylobetadiversity paints a nuanced picture of how connected different regions have been historically.

“Isolated regions like Australia and Madagascar harbor mammal assemblages that are much less diverse than expected based on environment alone and those mammals possess unique combinations of functional traits, reflecting the distinct evolutionary paths they’ve taken,” Williams said. “It’s a fascinating idea that the biodiversity patterns we see in today’s world were not inevitable.”

The key factor in biodivergence for isolated mammals seems to be the duration of isolation.

Regions like Australia, isolated for 30-35 million years, have had ample time for unique mammal lineages to evolve. In contrast, continents like North and South America, which were once separated but reconnected during the Great American Biotic Interchange 2.7 million years ago, show more convergence in their mammal communities, with similar climates selecting for similar functional traits.

Though the evolution of mammals was heavily impacted by the isolation of land masses, the study shows birds reacted quite differently.

Birds, with their greater ability to fly across vast distances, can more easily overcome geographic barriers. This constant movement and mixing of bird populations across continents has led to a homogenization of bird communities globally, with environmental factors playing a stronger role in shaping their diversity.

Interestingly, bats told a completely different story. As the only flying mammal group, bats in the Western Hemisphere, such as vampire bats and fish-eating bats, exhibit a much higher degree of functional diversity compared with their counterparts in the Eastern Hemisphere. This, the researchers suggest, is likely a consequence of their independent evolutionary trajectories shaped by the long-standing separation of landforms in the different regions.

Unlike other mammals, most bats didn’t have the cold tolerance to traverse the Beringia land bridge that, long ago, connected Alaska and Siberia, leading to their continued isolation and modern divergent species across hemispheres.

The team at the Zipkin lab aims to continue this line of research, conducting additional studies to look further into mammalian histories and how biogeographic divides have shaped the biota on our planet.

“This is just the beginning of our journey toward a deeper understanding of the world around us,” Zipkin said.