Systemic Humoral Immunity in the Partially Migratory Bat Leptonycteris yerbabuenae is Linked to the Gut Microbiota in a Sex-Specific Manner

{“title”:”Gut Microbes Shape Bat Immunity Differently in Males and Females”,”excerpt”:”A new study of the lesser long-nosed bat reveals that gut bacterial communities are linked to systemic humoral immunity in patterns that differ sharply between males and migrating females.”,”subject”:”Sex-specific links between gut microbiota and humoral immunity in the partially migratory bat Leptonycteris yerbabuenae”,”tags”:[“gut microbiota”,”humoral immunity”,”bats”,”Leptonycteris yerbabuenae”,”migration”,”immunoglobulin G”,”bacterial killing ability”,”microbiome”,”wildlife immunology”,”16S rRNA”,”sex differences”,”microbial ecology”],”html”:”In the deserts and dry forests of Mexico, the lesser long-nosed bat, Leptonycteris yerbabuenae, undertakes one of the most remarkable reproductive strategies among mammals. Males of the species tend to stay put, forming resident populations, while many females embark on long seasonal journeys to complete their reproductive cycle, tracking the blooms of cactus and agave flowers on which they feed. A new study published in the journal Microbial Ecology suggests that this split lifestyle may leave a measurable imprint deep inside the animals’ bodies, shaping how their immune systems relate to the trillions of microbes that inhabit their guts. The research, led by David Alfonso Rivera-Ruiz of the National Autonomous University of Mexico together with colleagues, provides some of the clearest evidence yet that in a wild migratory mammal, the connection between gut bacteria and circulating immune factors differs between the sexes.

The immune system and the gut microbiota are widely recognized as intertwined pillars of host health, but in wildlife, particularly in migratory species, the nature of this relationship remains poorly charted. Migratory animals pass through a succession of environments, each exposing them to different food resources, pathogens, and environmental microorganisms, all of which can alter both their microbial communities and their immune defenses. To probe this connection, the research team focused on two complementary measures of systemic humoral immunity, the arm of the immune system that operates through soluble proteins in the blood rather than through cells. The first measure was bacterial killing ability, abbreviated BKA, which reflects the capacity of blood plasma to inactivate a standardized bacterial challenge, integrating the activity of complement proteins, natural antibodies, and other circulating factors. The second was the total concentration of immunoglobulin G, or tIgG, the most abundant antibody class in mammalian blood and a key player in long-term immune protection.

On the microbial side, the researchers characterized the diversity and composition of the gut bacterial communities using 16S ribosomal RNA gene amplicon sequencing, the standard molecular tool for surveying microbial diversity without needing to culture the organisms. Fecal samples served as a non-invasive window into the intestinal microbiota of the bats, allowing the team to work with free-ranging animals captured in the field. The study was conducted with the logistic support of the Chamela Biological Station in Jalisco, Mexico, and was approved by the Ethics Committee in Research and Teaching of the Institute of Biology at the National Autonomous University of Mexico, under permits from the Mexican wildlife authority.

The results revealed a relationship that is both real and, strikingly, sex-specific. In females, total immunoglobulin G concentrations were negatively correlated with the Shannon index, a common metric of microbial diversity that accounts for both the number of bacterial types present and how evenly they are distributed. In plain terms, female bats with more diverse gut bacterial communities tended to carry lower circulating levels of this key antibody. No comparable relationship emerged for bacterial killing ability, with one notable exception: in females, the beta diversity of the microbiota, which captures differences in community composition between individuals rather than diversity within a single gut, showed a significant association with BKA. In males, neither alpha diversity metric tracked humoral immune measures in a significant way.

Where diversity metrics fell short, composition stepped in. Across both sexes, humoral immunity was significantly related to the relative abundance of specific fecal bacterial genera, and the identities of those genera carried biological weight. Some of the bacteria associated with immune measures are known to harbor immunostimulatory species, microbes capable of activating immune signaling pathways and thereby influencing circulating antibody levels or complement activity. Others are linked to the integrity of the intestinal mucosa, the single-cell-thick barrier that separates the densest microbial community in the body from the bloodstream and that must remain intact to prevent chronic inflammatory activation. A third category comprised infection-associated species, bacteria whose presence can signal or accompany active microbial challenge. That all three functional groups correlated with blood-borne immune measures fits the emerging picture of the gut as an immune training ground, where microbial products continually calibrate systemic defenses.

Intriguingly, the study also found that free-living and unclassified bacterial genera, organisms whose ecological roles remain poorly described, were associated with immunity in a manner specific to each sex. This detail matters because it suggests that the microbiota-immunity link in L. yerbabuenae is not a uniform phenomenon that can be summarized with a single rule applying to the whole population. Instead, the physiological context of the host, including sex-associated traits such as reproductive state, hormone profiles, and, crucially in this species, migratory behavior, appears to modulate which microbes matter and how their presence translates into immune signaling.

The sex-specific pattern takes on added significance when viewed against the species’ natural history. Because some female lesser long-nosed bats migrate while males largely remain resident, the two sexes encounter different suites of microorganisms across the annual cycle, consume different resources at different times, and face different energetic demands tied to pregnancy and lactation. Each of these factors can reshape gut microbial composition, and each can independently modulate immune investment. The finding that tIgG declined with microbial diversity in females but not in males hints that migration and its associated exposures may restructure the relationship between microbial richness and antibody levels, perhaps because traveling females balance the immunological novelty of new environments against the energetic costs of mounting immune responses.

The authors conclude that gut microbiota composition, and to a lesser extent diversity, is linked to systemic humoral immunity in this species, and that the distinct relationship exhibited by each sex suggests migration and other sex-associated traits may be crucial to understanding the natural variation of immunity in wildlife. This framing carries implications well beyond a single bat species. If the microbiota-immunity axis differs between sexes within a population, studies of wildlife immunology that pool the sexes, or that ignore microbial covariates, may be missing or misattributing important sources of variation. For migratory species in particular, which include many pollinators, seed dispersers, and disease reservoirs of conservation and public health concern, accounting for the gut microbial community could sharpen predictions about how animals respond to environmental change, habitat fragmentation, and emerging infectious threats.

Technically, the study demonstrates the value of pairing non-invasive fecal sampling with dual immune assays in free-ranging mammals. Bacterial killing ability offers a broad functional snapshot of constitutive innate and natural antibody-mediated defense, while total immunoglobulin G provides a window into adaptive humoral investment. Combining these with high-throughput 16S amplicon sequencing allowed the researchers to ask not simply whether immunity and microbes are connected, but which dimension of the microbial community, richness, evenness, compositional turnover, or the abundance of particular genera, carries the signal. The answer, that composition outweighs diversity and that the signal differs by sex, refines a question that ecologists and immunologists have increasingly pursued in wild vertebrates.

As bats continue to attract attention for their unusual immune resilience and their roles as reservoirs of viruses with zoonotic potential, studies like this one anchor that interest in ecological reality. The lesser long-nosed bat, a vital pollinator of agaves and columnar cacti across Mexico, now offers a model for understanding how movement across landscapes, sex, and the invisible communities of the gut jointly sculpt the immune defenses of a wild mammal. The work forms part of the doctoral research of Rivera-Ruiz at the National Autonomous University of Mexico and was funded by grants from the university’s DGAPA program and from Mexico’s Secretariat of Science, Humanities, Technology and Innovation.

“}“Subject of Research: Sex-specific links between gut microbiota and systemic humoral immunity in the partially migratory bat Leptonycteris yerbabuenae.

Article Title: Systemic Humoral Immunity in the Partially Migratory Bat Leptonycteris yerbabuenae is Linked to the Gut Microbiota in a Sex-Specific Manner

Article References: Rivera-Ruiz, D. A., et al. (2026). Systemic Humoral Immunity in the Partially Migratory Bat Leptonycteris yerbabuenae is Linked to the Gut Microbiota in a Sex-Specific Manner. Microbial Ecology. https://doi.org/10.1007/s00248-026-02881-5

Image Credits: AI Generated

DOI: 10.1007/s00248-026-02881-5

Keywords: gut microbiota, humoral immunity, bats, Leptonycteris yerbabuenae, migration, immunoglobulin G, bacterial killing ability, sex differences, 16S rRNA, microbial ecology

Subject of Research: Systemic Humoral Immunity in the Partially Migratory Bat Leptonycteris yerbabuenae is Linked to the Gut Microbiota in a Sex-Specific Manner

Article Title: Systemic Humoral Immunity in the Partially Migratory Bat Leptonycteris yerbabuenae is Linked to the Gut Microbiota in a Sex-Specific Manner

Article References: Rivera-Ruiz, D. A., Flores-Martínez, J. J., Rosales, C., Falcón, L. I., Gaona, O., Solano de la Cruz, M. T., & Herrera M., L. G. (2026). Systemic Humoral Immunity in the Partially Migratory Bat Leptonycteris yerbabuenae is Linked to the Gut Microbiota in a Sex-Specific Manner. Microbial Ecology. https://doi.org/10.1007/s00248-026-02881-5

Image Credits: AI Generated

DOI: 10.1007/s00248-026-02881-5

Keywords: Systemic, Humoral, Immunity, Partially, Migratory, Leptonycteris, yerbabuenae, Linked, Microbiota, Sex-Specific, Manner, scientific research