The immune memory of amphibians is mostly lost after metamorphosis, generating fluctuating immune response sophistication across life stages. To investigate whether the developmental trajectory of host immunity influences interactions between concurrently infecting parasites, we concurrently exposed Cuban treefrogs (Osteopilus septentrionalis) to a fungus (Batrachochytrium dendrobatidis, Bd) and a nematode (Aplectana hamatospicula) across tadpole, metamorphic, and post-metamorphic life stages. Metrics of host immunity, health status, and parasite density were measured by us. Our prediction is that co-infecting parasites would display facilitative interactions, given that the array of immune responses the hosts mobilize to combat these infectious agents are energetically costly and difficult to activate simultaneously. We detected ontogenetic differences in IgY levels and cellular immunity, but found no indication that metamorphic frogs displayed more immunosuppression than tadpoles. Substantially, there was little proof that these parasites assisted each other, and no proof that an A. hamatospicula infection modified the host's immune system or overall well-being. Although Bd is known to suppress the immune system, it impaired the immunity of metamorphic frogs during their metamorphosis. The metamorphic stage of frogs exhibited diminished resistance and tolerance to Bd infection compared to other developmental stages. Immune system fluctuations, as indicated by these findings, led to changes in how the host reacted to parasite exposures throughout development. This article, part of the theme issue 'Amphibian immunity stress, disease and ecoimmunology,' delves into the intricacies of the topic.

The growing concern over emerging diseases underscores the importance of discovering and thoroughly understanding new methods of prophylactic protection in vertebrate organisms. Resistance induction against emerging pathogens via prophylaxis is an optimal management approach, capable of impacting the pathogen and the associated host microbiome. Although the host microbiome is acknowledged as essential for immunity, the consequences of prophylactic inoculation on this complex ecosystem remain elusive. This study examines the impact of prophylactic measures on the host microbiome's composition, concentrating on the selection of antimicrobial agents that enhance host immunity within a model host-fungal disease system, namely, amphibian chytridiomycosis. A prophylactic based on Bd metabolites was used to inoculate larval Pseudacris regilla, providing them with protection against the fungal pathogen Batrachochytrium dendrobatidis (Bd). Prophylactic concentrations and exposure durations showed a strong association with significant increases in putatively Bd-inhibitory host-associated bacterial taxa, indicating a prophylactic-induced shift towards antagonistic microbiome members. The adaptive microbiome hypothesis, which predicts a modification of the microbiome in response to a pathogen, to enhance the microbiome's capacity for future pathogen encounters, is consistent with our observations. Our research advances knowledge of the temporal evolution of microbiome memory, focusing on the contribution of prophylaxis-driven alterations in microbial composition to overall prophylaxis success. Included within the thematic issue 'Amphibian immunity stress, disease and ecoimmunology' is this article.

Immune function is regulated by testosterone (T), exhibiting both immunostimulatory and immunosuppressive effects across various vertebrate species. Corticosterone (CORT) and testosterone (T) plasma concentrations were investigated in relation to immune responses, including bacterial killing ability (BKA) and neutrophil-to-lymphocyte ratio (NLR), in free-living male Rhinella icterica toads, both during and outside the breeding season. Our findings indicated a positive correlation between steroid use and immune responses, specifically in toads. Elevated T, CORT, and BKA levels were observed during their reproductive season. The impact of transdermal T application on captive toads' T, CORT, blood cell phagocytic activity, BKA levels, and NLR counts was analyzed. Eight consecutive days of treatment with either T (1 gram, 10 grams, or 100 grams) or sesame oil (vehicle) were administered to toads. Blood samples were collected from animals on the first and eighth days of treatment. T-treatment manifested increased plasma T levels on the initial and terminal days, with subsequent increases in BKA levels following all T doses administered on the last day; a noteworthy positive correlation between T and BKA was observed. Plasma CORT, NLR, and phagocytosis increased in all T-treated and vehicle-control groups on the very last day of the experiment. In R. icterica males, field and captive investigations indicated a positive association between T and immune characteristics. This is supported by T's augmentation of BKA, thus suggesting an immunoenhancing effect of T. This article participates in the thematic coverage of 'Amphibian immunity stress, disease, and ecoimmunology'.

A concerning global decline in amphibian populations is attributable to the intersecting challenges of infectious disease outbreaks and shifts in global climate patterns. Ranavirosis and chytridiomycosis are among the principal infectious agents driving amphibian population declines, a phenomenon that has generated considerable recent interest. While the fate of some amphibian populations hangs in the balance, others are naturally resistant to disease. While the host's immune system is paramount in combating diseases, the intricate immune mechanisms governing amphibian disease resilience and host-pathogen interactions remain largely unexplored. Variations in temperature and rainfall significantly impact the stress response of amphibians, due to their ectothermic nature, influencing physiological processes like immunity and the pathogen physiology associated with diseases. The interplay of stress, disease, and ecoimmunology contexts is indispensable for a more thorough comprehension of amphibian immunity. The ontogeny of the amphibian immune system, encompassing crucial innate and adaptive immune functions, and the resultant impact on resistance to diseases, are the focus of this issue. Moreover, the papers compiled in this edition showcase a unified understanding of the amphibian immune system, emphasizing the role of stress in modulating immune-endocrine interactions. The research compilation presented here provides useful understanding of the processes behind disease outcomes in natural populations, especially in the face of changing environmental conditions. Forecasting effective conservation strategies for amphibian populations could ultimately be aided by these findings. This contribution is a component of the 'Amphibian immunity stress, disease and ecoimmunology' thematic issue.

Amphibians occupy a key evolutionary position bridging the gap between the mammalian line and older, jawed vertebrates. Currently, many amphibian species are under attack by diseases, and the understanding of their immune systems is crucial, and significant beyond their value as research models. Xenopus laevis, the African clawed frog, shares a remarkably conserved immune system with mammals. For both the adaptive and innate immune systems, the common presence of B cells, T cells, and a subset of innate-like T cells is noteworthy. The study of *Xenopus laevis* tadpoles offers unique opportunities to investigate the immune system's formative stages. Tadpoles' innate immune responses, involving pre-configured or innate-like T cells, are their primary defense mechanisms until the point of metamorphosis. The review comprehensively examines the known aspects of the innate and adaptive immune system in X. laevis, specifically analyzing lymphoid organs, and drawing comparisons and contrasts with the immune systems of other amphibians. Iranian Traditional Medicine Beyond that, the amphibian immune system's capacity to counter viral, bacterial, and fungal aggressions will be examined. The 'Amphibian immunity stress, disease and ecoimmunology' special issue encompasses this article.

Significant changes in the body condition of animals can result from the variability of their food resources. bone biomechanics Lowering body weight can disturb the established patterns of energy distribution, causing stress and thereby affecting the proper functioning of the immune system. This research explored the connection between variations in the body mass of captive cane toads (Rhinella marina), alterations in their blood leukocyte counts, and their performance in immune-based assays. Weight loss in captive toads over a three-month span was associated with heightened levels of monocytes and heterophils and a reduction in eosinophils. The relationship between basophil and lymphocyte levels and changes in mass was nonexistent. Mass loss, associated with elevated heterophil levels and consistent lymphocyte levels, contributed to a heightened ratio of these cell types, thus potentially mirroring a stress response. A correlation was found between weight loss in toads and a superior phagocytic ability of whole blood, which was directly proportional to the elevated levels of circulating phagocytic cells. Nigericin The alteration in mass showed no connection to other measures of immune function. Expanding their range into novel environments presents considerable challenges to invasive species, including the significant seasonal changes in food availability that were absent in their native ranges, as these results demonstrate. Individuals who are experiencing energy limitations may alter their immune functions to utilize more economical and generalized strategies for battling pathogens. Encompassed within the broader thematic issue of 'Amphibian immunity stress, disease and ecoimmunology,' this article is included.

Infection defense in animals relies on two interconnected strategies: tolerance and resistance. Whereas resistance describes the ability to lessen the intensity of an infection, tolerance indicates the capacity of an animal to curtail the detrimental consequences stemming from that infection. Infections with high prevalence, persistence, or endemic status, where traditional resistance-based mitigation strategies are either less effective or evolutionarily stable, demonstrate the critical value of tolerance as a defense mechanism.