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1. An effective way to mark cohorts of juvenile terrestrial direct-developing frogs

   Pena-Jimenez, J.A.; Burrowes, P.A. (August 2021, Herpetology notes)

   Kaiser, Hinrich; Zagar, Anamarija; Müller, Hendrik (Ed.)

   Abstract. Marking juveniles of terrestrial direct-developing frogs is challenging because of their small size (< 18 mm) and fragility. This difficulty has limited studies on demography or population dynamics where empirical data on the survivorship of juveniles or their recruitment to adulthood are missing. In a controlled laboratory experiment, we tested the survivorship of wild-caught juvenile Eleutherodactylus coqui Thomas, 1966 to marking with a single colour visual internal elastomer (VIE) in the thigh, with and without additional ventral skin-swabbing for disease or microbiome monitoring. Results revealed 100% survival in all groups, and all juveniles remained unharmed, moved freely, and fed actively during three days after treatment, suggesting that this type of manipulation does not cause direct mortality. After 17 months of the experiment, we have recaptured 11% of the marked juveniles as adults, indicating that they can survive to recruitment age. We propose the use of a single VIE colour as a method to mark and follow date-specific cohorts of juvenile direct-developing frogs or young metamorphs until they reach older and larger age classes. This marking method can be used safely together with skin swabbing and provide valuable information for studies on population biology and age-specific response to environmental or disease stressors. 

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2. Diverse Relationships between Batrachochytrium Infections and Antimicrobial Peptide Defenses Across Leopard Frog Populations

   https://doi.org/10.1093/icb/icae130  

   Le Sage, Emily_H; Reinert, Laura_K; Ohmer, Michel_E_B; LaBumbard, Brandon_C; Altman, Karie_A; Brannelly, Laura_A; Latella, Ian; McDonnell, Nina_B; Saenz, Veronica; Walsman, Jason_C; et al (August 2024, Integrative And Comparative Biology)

   Synopsis Antimicrobial peptides (AMPs) play a fundamental role in the innate defense against microbial pathogens, as well as other immune and non-immune functions. Their role in amphibian skin defense against the pathogenic fungus Batrachochytrium dendrobatidis (Bd) is exemplified by experiments in which depletion of host’s stored AMPs increases mortality from infection. Yet, the question remains whether there are generalizable patterns of negative or positive correlations between stored AMP defenses and the probability of infection or infection intensity across populations and species. This study aims to expand on prior field studies of AMP quantities and compositions by correlating stored defenses with an estimated risk of Bd exposure (prevalence and mean infection intensity in each survey) in five locations across the United States and a total of three species. In all locations, known AMPs correlated with the ability of recovered secretions to inhibit Bd in vitro. We found that stored AMP defenses were generally unrelated to Bd infection except in one location where the relative intensity of known AMPs was lower in secretions from infected frogs. In all other locations, known AMP relative intensities were higher in infected frogs. Stored peptide quantity was either positively or negatively correlated with Bd exposure risk. Thus, future experiments coupled with organismal modeling can elucidate whether Bd infection affects secretion/synthesis and will provide insight into how to interpret amphibian ecoimmunology studies of AMPs. We also demonstrate that future AMP isolating and sequencing studies can focus efforts by correlating mass spectrometry peaks to inhibitory capacity using linear decomposition modeling. 

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3. Arduino allows development of a low-cost, high-resolution metabolic and behavioral phenotyping system for birds

   https://doi.org/10.1242/jeb.249921  

   Rogers, Elizabeth J; Elowe, Cory; Stager, Maria; Gerson, Alexander R (April 2025, Journal of Experimental Biology)

   Technological advancements now enable the use of flow-through respirometry for rapid, high-throughput metabolic phenotyping, though live-in systems currently do not exist for birds. We designed live-in respirometry chambers for small birds with an Arduino-based electronic system to continuously monitor bird body weight, food intake, and water intake in sync with metabolic data collection. To demonstrate how this system can be implemented, we kept birds in the metabolic phenotypic chambers for 10 days while we progressively lowered the temperature from 25 °C to 5 °C. We used the data to calculate hourly energy expenditure and food/water intake during acute cold acclimation. We provide all plans and code for the live-in chambers, Arduino biomonitoring system, and additional RFID module as a low-cost, DIY alternative to commercially available systems and to enable the use of standard respirometry equipment for metabolic phenotyping in birds. 

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4. Thermal acclimation in a non-migratory songbird occurs via changes to thermogenic capacity, but not conductance

   https://doi.org/10.1242/jeb.245208  

   Schweizer, Rena M.; Romero, Abimael; Tobalske, Bret W.; Semenov, Georgy A.; Carling, Matt D.; Rice, Amber M.; Taylor, Scott A.; Cheviron, Zachary A. (October 2023, Journal of Experimental Biology)

   Thermoregulatory performance can be modified through changes in various subordinate traits, but the rate and magnitude of change in these traits is poorly understood. We investigated flexibility in traits that affect thermal balance between black-capped chickadees (Poecile atricapillus) acclimated for 6 weeks to cold (−5°C) or control (23°C) environments (n=7 per treatment). We made repeated measurements of basal and summit metabolic rates via flow-through respirometry and of body composition using quantitative magnetic resonance of live birds. At the end of the acclimation period, we measured thermal conductance of the combined feathers and skins. Cold-acclimated birds had a higher summit metabolic rate, reflecting a greater capacity for endogenous heat generation, and an increased lean mass. However, birds did not alter their thermal conductance. These results suggest that chickadees respond to cold stress by increasing their capacity for heat production rather than increasing heat retention, an energetically expensive strategy. 

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5. Preparatory immunity: Seasonality of mucosal skin defences and Batrachochytrium infections in Southern leopard frogs

   https://doi.org/10.1111/1365-2656.13386  

   Le Sage, Emily H.; LaBumbard, Brandon C.; Reinert, Laura K.; Miller, Brian T.; Richards‐Zawacki, Corinne L.; Woodhams, Doug C.; Rollins‐Smith, Louise A.; Bielby, ed., Jon (November 2020, Journal of Animal Ecology)

   Abstract Accurately predicting the impacts of climate change on wildlife health requires a deeper understanding of seasonal rhythms in host–pathogen interactions. The amphibian pathogen,Batrachochytrium dendrobatidis(Bd), exhibits seasonality in incidence; however, the role that biological rhythms in host defences play in defining this pattern remains largely unknown.The aim of this study was to examine whether host immune and microbiome defences againstBdcorrespond with infection risk and seasonal fluctuations in temperature and humidity.Over the course of a year, five populations of Southern leopard frogs (Rana[Lithobates]sphenocephala) in Tennessee, United States, were surveyed for host immunity, microbiome and pathogen dynamics. Frogs were swabbed for pathogen load and skin bacterial diversity and stimulated to release stored antimicrobial peptides (AMPs). Secretions were analysed to estimate total hydrophobic peptide concentrations, presence of known AMPs and effectiveness ofBdgrowth inhibition in vitro. The diversity and proportion of bacterial reads with a 99% match to sequences of isolates known to inhibitBdgrowth in vitro were used as an estimate of predicted anti‐Bdfunction of the skin microbiome.Batrachochytrium dendrobatidisdynamics followed the expected seasonal fluctuations—peaks in cooler months—which coincided with when host mucosal defences were most potent againstBd. Specifically, the concentration and expression of stored AMPs cycled synchronously withBddynamics. Although microbiome changes followed more linear trends over time, the proportion of bacteria that can function to inhibitBdgrowth was greatest when risk ofBdinfection was highest.We interpret the increase in peptide storage in the fall and the shift to a more anti‐Bdmicrobiome over winter as a preparatory response for subsequent infection risk during the colder periods when AMP synthesis and bacterial growth is slow and pathogen pressure from this cool‐adapted fungus is high. Given that a decrease in stored AMP concentrations as temperatures warm in spring likely means greater secretion rates, the subsequent decrease in prevalence suggests seasonality ofBdin this host may be in part regulated by annual immune rhythms, and dominated by the effects of temperature. 

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