Integrative and Comparative Biology最新文献

The glucocorticoid mediated stress response plays a major role in coping with both gradual and rapid changes in environmental conditions and may be especially important when conditions depart from expectations. Conceptual models of endocrine flexibility suggest that individual flexibility, measured using reaction norms along an environmental gradient, might predict differences in the ability to cope with challenges. For example, differences in the speed or scope of acute endocrine responses might underpin coping ability. However, empirical results have been limited by the inability to accurately measure individual level endocrine reaction norms. Here, we took advantage of a database of corticosterone measures in 1,727 individuals of 99 bird species sampled around the world to extend the concept of endocrine reaction norms to species differences. We first describe a global reaction norm for birds and then demonstrate species-specific differences in reaction norms for baseline corticosterone, maximum corticosterone, and the speed of corticosterone increase to both absolute temperature and to the difference between current and expected temperature. Overall, we found that in addition to changes in absolute corticosterone, the speed of the acute response increased when minimum daily temperature dropped below 0-2°C. In contrast, we found little evidence for increases at higher temperatures. We found a similar pattern when temperature was colder than expected given the location and date regardless of absolute temperature, but this effect was only seen for baseline corticosterone. Our models also consistently indicated that species differed in the shape of their corticosterone reaction norm to absolute temperature and temperature deviations. However, we did not have adequate data to fully characterize species-specific reaction norms. We suggest that the endocrine flexibility and reaction norm framework applied in a comparative context could help predict species sensitivity to changing climate, but that additional field data will be needed to fully test this idea.

Aquatic environments are contaminated through anthropogenic activities, leading to an increase in a variety of pollutants, including pesticides and algal toxins. The cyanobacterium Microcystis aeruginosa produces the toxin microcystin-LR and is found in various freshwater environments. Microcystin-LR causes liver and tissue damage in aquatic organisms. Atrazine is a commonly applied herbicide in the United States and is toxic following acute exposures. These toxins can often be found together in aquatic environments and thus may lead to combined toxicological effects; however, very little information is available regarding their cumulative effects on tissues such as the hepatopancreas (or liver). To examine the combined effects, we exposed crayfish (Faxonius virilis) to 10 ppb atrazine, 10 ppb microcystin-LR, a combination of 10 ppb of both, and a control for 96 hours. The hepatopancreas was examined and tubular morphology of each group of crayfish was compared. We found that morphological defects such as vacuolization, lumen dilation, and epithelial degeneration were seen following exposures to both atrazine and microcystin-LR individually and in combination. Combined exposures led to a significant increase in vacuolization of tubular epithelium. Following all exposures, lumen proportion increased, epithelial height decreased, and there was degeneration of the microvillar brush border. Overall, hepatopancreas morphology was significantly altered post-exposure in all treatments. These changes could lead to impairment of hepatopancreas and subsequent changes in biotransformation, detoxification, digestion, reproduction, and molting, causing a reduction in crayfish population size. Furthermore, similar cellular and morphological changes may also occur in other crustaceans inhabiting the same environment.

Cardueline finches readily occupy bird feeders in high numbers, but they are at risk of being infected by pathogens, such as Salmonella spp. Historically, pine siskins (Spinus pinus) often develop salmonellosis and succumb to the pathogen in high numbers during outbreaks in comparison to other Cardueline finches. Even though Salmonella spp. outbreaks in pine siskins are well-documented, there are no studies explaining why they die of salmonellosis at a higher rate than other birds. We hypothesized that pine siskins have a decreased bactericidal ability when compared to other Cardueline finches. We tested this with a bacteria killing assay (BKA) against Salmonella Typhimurium cultured from a local pine siskin that succumbed to the pathogen. We compared their BKA results against S. Typhimurium to three other local finches: lesser goldfinches (Spinus psaltria), American goldfinches (Spinus tristis), and house finches (Haemorhous mexicanus). We found that the Spinus spp. cannot kill S. Typhimurium as effectively as house finches. There were no significant differences between the two goldfinches, but the BKA results for pine siskins were significantly higher than those of the goldfinches. House finches had killing activity nearly twice that of pine siskins and more than twice that of the goldfinches. Our results highlight that the constitutive innate immune response against Salmonella spp. in some finches may be best explained at the genus level. We speculate that pine siskins' poor constitutive innate immunity and their irruptive behavior may make them more susceptible to Salmonella spp. over their less irruptive congeners.

Host-associated microbial communities impact the brain and behavior through the microbiota-gut-brain (MGB) axis. Most studies of the gut microbiota use mammals in biomedical contexts; much less is known regarding wildlife species. We used larval amphibians to study the impact of the aquatic microbial environment on the gut and skin microbiota, brain, and antipredator behavior. We raised Northern Leopard Frog (Lithobates pipiens) tadpoles in pond water that was autoclaved or not autoclaved (natural); other studies show that these treatments produce variation in the tadpole gut microbiota. Tadpoles were also raised in the presence of stressors: predation-derived chemical cues and corticosterone. Compared to tadpoles raised in natural pond water, tadpoles raised in autoclaved pond water had altered gut and skin microbial communities, body size, brain size, brain shape and behavioral responses to alarm pheromones. There was no effect of microbial environment or stressors on differential gene expression of the whole brain. The gut microbiota, but not the skin microbiota, was a significant predictor of behavioral endpoints. We found surprisingly few impacts of stressors on the tadpoles, although stressor treatments interacted with pond water treatments to influence the composition of the gut microbiota. Our findings demonstrate that tadpole behavior is modulated by the aquatic microbial community experienced during development in ways that are likely to affect survival.

The ability to regenerate can greatly vary between animal groups and cell types. Some of the outstanding questions in the field of regeneration include: 1) how has regeneration evolved? and 2) what features underlie differences in regeneration potential between animals? Whether regeneration evolved once and diversified or if it evolved multiple times independently by co-opting similar pathways remains unknown. Current research seeks to identify conserved cellular and molecular features that allow for regeneration. However, comparisons between distantly related regenerating animals have revealed a large amount of diversity. In this perspective, I review discussions on the mechanisms, cell types, and genes underlying regeneration. I propose using Cnidaria as a group in which to investigate the evolution of regeneration. As the sister group to Bilateria with notable regenerative capacity, studies in Cnidaria offer insights into the evolutionary history and conservation of regenerative mechanisms. I then highlight how genome-wide studies, single-cell genomics, multi-omics, and gene editing can be used to identify cell types and unknown features of regeneration. Applying these approaches across organisms will give insight into the cell and molecular features that allow for regeneration competency and may be used to alter an organism's regeneration potential.

Microbiomes play an important role in physiology and development in cnidarians, but how these communities influence tissue regeneration is poorly understood. Here, we examined the effects of antibiotic exposure on regeneration and microbial communities in two cnidarian models, the sea anemones Nematostella vectensis (non-symbiotic, hereafter, Nematostella) and Exaiptasia diaphana (symbiotic, hereafter, Aiptasia). Bisected animals were incubated in either sterile or antibiotic-treated artificial seawater for seven days and regeneration was monitored daily. After seven days, tentacle number and length were measured, and microbial communities were profiled using metabarcoding of the V4 region of the 16S rRNA. Microbiome disruption was observed under antibiotic treatment in both species, resulting in decreased microbial load and shifts in relative abundances of certain microbial taxa. Nematostella exhibited a greater reduction in microbial diversity and community shifts under antibiotic exposure, whereas Aiptasia showed only moderate changes in diversity. In both species, microbiome disruption was associated with slower regeneration rates and reduced tentacle number and length, suggesting a functional role for the microbiome in anemone regeneration. Our findings suggest that host-microbiome interactions in both symbiotic and aposymbiotic anemones are important for the maintenance of regenerative processes. These findings provide insight into how cnidarians and their microbiomes respond to environmental stressors, with implications for predicting cnidarian resilience in the context of emerging threats to the marine environment.

Freshwater salinization is an emerging threat to aquatic ecosystems across the planet, degrading habitats and negatively impacting wild populations. Deicing practices are a leading cause of freshwater salinization, particularly in the snowbelt region of North America where a variety of salts are widely applied to roads and other surfaces to melt snow and ice. Seasonal pools near roads are considered the most severely impacted aquatic habitats. Runoff into these low water-volume ponds can generate high salinity. Impacts of salt pollution are numerous, ranging from toxicity to population decline to impaired ecosystem function. Here, we investigate a suite of physiological consequences of salinization across multiple life history stages of the wood frog (Rana sylvatica), a pool-dwelling amphibian. Previous work has shown that salinized populations have diverged from unpolluted populations for a suite of physiological, morphological, and reproductive traits, and can experience severe edema (bloating) during the breeding season. Here, we measured swim performance before and after aspirating edema in wild captured wood frogs to show that edema compromises adult aquatic locomotion during breeding. We also found that wood frog mothers from salinized ponds produce ova with inherently higher rates of water uptake compared to mothers from unpolluted pools, consistent with countergradient adaptation, but the ova are smaller. Finally, we found that exposure to road salt inhibits expansion of vitelline membranes in developing embryos and is associated with reduced embryo growth. Together, these results reveal the complexity of population level responses to freshwater salinization, highlighting that impacts occur across multiple life history stages, and that local populations might be evolving adaptations to cope with anthropogenic salinity gradients in freshwater habitats.

The resource strategy of seedlings is an important aspect for understanding the adaptation of trees at this ontogenetic phase to abiotic changes. In this study, we sought to determine the patterns of response of functional traits of a shade-tolerant (A. platanoides) and a shade-intolerant (Q. robur) species along natural environmental light gradients. We conducted trait-based analyses at both individual and community levels using direct (leaf area index, LAI; diffuse non-interceptance, DIFN) and indirect (Ellenberg-indicator values, LC) methods in the Arboretum at Kórnik (Poland). Differences between the two species were found for some variables. Analysis of phenotypic plasticity indices of leaf, stem and root traits of seedlings had high values for both species. The values of plasticity indices of A. platanoides root traits were lower compared to the corresponding traits for Q. robur. Relationships between measures obtained from individual-level trait data were stronger than relationships with measures obtained from community-level trait data. The data obtained from the direct method, which included light measurements both at the community level (experimental plots) and at the individual level (seedlings), revealed the closest relationships between functional traits of seedlings and light changes at the individual level trait data for both species. Correlation links between LAI and leaf (leaf mass per area; specific leaf area) and stem (specific stem length; stem mass fraction) traits were less tight for Q. robur compared to A. platanoides. The indirect Ellenberg-indicator analysis revealed relationships between LC and leaf mass per area, and stem-to-root ratio of seedlings based on community-level trait data. Close relationships between LC and leaf mass fraction, and specific leaf area were not established, in contrast to LAI and DIFN. The closest relationships, representing among traits within the same organ system, and links, describing interactions between traits of different organ systems, were established at the community-level trait data.

The mucus coating around a fish's body is essential to its survival. It contains antimicrobial properties, aids in drag reduction, and protects against physical damage. It is versatile in the aquatic environment but little is known about the role of mucus in amphibious fishes. The Northern Snakehead (Channa argus) is a species of amphibious fish that is not only invasive to the Chesapeake Bay but is renowned for its ability to crawl on land. However, the role of their slippery mucus in terrestrial behaviors is currently unknown. This project aims to investigate how snakehead mucus affects friction during terrestrial locomotion, assess if snakehead mucus is adapted to facilitate terrestrial movements compared to the mucus of fully-aquatic fish (i.e., Common Carp, Cyprinus carpio), and determine how snakehead scales influence frictional anisotropy compared to scale-less fish (i.e., Blue Catfish, Ictalurus furcatus). This was tested by towing freshly euthanized fish along two different substrates in the forward and backward directions using a force meter to determine the force needed to overcome static friction. The same fish was tested with its mucus coat intact and again with it wiped off to allow for paired comparisons. Snakehead mucus significantly reduced terrestrial friction, and did so significantly more than carp mucus. Additionally, fish with scales exhibited frictional anisotropy, with less friction in the forward direction and more in the backward direction, similar to how snake scale anisotropy promotes forward movement. Amphibious fishes like snakeheads may have evolved particularly slippery mucus to aid in terrestrial locomotion by reducing friction and energy required to move overland, potentially facilitating overland movement between bodies of water. This study may also provide insight to the development of artificial fish mucus for amphibious robots and other applications.

Wingbeat frequency estimation is an important aspect for the study of avian flight, energetics, and behavioral patterns, among others. Hummingbirds, in particular, are ideal subjects to test a method for this estimation due to their fast wing motions and unique aerodynamics, which results from their ecological diversification, adaptation to high-altitude environments, and sexually selected displays. Traditionally, wingbeat frequency measurements have been done via "manual" image/sound processing. In this study, we present an automated method to detect, track, classify, and monitor hummingbirds in high-speed video footage, accurately estimating their wingbeat frequency using computer vision techniques and signal analysis. Our approach utilizes a zero-shot learning algorithm that eliminates the need for labeling during training. Results demonstrate that our method can produce automated wingbeat frequency estimations with minimal supervision, closely matching those performed by trained human observers. This comparison indicates that our method can, in some scenarios, achieve low or zero error compared to a human, making it a valuable tool for flight analysis. Automating video analysis can assist wingbeat frequency estimation by reducing processing time and, thus, lowering barriers to analyze biological data on fields such as aerodynamics, foraging behavior, and signaling.