Integrative Organismal Biology最新文献

Phylogenetic analyses of phenotypic characters in crown-group birds often recover results that are strongly incongruous with the findings of recent phylogenomic analyses. Furthermore, existing morphological datasets for crown birds are frequently limited by restricted taxon or character sampling, inconsistent character construction, incorrect scoring, or a combination of several of these factors. As part of an effort to address these limitations, in this study we focus on identifying phylogenetically informative characters of the avian pectoral girdle and forelimb skeleton, elements of which are commonly preserved as avian fossils. We assembled and vetted a dataset of 203 characters, which were then scored for a phylogenetically diverse range of 75 extant avian taxa and incorporated into phylogenetic analyses. Analyses run without topological constraints exhibited notable conflicts with the results of recent phylogenomic studies, possibly due to functional convergence and rapid cladogenesis in the early evolutionary history of crown birds. Qualitative anatomical comparisons and quantitative metrics of homoplasy further highlighted the fact that similar morphologies in pectoral girdle and forelimb elements have evolved repeatedly in distantly related groups of birds, representing a major confounding factor in avian morphological phylogenetics. However, the implementation of molecular scaffolds allowed the identification of diagnostic character combinations for numerous avian clades previously only recognized through molecular data, such as Phaethontimorphae, Aequornithes, and Telluraves. Although large morphological datasets may not guarantee increased congruence with molecular phylogenetic studies, they can nonetheless be valuable tools for identifying anatomical synapomorphies of key clades, placing fossils into phylogenetic context, and studying macroevolutionary patterns within major groups of organisms.

Sexual dichromatism is prevalent throughout the animal tree of life and can play an important role in visual signaling and mate choice in many species. Some instances of sexual dichromatism, however, result from a combination of mechanisms including sexual niche partitioning and intrasexual signaling to identify competitors. Sexual dichromatism is relatively rare in anuran amphibians (frogs and toads) but is striking and prevalent in the African reed frogs (Hyperoliidae). In sexually dichromatic hyperoliids, males and females exhibit shared coloration post-metamorphosis, but at the onset of maturity, females undergo a change in color and/or color pattern whereas males typically retain the juvenile coloration. Hypothesized functions of dichromatism in reed frogs include sexual niche partitioning such that males and females use different habitats and their different colorations provide more effective camouflage in their respective habitats or alternatively, that color patterns play a role in sex and/or mate recognition in dense breeding choruses. To test these hypotheses, we characterized several aspects of natural history, ecology, and physiology in a population of the sexually dichromatic forest reed frog (Hyperolius tuberculatus) on Bioko Island, Equatorial Guinea. We found that frogs were predominantly observed on green foliage regardless of coloration or sex, providing no support for sex and/or morph differences in habitat use. In addition, our visual modeling analyses demonstrated that both color morphs are likely detectable for typical vertebrate predators in bright light regardless of background foliage coloration. Analyses using a custom reed frog dual-rod photoreceptor visual model do not support the hypothesis that H. tuberculatus perceive chromatic (hue) differences between conspecific color morphs in dim light conditions, but instead suggest that both color morphs may be more conspicuous to conspecifics than to potential predators in dim light conditions. Finally, we documented multiple instances of mature males exhibiting female coloration and our preliminary steroid hormone exposure experiments indicate that exposure to estradiol induces a color change in adult male H. tuberculatus, as demonstrated in other members of the Hyperolius viridiflavus species complex. Collectively, our results demonstrate that the population of H. tuberculatus on Bioko Island is an excellent system for future studies investigating the behavioral, physiological, and molecular mechanisms underlying sexual dichromatism in reed frogs. Furthermore, the foundational data we present set the stage to characterize species discrimination and mate choice among sympatric and closely related species of reed frogs to investigate the roles of intra- or inter-specific female signaling in the evolution of dichromatism.

Venoms are complex bioactive mixtures that have independently evolved across diverse animal lineages, including snails, insects, sea anemones, spiders, scorpions, and snakes. Despite the growing interest in venom research, data is fragmented across disparate databases which lack standardization and interoperability. A vision for the proposed VenomsBase platform presented here seeks to address these challenges by using the best practices approach in creating a centralized, open-access platform adhering to FAIR principles (Findable, Accessible, Interoperable, and Reproducible). VenomsBase will unify venom datasets, standardize terminology, and enable comparative analyses across species, facilitating novel toxin discovery and functional annotation. Key features of VenomsBase include user-friendly data submission modules with built-in validation, advanced cross-species analysis tools, and integration of multidisciplinary datasets spanning genomics, transcriptomics, proteomics, functional assays, and ecological metadata. A modular, cloud-based design will ensure scalability, while heuristic scoring systems will guide users toward high-confidence data entries. To promote accessibility, the envisioned VenomsBase will provide tutorials, regular training sessions, case studies, and feedback loops, supporting researchers at all levels. By harmonizing venom research and addressing the limitations of outdated or nonstandardized methods, VenomsBase aims to revolutionize the field, while being continuously improved and refined by venom experts. This initiative will unlock venoms' potential to make groundbreaking discoveries, address global health challenges, and foster collaboration and innovation across the scientific community.

In the Mediterranean, populations of the spider crab Maja squinado are drastically declining. As a critical step toward restoration efforts, this study investigates ontogenetic metabolic changes from larvae to adults, accounting for size, molt stage, and sex. Routine metabolic rates were measured in reared larvae and juveniles, and wild-caught adults. Zoea 1, the first planktonic stage, showed higher metabolic rates than zoea 2, likely due to a greater proportion of metabolically inactive tissue and differing energy sources (egg reserves vs. exogenous feeding). From megalopa to benthic juvenile stages, metabolic rates increased exponentially, probably reflecting increased organ complexity and activity. However, rates declined significantly from 7-month-old juveniles to adults, potentially due to reduced growth, longer intermolt periods, and behavioral adaptations. Among adults, males exhibited metabolic rates twice as high as females, likely linked to greater territorial and reproductive activity. In 7-month-old juveniles at 14°C, mass-specific metabolic rate is inversely correlated with body size: individuals <20 g consumed oxygen at twice the mass-specific rate of those >80 g. The log₁₀ of oxygen consumption positively correlated with log₁₀ wet mass, with a "b" factor of 0.83. Molting also drastically influences metabolic activity, with lower rates observed in postmolt individuals than in individuals in premolt stages. The successful rearing of M. squinado and the significant physiological insights gained into the different developmental stages enhance our understanding of the species' biological processes, and pave the way for further analyses before the implementation of restoration trials.

Oil bees, which gather oil from flowers, transfer the floral oil collected from fore-legs, to middle-legs, and then to hind-legs, where they store the oil until release in the nest's brood cell. The complex leg maneuvers and the specialized hair types according to their location and function on the legs have been described in the past using morphological observations and in vivo behavioral monitoring, sometimes during flight. The aim of this work is to describe the different steps of oil transfer and to infer the role of the different hair types using a manipulative approach on isolated legs, controlled amounts of oil and high speed video recordings. A rapid and uni-directional capillary oil movement from the collecting ventral side of tarsi and/or tibiae to their dorsal side is observed in each fore-, middle-, and hind-legs. This suggests that plumose setae and pluridentate setae present different functionalities, acting either as oil donors or receptors, depending on their location on the legs. In the transfers observed, very little oil remains on the donor surface, so that a bee collecting oil from flower can quickly replenish the donor surface again.

Anurans are one of the most diverse groups of vertebrates but also most threatened by current climate change effects such as increasing environmental temperatures and more frequent and prolonged periods without rain. Many tropical anurans lay terrestrial eggs that are particularly vulnerable to drying and warming. In some such species, embryos hatch prematurely to escape from drying eggs. In red-eyed treefrogs, Agalychnis callidryas, embryos hatch early to escape both drying and excessive warming, expressing a behavioral thermal tolerance (i.e., VT_Max). Prior research suggested that drying reduces the VT_Max of embryos. However, because hydrated clutches warmed more slowly, the effect of drying on VT_Max was confounded with that of faster warming. To disentangle these dynamics, we designed a novel apparatus to warm terrestrial frog egg-clutches at controlled rates and minimize evaporative cooling. We independently manipulated clutch hydration and heat input to assess their individual and combined effects on embryo VT_Max. Proportional egg-volume loss was similar across hydration × heat input categories. High heat input resulted in higher clutch warming rates and shorter trial durations, across hydration levels. Within clutches, warming rates differed between back and surface thermocouple positions, generating thermal gradients as warming progressed. Clutch dehydration reduced embryo VT_Max, with no main or interacting effect of heat input. This evidence that egg drying reduces thermal tolerance across testing conditions supports a direct role for hydration in the behavioral decisions of warming embryos, rather than an indirect effect mediated by changes in evaporative cooling. It suggests that embryos assessing risk integrate information about hydration, and perhaps changes in hydration, with information about current and changing temperature. These findings highlight the value of methods to independently manipulate hydration and heating rate, showing the complexity of thermal ecology in embryonic ectotherms. We encourage further research on temperature and hydration effects on embryo hatching to better understand tropical anurans' adaptive strategies under climate change.

Birds that overwinter in temperate regions must be physiologically flexible to face the demands of living in a thermally fluctuating environment. Much of the previous literature on this topic focuses on whole-animal metabolic rates and corresponding cellular and molecular mechanisms that enable these birds to withstand the demands of changing environmental conditions. Basal and maximal shivering metabolic rates, as well as daily energy expenditure, typically increase in winter for small birds overwintering in cold climates, which might increase the production of reactive oxygen species (ROS) within mitochondria as a natural byproduct of aerobic metabolism. In this study, we measured summer to winter differences in oxidative balance in four species of resident passerine birds. Blood samples were taken from field-collected American goldfinch (Spinus tristis), black-capped chickadee (Poecile atricapillus), house finch (Haemorhous mexicanus), and house sparrow (Passer domesticus) during the summer and winter of 2023-2024 in South Dakota, USA. We determined plasma total antioxidant capacity and lipid oxidative damage, and red blood cell activities of three antioxidant enzymes: catalase (CAT), glutathione peroxidase (GPx), and superoxide dismutase (SOD). Lipid oxidative damage was significantly lower in winter for three of four species, and total antioxidant capacity for all species was significantly lower in winter compared with summer. Across all species, CAT activity was significantly higher in summer than in winter. In contrast, SOD activity was significantly higher in winter than in summer for all species. We also found species-level differences across the two seasons. These data suggest that the higher thermoregulatory costs in winter do not result in consistently elevated oxidative damage or antioxidant capacities relative to summer in small resident birds in cold climates, despite previously demonstrated winter increases in metabolic rates and energy expenditure. Such a result might occur as a function of either a reduction in dietary antioxidants and/or uncoupling of ROS production and metabolism in winter relative to summer or may be related to oxidative costs associated with reproduction.

In the northern coastal hemisphere, different ecotypes of the threespine stickleback (Gasterosteus aculeatus) can be distinguished phenotypically by a different number of lateral bone plates and by their body shape and size. We focused on (1) anadromous sticklebacks, which migrate from the sea to rivers to spawn and (2) freshwater sticklebacks, which live in rivers all year round. Migration behavior is a key feature in the evolution of ecotypes, but the underlying mechanisms of migration are poorly understood. To learn more about possible orientation mechanisms that could lead to goal-directed migration, we tested anadromous sticklebacks for their sun compass orientation and compared their orientation behavior with that of the freshwater ecotype. Behavioral experiments revealed ecotype-dependent differences, whereby the ability to orient is consistently present in the anadromous ecotype, whereas the orientation in the freshwater ecotype corresponds to a random directional distribution.

The plant most commonly known for producing latex is the Pará rubber tree, Hevea brasiliensis. There are, however, thousands of latex-bearing plant species, and these species exhibit a diverse array of different types of latex, each type in accordance with its producers' main selective pressure after injury. One key function of latex is to seal, but the most crucial necessities for wound sealing differ by the environment. For species growing in arid climates, for example, minimizing water loss is crucial whereas in tropical ecosystems a strong (chemical) defense against herbivores, parasites, and germs is of more imminent importance. This diversity of ecosystems and species' environments is mirrored by a respective diversity in latices' chemical compositions, material properties, and coagulation times. While some plant species solely rely on evaporation of water for their latex coagulation, the H. brasiliensis latex contains the coagulation assisting protein Hevein, allowing for coagulation in 30 min. With coagulation times of 10 s and below, species of the genus Campanula pose considerable challenge to the measurement of latex characteristics. We here present an overview to the coagulation of latex in the genus Campanula and reveal substantial differences to the latex coagulation of H. brasiliensis. For a collection of 6 different Campanula species, we determined coagulation times under different temperatures, latex dry weights, contact angles of water droplets on latex surfaces and imaged laticifer cross-sections using cryo-SEM. We found Campanula latex to coagulate significantly faster than Hevea latex and no evidence of Hevea-like lutoids in the laticifers. A coagulation test in a pressure chamber further revealed Campanula latex to coagulate at pressures of 8 bar, where latex coagulation in Ficus benjamina, which is described to have similar coagulation mechanism as Hevea, has previously been reported to be impaired. Our findings thus suggest Campanula latex coagulation to follow a different mechanism than the one described in Hevea.

Dermal denticles-microscopic tooth-like scales-are a major defining feature of elasmobranch skin, and are of interest to a wide array of fields, including paleontology, evolutionary biology, developmental biology, functional morphology, and bio-inspired design. While dermal denticle research is a growing field, there is currently no standardized vocabulary or framework to compare denticle morphology across research fields, siloing, and limiting denticle research efforts. Here, we present a morphological framework, which includes a character code that comprehensively captures denticle morphology from a wide diversity of denticle sampling types and imaging methods, and is backed by an easy-to-use google sheets-based coding tool and R package for replicating disparity analyses. The code is based on a wide-spread literature review of published denticle images, scanning electron microscope (SEMs), and computed tomography (CT) scans of extant shark denticles, and a review of tens of thousands of fossil denticles from pelagic ocean sediments dating back over 100 million years. The code's flexibility and replicability facilitate comparison across studies and independent research teams, and the addition of novel character categories. Denticle morphotypes are defined as denticles with unique combinations of character traits. This coding system facilitates morphologically backed disparity analyses of denticle morphological diversity, whether through deep time, across the body of a shark, or across a time-series of development, providing a more detailed, quantitative, and universal tool for analyzing denticle morphology across studies.