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Molecular Ecology Apr 2022Anthropogenic environmental changes are affecting biodiversity and microevolution worldwide. Ectothermic vertebrates are especially vulnerable because environmental...
Anthropogenic environmental changes are affecting biodiversity and microevolution worldwide. Ectothermic vertebrates are especially vulnerable because environmental changes can disrupt their sexual development and cause sex reversal, a mismatch between genetic and phenotypic sex. This can potentially lead to sex-ratio distortion and population decline. Despite these implications, there is scarce empirical knowledge on the incidence of sex reversal in nature. Populations in anthropogenic environments may be exposed to sex-reversing stimuli more frequently, which may lead to higher sex-reversal rate or, alternatively, these populations may adapt to resist sex reversal. We developed PCR-based genetic sex markers for the common toad (Bufo bufo) to assess the prevalence of sex reversal in wild populations living in natural, agricultural and urban habitats, and the susceptibility of the same populations to two ubiquitous oestrogenic pollutants in a common garden experiment. We found negligible sex-reversal frequency in free-living adults despite the presence of various endocrine-disrupting pollutants in their breeding ponds. Individuals from different habitat types showed similar susceptibility to sex reversal in the laboratory: all genetic males developed female phenotype when exposed to 1 µg L 17α-ethinylestradiol (EE2) during larval development, whereas no sex reversal occurred in response to 1 ng L EE2 and a glyphosate-based herbicide with 3 µg L or 3 mg L glyphosate. The latter results do not support that populations in anthropogenic habitats would have either increased propensity for or higher tolerance to chemically induced sex reversal. Thus, the extremely low sex-reversal frequency in wild toads compared to other ectothermic vertebrates studied before might indicate idiosyncratic, potentially species-specific resistance to sex reversal.
Topics: Animals; Bufo bufo; Bufonidae; Ecosystem; Environmental Pollutants; Ethinyl Estradiol; Female; Genetic Markers; Male; Water Pollutants, Chemical
PubMed: 35146823
DOI: 10.1111/mec.16388 -
Proceedings. Biological Sciences Nov 2022The shape and relative size of an ocular lens affect the focal length of the eye, with consequences for visual acuity and sensitivity. Lenses are typically spherical in...
The shape and relative size of an ocular lens affect the focal length of the eye, with consequences for visual acuity and sensitivity. Lenses are typically spherical in aquatic animals with camera-type eyes and axially flattened in terrestrial species to facilitate vision in optical media with different refractive indices. Frogs and toads (Amphibia: Anura) are ecologically diverse, with many species shifting from aquatic to terrestrial ecologies during metamorphosis. We quantified lens shape and relative size using 179 micro X-ray computed tomography scans of 126 biphasic anuran species and tested for correlations with life stage, environmental transitions, adult habits and adult activity patterns. Across broad phylogenetic diversity, tadpole lenses are more spherical than those of adults. Biphasic species with aquatic larvae and terrestrial adults typically undergo ontogenetic changes in lens shape, whereas species that remain aquatic as adults tend to retain more spherical lenses after metamorphosis. Further, adult lens shape is influenced by adult habit; notably, fossorial adults tend to retain spherical lenses following metamorphosis. Finally, lens size relative to eye size is smaller in aquatic and semiaquatic species than other adult ecologies. Our study demonstrates how ecology shapes visual systems, and the power of non-invasive imaging of museum specimens for studying sensory evolution.
Topics: Animals; Phylogeny; Anura; Bufonidae; Metamorphosis, Biological; Ecology; Larva
PubMed: 36382525
DOI: 10.1098/rspb.2022.0767 -
Proceedings. Biological Sciences Aug 2021The eyes of frogs and toads (Anura) are among their most fascinating features. Although several pupil shapes have been described, the diversity, evolution, and...
The eyes of frogs and toads (Anura) are among their most fascinating features. Although several pupil shapes have been described, the diversity, evolution, and functional role of the pupil in anurans have received little attention. Studying photographs of more than 3200 species, we surveyed pupil diversity, described their morphological variation, tested correlation with adult habits and diel activity, and discuss major evolutionary patterns considering iris anatomy and visual ecology. Our results indicate that the pupil in anurans is a highly plastic structure, with seven main pupil shapes that evolved at least 116 times during the history of the group. We found no significant correlation between pupil shape, adult habits, and diel activity, with the exception of the circular pupil and aquatic habits. The vertical pupil arose at least in the most-recent common ancestor of Anura + Caudata, and this morphology is present in most early-diverging anuran clades. Subsequently, a horizontal pupil, a very uncommon shape in vertebrates, evolved in most neobatrachian frogs. This shape evolved into most other known pupil shapes, but it persisted in a large number of species with diverse life histories, habits, and diel activity patterns, demonstrating a remarkable functional and ecological versatility.
Topics: Animals; Anura; Biological Evolution; Bufonidae; Phylogeny; Pupil
PubMed: 34403634
DOI: 10.1098/rspb.2021.1402 -
PloS One 2021Host-associated microbes can interact with macro-organisms in a number of ways that affect host health. Few studies of host-associated microbiomes, however, focus on...
Host-associated microbes can interact with macro-organisms in a number of ways that affect host health. Few studies of host-associated microbiomes, however, focus on fungi. In addition, it is difficult to discern whether a fungal organism found in or on an ectotherm host is associating with it in a durable, symbiotic interaction versus a transient one, and to what extent the habitat and host share microbes. We seek to identify these host-microbe interactions on an amphibian, the Colorado boreal toad (Anaxyrus boreas boreas). We sequenced the ITS1 region of the fungal community on the skin of wild toads (n = 124) from four sites in the Colorado Rocky Mountains, across its physiologically dynamic developmental life stages. We also sampled the common habitats used by boreal toads: water from their natal wetland and aquatic pond sediment. We then examined diversity patterns within different life stages, between host and habitat, and identified fungal taxa that could be putatively host-associated with toads by using an indicator species analysis on toad versus environmental samples. Host and habitat were strikingly similar, with the exception of toad eggs. Post-hatching toad life stages were distinct in their various fungal diversity measures. We identified eight fungal taxa that were significantly associated with eggs, but no other fungal taxa were associated with other toad life stages compared with their environmental habitat. This suggests that although pre- and post-metamorphic toad life stages differ from each other, the habitat and host fungal communities are so similar that identifying obligate host symbionts is difficult with the techniques used here. This approach does, however, leverage sequence data from host and habitat samples to predict which microbial taxa are host-associated versus transient microbes, thereby condensing a large set of sequence data into a smaller list of potential targets for further consideration.
Topics: Animals; Bufonidae; Chytridiomycota; Colorado; Host Microbial Interactions; Microbiota; Skin; Symbiosis
PubMed: 34411153
DOI: 10.1371/journal.pone.0256328 -
Anatomical Record (Hoboken, N.J. : 2007) Jun 2022Differences in male and female traits (sexual dimorphism [SD]) are widespread in animals. Dimorphism in morphological characters evolves under the effect of...
Differences in male and female traits (sexual dimorphism [SD]) are widespread in animals. Dimorphism in morphological characters evolves under the effect of environmental and genetic factors and is shaped by natural and sexual selection. In this study, intersexual differences in size and shape in common toad, Bufo bufo, populations in Turkey were investigated. For this, linear measurements of 27 body-related morphometric characters in a sample of 140 individuals (70 males and 70 females) were compiled. The data were analyzed using univariate and multivariate statistical methods. The results show SD in body size with females having larger body size, a trait related with fecundity and thus probably under sexual selection. Body shape differences, which are associated with head width and dorsal head, are likely to prey size. Male-biased differences observed in nasal characters and tympanum may also be associated with sexual selection (male-male competition). Our findings are consistent with previous studies of major of Anura and support a role for selection pressures acting differentially upon individuals from both sexes, resulting in the evolution of sexually dimorphic traits.
Topics: Animals; Body Size; Bufo bufo; Female; Male; Phenotype; Sex Characteristics; Turkey
PubMed: 34626158
DOI: 10.1002/ar.24801 -
Experimental Physiology May 1996Uptake of NaCl by amphibian tight epithelia, such as skin, urinary bladder and collecting duct, requires considerable thermodynamic work. By calculation it is... (Review)
Review
Uptake of NaCl by amphibian tight epithelia, such as skin, urinary bladder and collecting duct, requires considerable thermodynamic work. By calculation it is demonstrated that NaCl absorption from dilute external solutions ([NaCl] approximately 1 mM) demands more energy than can be provided by the Na(+)-K(+)-ATPase alone. Thus, in addition to the Na+ pump, another transport ATPase must be involved. Previously, we have suggested that the other transport ATPase is an apical proton pump in mitochondria-rich (MR) cells. By driving an apical Cl(-)-HCO3- exchange, a rheogenic H+ pump would energize entrance of Cl- across the apical membrane. Since Cl- channels are present in the basolateral membrane, the net result would be a transcellular active rheogenic uptake of Cl-, and secretion of H+ and HCO3-. At higher external concentrations, the Cl- uptake by MR cells is driven by the Na+ pump-generated transepithelial electrical potential difference, which also requires the presence of apical Cl- channels. Electrophysiological methods have been developed by which we have been able to study the polarity of single MR cells and identify apical and basolateral transport systems. We have verified the existence of rheogenic H+ pumps in the apical membrane and Cl- channels in both membranes.
Topics: Animals; Bicarbonates; Bufonidae; Chloride Channels; Electrophysiology; Epithelium; In Vitro Techniques; Membrane Potentials; Mitochondria; Patch-Clamp Techniques; Proton Pumps; Skin; Sodium Chloride
PubMed: 8737085
DOI: 10.1113/expphysiol.1996.sp003955 -
Scientific Reports Sep 2021Habitat selectivity has become an increasingly acknowledged mechanism shaping the structure of freshwater communities; however, most studies have focused on the effect...
Habitat selectivity has become an increasingly acknowledged mechanism shaping the structure of freshwater communities; however, most studies have focused on the effect of predators and competitors, neglecting habitat complexity and specialization. In this study, we examined the habitat selection of semiaquatic (amphibians: Bufonidae; odonates: Libellulidae) and aquatic organisms (true bugs: Notonectidae; diving beetles: Dytiscidae). From each family, we selected one habitat generalist species able to coexist with fish (Bufo bufo, Sympetrum sanguineum, Notonecta glauca, Dytiscus marginalis) and one species specialized in fishless habitats (Bufotes viridis, Sympetrum danae, Notonecta obliqua, Acilius sulcatus). In a mesocosm experiment, we quantified habitat selection decisions in response to the non-consumptive presence of fish (Carassius auratus) and vegetation structure mimicking different successional stages of aquatic habitats (no macrophytes; submerged and floating macrophytes; submerged, floating, and littoral-emergent macrophytes). No congruence between habitat specialists and generalists was observed, but a similar response to fish and vegetation structure defined both semiaquatic and aquatic organisms. While semiaquatic generalists did not distinguish between fish and fishless pools, specialists avoided fish-occupied pools and had a preferred vegetation structure. In aquatic taxa, predator presence affected habitat selection only in combination with vegetation structure, and all species preferred fishless pools with floating and submerged macrophytes. Fish presence triggered avoidance only in the generalist bug N. glauca. Our results highlight the significance of habitat selectivity for structuring freshwater ecosystems and illustrate how habitat selection responses to a top predator are dictated by specialization and life history.
Topics: Animal Distribution; Animals; Bufonidae; Coleoptera; Fishes; Food Chain; Fresh Water; Herbivory; Odonata; Predatory Behavior
PubMed: 34556794
DOI: 10.1038/s41598-021-98632-2 -
Journal of Biological Physics Sep 2021Vertebrate hearts have undergone marked morphological and structural changes to adapt to different environments and lifestyles as part of the evolutionary process....
Vertebrate hearts have undergone marked morphological and structural changes to adapt to different environments and lifestyles as part of the evolutionary process. Amphibians were the first vertebrates to migrate to land. Transition from aquatic to terrestrial environments required the ability to circulate blood against the force of gravity. In this study, we investigated the passive mechanical properties and histology of the ventricles of three species of Anura (frogs and toads) from different habitats, Xenopus laevis (aquatic), Pelophylax nigromaculatus (semiaquatic), and Bufo japonicus formosus (terrestrial). Pressure-loading tests demonstrated stiffer ventricles of P. nigromaculatus and B. j. formosus compared X. laevis ventricles. Histological analysis revealed a remarkable difference in the structure of cardiac tissue: thickening of the compact myocardium layer of P. nigromaculatus and B. j. formosus and enrichment of the collagen fibers of B. j. formosus. The amount of collagen fibers differed among the species, as quantitatively confirmed by second-harmonic generation light microscopy. No significant difference was observed in cardiomyocytes isolated from each animal, and the sarcomere length was almost the same. The results indicate that the ventricles of Anura stiffen during adaptation to life on land.
Topics: Animals; Anura; Biological Evolution; Bufonidae; Ecosystem; Xenopus laevis
PubMed: 34515919
DOI: 10.1007/s10867-021-09579-4 -
Biology Letters Jul 2020Telomere shortening with age has been documented in many organisms, but few studies have reported telomere length measurements in amphibians, and no information is...
Telomere shortening with age has been documented in many organisms, but few studies have reported telomere length measurements in amphibians, and no information is available for growth after metamorphosis, nor in wild populations. We provide both cross-sectional and longitudinal evidence of net telomere attrition with age in a wild amphibian population of natterjack toads (). Based on age-estimation by skeletochronology and qPCR telomere length measurements in the framework of an individual-based monitoring programme, we confirmed telomere attrition in recaptured males. Our results support that toads experience telomere attrition throughout their ontogeny, and that most attrition occurs during the first 1-2 years. We did not find associations between telomere length and inbreeding or body condition. Our results on telomere length dynamics under natural conditions confirm telomere shortening with age in amphibians and provide quantification of wide telomere length variation within and among age-classes in a wild breeding population.
Topics: Animals; Bufonidae; Cross-Sectional Studies; Male; Telomere; Telomere Shortening
PubMed: 32673551
DOI: 10.1098/rsbl.2020.0168 -
Scientific Reports Jul 2020The lungs and skin are important respiratory organs in Anura, but the pulmonary structure of amphibians remains unclear due to the lack of a suitable procedure. This... (Comparative Study)
Comparative Study
The lungs and skin are important respiratory organs in Anura, but the pulmonary structure of amphibians remains unclear due to the lack of a suitable procedure. This study improved the procedure used for fixing lungs tissues and used light microscopy, transmission electron microscopy and scanning electron microscopy to reveal the differences in the lung and skin morphologies between Pelophylax nigromaculatus (P. nigromaculatus) and Bufo gargarizans (B. gargarizans). In P. nigromaculatus and B. gargarizans, the cystic lungs comprise a continuous outer pulmonary wall on which primary, secondary, and tertiary septa attach, and a number of regular lattices form from raised capillaries and the pulmonary epithelium on the surfaces of the pulmonary wall and septa. Each lattice in P. nigromaculatus consists of several elliptical sheets and flat bottom, and the septa are distributed with denser sheets and have a larger stretching range than the pulmonary wall. The lattice in B. gargarizans consists of thick folds and an uneven bottom with several thin folds, and the septa have more developed thick and thin folds than the pulmonary wall. However, the density of the pulmonary microvilli, the area of a single capillary, the thicknesses of the blood-air barrier, pulmonary wall and septum, and the lung/body weight percentage obtained for B. gargarizans were higher than those found for P. nigromaculatus. In P. nigromaculatus, the dorsal skin has dense capillaries and a ring surface structure with mucus layer on the stratum corneum, and the ventral skin is slightly keratinized. In B. gargarizans, the stratum corneum in both the dorsal and ventral skins is completely keratinized. A fine ultrastructure analysis of P. nigromaculatus and B. gargarizans revealed that the pulmonary septa are more developed than the pulmonary walls, which means that the septa have a stronger respiratory function. The more developed lungs are helpful for the adaptation of B. gargarizans to drought environments, whereas P. nigromaculatus has to rely on more vigorous skin respiration to adapt to a humid environment.
Topics: Animals; Body Weight; Bufonidae; Capillaries; Epidermis; Epithelium; Image Processing, Computer-Assisted; Keratins; Lung; Microscopy, Electron, Scanning; Microscopy, Electron, Transmission; Ranidae; Skin; Species Specificity
PubMed: 32651399
DOI: 10.1038/s41598-020-65746-y