Search Results (31)

In many vertebrates, mature ovulated eggs are arrested at metaphase II prior to fertilization. The eggs exit meiotic arrest after fertilization-induced or parthenogenetic activation, followed by embryo development or egg degradation, respectively. Calcium-dependent activation of meiotically-arrested eggs has been thoroughly investigated in various species. In addition, several recent studies have detailed the excessive activation of ovulated frog eggs, so-called overactivation. This overview highlights the major events of overactivation observed in mature ovulated eggs of the African clawed frog Xenopus laevis with a focus on similarities and differences between spontaneous, oxidative stress-induced, and mechanical stress-induced overactivation. The dramatically different cell death scenarios that unfold in activated and overactivated eggs are also exposed in the article. Full article

The amphibian chytrid fungus, Batrachochytrium dendrobatidis (Bd), has been implicated as an agent of acute declines in amphibian populations worldwide. East Asian amphibians have been coexisting with Bd for long periods and thus are considered resistant; among the many is the Japanese tree frog, Dryophytes japonicus. Our study focused Bd infection effects on reproductive behaviors and physiological parameters in D. japonicus as a function of better understanding the chronic effect of the disease on long-term population viability. During the peak breeding season, we captured 70 males and quantified the chorus size, calling behaviors, physiological states, innate immunity, and sperm quality of individuals. In a simple comparison, all parameters were not significantly different. However, in the NMDS analysis, we were able to confirm subtle trends in some items according to infection and correlations between several items. Importantly, sperm density and sperm vitality tend to increase with Bd infection load, suggesting increased reproductive effort following infection. Additionally, this analysis indicated that innate immunity was positively related to Bd infection intensities, indicating the activation of immunity upon infection. These findings indicate that Bd-resistant D. japonicus maintains reproductive capabilities and physio-logical stability despite Bd infection, likely due to a co-evolved immune system. The present work offers insight into how amphibian populations may have some endurance in the presence of Bd and points out the importance of studying resistant species as a means to understand long-term ecological effects. Our results suggest that resistance to Bd may not simply prevent cata-strophic declines but actively contribute to the dynamics of Bd prevalence in amphibian communities, and confer implications for conservation strategies. Full article

This paper addresses the fifth-century comic coinage gnômotupos, which has not otherwise received scholarly attention. Translators of Aristophanes and Aristotle have typically glossed it into English as “maxim-coining” (with equivalents in other languages). This is a sensible inference from a fourth-century use of γνώμη, “maxim”, and the verb τύπτειν, “stamping”. It also tracks the importance of maxims to Sophistic-era adoption of wisdom-culture and the lore of the Seven Sages. Nevertheless, this typical gloss is incorrect. The term instead emphasizes “idea”, as an insight, technique, or view relevant to some matter. “Stamping” (τύπτειν) an idea means coming up with an apt idea and giving it shape and articulacy. In a characteristic use of the adjective, Aristophanes speaks of gnômotupoi andres (Frogs). These are men who are skilled at “fashioning ideas”, coming up with their content and their form. My claim is that Aristophanes has captured something crucial about the period we call the Sophistic movement or Greek enlightenment. The formulation, circulation, and competition of ideas is a matter of increasing self-consciousness in Athens. So too are those who formulate, circulate, and compete in them: intellectuals or, as gnômotupoi andres might be translated, “ideas-men.” I even contend that those referred to as “sophists”, sophistai, may in many ways be understood as gnômotupoi andres. Full article

Machine learning approaches for pattern recognition are increasingly popular. However, the underlying algorithms are often not open source, may require substantial data for model training, and are not geared toward specific tasks. We used open-source software to build a green toad breeding call detection algorithm that will aid in field data analysis. We provide instructions on how to reproduce our approach for other animal sounds and research questions. Our approach using 34 green toad call sequences and 166 audio files without green toad sounds had an accuracy of 0.99 when split into training (70%) and testing (30%) datasets. The final algorithm was applied to amphibian sounds newly collected by citizen scientists. Our function used three categories: “Green toad(s) detected”, “No green toad(s) detected”, and “Double check”. Ninety percent of files containing green toad calls were classified as “Green toad(s) detected”, and the remaining 10% as “Double check”. Eighty-nine percent of files not containing green toad calls were classified as “No green toad(s) detected”, and the remaining 11% as “Double check”. Hence, none of the files were classified in the wrong category. We conclude that it is feasible for researchers to build their own efficient pattern recognition algorithm. Full article

In all vertebrates, visual signals from each visual field project to the opposite midbrain tectum (called the superior colliculus in mammals). The tectum/colliculus computes visual salience to select targets for context-contingent visually guided behavior: a frog will orient toward a small, moving stimulus (insect prey) but away from a large, looming stimulus (a predator). In mammals, visual signals competing for behavioral salience are also transmitted to the visual cortex, where they are integrated with collicular signals and then projected via the dorsal visual stream to the parietal and frontal cortices. To control visually guided behavior, visual signals must be encoded in body-centered (egocentric) coordinates, and so visual signals must be integrated with information encoding eye position in the orbit—where the individual is looking. Eye position information is derived from copies of eye movement signals transmitted from the colliculus to the frontal and parietal cortices. In the intraparietal cortex of the dorsal stream, eye movement signals from the colliculus are used to predict the sensory consequences of action. These eye position signals are integrated with retinotopic visual signals to generate scaffolding for a visual scene that contains goal-relevant objects that are seen to have spatial relationships with each other and with the observer. Patients with degeneration of the superior colliculus, although they can see, behave as though they are blind. Bilateral damage to the intraparietal cortex of the dorsal stream causes the visual scene to disappear, leaving awareness of only one object that is lost in space. This tutorial considers what we have learned from patients with damage to the colliculus, or to the intraparietal cortex, about how the phylogenetically older midbrain and the newer mammalian dorsal cortical visual stream jointly coordinate the experience of a spatially and temporally coherent visual scene. Full article

Agriculture can have different effects on wildlife depending on land-use type and extensive/intensive practices. The aim of this study was to establish the significance of rice fields in Central Bulgaria as anuran habitats. We used Audiomoth acoustic loggers to record calling activity at three sites near the city of Plovdiv—one shallow pond and two rice fields—from June to September in 2022 and 2023. We registered the three most widespread species in the region—Bufotes viridis, Hyla orientalis and Pelophylax ridibundus—and created pattern-matching models for them using the free web interface Arbimon, which enabled us to perform presence/absence counts and abundance estimates. At the beginning and the end of the rice vegetation period, water samples were collected and analysed for 62 substances. Substance concentrations were compared between ponds and with LC50 data from the available literature. We registered 19 and 21 substances in 2022 and 2023, respectively, with concentrations within the accepted limits, and although some metals were near risk levels, this was not reflected in the presence counts or the abundance estimates. The results indicated that frog activity was not related to any of the registered substances, but that it was positively correlated with daily rainfall and was higher in the rice fields. Full article

The karyosphere (karyosome) is a structure that forms in the oocyte nucleus—germinal vesicle (GV)—at the diplotene stage of meiotic prophase due to the assembly of all chromosomes in a limited portion of the GV. In some organisms, the karyosphere has an extrachromosomal external capsule, the marker protein of which is nuclear F-actin. Despite many years of theories about the formation of the karyosphere capsule (KC) in the GV of the common frog Rana temporaria, we present data that cast doubt on its existence, at least in this species. Specific extrachromosomal strands, which had been considered the main elements of the frog’s KC, do not form a continuous layer around the karyosphere and, according to immunogold labeling, do not contain structural proteins, such as actin and lamin B. At the same time, F-actin is indeed noticeably concentrated around the karyosphere, creating the illusion of a capsule at the light microscopy/fluorescence level. The barrier-to-autointegration factor (BAF) and one of its functional partners—LEMD2, an inner nuclear membrane protein—are not localized in the strands, suggesting that the strands are not functional counterparts of the nuclear envelope. The presence of characteristic strands in the GV of R. temporaria late oocytes may reflect an excess of SMC1 involved in the structural maintenance of diplotene oocyte chromosomes at the karyosphere stage, since SMC1 has been shown to be the most abundant protein in the strands. Other characteristic microstructures—the so-called annuli, very similar in ultrastructure to the nuclear pore complexes—do not contain nucleoporins Nup35 and Nup93, and, therefore, they cannot be considered autonomous pore complexes, as previously thought. Taken together, our data indicate that traditional ideas about the existence of the R. temporaria KC as a special structural compartment of the GV are to be revisited. Full article

Antimicrobial peptides (AMPs) can directly kill Gram-positive bacteria, Gram-negative bacteria, mycobacteria, fungi, enveloped viruses, and parasites. At sublethal concentrations, some AMPs and also conventional antibiotics can stimulate bacterial response increasing their resilience, also called the hormetic response. This includes stimulation of growth, mobility, and biofilm production. Here, we describe the discovery of AMPs that stimulate the growth of certain mycobacteria. Peptide 14 showed a growth stimulating effect on Mycobacteria tuberculosis (MTB), M. bovis, M. avium subsp. paratuberculosis (MAP), M. marinum, M. avium-intracellulare, M. celatum, and M. abscessus. The effect was more pronounced at low bacterial inocula. The peptides induce a faster transition from the lag phase to the log phase and keep the bacteria longer in the log phase before entering stationary phase when compared to nontreated controls. In some cases, an increase in the division rate was observed. An initial screen using MAP and a collection of 75 peptides revealed 13 peptides with a hormetic effect. For MTB, a collection of 25 artificial peptides were screened and 13 were found to reduce the time to positivity (TTP) by at least 5%, improving growth. A screen of 43 naturally occurring peptides, 11 fragments of naturally occurring peptides and 5 designed peptides, all taken from the database APD3, identified a further 44 peptides that also lowered TTP by at least 5%. Lasioglossin LL-III (Bee) and Ranacyclin E (Frog) were the most active natural peptides, and the human cathelicidin LL37 fragment GF-17 and a porcine cathelicidin protegrin-1 fragment were the most active fragments of naturally occurring peptides. Peptide 14 showed growth-stimulating activity between 10 ng/mL and 10 µg/mL, whereas the stability-optimised Peptide 14D had a narrow activity range of 0.1–1 µg/mL. Peptides identified in this study are currently in commercial use to improve recovery and culture for the diagnostics of mycobacteria in humans and animals. Full article

Amphibians are the most endangered class of vertebrate on Earth. Knowledge of their ecology is crucial to their conservation; however, many species have received scant attention from researchers, particularly in regions that are difficult to access or when traditional monitoring methods are impractical. In recent years, technological advancements in environmental audio collection techniques and signal detection algorithms (i.e., call recognition) have created a new set of tools for examining the ecology of amphibians. This study utilises these recent technological advancements to examine the calling phenology of a poorly known Australian mountain frog (Philoria kundagungan). Audio recordings and meteorological data were collected from six localities across the species range, with recordings made every hour for ten minutes between July 2016 and March 2018. We developed an audio recognition algorithm that detected over 1.8 million P. kundagungan calls in 8760 h of audio recordings with a true positive rate of 95%. Our results suggest that calling activity was driven by substrate temperature and precipitation, which has potential consequences for the species as the climate warms and seasonal precipitation patterns shift under climate change. With this detailed knowledge of P. kundagungan calling phenology, this difficult-to-find species will now be more reliably detected, removing a barrier that has hindered efforts to study and conserve this species. Full article

We describe a new species of terrestrial-breeding frog of the genus Pristimantis from the Peruvian Yungas ecoregion of central Peru, Junin Department. The description is based on the observation of morphological features, color patterns of fourteen specimens, bioacoustic traits of the advertisement calls, and a phylogenetic analysis using a sequence fragment of 16S rRNA. The new species is mainly characterized by having a rounded or truncate snout in dorsal view, presence of dorsolateral folds, tympanic membrane and annulus distinct, absence of flash marks on the hidden surfaces of flanks and hindlimbs, and a small size (maximum SVL 15.6 mm in males and 19.3 mm in females). We provide diagnostic traits to differentiate the new species from phylogenetically close relatives, as well as morphologically similar and sympatric species of Pristimantis. Full article

Females of frog-biting midges (Corethrellidae) obtain their blood meals from male calling frogs. While the morphology of the feeding apparatus is well studied in hematophagous Diptera that impact humans, frog-biting midges have received far less attention. We provide a detailed micromorphological examination of the piercing blood-sucking proboscis and maxillary palpus in three Corethrella species using scanning electron microscopy and histological semi-thin sectioning. We also compare the sensilla found on the proboscis tip and the palpus of Corethrella with other piercing blood-sucking Diptera. Corethrella spp. have a proboscis length of about 135 µm, equipped with delicate mandibular piercing structures composing the food canal together with the labrum and hypopharynx. Their proboscis composition is plesiomorphic and more similar to other short-proboscid hematophagous Culicomorpha (e.g., Simuliidae), in contrast to the phylogenetically more closely related long-proboscid Culicidae. As in other short-proboscid taxa, the salivary canal in Corethrella spp. transitions into an open salivary groove with one mandible forming a seal, whereas in Culicidae the salivary canal is closed until the tip of the proboscis. We discuss the possible functional constraints of very short, piercing blood-sucking proboscises (e.g., dimensions of host blood cells) that may limit the size of the food canal. Full article

The calling behavior of anurans should be studied in detail as it greatly influences their physiology and immunity, particularly in prolonged breeding species. The effect can be further complicated by the emergence timing in the breeding season. We conducted a study comparing the physiology and calling behavior of the Japanese tree frog (Dryophytes japonicus), a prolonged breeder species, according to the breeding timing. During the middle of the breeding season, a high chorus size appeared, indicating a breeding peak. However, chorus size did not dominate physiology and calling behavior. In the early breeding season, frogs had a high energy storage state and immunity. In the middle of the breeding season, individuals from the early breeding season were considered to have exhausted their energy stores and had low immunity. Towards the end of the breeding season, frogs appeared to have newly introduced, at which time energy stores and immunity were as high as in the beginning. However, unlike the physiology, the pattern of calling constantly varied as the breeding season progressed. Frogs from the early season conserved energy used for calling, and frogs from the late season showed a breeding spurt for mating. Our results can help in understanding the energy metabolism of calling behavior, physiology, and disease epidemiology in prolonged breeder species. They also suggest that individuals coordinate their participation in the breeding season and that the timing of their appearance at breeding sites may not be random. Full article

Prospective research in the area of Education Sciences and Physical-Sports Education agree on the need to design and implement educational programs that promote emotional competencies (ECs), interpersonal competencies (ICs), an adequate level of healthy physical activity (NAFS) and a good adherence to the Mediterranean diet (ADM). The main objective of the study is to design an intervention program in intra- and interpersonal competencies together with nutritional education and corporality called “MotivACTION”. The sample consisted of 80 primary schoolchildren aged 8 to 14 years (M = 12.70; SD = 2.76) (37 girls and 43 boys) from two schools in the Community of Madrid. An ad-hoc questionnaire was created to assess the participant’s perception of the usefulness of the “MotivACTION” educational experience. The program “MotivACTION: Feed your SuperACTION” is designed and implemented based on the development of a workshop organized through the Universidad Europea de Madrid. As the main preliminary results of the pilot study, the schoolchildren who experienced the “MotivACTION” workshop showed high satisfaction with the educational program. They were able to create a healthy menu with the frog chef. They also felt better and happier at the end of it, and they enjoyed practicing physical activity moving to the rhythm of the music while doing mathematical calculations. Full article

Many species produce alarm calls in response to predators, and the anti-predator signals are often used by other species. Eavesdropping on heterospecific alarm calls has been widely found in bird and mammal species. Other taxa, such as reptiles and amphibians, however, receive limited attention at present. Here, we selected three types of alarm calls of Japanese Tits (Parus minor) that were evoked by the Siberian Chipmunk (Eutamias sibiricus), Eurasian Sparrow Hawk (Accipiter nisus), and model snake (Elaphe spp.), respectively, and then carried out playback experiments to test whether three frog species changed their behaviors in response to the three treatments of Japanese Tit calls while the tit’s territory song was used as a control. The results showed that Little Torrent Frogs (Amolops torrentis), Ornamented Pygmy Frogs (Microhyla fissipes) and Spot-legged Treefrogs (Polypedates megacephalus) did not jump off their positions in response to the same four acoustic signals. They also did not change their calling behaviors in response to the alarm calls of Japanese Tits. This study found no evidence that these anuran species can eavesdrop on heterospecific tits’ alarm signals. Full article

Species belonging to the genus Microhyla are small-sized frogs that are widely distributed in southern, eastern, and south-eastern Asia. In China, the genus harbors many cryptic species, on two of which—M. beilunensis and M. fanjinshanensis—studies were recently published. In this study, we collected specimens from the Dabie Mountain range, which is at the junction of Anhui, Henan and Hubei Provinces, East China; these specimens belonged to a species previously identified as M. mixtura. Based on phylogenetic analyses, species delimitation analyses, morphological comparisons and advertisement calls comparisons, we found they were significantly different from other known congeners, and thus we describe them as a new species. This study enriches the diversity of Microhylidae, and clarifies the species of the genus Microhyla in the Dabie Mountains. Full article