Female Frogs Research Articles

Sex-based differences in the use of post-fire habitats by invasive cane toads (Rhinella marina)

Wildfires can modify habitat attributes, and those changes may differentially affect males versus females within a species if there is pre-existing niche divergence between the sexes. We used radio-tracking and dissections to study invasive cane toads (Rhinella marina), and performed transect counts on native frogs and cane toads 12 months after extensive fires in forests of eastern Australia. Both toads and native frogs were encountered more frequently in burned sites than in unburned sites. Most microhabitat features were similar between burned versus unburned areas, but fire had differential impacts on the ecology of male versus female toads. In burned areas females were less numerous but were larger, in better body condition, and had consumed more prey (especially, coleopterans and myriapods). The impact of fire on attributes of retreat-sites (e.g., temperature, density of vegetation cover) also differed between the sexes. More generally, intraspecific divergence in ecological traits within a species (as a function of body size as well as sex) may translate into substantial divergences in the impacts of habitat change.

Comparisons of biochemical compositions in marsh frog (Pelophylax ridibundus)(Anura; Ranidae) grown in different conditions; wild, semicultured and cultured ones

Frogs can be added to a list of different raw materials which have sustainable economic value to their producers. Therefore, the biochemical attributes of the frogs require further scientific scrutiny. The major objective of the current study is to investigate some biochemical compositions of edible portions of Pelophylax ridibundus (Pallas, 1771) grown in different conditions. The wild frogs, semicultured frogs, and cultured frogs were investigated regarding female and male specimens, leading to six groups that were determined to investigate the biochemical features of frogs. The results show that they (all frogs in all six groups) have low lipid contents (p < 0.05). The protein contents of the frogs varied in the range of 10.54%-16.10%. The lowest ash contents were found in semicultured male and female frogs. The average moisture contents were roughly 80% for all specimens. The major fatty acids were C16:0, C18:0, C18:1n9, C18:2n6, and C20:4n6 for wild, semicultured, and cultured frogs, respectively, for both sexes, showing their respective amounts varied among groups. All in all, the results show that there exist some differences in the nutritional content of frogs grown in different

Histological Comparison of the Edible Water Frog (Pelophylax ridibundus Pallas, 1771) Gonads Before and After Reproduction

In this study, testicular and ovarian structures of economically important edible Pelophylax ridibundus (Pallas, 1771) were histologically examined before and after reproduction in male and female individuals. Fourty eight (24 ♀, 24 ♂) adult frogs were collected from Gölbaşı Lake in Hatay. The average weight and length values of female frogs collected from nature were found to be 56.61±19.59 g and 79.54±7.07 mm; while, the average weight and length values of male frogs were 36.63±12.84 g and 69.29±9.15 mm, respectively. Frogs were brought to the frog farm established in Aydıncık and placed in breeding ponds with a width of 1m2. Frogs in the ponds were brought to the laboratory of Iskenderun Technical University in different periods, before breeding (March) and after breeding (June). Then, histological samples were taken from ovary and testis. The female frogs were determined ready for reproduction. Moreover, a large number of mature oocytes in the before breeding ovaries in vitellogenic stage, while after reproduction oocytes in primary structure and oocytes which have atresia status observed. Also, increase in the thickness of the theca layer was determined. In the male frog seminiferous tubules containing a large number of spermatogonia, spermatocyte, spermatid and a small number of spermatozoons including sperm bundles and leydig cells were found before reproduction. After the reproduciton, the density of spermatogonia, spermatocyte and spermatids were decreased; while, the density of spermatozoon and sperm bundle were increased in the seminiferous tubules. This study will contribute to the determination of mating and spawning in frog breeding by revealing the histological status of the gonad structure of P. ridibundus in the breeding process.

Woe is the loner: Female treefrogs prefer clusters of displaying males over single "hotshot" males.

Communal displays such as leks and choruses are puzzling phenomena, as it is not obvious why signalers or choosers should aggregate. It has been hypothesized that signalers in leks enjoy higher per-capita reproductive success because choosers prefer to sample among dense configurations ("clusters") that are easier to compare.Although female preferences as well as the signal features of attractive males are well characterized in many chorusing species, we know little about how mate sampling is influenced by the spatial dynamics within communal displays. Here, weask how female Eastern Gray Treefrogs (Hyla versicolor) respond toisolatedand clustered call stimuli in a simple one versus three playback design.We explored (i) whether females exhibit a general preference for call clusters, (ii) whether spatial preference is robust to call-feature preference, and (iii) how this affects the relative success of attractive and unattractive males in different spatial combinations. We found generalized spatial discrimination against lone callers but did observe fine-scale assessment of call features within clusters. The prominence of the spatial preference impacts the attractiveness of males, conferring particular advantage to attractive callers within clusters, while reducing attractiveness of isolated males regardless of their acoustic features. Our findings indicate that female frogs navigate complex choruses by initially orientating toward clusters of calling males, and then assess call features within them. This studyprovides novel insightinto the mate choice heuristics involved in animal choruses.

Sex and habitat differences in size and coloration of an amphibian's poison glands match differential predator pressures.

Chemical defenses are frequently accompanied by salient color patterns actively avoided by predators, a phenomenon referred to as aposematism. However, the production of both chemical defenses and pigments is costly, and is thus expected to be reduced under mild predator pressure. In this work, I compared the size and coloration of parotoid glands (2 dorsal, external swollen structures that secrete toxins in toads) of male and female Epidalea calamita toads from agrosystems and from pine groves. I also quantified the predator attacks received by plasticine toad models, whose "parotoid glands" differed in size and color conspicuousness, exposed in each habitat. Predators avoided models with large and conspicuous parotoid glands, but models in agrosystems were more often attacked. Concerning actual toads, agrosystem and male individuals had larger parotoid glands, presumably implying greater production of chemical defenses than in pine grove and female conspecifics. These findings are aligned with previous research suggesting that both agrosystem toads and males in this system are subjected to a more intense predator pressure. Difference between parotoid gland and dorsum coloration was greater in agrosystem toads. A marked internal pattern could function as an aposematic signal, which could counteract increased predator pressure.

SURGICAL MANAGEMENT OF A DIGESTIVE TRACT HERNIA IN A FREE RANGING WILD MARSH FROG (PELOPHYLAX RIDIBUNDUS)

A wild-caught mature female marsh frog (Pelophylax ridibundus) was presented for a left-sided dorsal swelling. No other abnormalities were detected during the examination. Fine needle aspiration was non-diagnostic. Baseline hematological and biochemical analyses were within normal range and medical imaging did not provide further useful information. Surgical exploration under general anaesthesia was performed. The swelling was confirmed to be a digestive tract hernia protruding through a breach of the dorsal muscles and coelomic membrane. Reduction was made difficult by the presence of multiple adhesions between the herniated tissue and the coelomic membrane, suggesting a relatively chronic lesion. A traumatic cause was hypothesised. One month later, the animal was healthy and was released back in the wild. Hernias in amphibians are poorly reported in literature, and are only ventral. To the best of authors’ knowledge, a dorsal hernia has never been described in a captive or a free ranging amphibian before.

Genome-Wide SNP Analysis of Male and Female Rice Field Frogs, Hoplobatrachus rugulosus, Supports a Non-Genetic Sex Determination System

Sex determination systems (SDSs) in anurans are diverse and have undergone independent evolutionary transitions among species. The mode of sexual reproduction of the rice field frog (Hoplobatrachus rugulosus)—an economically viable, edible amphibian species—is not well known. Previous studies have proposed that threshold temperature conditions may determine sex in these frogs. To elucidate the SDS in H. rugulosus, we karyotyped 10 male and 12 female frogs, and performed fluorescence in situ hybridization combined with sequencing analyses using DArTseq™. Our results revealed a highly conserved karyotype with no sex chromosome heteromorphism, and the sequencing analyses did not identify any consistent sex-linked loci, supporting the hypothesis of temperature-dependent sex determination. The results of this study, and others, on SDSs in the rice field frog and related species also provide support for the theory that heteromorphic sex chromosomes may lead to an evolutionary trap that prevents variable SDSs. These findings add important information to the body of knowledge on H. rugulosus and are likely to have a significant impact on the productivity and economic success of rice field frog farming.

Selective Oviposition by Oriental Fire-bellied Toads in Temporally Fluctuating Environments

Selective oviposition is widespread in anurans because it significantly affects the survivorship of their offspring, especially when environmental conditions are heterogeneous and potentially unfavorable. In the present study, we aimed to determine whether female oriental fire-bellied toads (Bombina orientalis) selectively lay eggs to increase their progeny's survival. We studied the Jeju Island population because the streams on this island are ephemeral, so the timing and site of egg-laying can be important for the survival of their progeny. We surveyed all pools in a specific area of an ephemeral stream for two years to determine whether female B. orientalis selectively lay eggs in certain pools to increase their progeny's survival. The characteristics of pools in our study sites varied especially in size that ranged from 0.01 to 36 m2 in surface area. We found that female B. orientalis avoid laying eggs in very small pools where the risk of desiccation or over-heating of water is high. However, unexpectedly, they also avoided large pools and primarily laid eggs in the pools that are not very small or large. In terms of timing, egg-laying took place in association with the timing of rain: the number of pools with egg clutches decreased as the number of days since the last rainfall increased. Females also avoided laying eggs in pools that were already occupied by tadpoles. Field experiments demonstrated that the degree of cannibalism on eggs by conspecific tadpoles is intense in this species. These findings collectively indicate that B. orientalis that live in a fluctuating environment show complicated oviposition behavior that mediate both desiccation and cannibalism risks.

The dual benefits of synchronized mating signals in a Japanese treefrog: attracting mates and manipulating predators.

In dense mating aggregations, such as leks and choruses, acoustic signals produced by competing male conspecifics often overlap in time. When signals overlap at a fine temporal scale the ability of females to discriminate between individual signals is reduced. Yet, despite this cost, males of some species deliberately overlap their signals with those of conspecifics, synchronizing signal production in the chorus. Here, we investigate two hypotheses of synchronized mating signals in a Japanese treefrog (Buergeria japonica): (1) increased female attraction to the chorus (the beacon effect hypothesis) and (2) reduced attraction of eavesdropping predators (the eavesdropper avoidance hypothesis). Our results from playback experiments on female frogs and eavesdropping micropredators (midges and mosquitoes) support both hypotheses. Signal transmission and female phonotaxis experiments suggest that away from the chorus, synchronized calls are more attractive to females than unsynchronized calls. At the chorus, however, eavesdroppers are less attracted to calls that closely follow an initial call, while female attraction to individual signals is not affected. Therefore, synchronized signalling likely benefits male B. japonica by both increasing attraction of females to the chorus and reducing eavesdropper attacks. These findings highlight how multiple selective pressures likely promoted the evolution and maintenance of this behaviour. This article is part of the theme issue 'Synchrony and rhythm interaction: from the brain to behavioural ecology'.

Obtaining Xenopus tropicalis Embryos by Natural Mating.

Xenopus is a powerful model system for cell and developmental biology in part because frogs produce thousands of eggs and embryos year-round. Natural matings are a simple and common method to obtain embryos for injection or other experimental use or to raise to adulthood. This method does not require sacrificing a male as in vitro fertilization (IVF) does. Male and female frogs are injected with an ovulation hormone, placed together in a mating bucket, and left for 4-6 h or overnight to mate. Embryos are then collected, treated with cysteine to remove the sticky jelly coat, and used for injections and/or raised to later stages or adulthood. For embryos raised past free-swimming stages, the cysteine step can optionally be skipped, and tadpoles can be allowed to hatch naturally from the jelly coat. Although there are many similarities between natural mating protocols for Xenopus laevis and Xenopus tropicalis, there are key differences such as hormone dosage, timing of ovulation, and embryo incubation temperature. Here we provide a specific protocol for inducing natural matings in X. tropicalis.

JNK/Elk1 signaling and PCNA protein expression in the brain of hibernating frog Pelophylax esculentus.

Mitogen activated protein kinase (MAPK) activation and neurogenesis are known to play a role in neuronal survival during hibernation. Herein, we investigate the activity of c-Jun N-terminal kinases (JNK) and Ets like-1 protein (Elk1) kinase involved in cell survival, as well as the expression of proliferating cell nuclear antigen (PCNA), a cell proliferation marker, in the brain of the frog Pelophylax esculentus. The study was conducted on female and male frogs collected during the annual cycle. Our results demonstrated that JNK activity increased during the hibernating phase in relation to the active phase. Interestingly, P-Elk1 levels were positively correlated with P-JNK levels, suggesting that the JNK/Elk1 pathway is pivotal in mediating neuroprotective adaptations that are essential to successful hibernation. On the contrary, we detected higher PCNA expression levels during the active period compared with the hibernating period. A sex dimorphism was observed in the expression levels of P-JNK/P-Elk1 that were specifically higher in males, and in the expression of PCNA reporting higher levels in female brains. Much remains to be learned regarding the regulation of hibernation, however, our findings provide new insights into the role of MAPK and proliferative pathways in hibernation, adding new knowledge concerning the mechanisms activated in the brain of ectothermic species to counteract the damage resulting from extreme temperatures.

Enigmatic Near‐Extirpation in a Boreal Toad Metapopulation in Northwestern Montana

ABSTRACTNorth America's protected lands harbor biodiversity and provide habitats where species threatened by a variety of stressors in other environments can thrive. Yet disease, climate change, and other threats are not limited by land management boundaries and can interact with conditions within protected landscapes to affect sensitive populations. We examined the population dynamics of a boreal toad (Anaxyrus boreas boreas) metapopulation at a wildlife refuge in northwestern Montana, USA, over a 16‐year period (2003–2018). We used robust design capture‐recapture models to estimate male population size, recruitment, and apparent survival over time and in relation to the amphibian chytrid fungus (Batrachochytrium dendrobatidis). We estimated female population size in years with sufficient captures. Finally, we examined trends in male and female toad body size and condition. We found no evidence of an effect of disease or time on male toad survival but detected a strong negative trend in recruitment of new males to the population. Estimates of male and female abundance decreased over time. Body size of males and females was inversely related to estimated population size, consistent with reduced recruitment to replace adults, but body condition of adult males was only weakly associated with abundance. Together, these results describe the demography of a near‐extirpation event, and point to dramatic decreases in the recruitment of new individuals to the breeding population as the cause of this decline. We surmise that processes related to the restoration of historical hydrology within the refuge adversely affected amphibian breeding habitat, and that these changes interacted with disease, life history, and other factors to restrict the recruitment of new individuals to the breeding population over time. Our results point to challenges in understanding and predicting factors that influence population change and highlight that current metrics for assessing population status can have limited predictive ability. Published 2021. This article is a U.S. Government work and is in the public domain in the USA.

Sexual selection in a tropical toad: Do female toads choose brighter males in a species with rapid colour change?

AbstractConspicuous visual signals play an important role in animal communication, both within and between species. Bright, colourful signals allow animals to discriminate between individuals and can inform behavioural decisions and social interactions. In many instances, conspicuous colouration appears to have evolved through sexual selection via female mate choice or male–male competition. Male Neotropical yellow toads, Incilius luetkenii, display bright‐yellow colouration during their brief explosive mating events and then revert to a cryptic, female‐like, brown colour following amplexus and fertilization. Recent research has revealed that the yellow colouration of males may serve as a sex identification signal and that males remain yellow in the presence of both males and females but darken without conspecific stimulus. However, there is considerable variation in the brightness of yellow colouration in courting males, ranging from dull olive‐green to vibrant lemon‐yellow. The function of this variation remains unknown. In this study, we conducted two‐choice model presentation trials to test one mechanism of sexual selection that may drive this variation: intersexual selection. Specifically, we set out to determine whether females differentiate between males based on their colouration. We presented females with two hyper‐realistic robotic model toads, with one model painted to match a bright‐yellow male and the other a dull‐yellow male. Using several metrics of choice, we found that females did not show a preference for bright or dull colouration. Our research suggests that variation in the intensity of male breeding colouration is not driven by female choice in this species. Our study is consistent with the idea that there may be limited opportunity for female choice to influence male‐trait expression in explosive breeders. Future research will address whether intrasexual selection may influence colour variation in male yellow toads.

Ex Vivo Brain Preparation to Analyze Vocal Pathways of Xenopus Frogs.

Understanding the neural basis of behavior is a challenging task for technical reasons. Most methods of recording neural activity require animals to be immobilized, but neural activity associated with most behavior cannot be recorded from an anesthetized, immobilized animal. Using amphibians, however, there has been some success in developing in vitro brain preparations that can be used for electrophysiological and anatomical studies. Here, we describe an ex vivo frog brain preparation from which fictive vocalizations (the neural activity that would have produced vocalizations had the brain been attached to the muscle) can be elicited repeatedly. When serotonin is applied to the isolated brains of male and female African clawed frogs, Xenopus laevis, laryngeal nerve activity that is a facsimile of those that underlie sex-specific vocalizations in vivo can be readily recorded. Recently, this preparation was successfully used in other species within the genus including Xenopus tropicalis and Xenopus victorianus This preparation allows a variety of techniques to be applied including extracellular and intracellular electrophysiological recordings and calcium imaging during vocal production, surgical and pharmacological manipulation of neurons to evaluate their impact on motor output, and tract tracing of the neural circuitry. Thus, the preparation is a powerful tool with which to understand the basic principles that govern the production of coherent and robust motor programs in vertebrates.

Novel reproductive behavior in an Asian frog: sex‐reversed inguinal amplexus

AbstractAmphibians exhibit diverse reproductive behaviors, including nine documented types of amplexus, the behavior in which male and female frogs position themselves for courtship, oviposition, and fertilization. All known forms of amplexus involve the male on top of or in line horizontally (cloacal apposition) with the female. Here, we report a novel form of amplexus observed in Lau’s leaf litter toad (Leptobrachella laui; Megophryidae) in Hong Kong, China. Termed “sex‐reversed inguinal amplexus,” the female climbs on top of a male and the male transports the female to a concealed breeding site. We were unable to determine whether this was the amplectant position in which frogs engaged during oviposition or solely during courtship and prior to oviposition, but there are a number of possible evolutionary drivers that may have given rise to this behavior, including limiting suitable oviposition sites or strong competition for males among females. Further research will be necessary to understand the evolutionary origins of this novel reproductive behavior.

High Rate of Endoparasites (Helminth) Infection of Toad (Anurans) in the Dir Lower, Khyber Pakhtunkhwa, Pakistan

The results emphasise the significance of further studies in the Dir Lower to get well understanding of the helminth parasites with ecological relations of their hosts. Twenty-seven specimens of Bufo stomaticus (Lutken, 1864) (Anura: Bufonidae) were collected in the Dir Lower, Khyber Pakhtunkhwa province of Pakistan in the period from April to August 2016, and examined for helminths (endoparasites) parasites. Twelve (44.44%) specimens were infected by two types of helminths parasites. Total of forty-one helminths parasites were collected, among them six were identified Cestode and the remaining thirty-five were nematodes. The dominant parasites were nematodes (Cosmocerca sp. with 56.09% followed by Cosmocercoides sp. with 29.26%). But the Cestodes were found with single species (Nematotania dispar with 14.63%). Female toads showed higher parasite diversity than male toads.

The Combined Effects of Road Salt and Biotic Stressors on Amphibian Sex Ratios.

Aquatic systems worldwide are threatened by the anthropogenic use of synthetic chemicals, including pesticides, pharmaceuticals, and road de-icers. Exposure to contaminants can alter the behavior, morphology, and physiology of organisms if it occurs during sensitive life stages. For instance, past studies have documented feminization of male amphibians following herbicide exposure and skewed sex ratios among amphibian populations exposed to road salt. However, many of these studies lack the complexities found within natural environments, such as competition with conspecifics or threat of predation, which are also known to influence development. Thus, it is important to understand how anthropogenic and natural stressors interact to alter animal sex ratios. Given the growing concern of secondary salinization of freshwater systems, we exposed larval wood frogs (Rana sylvatica) to either road salt (sodium chloride [NaCl]) or an alternative salt mixture (NaCl, magnesium chloride [MgCl2 ], and potassium chloride [KCl]) at 3 concentrations (200, 600, and 1000 mg Cl- /L) crossed with 3 biotic stressors (no-stressor control, competition, or predator cues) to examine their potentially interactive effects on sex. Exposure to biotic stressors and NaCl did not influence wood frog sex ratios. In contrast, tadpole exposure to the intermediate salt mixture concentration significantly reduced the proportion of female frogs. Future studies are needed to determine whether such changes in sex are widespread among sensitive species with complex life cycles, and to assess the consequences of sex ratio changes on long-term population dynamics. Environ Toxicol Chem 2021;40:231-235. © 2020 SETAC.

A Sensorimotor Numerosity System.

Incoming sensory input provides information for the planning and execution of actions, which yield motor outcomes that are themselves sensory inputs. One dimension where action and perception strongly interact is numerosity perception. Many non-human animals can estimate approximately the number of external elements as well as their own actions, and neurons have been identified that respond to both. Recent psychophysical adaptation studies on humans also provide evidence for neural mechanisms responding to both the number of externally generated events and self-produced actions. Here we advance the idea that these strong connections may arise from dedicated sensorimotor mechanisms in the brain, part of a more generalized system interfacing action with the processing of other quantitative magnitudes such as space and time.

Shrinking before our isles: the rapid expression of insular dwarfism in two invasive populations of guttural toad (Sclerophrys gutturalis).

Island ecosystems have traditionally been hailed as natural laboratories for examining phenotypic change, including dramatic shifts in body size. Similarly, biological invasions can drive rapid localized adaptations within modern timeframes. Here, we compare the morphology of two invasive guttural toad (Sclerophrys gutturalis) populations in Mauritius and Réunion with their source population from South Africa. We found that female toads on both islands were significantly smaller than mainland counterparts (33.9% and 25.9% reduction, respectively), as were males in Mauritius (22.4%). We also discovered a significant reduction in the relative hindlimb length of both sexes, on both islands, compared with mainland toads (ranging from 3.4 to 9.0%). If our findings are a result of natural selection, then this would suggest that the dramatic reshaping of an amphibian's morphology-leading to insular dwarfism-can result in less than 100 years; however, further research is required to elucidate the mechanism driving this change (e.g. heritable adaptation, phenotypic plasticity, or an interaction between them).

Comment on "Female toads engaging in adaptive hybridization prefer high-quality heterospecifics as mates".

Chen and Pfennig (Reports, 20 March 2020, p. 1377) analyze the fitness consequences of hybridization in toads but do not account for differences in survival among progeny. Apparent fitness effects depend on families with anomalously low survival, yet survival is crucial to evolutionary fitness. This and other analytical shortcomings demonstrate that a conclusion of adaptive mate choice is not yet justified.