Showing papers on "Toad published in 2021"

A large genome with chromosome‐scale assembly sheds light on the evolutionary success of a true toad (Bufo gargarizans)

Abstract: We present a high-quality genome assembly for the Asiatic toad (Bufo gargarizans) and explore the evolution of several large gene families in amphibians. With a large genome assembly size of 4.55 Gb, the chromosome-scale assembly includes 747 scaffolds with an N50 of 539.8 Mb and 1.79% gaps. Long terminal repeats (LTRs) constitute a high proportion of the genome and their expansion is a key contributor to the inflated genome size in this species. This is very different from other small amphibian genomes, but similar to that of the enormous axolotl genome. The genome retains a large number of duplicated genes, with tandem (TD) and proximal duplications (PD) the predominant mode of duplication. A total of 122 gene families have undergone significant expansion and were mainly enriched in sensory perception of smell and bitter taste. The CYP2C subfamily, which plays an important role in metabolic detoxification, specifically expanded via TD and PD in the Asiatic toad and the cane toad (true toads). Most of Na+ /K+ -ATPase genes experienced accelerated evolution along Bufonid lineages and two amino acid sites involving toad-toxin resistance were found to experience positive selection. We also revealed a dynamic evolution of olfactory and vomeronasal receptor gene families which was likely driven by the water-to-land transition. The high-quality genome of the Asiatic toad will provide a solid foundation to understand the genetic basis of its many biological processes.

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

Abstract: 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.

Morphological and histological abnormalities of the neotropical toad, Rhinella arenarum (Anura: Bufonidae) larvae exposed to dexamethasone.

Abstract: Dexamethasone (DEX) is a glucocorticoid highly effective as an anti-inflammatory, immunosuppressant and decongestant drug. In the present study, a preliminary acute toxicity test was assayed in ord...

A pore-forming protein drives macropinocytosis to facilitate toad water maintaining

Abstract: Maintaining water balance is a real challenge for amphibians in terrestrial environments. Our previous studies with toad Bombina maxima discovered a secretory aerolysin family pore-forming protein and trefoil factor complex {beta}{gamma}-CAT, which is assembled under tight regulation depending on environmental cues. Here we report an unexpected role for {beta}{gamma}-CAT in toad water maintaining. Deletion of toad skin secretions, in which {beta}{gamma}-CAT is a major component, increased animal mortality under hypertonic stress. {beta}{gamma}-CAT was constitutively expressed in toad osmoregulatory organs, which was inducible under the variation of osmotic conditions. The protein induced and participated in macropinocytosis in vivo and in vitro. During extracellular hyperosmosis, {beta}{gamma}-CAT stimulated macropinocytosis to facilitate water intake and enhanced exosomes release, which simultaneously regulated aquaporins distribution. Collectively, these findings uncovered that besides membrane integrated aquaporins, a secretory pore-forming protein can facilitate toad water maintaining via macropinocytosis induction and exocytosis modulation, especially in responses to osmotic stress.

Signals from predators, injured conspecifics, and pesticide modify the swimming behavior of the gregarious tadpole of the Dorbigny’s Toad, Rhinella dorbignyi (Anura: Bufonidae)

Abstract: Tadpoles detect chemical signals released from predators and conspecifics, as well as those present in the environment, and adjust their behavioral responses. This study evaluated the swimming acti...

Chemical cues that attract cannibalistic cane toad (Rhinella marina) larvae to vulnerable embryos.

Abstract: Chemical cues produced by late-stage embryos of the cane toad (Rhinella marina) attract older conspecific larvae, which are highly cannibalistic and can consume an entire clutch. To clarify the molecular basis of this attraction response, we presented captive tadpoles with components present in toad eggs. As previously reported, attractivity arises from the distinctive toxins (bufadienolides) produced by cane toads, with some toxins (e.g., bufagenins) much stronger attractants than others (e.g., bufotoxins). Extracts of frozen toad parotoid glands (rich in bufagenins) were more attractive than were fresh MeOH extracts of the parotoid secretion (rich in bufotoxins), and purified marinobufagin was more effective than marinobufotoxin. Cardenolide aglycones (e.g., digitoxigenin) were active attractors, whereas C-3 glycosides (e.g., digoxin, oubain) were far less effective. A structure-activity relationship study revealed that tadpole attractant potency strongly correlated with Na+/K+ ATPase inhibitory activity, suggesting that tadpoles monitor and rapidly react to perturbations to Na+/K+ ATPase activity.

Novel Indole derivative as first P-glycoprotein inhibitor from the skin of Indian toad (Bufo melanostictus)

Abstract: Objective: To study the inhibitory effect of Novel Indole Derivative (NID) from Indian toad skin (Bufo melanostictus) on P-glycoprotein. Materials and methods: Dried Indian Toad skin was used to isolate NID with column chromatography, and its structure was elucidated by IR Spectra, 13C NMR, 1H NMR Spectra, and LC-MS. Female Wistar rats were used to determine LD50, In vitro permeability studies were done with the intestinal sac method, and In vivo pharmacokinetic studies were carried out to prove P-gp inhibition using the rat model. Results: The NID has shown increased apparent permeability Papp(x10-6cm/sec) significantly (p<0.001) from 1.04±0.11 to 2.90±0.08 in ileum 1.44±0.14 to 3.92±0.13 in jejunum this in vitro results confirmed that P-gp inhibited, this was further confirmed by in vivo studies and found to observe the increased oral bioavailability of digoxin significantly in NID treated groups from 3.26±0.25 to 7.47±0.18 ng/mL, the volume of distribution decreased from 232.56±64.59 to 86.57±7.04 L/kg. AUC increased from 37.89±1.13 to 64.62±0.70 ng/mL/hr. This demonstrates NID increased the oral bioavailability of digoxin significantly. Conclusion: Many compounds were isolated from Indian toad skin. This NID was not reported earlier. Results demonstrate NID increased the oral bioavailability of digoxin significantly. The isolated NID from Indian toad skin proved as a potent P-gp inhibitor in both in vitro and in vivo studies, and further studies needed to develop as a possible new drug candidate.

Emergence of a bufonid herpesvirus in a population of the common toad Bufo bufo in Germany

Abstract: Bufonid herpesvirus 1 (BfHV1) was initially described in 2014 from cases of mortalities and dermatitis in Swiss populations of the common toad Bufo bufo. We identified a closely related herpesvirus strain in a German common toad population affected by an ongoing epidemic of multifocal proliferative to ulcerative skin disease since 2018.