Evidence that catecholaminergic systems mediate dynamic colour change during explosive breeding events in toads

Many animals communicate by rapidly (within minutes or seconds) changing their body coloration; however, we know little about the physiology of this behaviour. Here we study how catecholaminergic hormones regulate rapid colour change in explosive breeding toads (Duttaphrynus melanostictus), where large groups of males gather and quickly change their colour from brown to bright yellow during reproduction. We find that both epinephrine (EP) and/or norepinephrine (NE) cause the toads' skin to become yellow in minutes, even in the absence of social and environmental cues associated with explosive breeding. We hypothesize that natural selection drives the evolution of rapid colour change by co-opting the functional effects of catecholaminergic action. If so, then hormones involved in ‘fight or flight’ responses may mechanistically facilitate the emergence of dynamic visual signals that mediate communication in a sexual context.

Characterization of the microbiome of the invasive Asian toad in Madagascar across the expansion range and comparison with a native co-occurring species

Biological invasions are on the rise, with each invader carrying a plethora of associated microbes. These microbes play important, yet poorly understood, ecological roles that can include assisting the hosts in colonization and adaptation processes or as possible pathogens. Understanding how these communities differ in an invasion scenario may help to understand the host's resilience and adaptability. The Asian common toad, Duttaphrynus melanostictus is an invasive amphibian, which has recently established in Madagascar and is expected to pose numerous threats to the native ecosystems. We characterized the skin and gut bacterial communities of D. melanostictus in Toamasina (Eastern Madagascar), and compared them to those of a co-occurring native frog species, Ptychadena mascareniensis, at three sites where the toad arrived in different years. Microbial composition did not vary among sites, showing that D. melanostictus keeps a stable community across its expansion but significant differences were observed between these two amphibians. Moreover, D. melanostictus had richer and more diverse communities and also harboured a high percentage of total unique taxa (skin: 80%; gut: 52%). These differences may reflect the combination of multiple host-associated factors including microhabitat selection, skin features and dietary preferences.

Molecular identification of genus Duttaphrynus from Punjab, Pakistan

The Indus valley toad and common Asian toad are widely distributed toads in Pakistan. There is doubt in the taxonomic position of species within the genus Duttaphrynus in Pakistan as most of the species identified on morphology. Previously, Bufo melanostictus hazarensis identified on morphology but during the present study, it is confirmed as Duttaphrynus melanostictus-based COI sequences (MK941836). The interspecific divergence between Duttaphrynus stomaticus and D. melanostictus was 16%. The intraspecific divergence of D. stomaticus (MK947909.1) was ranging from 0% to 1% while the intraspecific divergence of D. melanostictus (MK941836) was high ranging from 10% to 11%. Overall, genetic variation between the species of genus Duttaphrynus based on p-distance was 14%. In our recommendation, a large-scale molecular identification of amphibians should take into consideration for exact species identification to report any new species from Pakistan.

Morphological description of Opalina obtrigonoidea Metcalf, 1923 (Heterokonta, Opalinea) from Duttaphrynus melanostictus and evaluation of the ITS region as a suitable genetic marker for inter-species identification in Opalina

The redescription of Opalina obtrigonoidea Metcalf, 1923, collected from the rectum of the toads Duttaphrynus melanostictus, is presented in this paper based on detailed morphological information and molecular data. Our results revealed that O. obtrigonoidea varies greatly in body dimensions. Its morphological characteristics allow its differentiation from Opalina undulata. Surprisingly, we sequenced its SSU rDNA-ITS1-5.8S rDNA-ITS2-LSU rDNA (5' end) and found the SSU rDNA of O. obtrigonoidea is nearly identical to that of O. undulata. However, there are differences in both the ITS1 and ITS2 regions that allow their distinction and confirm the morphological differences. Our results indicate that O. obtrigonoidea and O. undulata are closely related species in which morphological and genetic markers have evolved at different speeds. Due to this, the SSU rDNA gene may not be a valid marker for inter-species identification in Opalina, but the ITS is a valid marker for differentiating species in this genus.

Geographic body size variation of a tropical anuran: effects of water deficit and precipitation seasonality on Asian common toad from southern Asia

Background

Two previous studies on interspecific body size variation of anurans found that the key drivers of variation are the species’ lifestyles and the environments that they live in. To examine whether those findings apply at the intraspecific level, we conducted a study of the Asian common toad (Duttaphrynus melanostictus), a terrestrial anuran distributed in tropical regions. The body size of toads from 15 locations, covering the majority of their geographic range, and local environmental data were summarized from published literature. We used a model selection process based on an information-theoretic approach to examine the relationship between toad body size and those environmental parameters.

Results

We found a positive correlation between the body size of the Asian common toad and the water deficit gradient, but no linkage between body size and temperature-related parameters. Furthermore, there was a positive correlation between the seasonality of precipitation and body size of females from different sampled populations.

Conclusions

As a terrestrial anuran, the Asian common toad should experience greater pressure from environmental fluctuations than aquatic species. It is mainly distributed in tropical regions where temperatures are generally warm and stable, but water availability fluctuates. Therefore, while thermal gradients are not strong enough to generate selection pressure on body size, the moisture gradient is strong enough to select for larger size in both males and females in dryer regions. Larger body size supports more efficient water conservation, a pattern in accordance with the prediction that lifestyles of different species and their local habitats determine the relationship between body size and environment. In addition, larger females occur in regions with greater seasonality in precipitation, which may happen because larger females can afford greater reproductive output in a limited reproductive season.

Protein identification from the parotoid macrogland secretion of Duttaphrynus melanostictus

Background:

Bufonid parotoid macrogland secretion contains several low molecular mass molecules, such as alkaloids and steroids. Nevertheless, its protein content is poorly understood. Herein, we applied a sample preparation methodology that allows the analysis of viscous matrices in order to examine its proteins.

Methods:

Duttaphrynus melanostictus parotoid macrogland secretion was submitted to ion-exchange batch sample preparation, yielding two fractions: salt-displaced fraction and acid-displaced fraction. Each sample was then fractionated by anionic-exchange chromatography, followed by in-solution proteomic analysis.

Results:

Forty-two proteins could be identified, such as acyl-CoA-binding protein, alcohol dehydrogenase, calmodulin, galectin and histone. Moreover, de novo analyses yielded 153 peptides, whereas BLAST analyses corroborated some of the proteomic-identified proteins. Furthermore, the de novo peptide analyses indicate the presence of proteins related to apoptosis, cellular structure, catalysis and transport processes.

Conclusions:

Proper sample preparation allowed the proteomic and de novo identification of different proteins in the D. melanostictus parotoid macrogland secretion. These results may increase the knowledge about the universe of molecules that compose amphibian skin secretion, as well as to understand their biological/physiological role in the granular gland.

Description of a New Species of Rhabdias Stiles and Hassall, 1905 (Nematoda, Rhabdiasidae) in Duttaphrynus melanostictus (Schneider, 1899) from West Bengal, India

AIMS

The purpose of this article is to describe a new species of Rhabdias Stiles and Hassall, 1905 from West Bengal, India. Rhabdias bengalensis sp. nov. (Nematoda, Rhabdiasidae) recovered from the lungs of Asian common toad, Duttaphrynus melanostictus (Schneider, 1899), collected from Illambazar town, Birbhum district of West Bengal, India.

METHODS

The collected nematode specimens were clean by shaking them in 0.67% NaCl solution and were killed and fixed in steaming 70% alcohol; lactophenol was used as a mounting medium for light microscopic examination. The lactophenol treated specimens after examination were directly transferred to 70% alcohol and could be stored satisfactorily.

RESULTS

The new species is named as, R. bengalensis sp. nov. (Nematoda, Rhabdiasidae), in reference to its locality of collection, West Bengal, India. The worms are small [(2.84-2.96 mm) in length], anterior end somewhat truncated and posterior end tapering. R. bengalensis sp. nov. is characterised by rounded mouth without lips, inflated cuticle, cup-shaped buccal capsule, pre-equatorial vulva and a conical tail.

CONCLUSION

The present nematodes, thus, appear to be new in the field of science and name R. bengalensis sp. nov. is proposed for them. R. bengalensis sp. nov. represents 17th species described from oriental region and the 10th species from India.

Effects of the insecticide chlorpyrifos, on hatching, mortality and morphology of Duttaphrynus melanostictus embryos

In an attempt to assess the effects of chlorpyrifos [O,O-diethyl O-(3,5,6-trichloropyridin-2-yl) phosphorothioate], the second largest selling insecticide in India, studies were made with reference to some non-target organisms. The present study was undertaken to evaluate the effects in the embryos of Duttaphrynus melanostictus caused by the commercial formulations of chlorpyrifos (Tricel, chlorpyrifos, 20% EC). The LC₅₀ value for Duttaphrynus melanostictus embryos after 48 h (h) of treatment with chlorpyrifos was found to be 57.525 ppm. The mortality of the embryo was significantly affected by different concentrations of chlorpyrifos when compared with the control groups. An increase in concentration of chlorpyrifos resulted in the simultaneous decrease of the hatching percentage and an increase in the morphological abnormalities such as compression of the embryo, reduced body size and curling of tail.

Sexual dimorphism in baseline urinary corticosterone metabolites and their association with body-condition indices in a peri-urban population of the common Asian toad (Duttaphrynus melanostictus)

Field endocrinology research through the quantification of glucocorticoids or stress hormones in free-living wildlife is crucial for assessing their physiological responses towards pervasive environmental changes. Urinary corticosterone metabolite (UCM) enzyme-immunoassay (EIA) has been validated for numerous amphibian species as a non-invasive measure of physiological stress. Body-condition indices (BCIs) have also been widely used in amphibians as an indirect measure of animal health. Field endocrinology research on amphibian species in Asia is limited. In this study, we validated a UCM EIA in a peri-urban sub-population of the common Asian toad (Duttaphrynus melanostictus) in Pune, Maharashtra, India. We determined the baseline levels of UCMs in male (n=39) and female (n=19) toads. Secondly, we used a standard capture handling protocol to quantify changes in UCMs during short-term captivity. We also determined BCIs in the male and female toads using Fulton's index (K) and residual condition index (RCI). The results showed that mean baseline levels of UCMs were significantly higher in male toads than in females. There was no significant change in mean levels of UCMs of males and females between capture and captivity (0-12h). This highlights plausible habituation of the species to the peri-urban environment. Associations between UCMs with BCIs (K and R) were positive in male toads but negative in females. In conclusion, our UCMs EIA can be applied with BCIs to assess health of the Asian toads. We also suggest that direct fitness parameters such as sperm and oocyte quality, reproductive ecology and immunocompetence measurements should be applied in combination with these conservation physiology tools to quantify the fitness consequences of pervasive environmental changes on native amphibians.