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1.
Glob Chang Biol ; 26(5): 2829-2840, 2020 05.
Artigo em Inglês | MEDLINE | ID: mdl-32034982

RESUMO

Invasive vertebrates are frequently reported to have catastrophic effects on the populations of species which they directly impact. It follows then, that if invaders exert strong suppressive effects on some species then other species will indirectly benefit due to ecological release from interactions with directly impacted species. However, evidence that invasive vertebrates trigger such trophic cascades and alter community structure in terrestrial ecosystems remains rare. Here, we ask how the cane toad, a vertebrate invader that is toxic to many of Australia's vertebrate predators, influences lizard assemblages in a semi-arid rangeland. In our study area, the density of cane toads is influenced by the availability of water accessible to toads. We compared an index of the abundance of sand goannas, a large predatory lizard that is susceptible to poisoning by cane toads and the abundances of four lizard families preyed upon by goannas (skinks, pygopods, agamid lizards and geckos) in areas where cane toads were common or rare. Consistent with the idea that suppression of sand goannas by cane toads initiates a trophic cascade, goanna activity was lower and small lizards were more abundant where toads were common. The hypothesis that suppression of sand goannas by cane toads triggers a trophic cascade was further supported by our findings that small terrestrial lizards that are frequently preyed upon by goannas were more affected by toad abundance than arboreal geckos, which are rarely consumed by goannas. Furthermore, the abundance of at least one genus of terrestrial skinks benefitted from allogenic ecosystem engineering by goannas where toads were rare. Overall, our study provides evidence that the invasion of ecosystems by non-native species can have important effects on the structure and integrity of native communities extending beyond their often most obvious and frequently documented direct ecological effects.


Assuntos
Ecossistema , Lagartos , Animais , Austrália , Bufo marinus , Espécies Introduzidas
2.
Mol Phylogenet Evol ; 145: 106723, 2020 04.
Artigo em Inglês | MEDLINE | ID: mdl-31891757

RESUMO

The high levels of Neotropical biodiversity are commonly associated with the intense Neogene-Quaternary geological events and climate dynamics. Here, we investigate the evolutionary history of two species of Neotropical closely related amphibians (R. horribilis and R. marina). We combine published data with new mitochondrial DNA sequences and multiple nuclear markers, including 12 microsatellites. The phylogenetic analyses showed support for grouping the samples in two main clades; R. horribilis (Central America and Mexico) and R. marina (South America east of the Andes). However, the phylogenetic inferences also show an evident mito-nuclear discordance. We use Approximate Bayesian Computation (ABC) to test the role of different events in the diversification between the two groups recovered. We found that both species were affected primarily by a recent Pleistocene divergence, which was similar to the divergence estimate revealed by the Isolation-with-Migration model, under persistent bidirectional gene flow through time. We provide the first evidence that R. horribilis is differentiated from the South American R. marina at the nuclear level supporting the taxonomic status of R. horribilis, which has been controversial for more than a century.


Assuntos
Bufo marinus/classificação , Animais , Teorema de Bayes , Evolução Biológica , Bufo marinus/genética , América Central , Citocromos b/química , Citocromos b/classificação , Citocromos b/genética , DNA Mitocondrial/genética , Fluxo Gênico , Variação Genética , Repetições de Microssatélites/genética , Filogenia , Filogeografia , Proteínas Ribossômicas/química , Proteínas Ribossômicas/classificação , Proteínas Ribossômicas/genética , América do Sul
3.
J Chem Ecol ; 45(10): 838-848, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31677136

RESUMO

Many aquatic organisms detect and avoid damage-released cues from conspecifics, but the chemical basis of such responses, and the effects of prolonged exposure to such cues, remain poorly understood. Injured tadpoles of the cane toad (Rhinella marina) produce chemical cues that induce avoidance by conspecific tadpoles; and chronic exposure to those cues decreases rates of tadpole survival and growth, and reduces body size at metamorphosis. Such effects suggest that we might be able to use the cane toads' alarm cue for biocontrol of invasive populations in Australia. In the present study, we examined behavioral and ecological effects of compounds that are present in cane toad tadpoles and thus, might trigger avoidance of crushed conspecifics. Four chemicals (L-Arg, L-Leu-L-Leu-OH, L-Leu-L-Ile-OH and suberic acid) induced behavioral avoidance in toad tadpoles at some (but not all) dosage levels, so we then exposed toad larvae to these chemicals over the entire period of larval development. Larval survival and size at metamorphosis were decreased by chronic exposure to crushed conspecifics (consistent with earlier studies), but not by exposure to any of the four chemicals. Indeed, L-Arg increased body size at metamorphosis. We conclude that the behavioral response to crushed conspecifics by cane toad tadpoles can be elicited by a variety of chemical cues, but that consistent exposure to these individual chemical cues does not affect tadpole viability or developmental trajectory. The optimal behavioral tactic of a tadpole may be to flee if it encounters even a single chemical cue likely to have come from an injured conspecific (indicative of predation risk), whereas the continuing presence of that single chemical (but no others) provides a less reliable signal of predation risk. Our data are consistent with results from studies on fish, that suggest a role for multiple chemicals in initiating alarm responses to damage-released cues.


Assuntos
Arginina/farmacologia , Aprendizagem da Esquiva/efeitos dos fármacos , Bufo marinus/fisiologia , Caprilatos/farmacologia , Ácidos Dicarboxílicos/farmacologia , Oligopeptídeos/farmacologia , Animais , Tamanho Corporal/efeitos dos fármacos , Bufo marinus/crescimento & desenvolvimento , Larva/crescimento & desenvolvimento , Larva/fisiologia , Metamorfose Biológica/efeitos dos fármacos , Oligopeptídeos/química
4.
Ecohealth ; 16(4): 682-693, 2019 12.
Artigo em Inglês | MEDLINE | ID: mdl-31628632

RESUMO

Anthropogenic factors, including the spread of endocrine-disrupting chemicals, have been linked to alterations in the reproductive physiology, morphology, and behavior of wildlife. Few studies of endocrine disruption, however, focus on secondary sexual traits that affect mating signals, despite their importance for reproductive success. The larynx of many anurans (frogs and toads), for example, is larger in males than in females and is crucial for producing mating calls. We aim to determine if wild populations of cane toads (Rhinella marina) near sugarcane fields in Florida have demasculinized larynges when compared to populations near urban areas. We find evidence of demasculinization in both primary and secondary sexual traits in male toads living near sugarcane. Relative to body size, the laryngeal mass, vocal cord length, and dilator muscle width are all reduced in males from sugarcane regions compared to their urban counterparts. Strong correlations between primary and secondary male sexual traits indicate that demasculinization occurs in concert both within and across diverse organs, including the testes, larynx, and skin. Our results show that anurans near sugarcane fields have demasculinized reproductive systems, that this disruption extends to secondary sexual traits like the larynx, and that it is likely due to anthropogenic causes.


Assuntos
Anuros/fisiologia , Bufo marinus/fisiologia , Disruptores Endócrinos/efeitos adversos , Laringe/efeitos dos fármacos , Comportamento Sexual Animal/efeitos dos fármacos , Comportamento Sexual Animal/fisiologia , Prega Vocal/efeitos dos fármacos , Animais , Feminino , Florida , Masculino , Fatores Sexuais
5.
Vet Pathol ; 56(6): 921-931, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31526112

RESUMO

Infection due to Entamoeba spp. is known to cause serious disease in primates (Entamoeba histolytica) and snakes (Entamoeba invadens), but there are no detailed descriptions of the pathology associated with Entamoeba spp. infection in amphibians. In 2014, an outbreak of entamoebiasis associated with a novel species of Entamoeba induced clinical illness and poor body condition in free-ranging cane toads in Australia's Northern Territory. Here, we describe the gross pathology, histology, and clinical pathology linked to the outbreak. The study compared 25 toads with invasive entamoebiasis, defined as histologically visible amoebas within tissue, and 12 toads without invasive entamoebiasis. Grossly, affected toads had mild to marked congestion of colonic serosal vasculature, with variable thickening of the intestinal wall and serosanguineous to hemorrhagic colonic content. Histologically, invasive entamoebiasis manifested primarily as moderate to severe, variably hyperplastic to ulcerative colitis. The small intestine was affected in 10 of 25 toads, and 5 of 25 toads also had gastric lesions. Amoebas consistent in morphology with Entamoeba sp. were commonly intermingled with mucosal epithelium, frequently along the basement membrane, with deeper invasion into the superficial lamina propria in only 5 toads. Toads with invasive entamoebiasis had neutrophilia, monocytosis, and lymphopenia, and thus elevated neutrophil to lymphocyte ratios, suggestive of an inflammatory and/or stress leukogram.


Assuntos
Bufo marinus/parasitologia , Surtos de Doenças/veterinária , Entamebíase/veterinária , Animais , Austrália/epidemiologia , Entamebíase/epidemiologia , Entamebíase/parasitologia , Entamebíase/patologia , Feminino , Masculino
6.
Emerg Infect Dis ; 25(9): 1770-1771, 2019 09.
Artigo em Inglês | MEDLINE | ID: mdl-31441753

RESUMO

Cane toads, an invasive species in Australia, are resistant to fungal pathogens affecting frogs worldwide (Batrachochytrium dendrobatidis). From toad skin swabs, we detected higher proportions of bacteria with antifungal properties in Queensland, where toad and pathogen distributions overlap, than in other sites. This finding suggests that site-specific pathogen pressures help shape skin microbial communities.


Assuntos
Antifúngicos/farmacologia , Bactérias/isolamento & purificação , Bufo marinus/microbiologia , Quitridiomicetos/efeitos dos fármacos , Pele/microbiologia , Animais , Espécies Introduzidas , Queensland
7.
Biol Lett ; 15(8): 20190462, 2019 08 30.
Artigo em Inglês | MEDLINE | ID: mdl-31409244

RESUMO

A male cane toad (Rhinella marina) that mistakenly clasps another male (rather than a female) in a sexual embrace (amplexus) can be induced to dismount by a male-specific 'release call'. Although that sex-identifying system can benefit both males in that interaction, our standardized tests showed that one-third of male cane toads did not emit release calls when grasped. Most of those silent males were small, had small testes relative to body mass, and had poorly developed secondary sexual characteristics. If emitting a release call is costly (e.g. by attracting predators), a non-reproductive male may benefit by remaining silent; other cues (such as skin rugosity) will soon induce the amplexing male to dismount, and the 'opportunity cost' to being amplexed (inability to search for and clasp a female) is minimal for non-reproductive males. Hence, male toads may inform other males about their sexual identity only when it is beneficial to do so.


Assuntos
Espécies Introduzidas , Comportamento Sexual , Animais , Bufo marinus , Feminino , Masculino
8.
Biol Lett ; 15(7): 20190339, 2019 07 26.
Artigo em Inglês | MEDLINE | ID: mdl-31337295

RESUMO

As a colonizing species expands its range, individuals at the invasion front experience different evolutionary pressures than do those at the range-core. For example, low densities at the edge of the range mean that males should rarely experience intense sperm competition from rivals; and investment into reproduction may trade-off with adaptations for more rapid dispersal. Both of these processes are predicted to favour a reduction in testis size at the invasion front. To explore effects of invasion stage in Australian cane toads (Rhinella marina), we collected and dissected 214 adult males from three regions: one in the species' range-core (northeastern Australia), and two from invasion fronts (one in northwestern Australia and one in southeastern Australia). Despite the brief duration of separation between toads in these areas (approx. 85 years), testis masses averaged greater than 30% higher (as a proportion of body mass) in range-core males than in conspecifics sampled from either vanguard of the invasion. Previous work has documented low reproductive frequencies in female cane toads at the invasion front also, consistent with the hypothesis that evolutionary and ecological pressures unleashed by an invasion can favour relatively low resource allocation to reproduction in both sexes.


Assuntos
Espécies Introduzidas , Testículo , Animais , Austrália , Evolução Biológica , Bufo marinus , Feminino , Masculino
9.
Am J Physiol Regul Integr Comp Physiol ; 317(3): R379-R385, 2019 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-31242019

RESUMO

In this study, myography was used to determine the effect of arterial size on nitric oxide (NO) vasodilatory mechanisms in the hindlimb vasculature of the toad Rhinella marina. Immunohistochemical analysis showed NO synthase (NOS) 1 immunoreactivity in perivascular nitrergic nerves in the iliac and sciatic arteries. Furthermore, NOS3 immunoreactivity was observed in the vascular smooth muscle of the sciatic artery, but not the endothelium. Acetylcholine (ACh) was used to facilitate intracellular Ca2+ signaling to activate vasodilatory pathways in the arteries. In the iliac artery, ACh-mediated vasodilation was abolished by blockade of the soluble guanylate cyclase pathway with the soluble guanylate cyclase inhibitor ODQ (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, 10-5 M) and blockade of the prostaglandin signaling pathway with indomethacin (10-5 M). Furthermore, disruption of the endothelium had no effect on the ACh-mediated vasodilation in the iliac artery, and generic inhibition of NOS with Nω-nitro-l-arginine (3 × 10-4 M) significantly inhibited the vasodilation, indicating NO signaling. In contrast to the iliac artery, ACh-mediated vasodilation of the sciatic artery had a significant endothelium-dependent component. Interestingly, the vasodilation was not significantly affected by Nω-nitro-l-arginine, but it was significantly inhibited by the specific NOS1 inhibitor N5-(1-imino-3-butenyl)-l-ornithine (vinyl-l-NIO, 10-4 M). ODQ mostly inhibited the ACh-mediated vasodilation. In addition, indomethacin also significantly inhibited the ACh-mediated vasodilation, indicating a role for prostaglandins in the sciatic artery. This study found that the mechanisms of vasodilation in the hindlimb vasculature of R. marina vary with vessel size and that the endothelium is involved in vasodilation in the smaller sciatic artery.


Assuntos
Artérias/fisiologia , Membro Posterior/irrigação sanguínea , Vasodilatação/fisiologia , Animais , Artérias/anatomia & histologia , Bufo marinus , Feminino , Humanos , Imuno-Histoquímica , Masculino , Óxido Nítrico Sintase/química , Óxido Nítrico Sintase/metabolismo , Nitroarginina/farmacologia , Oxidiazóis , Quinoxalinas , Transdução de Sinais
10.
Biomed Res Int ; 2019: 2492315, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31214612

RESUMO

Skin secretions of frogs have a high chemical complexity. They have diverse types of biomolecules, such as proteins, peptides, biogenic amines, and alkaloids. These compounds protect amphibians' skin against growth of bacteria, fungi, and protozoa and participate in defense system against attack from predators. Therewith, this work performed biochemical and biological profile of macroglands parotoid secretion from cane toad. For poison analysis, we performed molecular exclusion and reverse phase chromatography, electrophoresis, and mass spectrometry. Antimicrobial, antiplasmodial, leishmanicidal, cytotoxicity, genotoxicity, and inflammatory activity of crude and/or fractions of R. marina secretion were also evaluated. Fractionation prior to filtration from poison showed separation of low mass content (steroids and alkaloids) and high molecular mass (protein). Material below 10 kDa two steroids, marinobufagin and desacetylcinobufagin, was detected. Crude extract and fractions were active against Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Plasmodium falciparum, Leishmania guyanensis, and Leishmania braziliensis. Crude extract was also active against cancer cells although it was not cytotoxic for normal cells. This extract did not show significant DNA damage but it showed an important inflammatory effect in vivo. The information obtained in this work contributes to the understanding of the constituents of R. marina secretion as well as the bioactive potential of these molecules.


Assuntos
Antibacterianos , Bufanolídeos , Glândula Parótida/metabolismo , Pseudomonas aeruginosa/crescimento & desenvolvimento , Pele/metabolismo , Staphylococcus aureus/crescimento & desenvolvimento , Animais , Antibacterianos/química , Antibacterianos/metabolismo , Antibacterianos/farmacologia , Bufanolídeos/química , Bufanolídeos/metabolismo , Bufanolídeos/farmacologia , Bufo marinus
11.
Proc Biol Sci ; 286(1902): 20190867, 2019 05 15.
Artigo em Inglês | MEDLINE | ID: mdl-31088275

RESUMO

Many animals capable of deploying chemical defences are reluctant to use them, suggesting that synthesis of toxins imposes a substantial cost. Typically, such costs have been quantified by measuring the elevation in metabolic rate induced by toxin depletion (i.e. during replenishment of toxin stores). More generally, we might expect that toxin depletion will induce shifts in a broad suite of fitness-relevant traits. In cane toads ( Rhinella marina), toxic compounds that protect against predators and pathogens are stored in large parotoid (shoulder) glands. We used correlational and experimental approaches in field and laboratory settings to investigate impacts of toxin depletion on growth rate and behaviour in cane toads. In free-ranging toads, larger toxin stores were associated with smaller gonads and livers, suggesting energetic trade-offs between toxin production and both reproduction and energy metabolism. Experimental removal of toxin (by manually squeezing parotoid glands) reduced rates of growth in body mass in both captive and free-ranging toads. Radio tracking demonstrated that de-toxined toads dispersed more slowly than did control toads. Given that toxin stores in cane toads take several months to fully replenish, deploying toxin to repel a predator may impose a substantial cost, explaining why toads use toxin only as a final line of defence.


Assuntos
Bufo marinus/fisiologia , Metabolismo Energético , Reprodução , Toxinas Biológicas/fisiologia , Animais , Bufo marinus/crescimento & desenvolvimento , Glândulas Exócrinas/química
12.
J Wildl Dis ; 55(3): 668-672, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-30768916

RESUMO

Ranaviruses and the fungus Batrachochytrium dendrobatidis are globally important agents of emerging infectious amphibian diseases. Amphibians on Oahu, the Hawaiian Island with the greatest potential for disease introduction through the movement of goods and people, have never been surveyed for ranaviruses or B. dendrobatidis. We surveyed all five species of frogs on Oahu, Hawaii, US for these pathogens. Of 325 individuals sampled from six sites, none were positive for ranavirus. However, we found B. dendrobatidis in a total of four individuals of three species, the cane toad (Bufo marinus), the American bullfrog (Rana catesbeiana), and the greenhouse frog (Eleutherodactylus planirostris), but not in the green and black poison dart frog (Dendrobates auratus) or the Japanese wrinkled frog (Rana rugosa). The apparent lack of ranavirus and low prevalence of B. dendrobatidis are noteworthy given how widespread these pathogens are in terms of both global distribution and host range. Surveillance should continue to document any changes in B. dendrobatidis prevalence or the arrival of ranaviruses in Hawaii.


Assuntos
Bufo marinus/microbiologia , Quitridiomicetos/isolamento & purificação , Espécies Introduzidas , Micoses/veterinária , Ranavirus/isolamento & purificação , Ranidae/microbiologia , Animais , Infecções por Vírus de DNA/epidemiologia , Infecções por Vírus de DNA/veterinária , Infecções por Vírus de DNA/virologia , Hawaii/epidemiologia , Micoses/epidemiologia , Micoses/microbiologia
13.
Sci Rep ; 9(1): 18, 2019 01 10.
Artigo em Inglês | MEDLINE | ID: mdl-30631140

RESUMO

Amphibian oocytes have been extensively used for heterologous expression of membrane proteins for studying their biochemical and biophysical properties. So far, Xenopus laevis is the main amphibian used as oocytes source to express aquaglyceroporins in order to assess water and solutes permeability. However, this well-established amphibian model represents a threat to the biodiversity in many countries, especially in those from tropical regions. For that reason, the import of Xenopus laevis is subjected to strict control, which essentially has restricted its use in these regions. Therefore, a wider variety of expression systems for aquaglyceroporins is needed. Rhinella marina is extensively distributed in the Americas and its native range spreads from South America to Texas, US. Here we report the use of Rhinella marina oocytes as an alternative expression system for aquaglyceroporins and demonstrated its suitability to determine the permeability to water and non-ionic solutes. Rhinella marina oocytes were able to functionally express channels from human and the protozoan pathogen Trypanosoma brucei, two very distant organisms on the evolutionary scale. Permeability values obtained from Rhinella marina oocytes expressing members of aquaporin family were similar and comparable to those values reported in the literature for the same channels expressed in Xenopus laevis oocytes.


Assuntos
Aquagliceroporinas/biossíntese , Bufo marinus , Expressão Gênica , Oócitos , Proteínas Recombinantes/biossíntese , Trypanosoma brucei brucei/enzimologia , Animais , Aquagliceroporinas/genética , Proteínas Recombinantes/genética , Trypanosoma brucei brucei/genética
15.
J Sep Sci ; 42(7): 1384-1392, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30667156

RESUMO

Marinobufagenin is a bufadienolide compound detected mainly in skin and parotoid gland secretions of Rhinella marina (L.) toad. Bufadienolides regulate the Na+ /K+ -ATPase pump by inhibiting the cardiotonic steroid dependent-site and act as cardiac inotropes with vasoconstrictive properties. Marinobufagenin and other bufadienolides, such as telocinobufagin and bufalin, are thought to be found endogenously in mammals in salt-sensitive hypertensive states such as essential hypertension, congestive heart-failure, and preeclampsia. The role of marinobufagenin as antimicrobial agent and its cytotoxic potential have also been recognized. The particular interest around marinobufagenin prompts us to consider the Rhinella marina toad venom as a possible source for molecules with pharmacological and/or diagnostic potential. In this article, two different approaches of extraction and purification of marinobufagenin from Rhinella marina (L.) venom are studied: (i) Preparative thin-layer chromatography combined to mass spectrometry and/or ultraviolet detection and (ii) solid-phase extraction coupled with fractionation on high-performance liquid chromatography. Different chromatographic conditions are tested for each approach. The solid-phase extraction combined with high-performance liquid chromatography fractionation approach was preferred as it offered a greater yield, was less time-consuming and allowed us to selectively isolate marinobufagenin. Both protocols aim to provide efficient and convenient methods for toad venom extraction, based on an easily automatable and systematized strategy.


Assuntos
Bufanolídeos/isolamento & purificação , Glândula Parótida/química , Animais , Bufanolídeos/química , Bufo marinus , Conformação Molecular
16.
Sci Rep ; 9(1): 230, 2019 01 18.
Artigo em Inglês | MEDLINE | ID: mdl-30659222

RESUMO

Plastic responses may allow individuals to survive and reproduce in novel environments, and can facilitate the establishment of viable populations. But can novel environments reveal plasticity by causing a shift in a behavior as fundamental and conspicuous as daily activity? We studied daily activity times near the invasion front of the cane toad (Rhinella marina), an invasive species that has colonized much of northern Australia. Cane toads in Australia are nocturnal, probably because diurnal activity would subject them to intolerably hot and dry conditions in the tropical savannah during the dry season. Our study can demonstrate, however, that upon reaching novel environments some toad populations became diurnal. Sandstone gorges offered cane toads novel, deeply shaded habitat. Gorges with an east-west axis (day-long northern shadow), narrow gorges and narrow sections of gorges contained toads that were primarily diurnal, while gorges with a north-south axis, wide gorges and wide sections of gorges contained mainly nocturnal toads. For example, remote camera data (1314 observations of toad activity times over 789 trap days) revealed strictly nocturnal activity at four 'exposed' sites (99% of 144 observations over 179 days), compared to mostly diurnal activity at a 'shaded' site (78% of 254 observations). Visual encounter surveys confirmed that diurnal activity occurred exclusively at shaded sites, while most nocturnal activity occurred at exposed sites. The close proximity of diurnal and nocturnal toads (4-7 km) provided compelling evidence for the abovementioned physical factors as the proximate cause of the behavioral dichotomy, and for a novel (deeply shaded gorges) environment causing the shift to diurnal activity.


Assuntos
Adaptação Fisiológica , Comportamento Animal , Bufo marinus/fisiologia , Ritmo Circadiano , Ecossistema , Animais , Austrália , Espécies Introduzidas
17.
Oecologia ; 189(2): 307-316, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30535812

RESUMO

The invasion of habitats with novel environmental challenges may require physiological tolerances not seen in conspecifics from the native range. We used a combination of field and laboratory-based experiments to assess physiological tolerance to limited water access at four sites distributed across the historical invasion path of cane toads (Rhinella marina) in Australia that, from east to west, alternated between mesic and seasonally xeric habitats. Toads from all locations were well hydrated at the time of capture. However, experimental dehydration caused greater mass loss, higher plasma osmolality, and inhibition of lytic ability in toads from xeric compared to mesic locations. These results suggest somewhat surprisingly that toads from xeric environments are physiologically more vulnerable to water loss. In contrast, bactericidal ability was not sensitive to hydric state and was greater in toads from eastern (long-colonized) areas. Similar patterns in lytic ability in hydrated toads and agglutination ability in wild toads suggest that toads along the invasion front face a tradeoff between enhanced dispersal ability and physiological responses to dehydration. The ability of this invasive species to spread into drier environments may be underpinned by a combination of phenotypic plasticity and evolved (heritable) traits.


Assuntos
Espécies Introduzidas , Água , Animais , Austrália , Bufo marinus , Ecossistema
18.
Toxicol Lett ; 302: 1-6, 2019 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-30502385

RESUMO

Due to their potent coagulotoxicity, Australian elapid venoms are unique relative to non-Australian members of the Elapidae snake family. The majority of Australian elapids possess potent procoagulant venom, while only a few species have been identified as possessing anticoagulant venoms. The majority of research to-date has concentrated on large species with range distributions overlapping major city centres, such as brown snakes (Pseudonaja spp.) and taipans (Oxyuranus spp.). We investigated the venom from the poorly studied genus Denisonia and documented anticoagulant activities that were differentially potent on amphibian, avian, and human plasmas. Both species were potently anticoagulant upon amphibian plasma, consistent with these snakes preying upon frogs as their primary food source. While D. devisi was only relatively weakly active on avian and human plasma, D. maculata was potently anticoagulant to amphibian, avian, and human plasma. The mechanism of anticoagulant action was determined to be the inhibition of prothrombin activation by Factor Xa by blocking the formation of the prothrombinase complex. Fractionation of D. maculata venom followed by MS sequencing revealed that the toxins responsible were Group I phospholipase A2. As no antivenom is produced for this species or its near relatives, we examined the ability of Seqirus Australian snake polyvalent antivenom to neutralise the anticoagulant effects, with this antivenom shown to be effective. These results contribute to the body of knowledge regarding adaptive evolution of venom, revealing a unique taxon-specific anticoagulant effect for D. devisi venom. These results also reveal the potential effects and mechanisms behind envenomation by the potently acting D. maculata venom on human plasma, while the discovery of the efficacy of an available antivenom provides information crucial to the design of snakebite management strategies.


Assuntos
Antivenenos/farmacologia , Coagulação Sanguínea/efeitos dos fármacos , Venenos Elapídicos/metabolismo , Elapidae/metabolismo , Fator V/antagonistas & inibidores , Inibidores do Fator Xa/farmacologia , Mordeduras de Serpentes/tratamento farmacológico , Animais , Antivenenos/metabolismo , Bufo marinus/sangue , Galinhas/sangue , Relação Dose-Resposta a Droga , Fator V/metabolismo , Fator Xa/metabolismo , Inibidores do Fator Xa/metabolismo , Humanos , Mordeduras de Serpentes/sangue , Especificidade da Espécie
19.
Conserv Biol ; 33(1): 112-121, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-29896894

RESUMO

Targeted gene flow is an emerging conservation strategy. It involves translocating individuals with favorable genes to areas where they will have a conservation benefit. The applications for targeted gene flow are wide-ranging but include preadapting native species to the arrival of invasive species. The endangered carnivorous marsupial, the northern quoll (Dasyurus hallucatus), has declined rapidly since the introduction of the cane toad (Rhinella marina), which fatally poisons quolls that attack them. There are, however, a few remaining toad-invaded quoll populations in which the quolls survive because they know not to eat cane toads. It is this toad-smart behavior we hope to promote through targeted gene flow. For targeted gene flow to be feasible, however, toad-smart behavior must have a genetic basis. To assess this, we used a common garden experiment, comparing offspring from toad-exposed and toad-naïve parents raised in identical environments, to determine whether toad-smart behavior is heritable. Offspring from toad-exposed populations were substantially less likely to eat toads than those with toad-naïve parents. Hybrid offspring showed similar responses to quolls with 2 toad-exposed parents, indicating the trait may be dominant. Together, these results suggest a heritable trait and rapid adaptive response in a small number of toad-exposed populations. Although questions remain about outbreeding depression, our results are encouraging for targeted gene flow. It should be possible to introduce toad-smart behavior into soon to be affected quoll populations.


Assuntos
Fluxo Gênico , Marsupiais , Animais , Bufo marinus , Conservação dos Recursos Naturais , Espécies Introduzidas
20.
Environ Toxicol Chem ; 38(2): 361-367, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30370675

RESUMO

Owing to the dynamic interaction between frog skin and the environment, xenobiotics in frog habitats are of particular concern, and knowledge of percutaneous absorption in frog skin is necessary for risk-mitigation purposes. Baseline transdermal kinetics in adult aquatic and arboreal frog species have recently been reported; however, there is little information regarding absorption kinetics in adult terrestrial species. The present study investigated the in vitro absorption kinetics of 3 model chemicals-caffeine, benzoic acid, and ibuprofen-through different skin regions in the terrestrial toad Rhinella marina. Caffeine flux was consistently higher than that of the other 2 chemicals (p < 0.001), whereas the fluxes of the moderately and highly lipophilic chemicals (benzoic acid and ibuprofen) were similar, regardless of skin region. When considering individual chemicals, caffeine demonstrated increased flux through the ventral pelvic skin compared with the ventral thoracic or dorsal skin regions. Flux did not differ between skin regions for either benzoic acid or ibuprofen. These findings have implications for management of environmental contamination in frog habitats, as many environmental xenobiotics are of moderate to high lipophilicity and would be expected to be equally absorbed from all skin surfaces in terrestrial toads. Environ Toxicol Chem 2019;38:361-367. © 2018 SETAC.


Assuntos
Bufo marinus/metabolismo , Absorção Cutânea , Pele/metabolismo , Xenobióticos/farmacocinética , Animais , Ácido Benzoico/química , Ácido Benzoico/farmacocinética , Cafeína/química , Cafeína/farmacocinética , Ecossistema , Ibuprofeno/química , Ibuprofeno/farmacocinética , Técnicas In Vitro , Cinética , Masculino , Fatores de Tempo , Xenobióticos/química
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