An uptake system for dietary alkaloids in poison frogs (Dendrobatidae)
TL;DR: The skin of poison frogs contains a wide variety of alkaloids that presumably serve a defensive role, and an alkaloid uptake system provides a means of maintaining skin alkaloidal levels and suggests that some if not all such 'dendrobatid alkal steroids' may have a dietary origin.
About: This article is published in Toxicon.The article was published on 1994-06-01. It has received 141 citations till now. The article focuses on the topics: Phyllobates & Colostethus.
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TL;DR: A new, monophyletic taxonomy for dendrobatids is proposed, recognizing the inclusive clade as a superfamily (Dendrobatoidea) composed of two families (one of which is new), six subfamilies (three new), and 16 genera (four new).
Abstract: The known diversity of dart-poison frog species has grown from 70 in the 1960s to 247 at present, with no sign that the discovery of new species will wane in the foreseeable future. Although this growth in knowledge of the diversity of this group has been accompanied by detailed investigations of many aspects of the biology of dendrobatids, their phylogenetic relationships remain poorly understood. This study was designed to test hypotheses of dendrobatid diversification by combining new and prior genotypic and phenotypic evidence in a total evidence analysis. DNA sequences were sampled for five mitochondrial and six nuclear loci (approximately 6,100 base pairs [bp]; x¯ = 3,740 bp per terminal; total dataset composed of approximately 1.55 million bp), and 174 phenotypic characters were scored from adult and larval morphology, alkaloid profiles, and behavior. These data were combined with relevant published DNA sequences. Ingroup sampling targeted several previously unsampled species, including Ar...
577 citations
Cites background from "An uptake system for dietary alkalo..."
...The hydrophilic alkaloid tetrodotoxin has also been detected in one species of dendrobatid (Daly et al., 1994b), and it is unknown if its occurrence is of symbiotic or dietary origin....
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...It has become clear that some kind of sequestration mechanism is responsible for obtaining alkaloids from the diet and incorporating them into the skin (Daly et al., 1994a), but the details of the mechanism are unknown, as are the dietary sources of the vast majority of dendrobatid alkaloids....
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TL;DR: This review covers the isolation, structure determination, synthesis, chemical transformations and biological activity of indolizidine and quinolIZidine alkaloids.
281 citations
TL;DR: Using expanded taxon and character sampling and simulations, the phylogenetic correlation between the origins of toxicity and warning coloration is reexamined and it is found that diet specialization is linked with the evolution of aposematism.
Abstract: Aposematism is the association, in a prey organism, of the presence of a warning signal with unprofitability to predators. The origin of aposematism is puzzling, because of its predicted low probability of establishment in a population due to the prey's increased conspicuousness. Aposematism is a widespread trait in invertebrate taxa, but, in vertebrates, it is mostly evident in amphibians, reptiles, and fishes. Poison frogs (Dendrobatidae) are one of the most well known examples of the co-occurrence of warning coloration and toxicity. This monophyletic group of mostly diurnal leaf-litter Neotropical anurans has both toxic/colorful and palatable/cryptic species. Previous studies suggested a single origin of toxicity and warning coloration, dividing the family in two discrete groups of primitively cryptic and more derived aposematic frogs. Recent molecular phylogenetic analyses using mostly aposematic taxa supported this conclusion and proposed a single tandem origin of toxicity and conspicuous warning coloration. By using expanded taxon and character sampling, we reexamined the phylogenetic correlation between the origins of toxicity and warning coloration. At least four or five independent origins of aposematism have occurred within poison frogs; by using simulations, we rejected hypotheses of one, two, or three origins of aposematism (P < 0.002). We also found that diet specialization is linked with the evolution of aposematism. Specialization on prey, such as ants and termites, may have evolved independently at least two times.
261 citations
TL;DR: Comparative analysis of the evolutionary relationships among representative species of poison frogs indicated a significant correlation between the evolution of toxicity and coloration across this family, consistent with the hypothesis that coloration in this group is aposematic.
Abstract: The poison frogs (family Dendrobatidae) are terrestrial anuran amphibians displaying a wide range of coloration and toxicity. These frogs generally have been considered to be aposematic, but relatively little research has been carried out to test the predictions of this hypothesis. Here we use a comparative approach to test one prediction of the hypothesis of aposematism: that coloration will evolve in tandem with toxicity. Recently, we developed a phylogenetic hypothesis of the evolutionary relationships among representative species of poison frogs, using sequences from three regions of mitochondrial DNA. In our analysis, we use that DNAbased phylogeny and comparative analysis of independent contrasts to investigate the correlation between coloration and toxicity in the poison frog family (Dendrobatidae). Information on the toxicity of different species was obtained from the literature. Two different measures of the brightness and extent of coloration were used. (i) Twenty-four human observers were asked to rank different photos of each different species in the analysis in terms of contrast to a leaf-littered background. (ii) Color photos of each species were scanned into a computer and a computer program was used to obtain a measure of the contrast of the colors of each species relative to a leaf-littered background. Comparative analyses of the results were carried out with two different models of character evolution: gradual change, with branch lengths proportional to the amount of genetic change, and punctuational change, with all change being associated with speciation events. Comparative analysis using either method or model indicated a significant correlation between the evolution of toxicity and coloration across this family. These results are consistent with the hypothesis that coloration in this group is aposematic.
231 citations
01 Jan 2014
TL;DR: This chapter provides a general historical background, with definitions and information of free radicals, antioxidants and oxidative stress and examines how mild doses of stress can have stimulatory effects on organismal performance through hormetic mechanisms and that this may significantly relate to evolutionary fitness and to the ecology of species.
Abstract: The transition from a reducing to an oxidising chemistry in the atmosphere and oceans paved the way for the diversification of life. Oxygen expanded metabolic and biochemical capacities of organisms. Over the incipient stages of evolution of oxidative metabolism, organisms also needed to develop mechanisms to mitigate the toxic effects of oxygen derivatives, such as free radicals and nonradical reactive species. This chapter provides a general historical background, with definitions and information of free radicals, antioxidants and oxidative stress. This chapter also examines how mild doses of stress can have stimulatory effects on organismal performance through hormetic mechanisms and that this may significantly relate to evolutionary fitness and to the ecology of species. Finally, the chapter explains the concept of life-history trade-offs and highlights how the need to manage oxidative stress in an optimal way may be an important mechanism driving the outcome of many of these trade-offs. 1.1 The Great Oxidation Event: From a Reducing to an Oxidising World The planet Earth is approximately 4.5 billion years old. The atmosphere of the primeval Earth was quite different from what we observe nowadays. It was mildly reducing, with large proportions of methane, ammonia and hydrogen and a low concentration of oxygen (Schopf and Klein 1992; Sessions et al. 2009). Around 2.45 billion years ago, atmospheric oxygen rose suddenly in what is now termed the Great Oxidation Event (Sessions et al. 2009). A second significant increase in atmospheric oxygen occurred at around 600–800 million years ago and was accompanied by the oxygenation of the deep oceans and emergence of multicellular animals (Sessions et al. 2009). The increase in oxygen concentration in the atmosphere and oceans paved the way for the diversification of life (Fig. 1.1). D. Costantini, Oxidative Stress and Hormesis in Evolutionary Ecology and Physiology, DOI: 10.1007/978-3-642-54663-1_1, Springer-Verlag Berlin Heidelberg 2014 1 The transition from a reducing to an oxidising atmosphere was characterised by the evolution of metabolic networks of increasing complexity (Raymond and Segrè 2006). Adaptation to molecular oxygen has also likely taken place independently in species from diverse lineages, even if it is unclear whether it contributed to shaping taxonomical diversity (Raymond and Segrè 2006). Certainly, oxygen expanded metabolic and biochemical capacities of organisms. The stimulatory effect of oxygen on the evolution of metabolic networks was not cost-free. Beyond diversification of mechanisms using oxygen to produce energy, organisms also needed to evolve mechanisms to mitigate the toxic effects of oxygen derivatives, such as free radicals and non-radical reactive species. 1.2 Reactive Species, Antioxidants and Oxidative Stress 1.2.1 On the Nature of Free Radicals and Other Reactive Species The discovery of organic free radicals dates back to over a century ago, when the scientist Gomberg (1900) at the University of Michigan identified the triphenylmethyl The primeval Earth’s atmosphere was mildly reducing. Photochemical reactions between simple gas elements 2H2 + CO2 → H2CO + H2O Evolution of anaerobic bacteria H2S + CO2 → (H2CO)n + S Evolution of photosynthetic organisms H2O + CO2 → (H2CO)n + O2 Evolution of aerobic eukaryotes; aerobic pathways produce much more energy than anaerobic pathways O2 + (H2CO)n → H2O + CO2 Aerobic pathways generate oxygen free radicals and non-radical species. Hence, evolution of antioxidant mechanisms to cope with oxidative stress. Fig. 1.1 Sequence of main transitions in energetic metabolism induced by changes in atmosphere and ocean chemistry (see Falkowski 2006) 2 1 Historical and Contemporary Issues of Oxidative Stress
229 citations
References
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01 Jan 1991
TL;DR: In this paper, the total synthesis of amaryllidaceae alkaloids has been studied using radical cyclization reactions in total syntheses of naturally occurring indole alkaloid.
Abstract: Chapter headings. Carbon-13 and proton NMR shift assignments and physical constants of diterpenoid alkaloids. Supercritical fluid extraction of alkaloids. Recent advances in the total synthesis of amaryllidaceae alkaloids. Applications of radical cyclization reactions in total syntheses of naturally occurring indole alkaloids.
1,263 citations
TL;DR: Cutaneous granular glands are a shared character of adult amphibians, including caecilians, and are thought to be the source of most biologically active compounds in amphibian skin, which clearly prove the defensive value of these diverse metabolites.
360 citations
TL;DR: Three passerine species in the genus Pitohui, endemic to the New Guinea subregion, contain the steroidal alkaloid homobatrachotoxin, apparently as a chemical defense, suggesting that birds and frogs independently evolved this class of alkaloids.
Abstract: Three passerine species in the genus Pitohui, endemic to the New Guinea subregion, contain the steroidal alkaloid homobatrachotoxin, apparently as a chemical defense. Toxin concentrations varied among species but were always highest in the skin and feathers. Homobatrachotoxin is a member of a class of compounds collectively called batrachotoxins that were previously considered to be restricted to neotropical poison-dart frogs of the genus Phyllobates. The occurrence of homobatrachotoxin in pitohuis suggests that birds and frogs independently evolved this class of alkaloids.
205 citations
TL;DR: A wide range of biological activity of the dendrobatid alkaloids is indicated by injection of unresolved alkaloid fractions into white mice: extracts from different species of Dendrobates produce reactions as diverse as Straub tail, penile erection, prostration, convulsions and salivation.
155 citations
TL;DR: The regulatory site controlling sodium-channel activation and permeability appears to have been minimally altered to prevent interaction with batrachotoxin, but is still sensitive to other sodium conductance activators (veratridine, grayanotoxin) to which the frogs are not exposed naturally.
Abstract: Batrachotoxin is present in remarkably high amounts in the skin of Phyllobates terribilis. Levels of batrachotoxin tend to be reduced when P. terribilis is maintained in captivity, but even after being confined for up to 6 years, these frogs were still at least five times more toxic than other Phyllobates species used by natives for poisoning blowgun darts. Batrachotoxin was not detectable in F1 progeny reared to maturity in captivity. Nerve and muscle preparations from wild-caught frogs and from the nontoxic F1 frogs were both insensitive to batrachotoxin. The regulatory site controlling sodium-channel activation and permeability appears to have been minimally altered to prevent interaction with batrachotoxin, but is still sensitive to other sodium conductance activators (veratridine, grayanotoxin) to which the frogs arenot exposed naturally.
99 citations