Lucibufagins: Defensive steroids from the fireflies Photinus ignitus and P. marginellus (Coleoptera: Lampyridae)

Sensational site: the sodium pump ouabain-binding site and its ligands

Cardiotonic steroids (CTS), used by certain insects, toads, and rats for protection from predators, became, thanks to Withering's trailblazing 1785 monograph, the mainstay of heart failure (HF) therapy. In the 1950s and 1960s, we learned that the CTS receptor was part of the sodium pump (NKA) and that the Na+/Ca2+ exchanger was critical for the acute cardiotonic effect of digoxin- and ouabain-related CTS. This "settled" view was upended by seven revolutionary observations. First, subnanomolar ouabain sometimes stimulates NKA while higher concentrations are invariably inhibitory. Second, endogenous ouabain (EO) was discovered in the human circulation. Third, in the DIG clinical trial, digoxin only marginally improved outcomes in patients with HF. Fourth, cloning of NKA in 1985 revealed multiple NKA α and β subunit isoforms that, in the rodent, differ in their sensitivities to CTS. Fifth, the NKA is a cation pump and a hormone receptor/signal transducer. EO binding to NKA activates, in a ligand- and cell-specific manner, several protein kinase and Ca2+-dependent signaling cascades that have widespread physiological effects and can contribute to hypertension and HF pathogenesis. Sixth, all CTS are not equivalent, e.g., ouabain induces hypertension in rodents while digoxin is antihypertensinogenic ("biased signaling"). Seventh, most common rodent hypertension models require a highly ouabain-sensitive α2 NKA and the elevated blood pressure is alleviated by EO immunoneutralization. These numerous phenomena are enabled by NKA's intricate structure. We have just begun to understand the endocrine role of the endogenous ligands and the broad impact of the ouabain-binding site on physiology and pathophysiology.

Predatory fireflies and their toxic firefly prey have evolved distinct toxin resistance strategies

Toxic cardiotonic steroids (CTSs) act as a defense mechanism in many firefly species (Lampyridae) by inhibiting a crucial enzyme called Na+,K+-ATPase (NKA). Although most fireflies produce these toxins internally, species of the genus Photuris acquire them from a surprising source: predation on other fireflies. The contrasting physiology of toxin exposure and sequestration between Photuris and other firefly genera suggests that distinct strategies may be required to prevent self-intoxication. Our study demonstrates that both Photuris and their firefly prey have evolved highly resistant NKAs. Using an evolutionary analysis of the specific target of CTS (ATPα) in fireflies and gene editing in Drosophila, we find that the initial steps toward resistance were shared among Photuris and other firefly lineages. However, the Photuris lineage subsequently underwent multiple rounds of gene duplication and neofunctionalization, resulting in the development of ATPα paralogs that are differentially expressed and exhibit increasing resistance to CTS. By contrast, other firefly species have maintained a single copy. Our results implicate gene duplication as a facilitator in the transition of Photuris to its distinct ecological role as a predator of toxic firefly prey.

Predatory fireflies and their toxic firefly prey have evolved distinct toxin resistance strategies

Toxic cardiotonic steroids (CTS) act as a defense mechanism in many firefly species (Lampyridae) by inhibiting a crucial enzyme called Na+,K+-ATPase (NKA). While most fireflies produce these toxins internally, species of the genus Photuris acquire them from a surprising source: predation on other fireflies. The contrasting physiology of toxin exposure and sequestration between Photuris and other firefly genera suggests that distinct strategies may be required to prevent self-intoxication. Our study demonstrates that both Photuris and their firefly prey have evolved highly-resistant NKAs. Using an evolutionary analysis of the specific target of CTS (ATPα) in fireflies, and gene-editing in Drosophila, we find that the initial steps towards resistance were shared among Photuris and other firefly lineages. However, the Photuris lineage subsequently underwent multiple rounds of gene duplication and neofunctionalization, resulting in the development of ATPα paralogs that are differentially expressed and exhibit increasing resistance to CTS. In contrast, other firefly species have maintained a single copy. Our results implicate gene duplication as a facilitator in the transition of Photuris to its distinct ecological role as predator of toxic firefly prey.

Egg toxic compounds in the animal kingdom. A comprehensive review

Covering: 1951 to 2022Packed with nutrients and unable to escape, eggs are the most vulnerable stage of an animal's life cycle. Consequently, many species have evolved chemical defenses and teamed up their eggs with a vast array of toxic molecules for defense against predators, parasites, or pathogens. However, studies on egg toxins are rather scarce and the available information is scattered. The aim of this review is to provide an overview of animal egg toxins and to analyze the trends and patterns with respect to the chemistry and biosynthesis of these toxins. We analyzed their ecology, distribution, sources, occurrence, structure, function, relative toxicity, and mechanistic aspects and include a brief section on the aposematic coloration of toxic eggs. We propose criteria for a multiparametric classification that accounts for the complexity of analyzing the full set of toxins of animal eggs. Around 100 properly identified egg toxins are found in 188 species, distributed in 5 phyla: cnidarians (2) platyhelminths (2), mollusks (9), arthropods (125), and chordates (50). Their scattered pattern among animals suggests that species have evolved this strategy independently on numerous occasions. Alkaloids are the most abundant and widespread, among the 13 types of egg toxins recognized. Egg toxins are derived directly from the environment or are endogenously synthesized, and most of them are transferred by females inside the eggs. Their toxicity ranges from ρmol kg^-1 to mmol kg^-1, and for some species, experiments support their role in predation deterrence. There is still a huge gap in information to complete the whole picture of this field and the number of toxic eggs seems largely underestimated.

Firefly genomes illuminate the evolution of beetle bioluminescent systems

Fireflies are one of the best-known bioluminescent organisms, and the reaction mechanism and ecological utility of bioluminescence have been well-studied. Genome assemblies of six species of bioluminescent beetles have recently been published. These studies have focused on the evolution of novelties; luciferase, and the biosynthesis of luciferin and defensive chemicals. For example, clustering of the luciferase gene with acyl-CoA synthetase genes on a chromosome in luminous beetle genomes suggests the involvement of tandem gene duplications and neofunctionalization during the evolution of beetle bioluminescence. Several candidate genes for critical roles in beetle bioluminescence have been identified, but their functional analyses are still ongoing. The establishment of a long-term mass-rearing system and strain will be the key for the post-genome research on bioluminescent beetles. Lastly, the application of contemporary chromosome-scale genome assembly techniques to luminous beetles will help resolve outstanding evolutionary questions, such as how many times bioluminescence evolved in this clade.

Witches, potions, and metabolites: an overview from a medicinal perspective

Witches were popularly imagined as older women (above middle age), with large warty noses, whose clothes were shabby and used pointy hats. They are usually associated with a cauldron and...

Insect Collections as an Untapped Source of Bioactive Compounds-Fireflies (Coleoptera: Lampyridae) and Cardiotonic Steroids as a Proof of Concept

Natural history collections provide an invaluable basis for systematics, ecology, and conservation. Besides being an important source of DNA, museum specimens may also contain a plethora of natural products. Especially, dried insect collections represent a global repository with billions of inventoried vouchers. Due to their vast diversity, insects possess a great variety of defensive compounds, which they either produce autogenously or derive from the environment. Here, we present a case study on fireflies (Coleoptera: Lampyridae), which produce bufadienolides as a defense against predators. These toxins belong to the cardiotonic steroids, which are used for the treatment of cardiac diseases and specifically inhibit the animal enzyme Na+/K+-ATPase. Bufadienolides have been reported from only seven out of approximately 2000 described firefly species. Using a non-destructive approach, we screened 72 dry coleopteran specimens for bufadienolides using HPLC-DAD and HPLC-MS. We found bufadienolides including five novel compounds in 21 species of the subfamily Lampyrinae. The absence of bufadienolides in the phylogenetically related net-winged beetles (Lycidae) and the lampyrid subfamilies Luciolinae and Lamprohizinae indicates a phylogenetic pattern of bufadienolide synthesis. Our results emphasize the value of natural history collections as an archive of chemical information for ecological and evolutionary basic research and as an untapped source for novel bioactive compounds.

Recent advances in chemical ecology: complex interactions mediated by molecules

Chemical ecology is the highly interdisciplinary study of biochemicals that mediate the behavior of organisms and the regulation of physiological changes that alter intraspecific and/or interspecific interactions. Significant advances are often achieved through the collaboration of chemists and biologists working to understand organismal survival strategies with an eye on the development of targeted technologies for controlling agricultural, forestry, medical, and veterinary pests in a sustainable world. We highlight recent advances in chemical ecology from multiple viewpoints and discuss future prospects for applications.

Fireflies produce ultrasonic clicks during flight as a potential aposematic anti-bat signal

Fireflies are known for emitting light signals for intraspecific communication. However, in doing so, they reveal themselves to many potential nocturnal predators from a large distance. Therefore, many fireflies evolved unpalatable compounds and probably use their light signals as anti-predator aposematic signals. Fireflies are occasionally attacked by predators despite their warning flashes. Bats are among the most substantial potential firefly predators. Using their echolocation, bats might detect a firefly from a short distance and attack it in between two flashes. We thus aimed to examine whether fireflies use additional measures of warning, specifically focusing on sound signals. We recorded four species from different genera of fireflies in Vietnam and Israel and found that all of them generated ultrasonic clicks centered around bats' hearing range. Clicks were synchronized with the wingbeat and are probably produced by the wings. We hypothesize that ultrasonic clicks can serve as part of a multimodal aposematic display.

Drug Discovery Insights from Medicinal Beetles in Traditional Chinese Medicine

Traditional Chinese medicine (TCM) was the primary source of medical treatment for the people inhabiting East Asia for thousands of years. These ancient practices have incorporated a wide variety of materia medica including plants, animals and minerals. As modern sciences, including natural products chemistry, emerged, there became increasing efforts to explore the chemistry of this materia medica to find molecules responsible for their traditional use. Insects, including beetles have played an important role in TCM. In our survey of texts and review articles on TCM materia medica, we found 48 species of beetles from 34 genera in 14 different families that are used in TCM. This review covers the chemistry known from the beetles used in TCM, or in cases where a species used in these practices has not been chemically studied, we discuss the chemistry of closely related beetles. We also found several documented uses of beetles in Traditional Korean Medicine (TKM), and included them where appropriate. There are 129 chemical constituents of beetles discussed.

Determining the effects of nutrition on the reproductive physiology of male mosquitoes

Nutrition affects multiple aspects of insect physiology such as body size and fecundity, but we lack a detailed understanding of how nutrition influences the reproductive physiology of male insects such as mosquitoes. Given that female mosquitoes are vectors of many deadly diseases and can quickly proliferate, understanding how male nutrition impacts female fecundity could be of critical importance. To uncover the relationship between nutrition in adult male mosquitoes and its impacts on reproductive physiology, we reared larvae of the Northern house mosquito, Culex pipiens, on a standard lab diet and divided adult males among three different dietary treatments: low (3%), moderate (10%), and high (20%) sucrose. We found that although overall body size did not differ among treatments, one-week-old males raised on the 3% sucrose diet had significantly smaller male accessory glands (MAGs) compared to males that consumed the 10% and the 20% sucrose diets. Diet affected whole-body lipid content but did not affect whole-body protein content. Using nuclear magnetic resonance (NMR) spectroscopy, we found that diet altered the metabolic composition of the MAGs, including changes in lactic acid, formic acid, and glucose. We also observed changes in protein and lipid abundance and composition in MAGs. Females who mated with males on the 3% diet were found to produce significantly fewer larvae than females who had mated with males on the 10% diet. Taken together, our results demonstrate that the diet of adult male mosquitoes clearly affects male reproductive physiology and female fecundity.

Cardiac glycosides with target at direct and indirect interactions with nuclear receptors

Cardiac glycosides are compounds isolated from plants and animals and have been known since ancient times. These compounds inhibit the activity of the sodium potassium pump in eukaryotic cells. Cardiac glycosides were used as drugs in heart ailments to increase myocardial contraction force and, at the same time, to lower frequency of this contraction. An increasing number of studies have indicated that the biological effects of these compounds are not limited to inhibition of sodium-potassium pump activity. Furthermore, an increasing number of data have shown that they are synthesized in tissues of mammals, where they may act as a new class of steroid hormones or other hormones by mimicry to modulate various signaling pathways and influence whole organisms. Thus, we discuss the interactions of cardiac glycosides with the nuclear receptor superfamily of transcription factors activated by low-weight molecular ligands (including hormones) that regulate many functions of cells and organisms. Cardiac glycosides of endogenous and exogenous origin by interacting with nuclear receptors can affect the processes regulated by these transcription factors, including hormonal management, immune system, body defense, and carcinogenesis. They can also be treated as initial structures for combinatorial chemistry to produce new compounds (including drugs) with the desired properties.

Dramatic dietary shift maintains sequestered toxins in chemically defended snakes

Unlike other snakes, most species of Rhabdophis possess glands in their dorsal skin, sometimes limited to the neck, known as nucho-dorsal and nuchal glands, respectively. Those glands contain powerful cardiotonic steroids known as bufadienolides, which can be deployed as a defense against predators. Bufadienolides otherwise occur only in toads (Bufonidae) and some fireflies (Lampyrinae), which are known or believed to synthesize the toxins. The ancestral diet of Rhabdophis consists of anuran amphibians, and we have shown previously that the bufadienolide toxins of frog-eating species are sequestered from toads consumed as prey. However, one derived clade, the Rhabdophis nuchalis Group, has shifted its primary diet from frogs to earthworms. Here we confirm that the worm-eating snakes possess bufadienolides in their nucho-dorsal glands, although the worms themselves lack such toxins. In addition, we show that the bufadienolides of R. nuchalis Group species are obtained primarily from fireflies. Although few snakes feed on insects, we document through feeding experiments, chemosensory preference tests, and gut contents that lampyrine firefly larvae are regularly consumed by these snakes. Furthermore, members of the R. nuchalis Group contain compounds that resemble the distinctive bufadienolides of fireflies, but not those of toads, in stereochemistry, glycosylation, acetylation, and molecular weight. Thus, the evolutionary shift in primary prey among members of the R. nuchalis Group has been accompanied by a dramatic shift in the source of the species' sequestered defensive toxins.

Cardiac Glycosides in Human Physiology and Disease: Update for Entomologists

Cardiac glycosides, cardenolides and bufadienolides, are elaborated by several plant or animal species to prevent grazing or predation. Entomologists have characterized several insect species that have evolved the ability to sequester these glycosides in their tissues to reduce their palatability and, thus, reduce predation. Cardiac glycosides are known to interact with the sodium- and potassium-activated adenosine triphosphatase, or sodium pump, through a specific receptor-binding site. Over the last couple of decades, and since entomologic studies, it has become clear that mammals synthesize endogenous cardenolides that closely resemble or are identical to compounds of plant origin and those sequestered by insects. The most important of these are ouabain-like compounds. These compounds are essential for the regulation of normal ionic physiology in mammals. Importantly, at physiologic picomolar or nanomolar concentrations, endogenous ouabain, a cardenolide, stimulates the sodium pump, activates second messengers, and may even function as a growth factor. This is in contrast to the pharmacologic or toxic micromolar or milimolar concentrations achieved after consumption of exogenous cardenolides (by consuming medications, plants, or insects), which inhibit the pump and result in either a desired medical outcome, or the toxic consequence of sodium pump inhibition.

The impact of artificial light at night on nocturnal insects: A review and synthesis

In recent decades, advances in lighting technology have precipitated exponential increases in night sky brightness worldwide, raising concerns in the scientific community about the impact of artificial light at night (ALAN) on crepuscular and nocturnal biodiversity. Long-term records show that insect abundance has declined significantly over this time, with worrying implications for terrestrial ecosystems. The majority of investigations into the vulnerability of nocturnal insects to artificial light have focused on the flight-to-light behavior exhibited by select insect families. However, ALAN can affect insects in other ways as well. This review proposes five categories of ALAN impact on nocturnal insects, highlighting past research and identifying key knowledge gaps. We conclude with a summary of relevant literature on bioluminescent fireflies, which emphasizes the unique vulnerability of terrestrial light-based communication systems to artificial illumination. Comprehensive understanding of the ecological impacts of ALAN on diverse nocturnal insect taxa will enable researchers to seek out methods whereby fireflies, moths, and other essential members of the nocturnal ecosystem can coexist with humans on an increasingly urbanized planet.

Bufadienolides from amphibians: A promising source of anticancer prototypes for radical innovation, apoptosis triggering and Na+/K+-ATPase inhibition

Amphibians present pharmacologically active aliphatic, aromatic and heterocyclic molecules in their skin as defense against microorganisms, predators and infections, such as steroids, alkaloids, biogenic amines, guanidine derivatives, proteins and peptides. Based on the discovered bioactive potential of bufadienolides, this work reviewed the contribution of amphibians, especially from members of Bufonidae family, as source of new cytotoxic and antitumor molecules, highlighting the mechanisms responsible for such amazing biological potentialities. Bufonidae species produce bufadienolides related to cholesterol through the mevalonate-independent and acidic bile acid pathways as polyhydroxy steroids with 24 carbons. In vitro antitumor studies performed with skin secretions and its isolated components (specially marinobufagin, telocinobufagin, bufalin and cinobufagin) from Rhinella, Bufo and Rhaebo species have shown remarkable biological action on hematological, solid, sensitive and/or resistant human tumor cell lines. Some compounds revealed higher selectivity against neoplastic lines when compared to dividing normal cells and some molecules may biochemically associate with Na⁺/K⁺-ATPase and there is structural similarity to the digoxin- and ouabain-Na⁺/K⁺-ATPase complexs, implying a similar mechanism of the Na⁺/K⁺-ATPase inhibition by cardenolides and bufadienolides. Some bufadienolides also reduce levels of antiapoptotic proteins and DNA synthesis, cause morphological changes (chromatin condensation, nuclear fragmentation, cytoplasm shrinkage, cytoplasmic vacuoles, stickiness reduction and apoptotic bodies), cell cycle arrest in G₂/M or S phases, mitochondrial depolarization, PARP [poly (ADPribose) polymerase] and Bid cleavages, cytochrome c release, activation of Bax and caspases (-3, -9, -8 and -10), increased expression of the Fas-Associated protein with Death Domain (FADD), induce topoisomerase II inhibition, DNA fragmentation, cell differentiation, angiogenesis inhibition, multidrug resistance reversion, and also regulate immune responses. Then, bufadienolides isolated from amphibians, some of them at risk of extinction, emerge as a natural class of incredible chemical biodiversity, has moderate selectivity against human tumor cells and weak activity on murine cells, probably due to structural differences between subunits of human and mice Na⁺/K⁺-ATPases.

Molecular characterization of firefly nuptial gifts: a multi-omics approach sheds light on postcopulatory sexual selection

Postcopulatory sexual selection is recognized as a key driver of reproductive trait evolution, including the machinery required to produce endogenous nuptial gifts. Despite the importance of such gifts, the molecular composition of the non-gametic components of male ejaculates and their interactions with female reproductive tracts remain poorly understood. During mating, male Photinus fireflies transfer to females a spermatophore gift manufactured by multiple reproductive glands. Here we combined transcriptomics of both male and female reproductive glands with proteomics and metabolomics to better understand the synthesis, composition and fate of the spermatophore in the common Eastern firefly, Photinus pyralis. Our transcriptome of male glands revealed up-regulation of proteases that may enhance male fertilization success and activate female immune response. Using bottom-up proteomics we identified 208 functionally annotated proteins that males transfer to the female in their spermatophore. Targeted metabolomic analysis also provided the first evidence that Photinus nuptial gifts contain lucibufagin, a firefly defensive toxin. The reproductive tracts of female fireflies showed increased gene expression for several proteases that may be involved in egg production. This study offers new insights into the molecular composition of male spermatophores, and extends our understanding of how nuptial gifts may mediate postcopulatory interactions between the sexes.

Total evidence phylogeny and the evolution of adult bioluminescence in fireflies (Coleoptera: Lampyridae)

Fireflies are some of the most captivating organisms on the planet. They have a rich history as subjects of scientific study, especially in relation to their bioluminescent behavior. Yet, the phylogenetic relationships of fireflies are still poorly understood. Here, we present the first total evidence approach to reconstruct lampyrid phylogeny using both a molecular matrix from six loci and an extensive morphological matrix. Using this phylogeny we test the hypothesis that adult bioluminescence evolved after the origin of the firefly clade. The ancestral state of adult bioluminescence is recovered as non-bioluminescent with one to six gains and five to ten subsequent losses. The monophyly of the family, as well as the subfamilies is also tested. Ototretinae, Cyphonocerinae, Luciolinae (incl. Pristolycus), Amydetinae, "cheguevarinae" sensu Jeng 2008, and Photurinae are highly supported as monophyletic. With the exception of four taxa, Lampyrinae is also recovered as monophyletic with high support. Based on phylogenetic and morphological data Lamprohiza, Phausis, and Lamprigera are transferred to Lampyridae incertae sedis.

Transcriptome analysis reveals candidate genes involved in luciferin metabolism in Luciola aquatilis (Coleoptera: Lampyridae)

Bioluminescence, which living organisms such as fireflies emit light, has been studied extensively for over half a century. This intriguing reaction, having its origins in nature where glowing insects can signal things such as attraction or defense, is now widely used in biotechnology with applications of bioluminescence and chemiluminescence. Luciferase, a key enzyme in this reaction, has been well characterized; however, the enzymes involved in the biosynthetic pathway of its substrate, luciferin, remains unsolved at present. To elucidate the luciferin metabolism, we performed a de novo transcriptome analysis using larvae of the firefly species, Luciola aquatilis. Here, a comparative analysis is performed with the model coleopteran insect Tribolium casteneum to elucidate the metabolic pathways in L. aquatilis. Based on a template luciferin biosynthetic pathway, combined with a range of protein and pathway databases, and various prediction tools for functional annotation, the candidate genes, enzymes, and biochemical reactions involved in luciferin metabolism are proposed for L. aquatilis. The candidate gene expression is validated in the adult L. aquatilis using reverse transcription PCR (RT-PCR). This study provides useful information on the bio-production of luciferin in the firefly and will benefit to future applications of the valuable firefly bioluminescence system.

New Bufadienolides Isolated from the Roots of Kalanchoe daigremontiana (Crassulaceae)

An aqueous extract from the roots of Kalanchoe daigremontiana turned out to be a rich source of bufadienolides. The existing literature data relate mainly to the aerial parts of Kalanchoe but there is no information about the metabolic profile of the roots, which are also used in traditional medicine. Our investigation concerning the roots of K. daigremontiana led to the isolation and characterization of eight new bufadienolides, namely 1β,3β,5β,14β,19-pentahydroxybufa-20,22-dienolide (1), 19-(acetyloxy)-1β,3β,5β,14β-tetrahydroxybufa-20,22-dienolide (2), 3β-O-α-l-rhamno-pyranosyl-5β,11α,14β,19-tetrahydroxybufa-20,22-dienolide (3), 19-(acetyloxy)-3β,5β,11α,14β-tetrahydroxybufa-20,22-dienolide (4), 3β,5β,11α,14β,19-pentahydroxy-12-oxo-bufa-20,22-dienolide (5), 19-(acetyloxy)-3β,5β,11α,14β-tetrahydroxy-12-oxo-bufa-20,22-dienolide (6), 19-(acetyloxy)-1β,3β,5β,11α,14β-pentahydroxy-12-oxo-bufa-20,22-dienolide (7) and 1β-(acetyloxy)-3β,5β,11α,14β,19-pentahydroxy-12-oxo-bufa-20,22-dienolide (8), together with seven known compounds: 11α,19-dihydroxytelocinobufagin (9), bersaldegenin-1-acetate (10), daigredorigenin-3-acetate (11), bersaldegenin-1,3,5-orthoacetate (12), bryotoxin B (13), bryophyllin B (14) and bersaldegenin (15). The structures were established applying extensive 1D- and 2D-NMR and MS spectroscopic analyses.

Mushroom chemical defense : Pungent sesquiterpenoid dialdehyde antifeedant to opossum

A new bioassay employing a natural fungivore, the opossumDidelphis virginiana, is described. Using this bioasssay, eighteen species of fungi were tested for palatability. Five species of mushrooms, all of which taste pungent to humans, were found to be unpalatable to the opossum. From the least palatable of these,Lentinellus ursinus, the pungent principle was isolated and identified as isovelleral, a previously described fungal metabolite. The compound was shown to be a potent antifeedant to opossums. By means of difference NOE and relaxation time NMR studies, the relative configuration and solution conformation of isovelleral were deduced.

Eco-evo bioluminescence on land and in the sea

This review discusses the evolution of bioluminescence organisms that inhabit various environments based on the current understanding of their unique ecologies and biochemistries. As shown here, however, there are still many unanswered questions regarding the functions and mechanisms of bioluminescence, which should be investigated in further studies. To facilitate future research in this field, we introduce our recent attempt, the bioluminescent organism DNA barcode initiative. This genetic reference library will provide resources for other scientists to efficiently identify unstudied bioluminescent organisms, focus their biochemical and genetic research goals, and will generally promote bioluminescence as a field of scientific study.

Pygidial secretions ofPasimachus subsulcatus (Coleoptera: Carabidae) deter predation byEumeces inexpectatus (Squamata: Scincidae)

The carabid beetlePasimachus subsulcatus is an abundant ground-dwelling insect in west central Florida that exudes a powerful mucous membrane irritant when disturbed. This secretion can be sprayed over 10 cm from the abdominal tip. The southeastern five-lined skink,Eumeces inexpectatus, is an abundant insectivorous lizard sympatric withPasimachus. We assessed the availability ofPasimachus toEumeces and found it to be within the foraging microenvironment of the lizard. Analysis ofEumeces gut contents and field feeding trials indicate thatPasimachus are not ingested by the lizard, yet arthropods of comparable size and exoskeletal thickness are ingested. The movement response ofEumeces to isolatedPasimachus secretion constituents, conducted in a modified Y-maze laboratory experiment, was used to assess the repellent capabilities of the secretion.Eumeces are consistently repelled byPasimachus secretion constituents, indicating that the beetle is protected chemically from the lizard.

Determinants of reproductive success across sequential episodes of sexual selection in a firefly

Because females often mate with multiple males, it is critical to expand our view of sexual selection to encompass pre-, peri- and post-copulatory episodes to understand how selection drives trait evolution. In Photinus fireflies, females preferentially respond to males based on their bioluminescent courtship signals, but previous work has shown that male paternity success is negatively correlated with flash attractiveness. Here, we experimentally manipulated both the attractiveness of the courtship signal visible to female Photinus greeni fireflies before mating and male nuptial gift size to determine how these traits might each influence mate acceptance and paternity share. We also measured pericopulatory behaviours to examine their influence on male reproductive success. Firefly males with larger spermatophores experienced dual benefits in terms of both higher mate acceptance and increased paternity share. We found no effect of courtship signal attractiveness or pericopulatory behaviour on male reproductive success. Taken together with previous results, this suggests a possible trade-off for males between producing an attractive courtship signal and investing in nuptial gifts. By integrating multiple episodes of sexual selection, this study extends our understanding of sexual selection in Photinus fireflies and provides insight into the evolution of male traits in other polyandrous species.

Chemical synthesis of the cardiotonic steroid glycosides and related natural products

The active components from the extracts of Digitalis, cardiotonic steroid glycosides, have been ingested by humans for more than 200 years as a medicinal therapy for heart failure and abnormal heart rhythms. The positive inotropic activity of the cardiotonic steroids that mediates clinically useful physiological effects in patients has been attributed largely to a high affinity inhibitory interaction with the extracellular surface of the membrane-bound sodium pump (Na(+)/K(+)-ATPase). However, previously unrecognized intracellular signaling pathways continue to be uncovered. This Review examines both partial and de novo synthetic approaches to the medicinally important and structurally captivating cardenolide and bufadienolide steroid families, with an emphasis on the stereocontrolled construction of the pharmacophoric aglycone (genin) framework.

Antileishmanial and antitrypanosomal activity of bufadienolides isolated from the toad Rhinella jimi parotoid macrogland secretion

Amphibian skin secretions are considered a rich source of biologically active compounds and are known to be rich in peptides, bufadienolides and alkaloids. Bufadienolides are cardioactive steroids from animals and plants that have also been reported to possess antimicrobial activities. Leishmaniasis and American Trypanosomiasis are parasitic diseases found in tropical and subtropical regions. The efforts toward the discovery of new treatments for these diseases have been largely neglected, despite the fact that the only available treatments are highly toxic drugs. In this work, we have isolated, through bioguided assays, the major antileishmanial compounds of the toad Rhinella jimi parotoid macrogland secretion. Mass spectrometry and (1)H and (13)C NMR spectroscopic analyses were able to demonstrate that the active molecules are telocinobufagin and hellebrigenin. Both steroids demonstrated activity against Leishmania (L.) chagasi promastigotes, but only hellebrigenin was active against Trypanosoma cruzi trypomastigotes. These steroids were active against the intracellular amastigotes of Leishmania, with no activation of nitric oxide production by macrophages. Neither cytotoxicity against mouse macrophages nor hemolytic activities were observed. The ultrastructural studies with promastigotes revealed the induction of mitochondrial damage and plasma membrane disturbances by telocinobufagin, resulting in cellular death. This novel biological effect of R. jimi steroids could be used as a template for the design of new therapeutics against Leishmaniasis and American Trypanosomiasis.

Poisonings in reptiles

Reptiles are increasingly being kept as pets in American households. The basic principles of emergency medicine are the same for all species, but reptilian species present special diagnostic challenges to veterinary clinicians when they become ill. Reptiles in captivity can become accidentally poisoned in a variety of ways. Veterinarians treating small animal emergencies must make an effort to familiarize themselves with the large body of literature and resources that are developing regarding both nontraditional exotic companion species and advances in toxicology.

Defensive Chemistry of Lycid Beetles and of Mimetic Cerambycid Beetles that Feed on Them

Beetles of the family Lycidae have long been known to be chemically protected. We present evidence that North American species of the lycid genera Calopteron and Lycus are rejected by thrushes, wolf spiders, and orb-weaving spiders, and that they contain a systemic compound that could account, at least in part, for this unacceptability. This compound, a novel acetylenic acid that we named lycidic acid, proved actively deterrent in feeding tests with wolf spiders and coccinellid beetles.Species of Lycus commonly figure as models of mimetic associations. Among their mimics are species of the cerambycid beetle genus Elytroleptus, remarkable because they prey upon the model lycids. We postulated that by doing so Elytroleptus might incorporate the lycidic acid from their prey for their own defense. However, judging from analytical data, the beetles practice no such sequestration, explaining why they remain relatively palatable (in tests with wolf spiders) even after having fed on lycids. Chemical analyses also showed the lycids to contain pyrazines, such as were already known from other Lycidae, potent odorants that could serve in an aposematic capacity to forestall predatory attacks.

Flash signal evolution, mate choice, and predation in fireflies

Many key advances in our understanding of firefly biology and signaling have been made over the past two decades. Here we review this recent research, which includes new phylogenetic results that shed light on the evolution of courtship signal diversity within the family Lampyridae, new insights into firefly flash control, and the discovery of firefly nuptial gifts. We present a comprehensive overview of sexual selection in lampyrids, including evidence from Photinus fireflies that females choose their mates on the basis of male flash signals, and discuss the importance of examining both precopulatory and postcopulatory sexual selection in this group. Finally, we review recent findings on firefly chemical defenses, and discuss their implications for flash signal evolution in response to generalist predators as well as specialist predatory fireflies. This review provides new insight into how firefly flash signals have been shaped by the dual evolutionary processes of sexual selection (mate choice) and natural selection (predation), and proposes several exciting directions for future research.

Energy and predation costs of firefly courtship signals

Animal courtship signals include many highly conspicuous traits and behaviors, and it is generally assumed that such signals must balance the benefits of attracting mates against some fitness costs. However, few studies have assessed the multiple costs potentially incurred by any one courtship signal, so we have limited understanding of the relative importance of different costs. This study provides the first comprehensive assessment of signal costs for Photinus fireflies (Coleoptera: Lampyridae), using controlled experiments to measure both the energy and predation costs associated with their bioluminescent courtship signals. We measured energy required to generate bioluminescent flashes, using differential open-flow respirometry, and found that flash signaling results in only a nominal increase in energy expenditure above resting levels. These results suggest that the energy required to generate bioluminescent flashes represents a minor component of the total cost of firefly courtship. However, controlled field experiments revealed that visually oriented predators imposed major costs on firefly courtship signals, with higher signaling rates significantly increasing the likelihood of predation. Together with previous results demonstrating that female fireflies prefer more conspicuous courtship signals, these results support the importance of multiple-receiver communication networks in driving signal evolution.

Personal Reflections on Receiving the Roger Adams Award in Organic Chemistry

The author reflects on his early experiences as a chemist, and on the subsequent shift in emphasis that his research has undergone from mechanistic and synthetic organic chemistry to natural products chemistry. Finally, the extension of the field of natural products chemistry into the emerging discipline of chemical ecology is noted. This essay concludes with a consideration of the importance of including science in the curricula of all college and university students.