Deter Predators Research Articles

Biological and chemical diversity of coral-derived microorganisms.

Coral-derived microorganisms have been a major focus of many research efforts on marine ecology in recent decades. Importantly, research on bioactive compounds from these diverse microorganisms, which include fungi and bacteria, has experienced an explosive growth during the past five years. This has unveiled the ecological roles of these microorganisms, which prevent antifouling, inhibit pathogenic bacteria, and deter predators in ocean ecosystems. Moreover, the structural diversity and pharmacological activity of the compounds produced by these microorganisms have also been studied extensively, leading not only to an understanding their roles within ecosystems, but also the potential value of their use in human health. In this review, 258 marine natural products, including polyketides, terpenoids, meroterpenoids, alkaloids, peptides, shikimates and lipids, all discovered in the past 24 years, are presented. 146 references are cited.

Exploring the molecular basis of monarch butterfly color pattern variation: a response to A. Hume's 'Myosin--a monarch of pigment transport?'.

Exploring the molecular basis of monarch butterfly color pattern variation: a response to A. Hume's 'Myosin--a monarch of pigment transport?'.

A molecular phylogeny of Eumorpha (Lepidoptera: Sphingidae) and the evolution of anti‐predator larval eyespots

AbstractMany insects possess conspicuous external circular ring markings that resemble the eye of a vertebrate. These ‘eyespots’ typically function to startle or otherwise deter predators, but few studies have examined how eyespots have evolved. We study the evolution of the posterior larval eyespot in the charismatic New World hawkmoth genus Eumorpha. While Eumorpha has a range of posterior larval eyespot shapes and sizes, little is known of how this trait has evolved because phylogenetic relationships of Eumorpha remain largely unknown. In this study, we included 62 individuals from 23 of 26 described Eumorpha species, and sequenced four genes (CAD, EF‐1α, Wingless and COI), totaling 3773 base pairs. Maximum likelihood and Bayesian phylogenetic methods produced largely congruent trees with well‐supported relationships. Our analyses reveal that Eumorpha probably had an ancestor with a posterior larval eyespot and that the eyespot was subsequently lost in at least three lineages. Eumorpha appears to have originated in Central and South America and expanded its distribution to North America.

Diversification of a single ancestral gene into a successful toxin superfamily in highly venomous Australian funnel-web spiders

BackgroundSpiders have evolved pharmacologically complex venoms that serve to rapidly subdue prey and deter predators. The major toxic factors in most spider venoms are small, disulfide-rich peptides. While there is abundant evidence that snake venoms evolved by recruitment of genes encoding normal body proteins followed by extensive gene duplication accompanied by explosive structural and functional diversification, the evolutionary trajectory of spider-venom peptides is less clear.ResultsHere we present evidence of a spider-toxin superfamily encoding a high degree of sequence and functional diversity that has evolved via accelerated duplication and diversification of a single ancestral gene. The peptides within this toxin superfamily are translated as prepropeptides that are posttranslationally processed to yield the mature toxin. The N-terminal signal sequence, as well as the protease recognition site at the junction of the propeptide and mature toxin are conserved, whereas the remainder of the propeptide and mature toxin sequences are variable. All toxin transcripts within this superfamily exhibit a striking cysteine codon bias. We show that different pharmacological classes of toxins within this peptide superfamily evolved under different evolutionary selection pressures.ConclusionsOverall, this study reinforces the hypothesis that spiders use a combinatorial peptide library strategy to evolve a complex cocktail of peptide toxins that target neuronal receptors and ion channels in prey and predators. We show that the ω-hexatoxins that target insect voltage-gated calcium channels evolved under the influence of positive Darwinian selection in an episodic fashion, whereas the κ-hexatoxins that target insect calcium-activated potassium channels appear to be under negative selection. A majority of the diversifying sites in the ω-hexatoxins are concentrated on the molecular surface of the toxins, thereby facilitating neofunctionalisation leading to new toxin pharmacology.

Diet, development and the optimization of warning signals in post‐metamorphic green and black poison frogs

Summary Many prey species are chemically defended and have conspicuous appearance to deter predators (i.e. aposematism). Such warning signals work because predators pay attention to the colour and size of signals, which they associate with unprofitability. Paradoxically, in early life stages, aposematic species are often warningly coloured, but their chemical defences are lacking because they have yet to be acquired through the diet or synthesized endogenously. This state of being conspicuous yet poorly defended must place individuals at increased risk of predation, but how they minimize this risk during development is unclear. We reared larval green and black poison frogs (Dendrobates auratus) on a relatively low or a higher food supply and tested the hypothesis that individuals with more resources should grow larger while reducing their investment in warning signals at metamorphic completion. We also assayed markers of oxidative balance (malondialdehyde, superoxide dismutase and total antioxidant capacity) to ascertain whether there were resource‐allocation trade‐offs that differed with diet treatments. Low‐food froglets were relatively small, and their body size and signal luminance (perceived brightness) were positively correlated. In contrast, in high‐food froglets body size and warning signal luminance were negatively correlated, suggesting either a resource‐allocation trade‐off or alternatively a facultative reduction in luminance exhibited by larger froglets. The reduction in luminance in relatively large, high‐food froglets did not appear to arise because of oxidative stress: signal luminance and markers of oxidative stress were positively correlated in high‐food froglets, but were negatively correlated in low‐food froglets suggesting a trade‐off. Our results highlight developmental plasticity in body size and coloration as affected by resource (i.e. food) supply. Such plasticity seems likely to minimize predation risk during the vulnerable period early in life when individuals are warningly coloured and must make the transition from an undefended phenotype to a mature aposematic state.

Spider-venom peptides that target voltage-gated sodium channels: Pharmacological tools and potential therapeutic leads

Voltage-gated sodium (NaV) channels play a central role in the propagation of action potentials in excitable cells in both humans and insects. Many venomous animals have therefore evolved toxins that modulate the activity of NaV channels in order to subdue their prey and deter predators. Spider venoms in particular are rich in NaV channel modulators, with one-third of all known ion channel toxins from spider venoms acting on NaV channels. Here we review the landscape of spider-venom peptides that have so far been described to target vertebrate or invertebrate NaV channels. These peptides fall into 12 distinct families based on their primary structure and cysteine scaffold. Some of these peptides have become useful pharmacological tools, while others have potential as therapeutic leads because they target specific NaV channel subtypes that are considered to be important analgesic targets. Spider venoms are conservatively predicted to contain more than 10 million bioactive peptides and so far only 0.01% of this diversity been characterised. Thus, it is likely that future research will reveal additional structural classes of spider-venom peptides that target NaV channels.

Trap barricading and decorating by a well-armored sit-and-wait predator: extra protection or prey attraction?

Animals may build multiple structures to provide benefits to counter the costs of building. Many orb web spiders add multiple structures, e.g., barricading barrier webs and silk decorations, to their webs and these structures have been hypothesized to function to deter predators or attract prey. The heavily armored spiny spiders construct barrier webs around their orb webs and decorate them with conspicuous silk tufts. Why these organisms, already well protected by a thick cuticle and spines, make the extra investment of building barrier webs and adding conspicuous silk decorations is not known. We predicted that these structures function to both attract prey and deter predators. Field experiments were conducted in two consecutive years using orb webs built by the East Asian spiny spider Thelacantha brevispina. We either (1) concealed the decoration, (2) removed the barrier webs, or (3) left the decorations and barrier webs intact. We found year and treatment to interactively influence prey interception rates. In 2010, but not in 2009, we found prey interception with T. brevispina webs to be greater when the decorations were conspicuous than when they were concealed suggesting that the decorations may lure prey. Prey interception was lower when the barrier webs were present without decorations compared to when they were absent without decorations. The prey-attracting function of the decorations thus may counter the reduction in prey interception incurred by adding a barrier web. Predatory wasp interactions were not influenced by any of our treatments, probably because the spiders’ thick cuticle is the primary means of protection from wasps. Bird predation events, while rare, occurred only when decorations were concealed or the barrier webs were removed. It is therefore plausible that the tuft decorations both lure prey and deter birds.

BLINDED BY THE LIGHT – THE FANTASTIC FLASH OF THE CLUSTERWINK SNAIL

![Figure][1] Bioluminescence, the biological production of light, is a breath-taking event to behold. Brilliant squid, elegant jellies and glowing fish use this strategy to attract mates, detect prey, camouflage themselves or deter predators. Extraordinary adaptations to transmit light are

Evolution of venom delivery structures in madtom catfishes (Siluriformes: Ictaluridae)

The use of venom to subdue prey or deter predators has evolved multiple times in numerous animal lineages. Catfishes represent one of the most easily recognized, but least studied groups of venomous fishes. Venom glands surround spines on the dorsal and pectoral fins that serve as venom delivery structures. Species of madtom catfishes in the genus Noturus were found to each have one of four venom delivery morphologies: (1) smooth spine with no venom gland; (2) smooth spine with venom gland associated with shaft of spine; (3) serrated spine with venom gland associated with shaft of spine; and (4) serrated spine with venom gland associated with shaft of spine and posterior serrations. Analyses accounting for the phylogenetic history of Noturus species suggest that a serrated pectoral spine with a venom gland is the ancestral condition for the genus. The presence of serrations and a venom gland have been largely conserved among Noturus species, but sting morphology has changed at least five times within the genus. Four of these changes have resulted in a loss of morphological complexity, including the loss of posterior serrations, loss of venom glands associated with the posterior serrations, and one complete loss of the venom gland. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102, 115–129.

Sponge spicules as blueprints for the biofabrication of inorganic–organic composites and biomaterials

While most forms of multicellular life have developed a calcium-based skeleton, a few specialized organisms complement their body plan with silica. However, of all recent animals, only sponges (phylum Porifera) are able to polymerize silica enzymatically mediated in order to generate massive siliceous skeletal elements (spicules) during a unique reaction, at ambient temperature and pressure. During this biomineralization process (i.e., biosilicification) hydrated, amorphous silica is deposited within highly specialized sponge cells, ultimately resulting in structures that range in size from micrometers to meters. Spicules lend structural stability to the sponge body, deter predators, and transmit light similar to optic fibers. This peculiar phenomenon has been comprehensively studied in recent years and in several approaches, the molecular background was explored to create tools that might be employed for novel bioinspired biotechnological and biomedical applications. Thus, it was discovered that spiculogenesis is mediated by the enzyme silicatein and starts intracellularly. The resulting silica nanoparticles fuse and subsequently form concentric lamellar layers around a central protein filament, consisting of silicatein and the scaffold protein silintaphin-1. Once the growing spicule is extruded into the extracellular space, it obtains final size and shape. Again, this process is mediated by silicatein and silintaphin-1, in combination with other molecules such as galectin and collagen. The molecular toolbox generated so far allows the fabrication of novel micro- and nanostructured composites, contributing to the economical and sustainable synthesis of biomaterials with unique characteristics. In this context, first bioinspired approaches implement recombinant silicatein and silintaphin-1 for applications in the field of biomedicine (biosilica-mediated regeneration of tooth and bone defects) or micro-optics (in vitro synthesis of light waveguides) with promising results.

Effect of abiotic factors on the foraging strategy of the orb-web spider Argiope keyserlingi (Araneae: Araneidae)

Abstract Environmental conditions such as light level, background contrast and temperature might influence a spider's prey capture success and risk of predation. Thus it may often be advantageous for spiders to adjust web-building behaviour in response to variation in these environmental conditions. This hypothesis was examined in a study of the construction of webs and web decorations (conspicuous strands of silk at the hub of the web) of the orb-web spider Argiope keyserlingi. Web decorations are thought to have one or more separate functions. They may attract prey, deter predators or advertise the web to oncoming birds, thus preventing web damage. In this series of experiments, relationships between weather parameters and the construction of webs and web decorations were considered. In complementary laboratory experiments, A. keyserlingi spiders were exposed to two different light levels (700 and 90 lx), background contrasts (black and white) and temperature conditions (20 and 26°C). Of the available weather parameters, only temperature was significantly related to web decorating behaviour but not to web size. In the laboratory, temperature also influenced web-decorating behaviour, and spiders in dim light (700 lx) constructed larger webs and longer decorations. Background contrast did not significantly alter web size or web decorations. These data suggest that when prey availability is reduced at low temperatures, spiders may use web decorations to attract prey to the web. Similarly, in dim light, spiders may build more and larger decorations to increase the visual signal to approaching prey or to advertise the web to oncoming birds.

Cognitive Dimensions of Predator Responses to Imperfect Mimicry

Many palatable animals, for example hoverflies, deter predators by mimicking well-defended insects such as wasps. However, for human observers, these flies often seem to be little better than caricatures of wasps—their visual appearance and behaviour are easily distinguishable from those which they are attempting to mimic. This imperfect mimicry baffles evolutionary biologists, because one might expect natural selection to do a more thorough job. Here we discuss two types of cognitive processes that might explain why distinguishable mimics could enjoy increased protection from predation. Speed–accuracy tradeoffs in predator decision making might give imperfect mimics sufficient time to escape, and predators under time constraint might avoid time-consuming discriminations between well-defended models and inaccurate edible mimics and instead adopt a “safety first” policy of avoiding insects with similar appearance. Categorisation of prey types by predators could mean that wholly dissimilar mimics may be protected, provided they share some common property with noxious prey. If predators use experience with multiple prey types to learn rules rather than just memorising the appearance of individual prey types, it follows that different individual predators should form different categories, each including separate types of novel prey. Experimental studies to test these hypotheses should be straightforward, because we can use the relatively simple signals (e.g., striped patterns) with which prey manipulate predator behaviour as tools for investigating cognitive processes that underlie decision making and object recognition in animals' daily lives.

How Do Predators Cope With Chemically Defended Foods?

Many prey species (including plants) deter predators with defensive chemicals. These defensive chemicals act by rendering the prey's tissues noxious, toxic, or both. Here, I explore how predators cope with the presence of these chemicals in their diet. First, I describe the chemosensory mechanisms by which predators (including herbivores) detect defensive chemicals. Second, I review the mechanisms by which predators either avoid or tolerate defensive chemicals in prey. Third, I examine how effectively free-ranging predators can overcome the chemical defenses of prey. The available evidence indicates that predators have mixed success overcoming these defenses. This conclusion is based on reports of free-ranging predators rejecting unpalatable but harmless prey, or voluntarily ingesting toxic prey.

Cognitive dimensions of predator responses to imperfect mimicry?

AbstractMany palatable insects, for example hoverflies, deter predators by mimicking well-defended insects such as wasps. However, for human observers, these flies often seem to be little better than caricatures of wasps – their visual appearance and behaviour are easily distinguishable. This imperfect mimicry baffles evolutionary biologists, because one might expect natural selection to do a more thorough job. Here we discuss two types of cognitive processes that might explain why mimics distinguishable mimics might enjoy increased protection from predation. Speed accuracy tradeoffs in predator decision making might give imperfect mimics sufficient time to escape, and predators under time constraint might avoid time-consuming discriminations between well-defended models and inaccurate edible mimics, and instead adopt a “safety first” policy of avoiding insects with similar appearance. Categorization of prey types by predators could mean that wholly dissimilar mimics may be protected, provided they share some common property with noxious prey.

Genetic Basis of Tetrodotoxin Resistance in Pufferfishes

Tetrodotoxin (TTX) is a highly potent neurotoxin that selectively binds to the outer vestibule of voltage-gated sodium channels. Pufferfishes accumulate extremely high concentrations of TTX without any adverse effect. A nonaromatic amino acid (Asn) residue present in domain I of the pufferfish, Takifugu pardalis, Na v1.4 channel has been implicated in the TTX resistance of pufferfishes . However, the effect of this residue on TTX sensitivity has not been investigated, and it is not known if this residue is conserved in all pufferfishes. We have investigated the genetic basis of TTX resistance in pufferfishes by comparing the sodium channels from two pufferfishes (Takifugu rubripes [fugu] and Tetraodon nigroviridis) and the TTX-sensitive zebrafish. Although all three fishes contain duplicate copies of Na v1.4 channels (Na v1.4a and Na v1.4b), several substitutions were found in the TTX binding outer vestibule of the two pufferfish channels. Electrophysiological studies showed that the nonaromatic residue (Asn in fugu and Cys in Tetraodon) in domain I of Na v1.4a channels confers TTX resistance. The Glu-to-Asp mutation in domain II of Tetraodon channel Na v1.4b is similar to that in the saxitoxin- and TTX-resistant Na+ channels of softshell clams . Besides helping to deter predators, TTX resistance enables pufferfishes to selectively feed on TTX-bearing organisms.

Defensive anointing: extended chemical phenotype and unorthodox ecology

Many animals acquire substances on their integument from heterospecifics through anointing. In active or self-anointing, animals rub against scent sources or they apply them by appendage or mouth. In passive anointing, animals adsorb emitted chemicals. Most investigators suggest that chemicals appropriated via anointing deter predators, ectoparasites, and/or microbial pathogens. Similarly, nesting birds and brood parasites of social insects acquire chemicals from and reside unmolested near or within insect colonies. The acquisition through anointing of chemicals that deter predators, ectoparasites, microbial pathogens, and other offenders, i.e. defensive anointing, constitutes an “extended phenotype”: the genetic machinery by which defensive compounds are synthesized does not reside with the anointing organisms, but the sensory mechanisms and/or behavioral tendencies by which chemicals are appropriated from heterospecifics do. The ecological relationships between anointing organisms and “chemical donors,” and between ”chemical donors” and those responding to chemicals appropriated via anointing, may be unorthodox. Interactions between anointing organisms and chemical donors typically entail abrasive contact with or other damage to the latter. These encounters sometimes are evidenced by telltale marks on chemical donors or by chemicals deposited on the integument of anointing organisms. The organisms furnishing chemicals and those affected by them may not interact, and they may even occupy different habitats, because mobile anointing organisms are the medium by which chemicals are disseminated. Thus, in allelochemical studies where anointing is involved, species can be tested, with ecological legitimacy, using chemicals from organisms they might fail to interact with in nature. Practical implications of anointing stem from its potential importance in conservation and captive management, where consideration is given to the protection that animals derive by accessing topically acquired chemicals from heterospecifics.

Effect of abiotic factors on the foraging strategy of the orb‐web spider Argiope keyserlingi (Araneae: Araneidae)

Abstract Environmental conditions such as light level, background contrast and temperature might influence a spider's prey capture success and risk of predation. Thus it may often be advantageous for spiders to adjust web‐building behaviour in response to variation in these environmental conditions. This hypothesis was examined in a study of the construction of webs and web decorations (conspicuous strands of silk at the hub of the web) of the orb‐web spider Argiope keyserlingi. Web decorations are thought to have one or more separate functions. They may attract prey, deter predators or advertise the web to oncoming birds, thus preventing web damage. In this series of experiments, relationships between weather parameters and the construction of webs and web decorations were considered. In complementary laboratory experiments, A. keyserlingi spiders were exposed to two different light levels (700 and 90 lx), background contrasts (black and white) and temperature conditions (20 and 26°C). Of the available weather parameters, only temperature was significantly related to web decorating behaviour but not to web size. In the laboratory, temperature also influenced web‐decorating behaviour, and spiders in dim light (700 lx) constructed larger webs and longer decorations. Background contrast did not significantly alter web size or web decorations. These data suggest that when prey availability is reduced at low temperatures, spiders may use web decorations to attract prey to the web. Similarly, in dim light, spiders may build more and larger decorations to increase the visual signal to approaching prey or to advertise the web to oncoming birds.

Signalling conflict between prey and predator attraction

Abstract Predators may utilize signals to exploit the sensory biases of their prey or their predators. The inclusion of conspicuous silk structures called decorations or stabilimenta in the webs of some orb-web spiders (Araneae: Araneidae, Tetragnathidae, Uloboridae) appears to be an example of a sensory exploitation system. The function of these structures is controversial but they may signal to attract prey and/or deter predators. Here, we test these predictions, using a combination of field manipulations and laboratory experiments. In the field, decorations influenced the foraging success of adult female St. Andrew’s Cross spiders, Argiope keyserlingi: inclusion of decorations increased prey capture rates as the available prey also increased. In contrast, when decorations were removed, prey capture rates were low and unrelated to the amount of available prey. Laboratory choice experiments showed that significantly more flies (Chrysomya varipes; Diptera: Calliphoridae) were attracted to decorated webs. However, decorations also attracted predators (adult and juvenile praying mantids, Archimantis latistylus; Mantodea: Mantidae) to the web. St. Andrew’s Cross spiders apparently resolve the conflicting nature of a prey- and predator-attracting signal by varying their decorating behaviour according to the risk of predation: spiders spun fewer decorations if their webs were located in dense vegetation where predators had greater access, than if the webs were located in sparse vegetation.

A Survey of Birds Odorous or Unpalatable to Humans: Possible Indications of Chemical Defense

We solicited information from field and museum ornithologists on the birds that they consider odorous and/or unpalatable in order to identify species that may use chemicals to deter predators. Ninety-two ornithologists from the Americas and Eastern Europe responded to our survey. Eighty genera and 10 families representing 17 orders, primarily Procellariiformes, Falconiformes, Psittaciformes, Cuculiformes, Piciformes, and Passeriformes, were cited as containing malodorous or uniquely odorous birds. Two orders (Opisthocomiformes and Trogoniformes), five families (Procellariidae, Cuculidae, Bucconidae, Picidae, and Furnriidae), and one subfamily (Drepanidinae) were reported to us as either containing many odorous species or consisting primarily of them. Thirty genera and three families representing 13 orders, primarily Passeriformes, were reported to us as unpalatable. The birds cited in our survey and those previously reported as odorous and/or unpalatable are tabulated. Our survey and review point to a number of taxa that may use chemicals to deter predators, although we acknowledge that compounds imparting aversive or unique odors or flavors may arise for a variety of reasons, e.g., as dietary by-products.

Cholinergic phytochemicals: From magic to medicine

The decline in cortical cholinergic activity in aging and degenerative diseases associated with dementia is, in conjunction with increasing genetic and molecular complexity, one of the most consistent observations in psychopathology. Numerous plants synthesize compounds, interacting with cholinergic systems which have been of value in exploring the role of the cholinergic system in aging and dementia. These chemicals deter predators by interfering with autonomic, central nervous or neuromuscular systems. The original hypothesis that memory loss in Alzheimer's disease relates to a central cholinergic deficiency was partly based on the experimental induction of related cognitive impairments in normal individuals exposed to the naturally occurring muscarinic antagonist scopolamine. Long before this, in ancient Greece, henbane (containing alkaloids such as atropine and scopolamine) was used to mimic 'dementia' and provoke prophesy. The tendency of such tropane alkaloids to induce hallucinations is consistent with low neocortical activities and the high incidence of psychotic features in Dementia with Lewy bodies (DLB). Other plant derived alkaloids such as physostigmine and galanthamine, inhibiting acetylcholinesterase, are among those including the synthetic chemical tacrine, being tested in dementia therapy. Cognitive enhancement, although significant, is limited and antipsychotic effects may be more prominent. The recent discovery of brain nicotinic receptors and the neuroprotective role of the tobacco alkaloid nicotine provides a further dimension to cholinergic therapy in retarding the neurodegenerative process. The potential for new cholinergic drug development based on the rich biodiversity of plant chemicals and principles of ethnobotany, in the context of modern pharmacology, is still largely unexplored in age-related mental disorders. Several plant species reputed to improve memory in European medicinal plant encyclopaedias have cholinergic activities which may be therapeutically relevant.