Journal articles: 'Chemical defence'

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Skelhorn, John, and Candy Rowe. "Frequency-dependent taste-rejection by avian predation may select for defence chemical polymorphisms in aposematic prey." Biology Letters 1, no. 4 (August 31, 2005): 500–503. http://dx.doi.org/10.1098/rsbl.2005.0359.

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Chemically defended insects advertise their unpalatability to avian predators using conspicuous aposematic coloration that predators learn to avoid. Insects utilize a wide variety of different compounds in their defences, and intraspecific variation in defence chemistry is common. We propose that polymorphisms in insect defence chemicals may be beneficial to insects by increasing survival from avian predators. Birds learn to avoid a colour signal faster when individual prey possesses one of two unpalatable chemicals rather than all prey having the same defence chemical. However, for chemical polymorphisms to evolve within a species, there must be benefits that allow rare chemical morphs to increase in frequency. Using domestic chicks as predators and coloured crumbs for prey, we provide evidence that birds taste and reject proportionally more of the individuals with rare defence chemicals than those with common defence chemicals. This indicates that the way in which birds attack and reject prey could enhance the survival of rare chemical morphs and select for chemical polymorphism in aposematic species. This is the first experiment to demonstrate that predators can directly influence the form taken by prey's chemical defences.

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Hantak, Maggie M., Daniel J. Paluh, and Ralph A. Saporito. "Bufadienolide and alkaloid-based chemical defences in two different species of neotropical anurans are equally effective against the same arthropod predators." Journal of Tropical Ecology 32, no. 2 (March 2016): 165–69. http://dx.doi.org/10.1017/s0266467416000055.

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Abstract:Defensive chemicals in anuran skin secretions function in protection against potential predators. Although studies have demonstrated that particular chemicals are effective against certain predators, very little is known about how different chemicals from different species function against the same predators. Understanding how different chemicals function as a defence against similar predators is fundamental to the ecology and evolution of chemical defences in frogs. In the present study, the defensive function of bufadienolide-based defences in adult Rhaebo haematiticus (Bufonidae) were compared with alkaloid-based defences in adult and juvenile Dendrobates auratus (Dendrobatidae) against the same predators. Most bufonids contain synthesized bufadienolides, whereas dendrobatids contain dietary-derived alkaloids. Predation trials were performed with two potential invertebrate predators, Paraponera clavata (bullet ant) and Cupiennius coccineus (ctenid spider), to determine how these predators respond to two different types of frog chemical defence. The non-chemically defended frog Craugastor fitzingeri served as a control in all predation trials. Our results suggest that bufadienolide defences of R. haematiticus and alkaloid defences of D. auratus are equally effective towards bullet ant and ctenid spider predators. The similar avoidance and cleaning behaviours exhibited by these ants and spiders after contact with bufadienolides and alkaloids suggest that both types of defence are unpalatable to these arthropod predators.

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Arbuckle, Kevin. "Chemical antipredator defence is linked to higher extinction risk." Royal Society Open Science 3, no. 11 (November 2016): 160681. http://dx.doi.org/10.1098/rsos.160681.

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Many attributes of species may be linked to contemporary extinction risk, though some such traits remain untested despite suggestions that they may be important. Here, I test whether a trait associated with higher background extinction rates, chemical antipredator defence, is also associated with current extinction risk, using amphibians as a model system—a group facing global population declines. I find that chemically defended species are approximately 60% more likely to be threatened than species without chemical defence, although the severity of the contemporary extinction risk may not relate to chemical defence. The results confirm that background and contemporary extinction rates can be predicted from the same traits, at least in certain cases. This suggests that associations between extinction risk and phenotypic traits can be temporally stable over long periods. The results also provide novel insights into the relevance of antipredator defences for species subject to conservation concerns.

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Skelhorn, John, and Candy Rowe. "Avian predators taste–reject aposematic prey on the basis of their chemical defence." Biology Letters 2, no. 3 (April 25, 2006): 348–50. http://dx.doi.org/10.1098/rsbl.2006.0483.

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Avian predators learn to avoid defended insects on the basis of their conspicuous warning coloration. In many aposematic species, the level of chemical defence varies, with some individuals being more defended than others. Sequestration and production of defence chemicals is often costly and therefore less defended individuals enjoy the benefits of the warning signal without paying the full costs of chemical production. This is a fundamental theoretical problem for the evolutionary stability of aposematism, since less defended individuals appear to be at a selective advantage. However, if predators sample aposematic prey and selectively reject individuals on the basis of their chemical investment, aposematism could become evolutionarily stable. Previous research aimed at testing whether birds can use taste to discriminate between palatable and unpalatable prey has been confounded by other experimental factors. Here, we show that birds can taste and reject prey entirely on the basis of an individual's level of chemical defence and more importantly, they can make decisions on whether or not to consume a defended individual based upon their level of chemical investment. We discuss these results in relation to the evolution of aposematism, mimicry and defence chemistry.

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Guan, Chi, Mahasweta Saha, and Florian Weinberger. "Chemical Defence of a Seagrass against Microfoulers and Its Seasonal Dynamics." Applied Sciences 9, no. 6 (March 26, 2019): 1258. http://dx.doi.org/10.3390/app9061258.

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In marine environments bacterial microfoulers are an important determinant for the settlement of algal and animal macrofoulers. At the same time fouling is usually subject to seasonal fluctuation. Additionally, the seagrass Zostera marina is prone to microfouling, although this marine spermatophyte is known to be chemically defended against bacterial settlers. Spermatophytes are often capable of induced or activated defences against biological enemies such as pathogens or herbivores, but it is still unknown whether they can fine-tune their antifouling-defence according to settlement pressure. We therefore assessed the seasonality of bacterial settlement pressure, defence against microsettlers and concentrations of a previously identified defence compound, rosmarinic acid, on surfaces of Z. marina. All examined variables peaked in summer, while they tended to be lower in spring and autumn. The seasonality of defence activity and rosmarinic acid surface concentration was positively correlated with the seasonal fluctuation of fouling pressure, which suggests that Z. marina can adjust its defence level to the relatively high bacterial fouling pressure in summer. Besides of biotic factors the seasonal change of environmental factors, such as nitrogen supply, and in particular temperature, also affected the defence level, either directly or through indirect effects on the microbial settlers.

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Rasher, Douglas B., and Mark E. Hay. "Competition induces allelopathy but suppresses growth and anti-herbivore defence in a chemically rich seaweed." Proceedings of the Royal Society B: Biological Sciences 281, no. 1777 (February 22, 2014): 20132615. http://dx.doi.org/10.1098/rspb.2013.2615.

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Many seaweeds and terrestrial plants induce chemical defences in response to herbivory, but whether they induce chemical defences against competitors (allelopathy) remains poorly understood. We evaluated whether two tropical seaweeds induce allelopathy in response to competition with a reef-building coral. We also assessed the effects of competition on seaweed growth and seaweed chemical defence against herbivores. Following 8 days of competition with the coral Porites cylindrica , the chemically rich seaweed Galaxaura filamentosa induced increased allelochemicals and became nearly twice as damaging to the coral. However, it also experienced significantly reduced growth and increased palatability to herbivores (because of reduced chemical defences). Under the same conditions, the seaweed Sargassum polycystum did not induce allelopathy and did not experience a change in growth or palatability. This is the first demonstration of induced allelopathy in a seaweed, or of competitors reducing seaweed chemical defences against herbivores. Our results suggest that the chemical ecology of coral–seaweed–herbivore interactions can be complex and nuanced, highlighting the need to incorporate greater ecological complexity into the study of chemical defence.

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Curley, Edward A. M., Hannah E. Rowley, and Michael P. Speed. "A field demonstration of the costs and benefits of group living to edible and defended prey." Biology Letters 11, no. 6 (June 2015): 20150152. http://dx.doi.org/10.1098/rsbl.2015.0152.

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Both theoretical and laboratory research suggests that many prey animals should live in a solitary, dispersed distribution unless they lack repellent defences such as toxins, venoms and stings. Chemically defended prey may, by contrast, benefit substantially from aggregation because spatial localization may cause rapid predator satiation on prey toxins, protecting many individuals from attack. If repellent defences promote aggregation of prey, they also provide opportunities for new social interactions; hence the consequences of defence may be far reaching for the behavioural biology of the animal species. There is an absence of field data to support predictions about the relative costs and benefits of aggregation. We show here for the first time using wild predators that edible, undefended artificial prey do indeed suffer heightened death rates if they are aggregated; whereas chemically defended prey may benefit substantially by grouping. We argue that since many chemical defences are costly to prey, aggregation may be favoured because it makes expensive defences much more effective, and perhaps allows grouped individuals to invest less in chemical defences.

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Braekman, J. C., and D. Daloze. "Chemical defence in sponges." Pure and Applied Chemistry 58, no. 3 (January 1, 1986): 357–64. http://dx.doi.org/10.1351/pac198658030357.

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Read, Jennifer, Emma Gras, Gordon D. Sanson, Fiona Clissold, and Charlotte Brunt. "Does chemical defence decline more in developing leaves that become strong and tough at maturity?" Australian Journal of Botany 51, no. 5 (2003): 489. http://dx.doi.org/10.1071/bt03044.

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Leaves that are expanding cannot be very tough or strong because of the constraints of cell expansion, and therefore are particularly vulnerable to being eaten. We predicted that expanding leaves would be better defended chemically than mature leaves, and that this difference would be most pronounced in species whose leaves are tougher and stronger at maturity, i.e. that chemical defence declines as the leaf increases its mechanical defences. We tested this hypothesis by comparing leaf mechanical properties and total phenolics in three species with relatively tough and strong mature leaves (Doryphora sassafras Endl., Acmena smithii (Poir.) Merr. & Perry and Nothofagus moorei (F.Muell.) Krasser) and two species with soft mature leaves (Eucryphia moorei F.Muell. and Toona ciliata M.Roem.).A significantly higher concentration of total phenolics per leaf dry weight was recorded in expanding leaves than in mature leaves in D. sassafras, N. moorei and A. smithii, but not in the two soft-leaved species. However, the decline in total phenolics in mature leaves of D. sassafras, N. moorei and A. smithii was entirely explained by dilution caused by increased concentration of cell wall. The absence of any difference in 'protoplasmic' concentrations of phenolics is consistent with the view of polyphenols as 'immobile' defences. High protoplasmic concentrations of polyphenols in expanding leaves may be less likely in species whose leaves become toughened and strengthened at maturity if they cannot quickly reclaim the chemical defence as its defence value declines. Instead, these species may be predicted to exhibit higher levels of mobile defences in expanding leaves. Despite the higher concentrations of phenolics in expanding leaves of D. sassafras and N. moorei they were eaten more by a generalist herbivore, Epiphyas postvittana, than were mature leaves, consistent with the higher nitrogen concentration in leaves that required less force and energy to chew.

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Nakano, Saya, Michio Oguro, Tomoyuki Itagaki, and Satoki Sakai. "Florivory defence: are phenolic compounds distributed non-randomly within perianths?" Biological Journal of the Linnean Society 131, no. 1 (July 29, 2020): 12–25. http://dx.doi.org/10.1093/biolinnean/blaa099.

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Abstract Plants might allocate chemical defences unequally within attractive units of flowers including petals, sepals, and bracts because of variations in the probability of florivory. Based on optimal defence theory, which predicts that plants allocate higher chemical defences to tissues with higher probabilities of herbivore attack, we predicted that distal parts and sepals would have higher chemical defence allocations than proximal parts and petals. To test this prediction, we compared total phenolics and condensed tannins concentrations as well as presence of florivory within attractive units of ten angiosperm species. In agreement with the prediction, the overall results showed that the distal parts had higher total phenolics and condensed tannins than the proximal parts. On the other hand, contrary to the prediction, petals and sepals showed no tissue-specific variations. Florivory was more severe on the distal parts than the proximal parts, although statistical support for the variation was slightly weak, while the variations in presence of florivory between petals and sepals differed between the distal and proximal parts. These results may support the prediction of the optimal defence theory because distal parts of attractive units had higher presence of florivory and concentration of chemical defences.

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Eggenberger, F., and M. Rowell-Rahier. "Chemical defence and genetic bariation." Science of Nature 78, no. 7 (July 1991): 317–20. http://dx.doi.org/10.1007/bf01221419.

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Iddles, Tracey L., Jennifer Read, and Gordon D. Sanson. "The potential contribution of biomechanical properties to anti-herbivore defence in seedlings of six Australian rainforest trees." Australian Journal of Botany 51, no. 1 (2003): 119. http://dx.doi.org/10.1071/bt02060.

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Biomechanical properties of leaves, such as strength and toughness, may contribute to anti-herbivore defence by making it physically difficult or energetically costly for animals to eat them. We investigated leaf strength and toughness in seedlings of six rainforest trees from eastern Australia and their potential contribution to defence. Strength and toughness (work to fracture) were measured at the scale of the whole leaf and of different leaf parts. Resources for herbivores (water and nitrogen) and potential chemical defences (phenolics, alkaloids and cyanogenic glycosides) were also investigated.Leaves of Nothofagus moorei (F.Muell.) Krasser, Ceratopetalum apetalum D.Don and Doryphora sassafras Endl. were generally the toughest and strongest of those studied. Toona ciliata M.Roemer showed high concentrations of nutritive resources and little investment in the defences investigated, consistent with its shorter leaf lifespan and higher growth rate. There were no significant correlations of mechanical properties with palatability, but the softest leaf (T. ciliata) was associated with high levels of leaf damage in bioassay trials. There was also evidence that some leaves that are well-defended mechanically (involving carbon-rich cell wall) may invest less in competing carbon-based chemical defences, such as phenolics.

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Ritmejerytė, Edita, Berin A. Boughton, Michael J. Bayly, and Rebecca E. Miller. "Divergent responses of above- and below-ground chemical defence to nitrogen and phosphorus supply in waratahs (Telopea speciosissima)." Functional Plant Biology 46, no. 12 (2019): 1134. http://dx.doi.org/10.1071/fp19122.

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Plant nutrition can affect the allocation of resources to plant chemical defences, yet little is known about how phosphorus (P) supply, and relative nitrogen (N) and P supply, affect chemical defences, especially in species with intrinsically conservative nutrient use adapted to P-impoverished soils. Waratah (Telopea speciosissima (Sm.) R.Br.), like other Proteaceae, is adapted nutrient-poor soils. It was identified as having cyanogenic glycosides (CNglycs) throughout the plant. T. speciosissima seedlings were grown for 15 weeks under two N and P concentrations. CNglycs (N-based defence) and nutrients were quantified in above- and below-ground organs; foliar carbon (C)-based phenolics and tannins were also quantified. CNglyc concentrations in roots were on average 51-fold higher than in above-ground tissues and were affected by both N and P supply, whereas foliar CNglyc concentrations only responded to N supply. Leaves had high concentrations of C-based defences, which increased under low N, and were not correlated with N-based defences. Greater root chemical defence against herbivores and pathogens may be important in a non-mycorrhizal species that relies on basal resprouting following disturbance. The differing responses of secondary chemistry in above- and below-ground organs to P and N demonstrate the importance of broadening the predominantly foliar focus of plant defence studies.

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Elger, Arnaud, Damien G. Lemoine, Michael Fenner, and Mick E. Hanley. "Plant ontogeny and chemical defence: older seedlings are better defended." Oikos 118, no. 5 (May 2009): 767–73. http://dx.doi.org/10.1111/j.1600-0706.2009.17206.x.

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Nevo, Omer, Kim Valenta, Alex G. Tevlin, Patrick Omeja, Sarah A. Styler, Derek J. Jackson, Colin A. Chapman, and Manfred Ayasse. "Fruit defence syndromes: the independent evolution of mechanical and chemical defences." Evolutionary Ecology 31, no. 6 (September 14, 2017): 913–23. http://dx.doi.org/10.1007/s10682-017-9919-y.

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Heil, Martin, Daniel Feil, Andrea Hilpert, and K. Eduard Linsenmair. "Spatiotemporal patterns in indirect defence of a South-East Asian ant-plant support the optimal defence hypothesis." Journal of Tropical Ecology 20, no. 5 (August 9, 2004): 573–80. http://dx.doi.org/10.1017/s0266467404001567.

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The optimal defence hypothesis predicts that plant parts characterized by a high value and/or a high risk of being attacked should exhibit the highest level of defence. We tested this hypothesis with Macaranga bancana ant-plants, which are protected efficiently by resident, mutualistic ants from herbivores, parasites and encroaching vegetation. Because cost-effective defence of the host by ants increases ant fitness, selection should act on ant behaviour to produce patterns of distribution of defence as predicted for direct chemical defence traits. Termites and pieces of tape were equally distributed over the uppermost ten leaves and over the leaf-bearing part of the stems (with termites mimicking a transient herbivore, while tape mimics a long-term stress caused by a climber or plant parasite). This arrangement allowed a separation of putative coevolutionary adaptations in the ants' behaviour from other potential sources of spatial patterns in ant defence, such as differences in herbivore pressure, in the vulnerability of different herbivores, or in direct plant defences. Ant activity dropped rapidly at termite baits, but remained high at tapes for at least 5 h, thereby demonstrating adaptive differential responses to the differences between the two stressors. Most importantly, ants preferentially defended young leaves and shoot parts. The temporal and spatial patterns of ant attention to exogenous stressors thus were clearly adaptive, varying with likely costs and benefits of defence as formulated in the optimal defence theory.

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Vázquez-González, Carla, Rafael Zas, Nadir Erbilgin, Scott Ferrenberg, Vicente Rozas, and Luis Sampedro. "Resin ducts as resistance traits in conifers: linking dendrochronology and resin-based defences." Tree Physiology 40, no. 10 (May 30, 2020): 1313–26. http://dx.doi.org/10.1093/treephys/tpaa064.

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Abstract Conifers have evolved different chemical and anatomical defences against a wide range of antagonists. Resin ducts produce, store and translocate oleoresin, a complex terpenoid mixture that acts as both a physical and a chemical defence. Although resin duct characteristics (e.g., number, density, area) have been positively related to biotic resistance in several conifer species, the literature reporting this association remains inconclusive. Axial resin ducts recorded in annual growth rings are an archive of annual defensive investment in trees. This whole-life record of defence investment can be analysed using standard dendrochronological procedures, which allows us to assess interannual variability and the effect of understudied drivers of phenotypic variation on resin-based defences. Understanding the sources of phenotypic variation in defences, such as genetic differentiation and environmental plasticity, is essential for assessing the adaptive potential of forest tree populations to resist pests under climate change. Here, we reviewed the evidence supporting the importance of resin ducts in conifer resistance, and summarized current knowledge about the sources of variation in resin duct production. We propose a standardized methodology to measure resin duct production by means of dendrochronological procedures. This approach will illuminate the roles of resin ducts in tree defence across species, while helping to fill pivotal knowledge gaps in plant defence theory, and leading to a robust understanding of the patterns of variation in resin-based defences throughout the tree’s lifespan.

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Winters, Anne E., Nerida G. Wilson, Cedric P. van den Berg, Martin J. How, John A. Endler, N. Justin Marshall, Andrew M. White, Mary J. Garson, and Karen L. Cheney. "Toxicity and taste: unequal chemical defences in a mimicry ring." Proceedings of the Royal Society B: Biological Sciences 285, no. 1880 (June 6, 2018): 20180457. http://dx.doi.org/10.1098/rspb.2018.0457.

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Mimicry of warning signals is common, and can be mutualistic when mimetic species harbour equal levels of defence (Müllerian), or parasitic when mimics are undefended but still gain protection from their resemblance to the model (Batesian). However, whether chemically defended mimics should be similar in terms of toxicity (i.e. causing damage to the consumer) and/or unpalatability (i.e. distasteful to consumer) is unclear and in many studies remains undifferentiated. In this study, we investigated the evolution of visual signals and chemical defences in a putative mimicry ring of nudibranch molluscs. First, we demonstrated that the appearance of a group of red spotted nudibranchs molluscs was similar from the perspective of potential fish predators using visual modelling and pattern analysis. Second, using phylogenetic reconstruction, we demonstrated that this colour pattern has evolved multiple times in distantly related individuals. Third, we showed that these nudibranchs contained different chemical profiles used for defensive purposes. Finally, we demonstrated that although levels of distastefulness towards Palaemon shrimp remained relatively constant between species, toxicity levels towards brine shrimp varied significantly. We highlight the need to disentangle toxicity and taste when considering chemical defences in aposematic and mimetic species, and discuss the implications for aposematic and mimicry signal evolution.

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Kronheim, Sarah, Martin Daniel-Ivad, Zhuang Duan, Sungwon Hwang, Andrew I. Wong, Ian Mantel, Justin R. Nodwell, and Karen L. Maxwell. "A chemical defence against phage infection." Nature 564, no. 7735 (December 2018): 283–86. http://dx.doi.org/10.1038/s41586-018-0767-x.

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Capon, John H. "The Chemical Defence Establishment halothane adsorber." Anaesthesia 33, no. 8 (February 22, 2007): 760–61. http://dx.doi.org/10.1111/j.1365-2044.1978.tb08486.x.

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Spiteller, Peter. "Chemical Defence Strategies of Higher Fungi." Chemistry - A European Journal 14, no. 30 (October 20, 2008): 9100–9110. http://dx.doi.org/10.1002/chem.200800292.

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BOANTZA, VICTOR D., and OFER GAL. "The ‘absolute existence’ of phlogiston: the losing party's point of view." British Journal for the History of Science 44, no. 3 (February 2, 2011): 317–42. http://dx.doi.org/10.1017/s000708741000155x.

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AbstractLong after its alleged demise, phlogiston was still presented, discussed and defended by leading chemists. Even some of the leading proponents of the new chemistry admitted its ‘absolute existence’. We demonstrate that what was defended under the title ‘phlogiston’ was no longer a particular hypothesis about combustion and respiration. Rather, it was a set of ontological and epistemological assumptions and the empirical practices associated with them. Lavoisier's gravimetric reduction, in the eyes of the phlogistians, annihilated the autonomy of chemistry together with its peculiar concepts of chemical substance and quality, chemical process and chemical affinity. The defence of phlogiston was the defence of a distinctly chemical conception of matter and its appearances, a conception which reflected the chemist's acquaintance with details and particularities of substances, properties and processes and his skills of adducing causal relations from the interplay between their complexity and uniformity.

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Flora, S. J. S. "Special Issue on Defence Against Biological and Chemical Agents." Defence Life Science Journal 1, no. 1 (June 1, 2016): 05. http://dx.doi.org/10.14429/dlsj.1.10099.

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WELCOME to the inaugural issue of the Defence Life Science Journal. The Defence Life Science Journal (DLSJ) is an international journal and is published by Defence Scientific Information & Documentation Centre (DESIDOC) on behalf of Defence Research and Development Organization (DRDO). The journal is dedicated to publishing research covering a wide spectrum of applications in the emerging field in the field of defence/military life support system. Broadly it will cover; Molecular biology, biophysics, biochemistry, psychology, physiology, biotechnology, pharmacology and toxicology (animals, plants, microbial and viral cells), and related areas like bio-medicine, bio-engineering, bio-electronics, etc.

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Rojas, Bibiana, Emily Burdfield-Steel, Hannu Pakkanen, Kaisa Suisto, Michael Maczka, Stefan Schulz, and Johanna Mappes. "How to fight multiple enemies: target-specific chemical defences in an aposematic moth." Proceedings of the Royal Society B: Biological Sciences 284, no. 1863 (September 27, 2017): 20171424. http://dx.doi.org/10.1098/rspb.2017.1424.

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Animals have evolved different defensive strategies to survive predation, among which chemical defences are particularly widespread and diverse. Here we investigate the function of chemical defence diversity, hypothesizing that such diversity has evolved as a response to multiple enemies. The aposematic wood tiger moth ( Arctia plantaginis ) displays conspicuous hindwing coloration and secretes distinct defensive fluids from its thoracic glands and abdomen. We presented the two defensive fluids from laboratory-reared moths to two biologically relevant predators, birds and ants, and measured their reaction in controlled bioassays (no information on colour was provided). We found that defensive fluids are target-specific: thoracic fluids, and particularly 2- sec -butyl-3-methoxypyrazine, which they contain, deterred birds, but caused no aversive response in ants. By contrast, abdominal fluids were particularly deterrent to ants, while birds did not find them repellent. Our study, to our knowledge, is the first to show evidence of a single species producing separate chemical defences targeted to different predator types, highlighting the importance of taking into account complex predator communities in studies on the evolution of prey defence diversity.

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Millen, John, and Paul Taylor. "Our jobs: In chemical and biological defence." RUSI Journal 144, no. 6 (December 1999): 7–16. http://dx.doi.org/10.1080/03071849908446459.

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Bertók, Lóránd. "Bile acids in physico-chemical host defence." Pathophysiology 11, no. 3 (December 2004): 139–45. http://dx.doi.org/10.1016/j.pathophys.2004.09.002.

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CARDOSO, MÁRCIO ZIKÁN. "Testing chemical defence based on pyrrolizidine alkaloids." Animal Behaviour 54, no. 4 (October 1997): 985–91. http://dx.doi.org/10.1006/anbe.1997.0505.

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Schulze, Birgit, and Dieter Spiteller. "Capsaicin: Tailored Chemical Defence Against Unwanted “Frugivores”." ChemBioChem 10, no. 3 (February 13, 2009): 428–29. http://dx.doi.org/10.1002/cbic.200800755.

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Martinez-Swatson, Karen, Rasmus Kjøller, Federico Cozzi, Henrik Toft Simonsen, Nina Rønsted, and Christopher Barnes. "Exploring evolutionary theories of plant defence investment using field populations of the deadly carrot." Annals of Botany 125, no. 5 (October 31, 2019): 737–50. http://dx.doi.org/10.1093/aob/mcz151.

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Abstract Background and Aims There are a number of disparate models predicting variation in plant chemical defences between species, and within a single species over space and time. These can give conflicting predictions. Here we review a number of these theories, before assessing their power to predict the spatial–temporal variation of thapsigargins between and within populations of the deadly carrot (Thapsia garganica). By utilizing multiple models simultaneously (optimum defence theory, growth rate hypothesis, growth–differentiation balance hypothesis, intra–specific framework and resource exchange model of plant defence), we will highlight gaps in their predictions and evaluate the performance of each. Methods Thapsigargins are potent anti-herbivore compounds that occur in limited richness across the different plant tissues of T. garganica, and therefore represent an ideal system for exploring these models. Thapsia garganica plants were collected from six locations on the island of Ibiza, Spain, and the thapsigargins quantified within reproductive, vegetative and below-ground tissues. The effects of sampling time, location, mammalian herbivory, soil nutrition and changing root-associated fungal communities on the concentrations of thapsigargins within these in situ observations were analysed, and the results were compared with our model predictions. Key Results The models performed well in predicting the general defence strategy of T. garganica and the above-ground distribution of thapsigargins, but failed to predict the considerable proportion of defences found below ground. Models predicting variation over environmental gradients gave conflicting and less specific predictions, with intraspecific variation remaining less understood. Conclusion Here we found that multiple models predicting the general defence strategy of plant species could likely be integrated into a single model, while also finding a clear need to better incorporate below-ground defences into models of plant chemical defences. We found that constitutive and induced thapsigargins differed in their regulation, and suggest that models predicting intraspecific defences should consider them separately. Finally, we suggest that in situ studies be supplemented with experiments in controlled environments to identify specific environmental parameters that regulate variation in defences within species.

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Spiteller, Peter. "Chemical ecology of fungi." Natural Product Reports 32, no. 7 (2015): 971–93. http://dx.doi.org/10.1039/c4np00166d.

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Hossie, T. J., C. Hassall, W. Knee, and T. N. Sherratt. "Species with a chemical defence, but not chemical offence, live longer." Journal of Evolutionary Biology 26, no. 7 (May 3, 2013): 1598–602. http://dx.doi.org/10.1111/jeb.12143.

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Schmidtberg, Henrike, Christian Röhrich, Heiko Vogel, and Andreas Vilcinskas. "A switch from constitutive chemical defence to inducible innate immune responses in the invasive ladybird Harmonia axyridis." Biology Letters 9, no. 3 (June 23, 2013): 20130006. http://dx.doi.org/10.1098/rsbl.2013.0006.

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The harlequin ladybird, Harmonia axyridis , has emerged as a model species for invasion biology, reflecting its remarkable capacity to outcompete native ladybird species when introduced into new habitats. This ability may be associated with its prominent resistance to pathogens and intraguild predation. We recently showed that the constitutive antibacterial activity present in the haemolymph of H. axyridis beetles can be attributed to the chemical defence compound harmonine. Here, we demonstrate that H. axyridis differs from other insects, including the native ladybird Coccinella septempunctata, by reducing rather than increasing the antimicrobial activity of its haemolymph following the injection of bacteria. However, both species produce new or more abundant proteins in the haemolymph, indicating that bacterial challenge induces innate immune responses associated with the synthesis of immunity-related proteins. Our results suggest that H. axyridis beetles can switch from constitutive chemical defence to inducible innate immune responses, supporting hypothesis that inducible antimicrobial peptides protect host beetles against pathogens that survive constitutive defences. These alternative antimicrobial defence mechanisms may reflect a trade-off resulting from fitness-related costs associated with the simultaneous synthesis of harmonine and antimicrobial peptides/proteins.

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Naglik, Julian R. "Candida Immunity." New Journal of Science 2014 (August 25, 2014): 1–27. http://dx.doi.org/10.1155/2014/390241.

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The human pathogenic fungus Candida albicans is the predominant cause of both superficial and invasive forms of candidiasis. C. albicans primarily infects immunocompromised individuals as a result of either immunodeficiency or intervention therapy, which highlights the importance of host immune defences in preventing fungal infections. The host defence system utilises a vast communication network of cells, proteins, and chemical signals distributed in blood and tissues, which constitute innate and adaptive immunity. Over the last decade the identity of many key molecules mediating host defence against C. albicans has been identified. This review will discuss how the host recognises this fungus, the events induced by fungal cells, and the host innate and adaptive immune defences that ultimately resolve C. albicans infections during health.

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McCall, Andrew C., and James A. Fordyce. "Can optimal defence theory be used to predict the distribution of plant chemical defences?" Journal of Ecology 98, no. 5 (July 13, 2010): 985–92. http://dx.doi.org/10.1111/j.1365-2745.2010.01693.x.

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Walters, Dale R., and Linda Paterson. "Parents lend a helping hand to their offspring in plant defence." Biology Letters 8, no. 5 (June 13, 2012): 871–73. http://dx.doi.org/10.1098/rsbl.2012.0416.

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Plants under attack by pathogens and pests can mount a range of inducible defences, encompassing both chemical and structural changes. Although few reports exist, it appears that plants responding to pathogen or herbivore attack, or chemical defence elicitors, may produce progeny that are better able to defend themselves against attack, compared with progeny from unthreatened or untreated plants. To date, all research on transgenerational effects of biotic stress has been conducted on dicotyledenous plants. We examined the possibility that resistance induced by application of chemical defence elicitors to the monocot plant barley, could be passed on to the progeny. Plants were treated with acibenzolar-S-methyl (ASM) or saccharin, and grain harvested at maturity. Germination was unaffected in seed collected from plants treated with saccharin, while germination was reduced significantly in seed collected from ASM-treated plants. The subsequent growth of the seedlings was not significantly different in any of the treatments. However, plants from parents treated with both ASM or saccharin exhibited significantly enhanced resistance to infection by Rhynchosporium commune, despite not being treated with elicitor themselves. These data hint at the possibility of producing disease-resistant plants by exposing parent plants to chemical elicitors.

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Nogueira-de-Sá, Flávia, and José Roberto Trigo. "Faecal shield of the tortoise beetle Plagiometriona aff. flavescens (Chrysomelidae: Cassidinae) as chemically mediated defence against predators." Journal of Tropical Ecology 21, no. 2 (February 16, 2005): 189–94. http://dx.doi.org/10.1017/s0266467404002147.

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Larvae of Plagiometriona aff. flavescens carry a structure on their back made of faeces and exuviae, called faecal shield, which may protect larvae against natural enemies. Previous investigations suggested that the nature of such protection was chemical. To test if chemicals found in the faecal shield of Plagiometriona aff. flavescens provided defence for larvae, experiments in the field and in the laboratory (using the ant Camponotus crassus, and chicks Gallus gallus as model predators) were undertaken. Both field and laboratory experiments showed that live larvae with faecal shields, as well as baits treated with faecal shield extracts, were rejected by predators, confirming the chemical nature of this kind of defence.

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PASTEELS, J. M., D. DALOZE, and M. ROWELL-RAHIER. "Chemical defence in chrysomelid eggs and neonate larvae." Physiological Entomology 11, no. 1 (March 1986): 29–37. http://dx.doi.org/10.1111/j.1365-3032.1986.tb00388.x.

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BÜNNIGE, MARTINA, MONIKA HILKER, and SUSANNE DOBLER. "Convergent evolution of chemical defence in Galerucine larvae." Biological Journal of the Linnean Society 93, no. 1 (December 17, 2007): 165–75. http://dx.doi.org/10.1111/j.1095-8312.2007.00912.x.

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Timmermans, Michel, Thierry Randoux, Désiré Daloze, Jean-Claude Braekman, Jacques M. Pasteels, and Laurent Lesages. "The chemical defence of Doryphorina beetles (Coleoptera: Chrysomelidae)." Biochemical Systematics and Ecology 20, no. 4 (June 1992): 343–49. http://dx.doi.org/10.1016/0305-1978(92)90047-h.

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Twigg, L. E., and L. V. Socha. "Physical versus chemical defence mechanisms in toxic Gastrolobium." Oecologia 108, no. 1 (1996): 21–28. http://dx.doi.org/10.1007/bf00333210.

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Hay, L., and J. M. M. Brown. "Plant chemical defence: Plant response to physical damage." Comparative Biochemistry and Physiology Part C: Comparative Pharmacology 101, no. 3 (April 1992): 537–39. http://dx.doi.org/10.1016/0742-8413(92)90083-j.

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Martinez-Swatson, Karen, Carmen Quiñonero-López, Madeleine Ernst, Nina Rønsted, Christopher James Barnes, and Henrik Toft Simonsen. "Thapsigargins and induced chemical defence in Thapsia garganica." Chemoecology 30, no. 5 (June 11, 2020): 255–67. http://dx.doi.org/10.1007/s00049-020-00315-3.

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Kuprewicz, Erin K., and Carlos García-Robledo. "Mammal and insect predation of chemically and structurally defended Mucuna holtonii (Fabaceae) seeds in a Costa Rican rain forest." Journal of Tropical Ecology 26, no. 3 (March 30, 2010): 263–69. http://dx.doi.org/10.1017/s0266467410000039.

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Abstract:To prevent seed losses from predation, plants have developed protective strategies. Seeds may utilize chemical or structural defences to deter predators. Mucuna holtonii (Fabaceae) has large seeds containing a toxic amino acid, L-dopa, and covered with a hard seed coat. Our study assessed the effectiveness of chemical and mechanical seed defences against vertebrate and invertebrate seed predators within Estación Biológica La Selva, Costa Rica. Pre-dispersal insect and fungus attack of M. holtonii seeds was low (95.7% of 1493 seeds were undamaged). Camera traps monitoring 90 marked M. holtonii seeds showed that the collared peccary (Pecari tajacu) consumed 98.6% of 69 removed seeds over 16 d. Field experiments involving 100 seeds with intact and 100 with opened seed coats found that only opened seeds had endosperm removed by Sericomyrmex amabilis ants (0.5–100% of endosperm removed). Shade-house experiments showed that seeds with high amounts of endosperm removed by ants resulted in low germination success and low seedling biomass production. Although M. holtonii seeds are rich in L-dopa, this compound is not an effective chemical defence against mammals that possess foregut fermentation. The seed coat of M. holtonii is an effective structural defence against invertebrate seed predators, preventing endosperm removal and enhancing seedling survival.

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Segovia, Júlio M. G., Kleber Del-Claro, and Rodrigo Hirata Willemart. "Defences of a Neotropical harvestman against different levels of threat by the recluse spider." Behaviour 152, no. 6 (2015): 757–73. http://dx.doi.org/10.1163/1568539x-00003252.

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The threat sensitive hypothesis predicts that animals modulate the defensive behaviour with the level of threat. Therefore, responses to predator cues may differ from responses to the actual predator in close range. Also, in high threat situations, prey would be expected to use their most dangerous defences. The recluse spider Loxosceles gaucho (Araneae, Sicariidae) is known to prey upon well defended harvestmen such as the laniatorid Mischonyx cuspidatus (Opiliones, Gonyleptidae), which has been reported to use tanathosis, chemical defences, pinching with sharp apophyses on legs, chelicerae and pedipalps. Because of harvestmen’s dependence on chemical stimuli, we tested if M. cuspidatus would change its locomotory behaviour in the presence of chemicals of the recluse spider (low threat situation: spider vs blank vs chemical control; one at a time). Subsequently, we tested harvestmen behaviour in the presence of the spider in close range, a high-threat situation. Finally, we looked at the survival rate of spiders after being pierced by sharp apophyses that M. cuspidatus have on legs IV. The harvestmen only showed defensive behaviours in the high threat situation. Surprisingly, their mostly known defensive behaviours (chemical defence, tanathosis, pinching with chelicerae and pedipalps) were not seen even in the high threat situation. This is the first evidence that these behaviours are not used against a natural predator that has an almost 80% predation success when attacking harvestmen. Pinching with the sharp legs IV apophyses may perforate but do not kill the spiders. We highlight the importance of the traditional descriptive approach with natural predators to understand the specificities of defensive behaviours against different types of predator.

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Furness, John B., and Jeremy J. Cottrell. "Signalling from the gut lumen." Animal Production Science 57, no. 11 (2017): 2175. http://dx.doi.org/10.1071/an17276.

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The lining of the gastrointestinal tract needs to be easily accessible to nutrients and, at the same time, defend against pathogens and chemical challenges. This lining is the largest and most vulnerable surface that faces the outside world. To manage the dual problems of effective nutrient conversion and defence, the gut lining has a sophisticated system for detection of individual chemical entities, pathogenic organisms and their products, and physico-chemical properties of its contents. Detection is through specific receptors that signal to the gut endocrine system, the nervous system, the immune system and local tissue defence systems. These effectors, in turn, modify digestive functions and contribute to tissue defence. Receptors for nutrients include taste receptors for sweet, bitter and savoury, free fatty acid receptors, peptide and phytochemical receptors, that are primarily located on enteroendocrine cells. Hormones released by enteroendocrine cells act locally, through the circulation and via the nervous system, to optimise digestion and mucosal health. Pathogen detection is both through antigen presentation to T-cells and through pattern-recognition receptors (PRRs). Activation of PRRs triggers local tissue defence, for example, by causing release of antimicrobials from Paneth cells. Toxic chemicals, including plant toxins, are sensed and then avoided, expelled or metabolised. It continues to be a major challenge to develop a comprehensive understanding of the integrated responses of the gastrointestinal tract to its luminal contents.

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MCCLINTOCK, JAMES B., ANDREW R. MAHON, KEVIN J. PETERS, CHARLES D. AMSLER, and BILL J. BAKER. "Chemical defences in embryos and juveniles of two common Antarctic sea stars and an isopod." Antarctic Science 15, no. 3 (September 2003): 339–44. http://dx.doi.org/10.1017/s0954102003001354.

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The brooded embryos and/or juveniles of the sea stars Neosmilaster georgianus (Studer, 1885) and Lysasterias perrieri (Studer, 1885) and the isopod Glyptonotus antarcticus (Eights, 1853) were examined for their acceptability using the sympatric sea star Odontaster validus (Koehler, 1906) as a predator. Organic extracts were prepared from embryos of both sea stars and juveniles of Lyasterias perrieri and Glyptonotus antarcticus and tested in alginate food pellets to confirm whether lack of acceptability was chemically based. We found both intact whole embryos and juveniles of the sea star Neosmilaster georgianus were not acceptable to Odontaster validus. A methanol extract of the embryos was palatable. This could be the result of either the sequestration of deterrent chemicals within embryos or the presence of noxious compounds that were not extractable in methanol. Embryos and juveniles of the sea star Lysasterias perrieri were not acceptable to sea stars. Food pellets containing methanol extracts of unacceptable embryos were deterrent against sea stars, suggesting a chemical defence. Juvenile brooded isopods (Glyptonotus antarcticus) were also found to be unacceptable in sea star feeding bioassays. Significant rejection of alginate pellets containing a lipophilic dichloromethane methanol extract of juveniles indicated that this lack of acceptability was chemically based. Our study provides further support for chemical defences in the offspring of brooding lecithotrophic Antarctic marine invertebrates.

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Bodnaryk, R. P., and R. T. Rymerson. "Effect of wounding and jasmonates on the physico-chemical properties and flea beetle defence responses of canola seedlings, Brassica napus L." Canadian Journal of Plant Science 74, no. 4 (October 1, 1994): 899–907. http://dx.doi.org/10.4141/cjps94-161.

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Inducible defence responses of seedlings of Brassica napus were investigated after cotyledons were mechanically wounded or treated topically with methyl jasmonate (MeJA). Flea beetles (Phyllotreta cruciferae Goeze) fed less (twofold) on wounded or jasmonate-treated seedlings, probably because their cotyledons were tougher (1.4-fold), the protein content was lower (by half), and the level of cysteine proteinase inhibitor was higher (twofold) than in untreated controls. Wound-induced defences in the cotyledons of B. napus appear to be based on multiple mechanisms (all relatively weak) that may be mediated by jasmonates.Remarkable increases (up to 25-fold) were observed in the viscosity of cotyledon extracts after wounding or treatment with MeJA. Altered tissue water content, DNA, sugars or sugar alcohols did not account for the increase in viscosity. Heating extracts at 100 °C, trichloroacetic acid precipitation, chloroform extraction, and anion–cation–exchange chromatography removed protein and greatly lowered viscosity, indicating that jasmonate-induced proteins may be responsible for elevated viscosity. It is uncertain whether the high viscosity of extracts reflects actual physico-chemical conditions within cotyledons or reflects stress, defence or hydraulic responses to wounding and jasmonates. Key words: Wounding, jasmonate, resistance, Insecta, Brassica napus, Phyllotreta cruciferae, plant defence

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Pedras, M. Soledade C. "AWARD LECTURE / CONFÉRENCE D'HONNEUR Prospects for controlling plant fungal diseases Alternatives based on chemical ecology and biotechnology." Canadian Journal of Chemistry 82, no. 9 (September 1, 2004): 1329–35. http://dx.doi.org/10.1139/v04-105.

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Plants produce a diverse array of secondary metabolites associated with important defence and resistance mechanisms. In general, within the same plant family the chemical structures of these metabolites are related and suggest common biogenetic precursors. Crucifers are known to produce constitutive and induced tryptophan derived metabolites. Pathogenic fungi can resist such defences utilizing a variety of processes, as for example, enzymatic detoxification. On the other hand, to facilitate their penetration and colonization of the plant tissues, fungal phytopathogens can produce phytotoxic metabolites, some of which are selectively toxic to host-plants. However, plants may be resistant to these pathogens partly due to their ability to detoxify these selective phytotoxins. Nonetheless, the outcome of these interactions frequently favours the pathogen and can lead to enormous yield losses or even major plant epidemics. An overview of some of the most recent studies of metabolic pathways and stress responses in crucifers and several of their pathogens is presented. Potential strategies to prevent and control plant microbial diseases based on chemical ecology studies and biotechnology will be discussed. Key words: phytoalexin, phytotoxin, chemical defence, metabolic detoxification, destruxin B.

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Hallam, Amy, and Jennifer Read. "Do tropical species invest more in anti-herbivore defence than temperate species? A test in Eucryphia (Cunoniaceae) in eastern Australia." Journal of Tropical Ecology 22, no. 1 (December 21, 2005): 41–51. http://dx.doi.org/10.1017/s0266467405002919.

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Tropical plants have been suggested to have higher levels of mechanical, chemical and biotic defences than temperate plants. However, comparisons have usually included deciduous species within the temperate group, which confounds the analysis since deciduous species are predicted to have a different strategy with respect to investment, nutrition and defence than evergreen species. In this study we examined levels of defence and nutrition in five evergreen species of Eucryphia occurring along a latitudinal gradient in eastern Australia, grown under common conditions in a glasshouse. From the resource-availability hypothesis we predicted the opposite gradient in defence investment, i.e. that lowest levels of defence will occur in tropical species with potentially high growth rates and annual productivity. However, we found an increase in cell wall content, total phenolics and tannin activity, and a decrease in protein availability, with decreasing latitude and/or increasing mean annual temperature. Hence, there was a trend of increasing defence (although not in leaf toughness) and declining nutritional quality towards the tropics. These latitudinal trends were recorded in both mature and expanding leaves. The same trends were observed in leaves of two species collected from the field, indicating that the results were not peculiar to the experimental growth regime. The latitudinal trend in defence did not support our prediction based on the resource availability hypothesis and may indicate that herbivore pressure is providing an overriding selection pressure, although there are alternative explanations.

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Pearson, Graham S. "Chemical and biological defence: An essential national security requirement." RUSI Journal 140, no. 4 (August 1995): 20–27. http://dx.doi.org/10.1080/03071849508445938.

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Journal articles on the topic 'Chemical defence'

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