Sequestration of cardenolides inOncopeltus fasciatus: Morphological and physiological adaptations

Scudder, G. G. E.; Moore, Lynn V.; Isman, Murray B.

doi:10.1007/bf01639003

Cited by 72 publications

(66 citation statements)

References 58 publications

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“…The shape depends on many factors, including the predator's ability to detect the toxin at different concentrations and its susceptibility to the toxin; in addition, it will depend on the tissue(s) in which the prey store the toxin and on whether the toxin is excreted in response to predators [9,[41][42][43][44][45]. Since little is currently known about the shape of this function, some hypothetical examples have been explored ( figure 3).…”

Section: Discussionmentioning

confidence: 99%

Disentangling taste and toxicity in aposematic prey

Holen

2013

Proc. R. Soc. B.

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Many predators quickly learn to avoid attacking aposematic prey. If the prey vary in toxicity, the predators may alternatively learn to capture and tastesample prey carefully before ingesting or rejecting them (go-slow behaviour). An increase in prey toxicity is generally thought to decrease predation on prey populations. However, while prey with a higher toxin load are more harmful to ingest, they may also be easier to recognize and reject owing to greater distastefulness, which can facilitate a taste-sampling foraging strategy. Here, the classic diet model is used to study the separate effects of taste and toxicity on predator preferences. The taste-sampling process is modelled using signal detection theory. The model is applicable to automimicry and Batesian mimicry. It shows that when the defensive toxin is sufficiently distasteful, a mimicry complex may be less profitable to the predator and better protected against predation if the models are moderately toxic than if they are highly toxic. Moreover, taste mimicry can reduce the profitability of the mimicry complex and increase protection against predation. The results are discussed in relation to the selection pressures acting on prey defences and the evolution of mimicry.

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Section: Discussionmentioning

confidence: 99%

Disentangling taste and toxicity in aposematic prey

Holen

2013

Proc. R. Soc. B.

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“…In the monarch butterfly, Danaus plexippus, and the large milkweed bug, Oncopeltus fasciatus, in vitro assays showed that these species possess Na,K-ATPases that have a dramatically lowered binding affinity to cardenolides (ouabain) (19)(20)(21)(22). Molecular investigations later demonstrated that this insensitivity may be explained in the monarch butterfly, at least in part, by an amino acid substitution of asparagine for histidine at position 122 (N122H) in the first extracellular loop of the Na,KATPase (19,23).…”

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confidence: 99%

Community-wide convergent evolution in insect adaptation to toxic cardenolides by substitutions in the Na,K-ATPase

Dobler

Dalla

Wagschal

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

266

288

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The extent of convergent molecular evolution is largely unknown, yet is critical to understanding the genetics of adaptation. Target site insensitivity to cardenolides is a prime candidate for studying molecular convergence because herbivores in six orders of insects have specialized on these plant poisons, which gain their toxicity by blocking an essential transmembrane carrier, the sodium pump (Na,K-ATPase). We investigated gene sequences of the Na,KATPase α-subunit in 18 insects feeding on cardenolide-containing plants (spanning 15 genera and four orders) to screen for amino acid substitutions that might lower sensitivity to cardenolides. The replacement N122H that was previously shown to confer resistance in the monarch butterfly (Danaus plexippus) and Chrysochus leaf beetles was found in four additional species, Oncopeltus fasciatus and Lygaeus kalmii (Heteroptera, Lygaeidae), Labidomera clivicollis (Coleoptera, Chrysomelidae), and Liriomyza asclepiadis (Diptera, Agromyzidae). Thus, across 300 Myr of insect divergence, specialization on cardenolide-containing plants resulted in molecular convergence for an adaptation likely involved in coevolution. Our screen revealed a number of other substitutions connected to cardenolide binding in mammals. We confirmed that some of the particular substitutions provide resistance to cardenolides by introducing five distinct constructs of the Drosophila melanogaster gene into susceptible eucaryotic cells under an ouabain selection regime. These functional assays demonstrate that combined substitutions of Q 111 and N 122 are synergistic, with greater than twofold higher resistance than either substitution alone and >12-fold resistance over the wild type. Thus, even across deep phylogenetic branches, evolutionary degrees of freedom seem to be limited by physiological constraints, such that the same molecular substitutions confer adaptation.insect-plant interactions | specialist herbivores | target site insensitivity | toxin resistance | cardiac glycosides

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“…We detected a unique doublelayered epidermis in O. fasciatus and showed that cardenolides accumulated in the innermost layer, with the integument having special pores for their release. We undertook an experimental investigation of a number of special physiological adaptations in O. fasciatus associated with cardenolide uptake, regulation, and release (56,107,108), including the ability of the Malpighian tubules to excrete ouabain (53), and we showed the presence of ouabainresistant Na, K-ATPases in this insect (55).…”

Section: Wwwannualreviewsorg • Life and Research Of An Entomologistmentioning

confidence: 99%

Threads and Serendipity in the Life and Research of an Entomologist

Scudder

2008

Annu. Rev. Entomol.

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This article presents an account of the development of Geoffrey Scudder's interest in entomology, with an emphasis on threads and serendipity. Early interests in Hemiptera, insect dispersal, evolution, and chemical ecology were followed by research on insect genitalia and seed bug systematics while at Oxford University. A faculty appointment in Canada led to research on water boatmen, water striders, cardenolides, faunistics, biodiversity, and habitat restoration. Since retirement, activities have diversified to include biodiversity mapping, conservation planning, and enhancing raised-bog integrity.

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Sequestration of cardenolides inOncopeltus fasciatus: Morphological and physiological adaptations

Cited by 72 publications

References 58 publications

Disentangling taste and toxicity in aposematic prey

Disentangling taste and toxicity in aposematic prey

Community-wide convergent evolution in insect adaptation to toxic cardenolides by substitutions in the Na,K-ATPase

Threads and Serendipity in the Life and Research of an Entomologist

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