1
|
Espinosa Del Alba L, Petschenka G. No physiological costs of dual sequestration of chemically different plant toxins in the milkweed bug Spilostethus saxatilis (Heteroptera: Lygaeidae). JOURNAL OF INSECT PHYSIOLOGY 2023; 147:104508. [PMID: 37011856 DOI: 10.1016/j.jinsphys.2023.104508] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2022] [Revised: 02/06/2023] [Accepted: 03/31/2023] [Indexed: 06/02/2023]
Abstract
Many herbivorous insects not only cope with plant toxins but also sequester them as a defense against predators and parasitoids. Sequestration is a product of the evolutionary arms race between plants and herbivorous insects and has been hypothesized to incur physiological costs due to specific adaptations required. Contradictory evidence about these costs exists for insects sequestering only one class of toxin, but very little is known about the physiological implications for species sequestering structurally different classes of compounds. Spilostethus saxatilis is a milkweed bug belonging to the cardenolide-sequestering heteropteran subfamily Lygaeinae (Heteroptera: Lygaeidae) that has shifted to the colchicine-containing plant Colchicum autumnale, a resource of chemically unrelated alkaloids. Using feeding-assays on artificial diet and chemical analysis, we assessed whether S. saxatilis is still able to sequester cardenolides apart from colchicine and related metabolites (colchicoids), and tested the effect of (1) either a natural cardenolide concentration (using ouabain as a model compound) or a natural colchicine concentration, (2) an increased concentration of both toxins, and (3) seeds of either Asclepias syriaca (cardenolides) or C. autumnale (colchicoids) on a set of life-history traits. For comparison, we assessed the same life-history traits in the milkweed bug Oncopeltus fasciatus exposed to cardenolides only. Although cardenolides and colchicoids have different physiological targets (Na+/K+-ATPase vs tubulin) and thus require different resistance traits, chronic exposure and sequestration of both isolated toxins caused no physiological costs such as reduced growth, increased mortality, lower fertility, or shorter adult life span in S. saxatilis. Indeed, an increased performance was observed in O. fasciatus and an according trend was found in S. saxatilis when feeding on isolated ouabain and isolated colchicine, respectively. Positive effects were even more pronounced when insects were provided with natural toxic seeds (i.e. C. autumnale for S. saxatilis and A. syriaca for O. fasciatus), especially in O. fasciatus. Our findings suggest, that S. saxatilis can sequester two chemically unrelated classes of plant compounds at a cost-free level, and that colchicoids may even play a beneficial role in terms of fertility.
Collapse
Affiliation(s)
- Laura Espinosa Del Alba
- Department of Applied Entomology, Institute of Phytomedicine, University of Hohenheim, Otto-Sander Straße 5, 70599 Stuttgart, Germany
| | - Georg Petschenka
- Department of Applied Entomology, Institute of Phytomedicine, University of Hohenheim, Otto-Sander Straße 5, 70599 Stuttgart, Germany.
| |
Collapse
|
2
|
Heyworth HC, Pokharel P, Blount JD, Mitchell C, Petschenka G, Rowland HM. Antioxidant availability trades off with warning signals and toxin sequestration in the large milkweed bug ( Oncopeltus fasciatus). Ecol Evol 2023; 13:e9971. [PMID: 37038513 PMCID: PMC10082154 DOI: 10.1002/ece3.9971] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2022] [Revised: 03/13/2023] [Accepted: 03/17/2023] [Indexed: 04/12/2023] Open
Abstract
In some aposematic species the conspicuousness of an individual's warning signal and the concentration of its chemical defense are positively correlated. Several mechanisms have been proposed to explain this phenomenon, including resource allocation trade-offs where the same limiting resource is needed to produce both the warning signal and chemical defense. Here, the large milkweed bug (Oncopeltus fasciatus: Heteroptera, Lygaeinae) was used to test whether allocation of antioxidants, that can impart color, trade against their availability to prevent self-damage caused by toxin sequestration. We investigated if (i) the sequestration of cardenolides is associated with costs in the form of changes in oxidative state; and (ii) oxidative state can affect the capacity of individuals to produce warning signals. We reared milkweed bugs on artificial diets with increasing quantities of cardenolides and examined how this affected signal quality (brightness and chroma) across different instars. We then related the expression of warning colors to the quantity of sequestered cardenolides and indicators of oxidative state-oxidative lipid damage (malondialdehyde), and two antioxidants: total superoxide dismutase and total glutathione. Bugs that sequestered more cardenolides had significantly lower levels of the antioxidant glutathione, and bugs with less total glutathione had less luminant orange warning signals and reduced chroma of their black patches compared to bugs with more glutathione. Bugs that sequestered more cardenolides also had reduced red-green chroma of their black patches that was unrelated to oxidative state. Our results give tentative support for a physiological cost of sequestration in milkweed bugs and a mechanistic link between antioxidant availability, sequestration, and warning signals.
Collapse
Affiliation(s)
- H. Cecilia Heyworth
- Predators and Toxic Prey Research GroupMax Planck Institute for Chemical EcologyJenaGermany
- Centre for Ecology and Conservation, College of Life and Environmental SciencesUniversity of ExeterExeterUK
| | - Prayan Pokharel
- Department of Applied Entomology, Institute of PhytomedicineUniversity of HohenheimStuttgartGermany
| | - Jonathan D. Blount
- Centre for Ecology and Conservation, College of Life and Environmental SciencesUniversity of ExeterExeterUK
| | - Christopher Mitchell
- Centre for Ecology and Conservation, College of Life and Environmental SciencesUniversity of ExeterExeterUK
| | - Georg Petschenka
- Department of Applied Entomology, Institute of PhytomedicineUniversity of HohenheimStuttgartGermany
| | - Hannah M. Rowland
- Predators and Toxic Prey Research GroupMax Planck Institute for Chemical EcologyJenaGermany
| |
Collapse
|
3
|
Obermeier C, Mason AS, Meiners T, Petschenka G, Rostás M, Will T, Wittkop B, Austel N. Perspectives for integrated insect pest protection in oilseed rape breeding. TAG. THEORETICAL AND APPLIED GENETICS. THEORETISCHE UND ANGEWANDTE GENETIK 2022; 135:3917-3946. [PMID: 35294574 PMCID: PMC9729155 DOI: 10.1007/s00122-022-04074-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Accepted: 03/01/2022] [Indexed: 05/02/2023]
Abstract
In the past, breeding for incorporation of insect pest resistance or tolerance into cultivars for use in integrated pest management schemes in oilseed rape/canola (Brassica napus) production has hardly ever been approached. This has been largely due to the broad availability of insecticides and the complexity of dealing with high-throughput phenotyping of insect performance and plant damage parameters. However, recent changes in the political framework in many countries demand future sustainable crop protection which makes breeding approaches for crop protection as a measure for pest insect control attractive again. At the same time, new camera-based tracking technologies, new knowledge-based genomic technologies and new scientific insights into the ecology of insect-Brassica interactions are becoming available. Here we discuss and prioritise promising breeding strategies and direct and indirect breeding targets, and their time-perspective for future realisation in integrated insect pest protection of oilseed rape. In conclusion, researchers and oilseed rape breeders can nowadays benefit from an array of new technologies which in combination will accelerate the development of improved oilseed rape cultivars with multiple insect pest resistances/tolerances in the near future.
Collapse
Affiliation(s)
- Christian Obermeier
- Department of Plant Breeding, Justus Liebig University, Heinrich-Buff-Ring 26-32, 35392, Giessen, Germany.
| | - Annaliese S Mason
- Plant Breeding Department, University of Bonn, Katzenburgweg 5, 53115, Bonn, Germany
| | - Torsten Meiners
- Institute for Ecological Chemistry, Plant Analysis and Stored Product Protection, Julius Kühn Institute, Koenigin-Luise-Str. 19, 14195, Berlin, Germany
| | - Georg Petschenka
- Department of Applied Entomology, University of Hohenheim, Otto-Sander-Straße 5, 70599, Stuttgart, Germany
| | - Michael Rostás
- Division of Agricultural Entomology, University of Göttingen, Grisebachstr. 6, 37077, Göttingen, Germany
| | - Torsten Will
- Insitute for Resistance Research and Stress Tolerance, Julius Kühn Insitute, Erwin-Baur-Str. 27, 06484, Quedlinburg, Germany
| | - Benjamin Wittkop
- Department of Plant Breeding, Justus Liebig University, Heinrich-Buff-Ring 26-32, 35392, Giessen, Germany
| | - Nadine Austel
- Institute for Ecological Chemistry, Plant Analysis and Stored Product Protection, Julius Kühn Institute, Koenigin-Luise-Str. 19, 14195, Berlin, Germany
| |
Collapse
|
4
|
Stage structured prey-predator model incorporating mortal peril consequential to inefficiency and habitat complexity in juvenile hunting. Heliyon 2022; 8:e11365. [DOI: 10.1016/j.heliyon.2022.e11365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Revised: 08/16/2022] [Accepted: 10/27/2022] [Indexed: 11/06/2022] Open
|
5
|
Pokharel P, Steppuhn A, Petschenka G. Dietary cardenolides enhance growth and change the direction of the fecundity-longevity trade-off in milkweed bugs (Heteroptera: Lygaeinae). Ecol Evol 2021; 11:18042-18054. [PMID: 35003656 PMCID: PMC8717354 DOI: 10.1002/ece3.8402] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 10/14/2021] [Accepted: 10/23/2021] [Indexed: 12/16/2022] Open
Abstract
Sequestration, that is, the accumulation of plant toxins into body tissues for defense, was predicted to incur physiological costs and may require resistance traits different from those of non-sequestering insects. Alternatively, sequestering species could experience a cost in the absence of toxins due to selection on physiological homeostasis under permanent exposure of sequestered toxins in body tissues. Milkweed bugs (Heteroptera: Lygaeinae) sequester high amounts of plant-derived cardenolides. Although being potent inhibitors of the ubiquitous animal enzyme Na+/K+-ATPase, milkweed bugs can tolerate cardenolides by means of resistant Na+/K+-ATPases. Both adaptations, resistance and sequestration, are ancestral traits of the Lygaeinae. Using four milkweed bug species (Heteroptera: Lygaeidae: Lygaeinae) and the related European firebug (Heteroptera: Pyrrhocoridae: Pyrrhocoris apterus) showing different combinations of the traits "cardenolide resistance" and "cardenolide sequestration," we tested how the two traits affect larval growth upon exposure to dietary cardenolides in an artificial diet system. While cardenolides impaired the growth of P. apterus nymphs neither possessing a resistant Na+/K+-ATPase nor sequestering cardenolides, growth was not affected in the non-sequestering milkweed bug Arocatus longiceps, which possesses a resistant Na+/K+-ATPase. Remarkably, cardenolides increased growth in the sequestering dietary specialists Caenocoris nerii and Oncopeltus fasciatus but not in the sequestering dietary generalist Spilostethus pandurus, which all possess a resistant Na+/K+-ATPase. We furthermore assessed the effect of dietary cardenolides on additional life history parameters, including developmental speed, longevity of adults, and reproductive success in O. fasciatus. Unexpectedly, nymphs under cardenolide exposure developed substantially faster and lived longer as adults. However, fecundity of adults was reduced when maintained on cardenolide-containing diet for their entire lifetime but not when adults were transferred to non-toxic sunflower seeds. We speculate that the resistant Na+/K+-ATPase of milkweed bugs is selected for working optimally in a "toxic environment," that is, when sequestered cardenolides are stored in the body.
Collapse
Affiliation(s)
- Prayan Pokharel
- Department of Applied EntomologyInstitute of PhytomedicineUniversity of HohenheimStuttgartGermany
| | - Anke Steppuhn
- Department of Molecular BotanyInstitute of BiologyUniversity of HohenheimStuttgartGermany
| | - Georg Petschenka
- Department of Applied EntomologyInstitute of PhytomedicineUniversity of HohenheimStuttgartGermany
| |
Collapse
|
6
|
Chan W, Shaughnessy AEP, van den Berg CP, Garson MJ, Cheney KL. The Validity of Brine Shrimp (Artemia Sp.) Toxicity Assays to Assess the Ecological Function of Marine Natural Products. J Chem Ecol 2021; 47:834-846. [PMID: 33713252 DOI: 10.1007/s10886-021-01264-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Revised: 02/19/2021] [Accepted: 03/03/2021] [Indexed: 11/26/2022]
Abstract
Many organisms employ toxic compounds for protection against predators. To understand the effectiveness of such compounds, chemoecological studies often use brine shrimp (Artemia spp.) as a model organism instead of more ecologically relevant species. This is mostly because brine shrimp assays are simple and quick, but also due to the ethical implications associated with inducing harm to vertebrate predators in toxicity assays. In this study, we examined whether brine shrimp assays produce similar results to ichthyological toxicity assays with the aim of validating the use of brine shrimp as a preliminary screening tool. We extracted compounds from eight nudibranch molluscs including six species that we consider to signal their chemical defenses via warning coloration to visually hunting vertebrate predators. We tested the relative toxicity of these compounds against brine shrimp and a vertebrate potential predator, the blue-green damselfish (Chromis viridis). We found that extracts toxic to brine shrimp were also toxic to damselfish; however, extracts non-toxic to brine shrimp may still be toxic to damselfish. We also produced and tested mantle vs whole-body extracts for some nudibranch species, which exhibited similar toxicities in both assays except for the whole-body extract of Goniobranchus splendidus which was harmless to shrimp but toxic to fish, while the mantle extract was toxic to both. Overall, we argue that the brine shrimp assay can reasonably indicate the potential toxicity of a compound to fish, but additional experiments with more ecologically relevant predators are required if a no dose-response is observed against brine shrimp.
Collapse
Affiliation(s)
- Weili Chan
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD, 4072, Australia.
| | | | - Cedric P van den Berg
- School of Biological Sciences, The University of Queensland, Brisbane, QLD, 4072, Australia
| | - Mary J Garson
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD, 4072, Australia
| | - Karen L Cheney
- School of Biological Sciences, The University of Queensland, Brisbane, QLD, 4072, Australia
| |
Collapse
|