The effects of host plant species and larval density on immune function in the polyphagous moth <i>Spodoptera littoralis</i>

Green, Kristina Karlsson

doi:10.1002/ece3.7802

Cited by 14 publications

(5 citation statements)

References 67 publications

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“…Moreover, similar study designs have been used repeatedly and successfully in previous insect immunity studies (e.g. Freitak et al, 2019;Green, 2021;Meister et al, 2017;Murzagulov et al, 2013;Srygley, 2012).…”

Section: Discussionmentioning

confidence: 99%

“…Although we focus only on one immune trait, it is imperative to note that the other immune traits expressed by BSF larvae may not follow the same pattern. For example, in the lepidopteran Spodoptera littoralis, PO activity had a positive relationship with larval density, whilst lysozyme activity was not significantly affected by larval density (Green, 2021). Thus, further research must be conducted to ascertain the relationship of other immune parameters with density in insects in general and in BSF and other commercially important insects in particular.…”

Section: Discussionmentioning

confidence: 99%

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High larval densities and high temperatures lead to a stronger immune response in the black soldier fly

Opare

Meister

Holm

et al. 2023

JIFF

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Organisms are expected to invest more in their immune function when the risk of disease infection is high. However, induction of a robust immune response is costly and may not be achievable in suboptimal environments. High conspecific density could simultaneously imply high infection risk and a suboptimal environment for many insect species. We focus on the economically important dipteran species (black soldier fly, BSF) that represents the insect order that has been ignored in previous research on density effects on immunity. The experimental part of the study was carried out to evaluate the effect of larval density (three density treatments: 1, 5 and 10 larvae/cm2) and temperature (three thermal treatments: 23, 27 and 30 °C) on the immune function of BSF larvae. The larvae that were reared at high compared to low larval densities and at higher than lower temperatures had significantly higher activity of phenoloxidase, an enzyme that plays an essential role in insect immune function. Sex did not have a significant effect on phenoloxidase activity and prepupal mass, pupal mass and adult mass were not affected by the levels of phenoloxidase activity of fifth instar larvae. In addition, we give an overview of larval density effects on insect immunity and show that density-dependent prophylaxis (stronger immune response in high larval density environments) is indeed common in the results of published case studies. However, cases with no correlation between density and immunity traits were as frequent. Moreover, in more than half of the studies, qualitatively different within-species patterns in different immunity traits were observed. We conclude that BSF larvae exhibit density-dependent prophylaxis, and larvae invest more into their immune system at high larval densities and temperatures than they do at low larval densities and temperatures.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

High larval densities and high temperatures lead to a stronger immune response in the black soldier fly

Opare

Meister

Holm

et al. 2023

JIFF

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“…Similar effects of diet on immune response have been shown in other studies; for example, in the fall webworm ( Hyphantria cunea, Erebidae), diets that resulted in poor larval performance also resulted in reduced caterpillar immune response ( Vyas and Murphy 2022 ). In another study using a generalist agricultural pest, diet had an impact on the immune response of Spodoptera littoralis (Noctuidae) caterpillars ( Green 2021 ): individuals fed on cabbage or cotton showed enhanced immune function compared to individuals that fed on maize. In the Baltimore checkerspot butterfly ( Euphydryas phaeton, Nymphalidae), larvae fed on an introduced host plant, Plantago lanceolata (Plantaginaceae), had lower immune function than those that fed on the native plant Chelone glabra (Plantaginaceae) ( Muchoney et al 2022 ).…”

Section: Discussionmentioning

confidence: 99%

Food and time: dietary plasticity of different sources of a generalist insect herbivore

Hernandez,

Bowers

2024

Journal of Insect Science

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Painted lady butterflies (Vanessa cardui L., Nymphalidae) are generalist herbivores and serve as a model system across several fields of biology. While it has been demonstrated that V. cardui caterpillars can develop on different host plants, much of this work has been done on commercially sourced caterpillars, which could limit our understanding of wild V. cardui populations. In this study, we sought to explore possible differences in how commercial and wild V. cardui caterpillars may respond to feeding on different host plants, and subsequently, how their diet impacts immune response and survival. Here, we analyzed performance, survival, and immune response of wild and commercially sourced V. cardui caterpillars over several generations on diets that consisted of either 1 of 4 different host plant species or a mixed diet including all 4 species. Qualitatively, we observed that wild larvae had a better larval performance and hemocyte counts compared to the commercial larvae. The results demonstrate that both wild and commercially sourced caterpillars grew and survived best on the same diet treatments (mallow, narrowleaf plantain, and a mixed diet) during development across generations. Immune responses showed similar patterns across host plants between wild and commercial populations, with individuals showing lowered immune responses on dandelion and lupine and higher ones on mallow, plantain and the mixed diet; although the relative rankings on those 3 diets varied. Survival also demonstrated similar patterns, in that individuals reared on dandelion and lupine had the lowest survival.

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“…Thus, viewed through the lens of evolution, the immune system of modern insects may be so exquisite and fine-tuned to the point of providing apparently paradoxical and contradictory observations. Summarizing, this study: i) provides new information on the BSF immune system and expands knowledge on the defense mechanisms of Diptera, ii) represents a platform of knowledge for future studies on the immune response of BSF larvae challenged with other infectious agents, such as fungi or viruses, and iii) is a prerequisite to manipulating the larval immune response by nutritional (i.e., the diet) (9) or environmental (i.e., rearing temperature or larval density) (104,105) factors, to increase resistance to pathogens and optimize health status during mass rearing.…”

Section: Discussionmentioning

confidence: 99%

Insights Into the Immune Response of the Black Soldier Fly Larvae to Bacteria

et al. 2021

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In insects, a complex and effective immune system that can be rapidly activated by a plethora of stimuli has evolved. Although the main cellular and humoral mechanisms and their activation pathways are highly conserved across insects, the timing and the efficacy of triggered immune responses can differ among different species. In this scenario, an insect deserving particular attention is the black soldier fly (BSF), Hermetia illucens (Diptera: Stratiomyidae). Indeed, BSF larvae can be reared on a wide range of decaying organic substrates and, thanks to their high protein and lipid content, they represent a valuable source of macromolecules useful for different applications (e.g., production of feedstuff, bioplastics, and biodiesel), thus contributing to the development of circular economy supply chains for waste valorization. However, decaying substrates bring the larvae into contact with different potential pathogens that can challenge their health status and growth. Although these life strategies have presumably contributed to shape the evolution of a sophisticated and efficient immune system in this dipteran, knowledge about its functional features is still fragmentary. In the present study, we investigated the processes underpinning the immune response to bacteria in H. illucens larvae and characterized their reaction times. Our data demonstrate that the cellular and humoral responses in this insect show different kinetics: phagocytosis and encapsulation are rapidly triggered after the immune challenge, while the humoral components intervene later. Moreover, although both Gram-positive and Gram-negative bacteria are completely removed from the insect body within a few hours after injection, Gram-positive bacteria persist in the hemolymph longer than do Gram-negative bacteria. Finally, the activity of two key actors of the humoral response, i.e., lysozyme and phenoloxidase, show unusual dynamics as compared to other insects. This study represents the first detailed characterization of the immune response to bacteria of H. illucens larvae, expanding knowledge on the defense mechanisms of this insect among Diptera. This information is a prerequisite to manipulating the larval immune response by nutritional and environmental factors to increase resistance to pathogens and optimize health status during mass rearing.

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The effects of host plant species and larval density on immune function in the polyphagous moth Spodoptera littoralis

Cited by 14 publications

References 67 publications

High larval densities and high temperatures lead to a stronger immune response in the black soldier fly

High larval densities and high temperatures lead to a stronger immune response in the black soldier fly

Food and time: dietary plasticity of different sources of a generalist insect herbivore

Insights Into the Immune Response of the Black Soldier Fly Larvae to Bacteria

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