Selection for cuticular melanism reveals immune function and life‐history trade‐offs in<i>Spodoptera littoralis</i>

Cotter, Sheena C.; Myatt, Julia P.; Benskin, C.; Wilson, Kenneth

doi:10.1111/j.1420-9101.2008.01587.x

Cited by 98 publications

(109 citation statements)

References 61 publications

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“…Similar observations were made with melanic S. littoralis [19], but it is important to note that compromised fecundity is not an inevitable outcome of enhanced immunity [39,40]. It therefore remains to be seen whether, if placed under constant selective pressure from exposure to B. bassiana, a stable melanic G. mellonella population would ever evolve with full fungal resistance if confronted with an increasing drain on its reproductive resources.…”

Section: Discussionmentioning

confidence: 61%

“…Our findings contrast with reports [6,7,11] that insects with density-induced melanism exhibit a gamut of enhanced lysozyme and haemolymph PO activity as well as increased encapsulation responses and cuticular PO activity. Cotter et al [19], conversely, suggest that diminished lysozyme activity is a trade-off for enhanced PO activity in the melanic form of the lepidopteran S. littoralis.…”

Section: Discussionmentioning

confidence: 99%

“…Typical manifestations of immunity costs include the diversion of resources away from other immune responses or, commonly, from reproductive or other life-history traits [16][17][18]. Cotter et al [19] showed that melanic lines of the phasepolyphenic lepidopteran Spodoptera littoralis had lower PO activity and higher lysozyme activity than non-melanic lines, suggesting a genetic trade-off between the two immune responses. In addition, lines with high PO activity had slower development rates, suggesting that investment in PO, rather than in melanism, is costly.…”

Section: Introductionmentioning

confidence: 99%

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More than a colour change: insect melanism, disease resistance and fecundity

et al. 2013

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A 'dark morph' melanic strain of the greater wax moth, Galleria mellonella, was studied for its atypical, heightened resistance to infection with the entomopathogenic fungus, Beauveria bassiana. We show that these insects exhibit multiple intraspecific immunity and physiological traits that distinguish them from a non-melanic, fungus-susceptible morph. The melanic and non-melanic morphs were geographical variants that had evolved different, independent defence strategies. Melanic morphs exhibit a thickened cuticle, higher basal expression of immunity-and stress-management-related genes, higher numbers of circulating haemocytes, upregulated cuticle phenoloxidase (PO) activity concomitant with conidial invasion, and an enhanced capacity to encapsulate fungal particles. These insects prioritize specific augmentations to those frontline defences that are most likely to encounter invading pathogens or to sustain damage. Other immune responses that target late-stage infection, such as haemolymph lysozyme and PO activities, do not contribute to fungal tolerance. The net effect is increased larval survival times, retarded cuticular fungal penetration and a lower propensity to develop haemolymph infections when challenged naturally (topically) and by injection. In the absence of fungal infection, however, the heavy defence investments made by melanic insects result in a lower biomass, decreased longevity and lower fecundity in comparison with their non-melanic counterparts. Although melanism is clearly correlated with increased fungal resistance, the costly mechanisms enabling this protective trait constitute more than just a colour change.

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Section: Discussionmentioning

confidence: 61%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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More than a colour change: insect melanism, disease resistance and fecundity

et al. 2013

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“…Furthermore, the investment in immunity may impair its development (Cotter et al. 2008; van der Most et al. 2011), thus caterpillars which do not develop faster may not benefit from developmental resistance and will succumb to viral infection.…”

Section: Discussionmentioning

confidence: 99%

Temperature and population density: interactional effects of environmental factors on phenotypic plasticity, immune defenses, and disease resistance in an insect pest

Silva

Elliot

2016

Ecology and Evolution

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Temperature and crowding are key environmental factors mediating the transmission and epizooty of infectious disease in ectotherm animals. The host physiology may be altered in a temperature‐dependent manner and thus affects the pathogen development and course of diseases within an individual and host population, or the transmission rates (or infectivity) of pathogens shift linearly with the host population density. To our understanding, the knowledge of interactive and synergistic effects of temperature and population density on the host–pathogen system is limited. Here, we tested the interactional effects of these environmental factors on phenotypic plasticity, immune defenses, and disease resistance in the velvetbean caterpillar Anticarsia gemmatalis. Upon egg hatching, caterpillars were reared in thermostat‐controlled chambers in a 2 × 4 factorial design: density (1 or 8 caterpillars/pot) and temperature (20, 24, 28, or 32°C). Of the immune defenses assessed, encapsulation response was directly affected by none of the environmental factors; capsule melanization increased with temperature in both lone‐ and group‐reared caterpillars, although the lone‐reared ones presented the most evident response, and hemocyte numbers decreased with temperature regardless of the population density. Temperature, but not population density, affected considerably the time from inoculation to death of velvetbean caterpillar. Thus, velvetbean caterpillars succumbed to Anticarsia gemmatalis multiple nucleopolyhedrovirus (AgMNPV) more quickly at higher temperatures than at lower temperatures. As hypothesized, temperature likely affected caterpillars' movement rates, and thus the contact between conspecifics, which in turn affected the phenotypic expression of group‐reared caterpillars. Our results suggest that environmental factors, mainly temperature, strongly affect both the course of disease in velvetbean caterpillar population and its defenses against pathogens. As a soybean pest, velvetbean caterpillar may increase its damage on soybean fields under a scenario of global warming as caterpillars may reach the developmental resistance faster, and thus decrease their susceptibility to biological control by AgMNPV.

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“…This may well be true for some phase-polyphenic insects, like Spodoptera caterpillars, that use density-dependent cues to trigger phenotypic changes that enhance dispersal to lower densities [22] and where trade-offs with constitutive immunity have been identified [13,16,23,24]. Alternatively, crowding-induced upregulation of immune function (or other costly phenotypic changes associated with phase-change) may deplete parents of resources that would otherwise be invested in offspring.…”

Section: Discussionmentioning

confidence: 99%

Transgenerational effects modulate density-dependent prophylactic resistance to viral infection in a lepidopteran pest

Wilson

Graham

2015

Biol. Lett.

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There is an increasing appreciation of the importance of transgenerational effects on offspring fitness, including in relation to immune function and disease resistance. Here, we assess the impact of parental rearing density on offspring resistance to viral challenge in an insect species expressing density-dependent prophylaxis (DDP); i.e. the adaptive increase in resistance or tolerance to pathogen infection in response to crowding. We quantified survival rates in larvae of the cotton leafworm (Spodoptera littoralis) from either gregarious-or solitary-reared parents following challenge with the baculovirus S. littoralis nucleopolyhedrovirus. Larvae from both the parental and offspring generations exhibited DDP, with gregarious-reared larvae having higher survival rates post-challenge than solitary-reared larvae. Within each of these categories, however, survival following infection was lower in those larvae from gregarious-reared parents than those from solitary-reared, consistent with a transgenerational cost of DDP immune upregulation. This observation demonstrates that crowding influences lepidopteran disease resistance over multiple generations, with potential implications for the dynamics of host-pathogen interactions.

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Selection for cuticular melanism reveals immune function and life‐history trade‐offs inSpodoptera littoralis

Cited by 98 publications

References 61 publications

More than a colour change: insect melanism, disease resistance and fecundity

More than a colour change: insect melanism, disease resistance and fecundity

Temperature and population density: interactional effects of environmental factors on phenotypic plasticity, immune defenses, and disease resistance in an insect pest

Transgenerational effects modulate density-dependent prophylactic resistance to viral infection in a lepidopteran pest

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