https://pubag.nal.usda.gov/download/50061/PDF

Weakness in the band: nutrient-mediated trade-offs between migration and immunity of Mormon crickets, Anabrus simplex

Summary

Animal immune systems must adaptively balance aggressive immune resistance (ability to destroy pathogens) with infection tolerance (ability to withstand the negative effects of infection; e.g. immunopathology or damage due to pathogen metabolism).
Insects offer unique insight into this balancing act because phenoloxidase (PO)-mediated melanization is a key feature of immune resistance, but PO activation obligates the production of nonspecific reactive species that can cause self-damage. The antioxidant glutathione (GSH) can provide protection against such reactive molecules, but high levels of GSH can impair melanization. In support of the hypothesis that GSH can protect insects (e.g. crickets) from self-damage during an immune response, we found that bacterially infected crickets showed a significant positive relationship between GSH haemolymph concentration and fecundity after controlling for bacterial growth rate. That is, GSH may be a mechanism of infection tolerance because it correlated with fecundity despite bacterial proliferation.
Next, we factorially manipulated food availability and immune activation in female crickets to examine whether the relative balance between a component of immune resistance (i.e. PO) and protection from self-damage (i.e. GSH) was plastic and sensitive to environmental conditions.
Glutathione and PO were positively correlated, and the PO:GSH ratio was robust and not affected by food availability or immune activation. Thus, increased investment in a mechanism of immune resistance may obligate a concomitant increase in GSH to reduce self-damage (i.e. increase infection tolerance). Chronic immune activation led to greater tolerance of oxidative stress suggesting that repeated immune activation upregulates infection tolerance mechanisms. Food limitation led to reduced PO activity, but not GSH concentration. This result suggests that mechanisms of immune resistance may be more sensitive to resource scarcity than mechanisms of infection tolerance.
We demonstrate that some mechanisms of immune resistance and infection tolerance can be correlated and that they can be affected by food availability or immune activation.

https://besjournals.onlinelibrary.wiley.com/doi/pdf/10.1111/1365-2435.12454

The double-edged sword of immune defence and damage control: do food availability and immune challenge alter the balance?

Synopsis Migration often is associated with movement away from areas with depleted nutrients or other resources, and yet migration itself is energetically demanding. Migrating Mormon crickets Anabrus simplex (Orthoptera: Tettigoniidae) lack nutrients, and supplementation of deficient nutrients slows migratory movements and enhances specific aspects of their immune systems. Migrants deficient in proteins have less spontaneous phenoloxidase (PO) activity, whereas those deficient in carbohydrates have lower lysozyme-like anti-bacterial titers with a proposed compromise between migratory and anti-bacterial activities. To investigate the relationship between diet, movement, and immunity further, we removed Mormon crickets from a migratory band and offered each cricket one of five diets: high protein, high carbohydrate, equal weight of proteins and carbohydrates (P þC), vitamins only, or water only for 1h. We then attached a radio, returned each to the migratory band, and recaptured them 18–24h later. Mormon crickets fed protein moved the furthest, those with only water or only vitamins moved less, and those fed carbohydrates or P þC moved the least. Standard intake trials also indicated that the Mormon crickets were deficient in carbohydrates. Consistent with a previous study, lysozyme-like anti-bacterial activity was greatest in those fed carbohydrates, and there was no difference between those fed water, protein, or P þC. Crickets were removed from the same migratory band and fed one of four diets: high P, high C, P þC, or vitamins only, for 1h. Then the crickets were held in captivity with water only for 4 or 24h before blood was drawn. Immunity measures did not differ between times of draw. Diet treatments had no effect on anti-bacterial activity of captive Mormon crickets, whereas total PO was greater in those fed protein. These results support the hypothesis of a direct compromise between migratory and anti-bacterial activities, whereas PO is compromised by low protein independent of migratory activities. We discuss the potential effects of climate on nutritional deficits and susceptibility to different pathogens.

http://drosophila.biology.kent.edu/users/plorch/LorchPdfs/Srygley2013.pdf

Coping with Uncertainty: Nutrient Deficiencies Motivate Insect Migration at a Cost to Immunity

The present study was carried out to investigate the effect of entomopathogenic fungus, Beauveria bassiana on immune response mediated Phenoloxidase enzyme of Spodoptera litura larvae. To measure the PO enzyme activity, haemolymph of 3rd, 4th and 5th instar larvae of S. litura were treated with different doses of 1.0×108, 2.0×107, 4.0×106 and 8.5×105 spores/ml of B. bassiana. The results indicated increase in PO activity with increase in B.bassiana infection but subsequently decreased in all instars. Significant increase in PO level was observed @ 4.0×106- 2.0×107 spores/ml after 24 hrs of infection in 3rd and 4th instar larvae. However, no significant effect of B. bassiana was observed on 5th instar larvae after 24 hr of treatment but there was a remarkable increase in PO level after 48 hrs. At higher concentration, after 48 hr of infection 3rd and 4th instar larvae showed significant decrease in PO activity. After72 hrs of infection all the treatments showed suppression in PO activity as compared to control. We would like to conclude that PO was an important key enzyme that triggered immune response in S. litura larvae against the invasion of B. bassiana.

https://www.entomoljournal.com/archives/2013/vol1issue6/PartC/41.pdf

Phenoloxidase activity in haemolymph of Spodoptera litura (Fabricius) mediating immune responses challenge with entomopathogenic fungus, Beauveria bassiana (Balsamo) Vuillmin

As a result of the increased potential for disease transmission, insects are predicted to show an increased constitutive immunity when crowded. Cannibalistic aggressive interactions further increase the risk of wounding and pathogen transmission in crowds. Nymphal Mormon crickets Anabrus simplex Haldeman were collected in Montana and reared in the laboratory either solitarily or at densities similar to that experienced by Mormon crickets in migratory bands. As teneral adults, solitarily-reared Mormon crickets tended to have greater phenoloxidase activity than those reared in groups. Sampling enzyme activity a second time when the adults were nearing reproductive maturity, group-reared Mormon crickets had elevated levels of prophenoloxidase and encapsulated foreign objects faster than solitarily-reared insects. Rearing density did not have a significant effect on either the darkness of the cuticle or antibacterial activity. This is the first report of age-related responses of adult insect immunity to crowding.

/pdf/age-and-density-dependent-prophylaxis-in-the-migratory-2a4k9r99z2.pdf

Age- and Density-Dependent Prophylaxis in the Migratory, Cannibalistic Mormon Cricket Anabrus simplex (Orthoptera: Tettigoniidae)

Beauveria bassiana (Fungi: Ascomycota) is an entomopathogenic fungus that serves as a biological control agent of Mormon crickets Anabrus simplex Haldeman (Orthoptera: Tettigoniidae) and other grasshopper pests. To measure the dose-dependent response of Mormon crickets to fungal attack, we applied B. bassiana strain GHA topically to adults using doses of 5.13 ×  1 0 4 to 1.75 ×  1 0 6 conidia in sunflower oil, with oil only as a control. After three weeks, we assessed the survivors' hemolymph for fungal cells, active phenoloxidase (PO), and lysozyme. Mortality increased and body mass of survivors decreased with conidial dose. survivors' PO activity was elevated to the same level independent of dose. Those with fungal cells visible in their hemolymph did not differ in PO activity from those with clear hemolymph. We conclude that circulating PO may be an important enzymatic defense against Beauveria infection and that it is associated with attempted clearing of Beauveria blastospores and hyphae from Mormon cricket hemolymph.

/pdf/immune-response-of-mormon-crickets-that-survived-infection-1fxadzudyg.pdf

Immune Response of Mormon Crickets That Survived Infection by Beauveria bassiana

Tri-trophic interactions are resilient to large shifts in precipitation levels in a wheat agroecosystem

Migration, Orientation and Navigation: Magnetic Compasses in Insects

Flight has evolved independently in birds, bats, and insects and was present in the Mesozoic pterosaurians that have disappeared. Of the roughly one million living animal species, more than three-quarters are flying insects. Flying is an extremely successful way of locomotion. At first glance, this seems surprising because leaving the ground and moving in the air is energetically expensive. We will therefore start with the question: why do some animals spend a substantial proportion of their life in the air? To generate lift, a few key features are required, and yet, animals show incredible diversity in their flight mechanics. We will review constraints imposed by body size including anatomical adaptations of the skeleton, muscles, and organs necessary to stay airborne with a special focus on the wings. Ecology of the aerial organism, such as diet or migration, has diversified flight styles and the physiological adaptations required to optimize performance. For example, animals are exposed to low temperatures and low oxygen pressure at high altitude, whereas overheating can pose a problem at low altitudes. Moreover, aerial prey can be particularly apparent to aerial predators resulting in selection on flight speed and maneuverability of predators and prey. Flight is energetically costly, much more costly than walking, with the majority of the cost dictated by body mass. Hence, adding weight load to fuel flight also adds to the cost of flight. We review energy supply for flight, and special adaptations for long-term flights. Aeroecology has resulted in extraordinary visual and aural sensory systems of predators, which in coordination with the locomotor system are under strong selection to detect and intercept prey in flight.

/pdf/physiological-aeroecology-anatomical-and-physiological-2ynl7s8wy7.pdf

Robert B. Srygley

Papers

Immune Response of Mormon Crickets That Survived Infection by Beauveria bassiana

Tri-trophic interactions are resilient to large shifts in precipitation levels in a wheat agroecosystem

Migration, Orientation and Navigation: Magnetic Compasses in Insects

Physiological Aeroecology: Anatomical and Physiological Adaptations for Flight