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Power Bars: Mormon Crickets Get Immunity Boost from Eating Grasshoppers
Robert B Srygley1, David H Branson1
1Pest Management Research Unit, Northern Plains Agricultural Research Laboratory, USDA-Agricultural Research Service, 1500 N. Central Ave., Sidney, MT 59270, USA.
Abstract:
In addition to feeding on plants, Mormon crickets Anabrus simplex Haldeman, 1852 predate on invertebrates, including one another, which effectively drives their migration. Carnivory derives from lack of dietary protein, with Mormon crickets deprived of protein having less phenoloxidase (PO) available to combat foreign invaders, such as fungal pathogens. Because Mormon crickets commonly occur with grasshoppers that feed on the same plants, we investigated interactions between grasshoppers and Mormon crickets, and hypothesized that if Mormon crickets are predatory on grasshoppers, grasshopper abundance would influence the protein available to Mormon crickets and their immunity. In a field setting, we varied densities of Mormon crickets (0, 10, or 20 per cage) and grasshoppers Melanoplus borealis (0, 15, 30, or 45) in 68 1-m2 cages. After one month, we measured Mormon cricket dietary preferences and PO activity. As predicted, artificial diet consumption shifted away from protein as grasshopper density increased, and immunocompetence, as measured by PO activity, also increased with grasshopper availability. Although nitrogen availability in the vegetation decreased with increasing insect density, predation became an important source of protein for Mormon crickets that enhanced immunity. Grasshoppers can be an important source of dietary protein for Mormon crickets, with prey availability affecting Mormon cricket immunity to diseases.
Insights
Mormon crickets prey on grasshoppers to boost their protein intake and immunity. Increased grasshopper availability enhances Mormon cricket immunocompetence, even as plant nitrogen decreases.
Area of Science:
- Ecology
- Insect behavior
- Animal physiology
Background:
- Mormon crickets (Anabrus simplex) exhibit predatory behavior on invertebrates, including conspecifics, driven by protein deficiency.
- Protein scarcity in Mormon crickets reduces phenoloxidase (PO) activity, compromising their immune response to pathogens.
- Interactions between Mormon crickets and grasshoppers (Melanoplus borealis) are common due to shared plant resources.
Purpose of the Study:
- To investigate the influence of grasshopper abundance on Mormon cricket diet and immune function.
- To test the hypothesis that predation on grasshoppers provides essential protein for Mormon crickets, thereby enhancing immunity.
Main Methods:
- Field experiment using 68 1-m² cages with varied densities of Mormon crickets (0, 10, 20) and grasshoppers (0, 15, 30, 45).
- Measurement of Mormon cricket dietary preferences and phenoloxidase (PO) activity after one month.
- Assessment of vegetation nitrogen content in relation to insect densities.
Main Results:
- Artificial diet consumption shifted from protein as grasshopper density increased.
- Mormon cricket immunocompetence, indicated by PO activity, positively correlated with grasshopper availability.
- Despite decreased vegetation nitrogen at higher insect densities, predation emerged as a significant protein source.
Conclusions:
- Grasshoppers serve as a crucial source of dietary protein for Mormon crickets.
- Prey availability directly impacts Mormon cricket immunity, highlighting the ecological role of predation in insect health.
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