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Dietary macronutrients regulate life span and aging, yet little is known about their evolutionary effects. Here, we examine the evolutionary response of these traits in decorated crickets (Gryllodes sigillatus) maintained on diets varying in caloric content and protein-to-carbohydrate ratio. After 37 generations, each population was split: half remained on the evolution diet, and half switched to a standardized diet. Crickets lived longer and aged slower when evolving on high-calorie (both sexes) and carbohydrate-biased (females only) diets and had lower baseline mortality on high-calorie (females only) diets. However, on the standardized diet, crickets lived longer when evolving on high-calorie diets (both sexes), aged slower on high-calorie (females only) and carbohydrate-biased (both sexes) diets, and had lower baseline mortality on high-calorie (males only) and protein-biased (both sexes) diets. Life span was longer, and baseline mortality was lower when provided with the evolution vs. the standardized diet, but the aging rate was comparable. Moreover, life span was longer, aging slower (females only), and baseline mortality was lower (males only) compared to our evolved baseline, suggesting varying degrees of dietary adaptation. Collectively, we show dietary components influence the evolution of life span and aging in different ways and highlight the value of combining experimental evolution with nutritional geometry.

 

Despite decades of focus on crickets (family: Gryllidae) as a popular commodity and model organism, we still know very little about their immune responses to microbial pathogens. Previous studies have measured downstream immune effects (e.g., encapsulation response, circulating hemocytes) following an immune challenge in crickets, but almost none have identified and quantified the expression of immune genes during an active pathogenic infection. Furthermore, the prevalence of covert (i.e., asymptomatic) infections within insect populations is becoming increasingly apparent, yet we do not fully understand the mechanisms that maintain low viral loads. In the present study, we measured the expression of several genes across multiple immune pathways in Gryllodes sigillatus crickets with an overt or covert infection of cricket iridovirus (CrIV). Crickets with overt infections had higher relative expression of key pathway component genes across the Toll, Imd, Jak/STAT, and RNAi pathways. These results suggests that crickets can tolerate low viral infections but can mount a robust immune response during an overt CrIV infection. Moreover, this study provides insight into the immune strategy of crickets following viral infection and will aid future studies looking to quantify immune investment and improve resistance to pathogens. 

Interest in developing food, feed, and other useful products from farmed insects has gained remarkable momentum in the past decade. Crickets are an especially popular group of farmed insects due to their nutritional quality, ease of rearing, and utility. However, production of crickets as an emerging commodity has been severely impacted by entomopathogenic infections, about which we know little. Here, we identified and characterized an unknown entomopathogen causing mass mortality in a lab-reared population of Gryllodes sigillatus crickets, a species used as an alternative to the popular Acheta domesticus due to its claimed tolerance to prevalent entomopathogenic viruses. Microdissection of sick and healthy crickets coupled with metagenomics-based identification and real-time qPCR viral quantification indicated high levels of cricket iridovirus (CrIV) in a symptomatic population, and evidence of covert CrIV infections in a healthy population. Our study also identified covert infections of Acheta domesticus densovirus (AdDNV) in both populations of G. sigillatus . These results add to the foundational research needed to better understand the pathology of mass-reared insects and ultimately develop the prevention, mitigation, and intervention strategies needed for economical production of insects as a commodity.