First evidence of protein-carbohydrate regulation in a plant bug (Lygus hesperus)

Fitness of Nutrition Regulation in a Caterpillar Pest Mythimna separata (Walker): Insights from the Geometric Framework

In nature, plants can contain variable nutrients depending upon the species, tissue, and developmental stage. Insect herbivores may regulate their nutrient intake behaviorally and physio- logically when encountering different foods. This study examined the nutritional regulation of the oriental armyworm, Mythimna separata, for the first time. In one experiment, we allowed the cater-pillars to choose between two nutritionally balanced but complementary diets. The caterpillars did not randomly consume the paired foods, but instead chose between the nutritionally balanced but complementary diets. This intake behavior was found to change with their developmental stages. Furthermore, the nutrient concentrations in food significantly impacted the insect's performance. In the other experiment, caterpillars were given one of eleven diets that reflected the different nutrient conditions in the field. The results showed that proteins were significantly associated with developmental time and fecundity. For example, by consuming protein-biased food, the caterpillars developed faster and produced more eggs. In contrast, carbohydrates were more strongly linked to lipid accumulation, and caterpillars accumulated more lipids when consuming the carbohydrate-biased food. Moreover, the caterpillars were also found to actively regulate their intake of proteins and carbohydrates based on food quality and to physiologically prepare for subsequent life stages. These findings enhance our understanding of how M. separata feeds and responds to different nutritional environments in the field, which could have implications for managing insect herbivores in agricultural settings.

The importance of time in nutrient regulation: a case study with spotted-wing Drosophila (Drosophila suzukii)

Introduction

The ability of living organisms to acquire the nutrients needed to carry out required physiological functions has important consequences for fitness. However, an organism must not simply meet the requirements for individual nutrients, but must ingest an optimal balance of multiple nutrients. Despite this, animals rarely consume truly balanced resources, and instead commonly feed selectively across multiple unbalanced resources to reach an optimal balance, i.e., intake target. Nutritional research has predominantly focused on the behavioral strategies employed during nutrient regulation, as well as the fitness consequence of failing to meet intake targets, but little work has been done on the temporal aspects of this process. For instance, within what timeframe must organisms reach their intake target before a fitness cost is incurred? Hours, days, weeks?

Methods

In this study, we investigated how nutrient regulation interval impacts consumption and performance in adult female spotted-wing Drosophila (Drosophila suzukii). Females were constrained to either a protein- orcarbohydrate-biased diet over different time intervals and at different schedules, while control flies were constrained to one diet for the entire feeding period.

Results

Regulation interval had a significant impact on feeding behavior and consumption. Total consumption was highest on the shorter interval treatments, where diets were alternated more frequently, and declined as the interval period increased. The relative consumption of both diets was statistically-different across intervals and was higher for the carbohydrate-biased diet. Consumption of the protein-biased diet was more variable across intervals and was more strongly impacted by the daily timing of diet switches. Performance data showed that shorter regulation intervals led to longer fly lifespans, a result commonly observed in studies exploring the impacts of diet macronutrient ratio variability on performance.

Discussion

These results show that the temporal aspects of nutrition, such as feeding intervals and the timing of resource availability, can have strong impacts on feeding behavior, nutrient regulation, and fitness. These results provide an insight into how consumers may deal with changes in host phenology, the availability of hosts, and changes in nutrient availability within hosts. Understanding these mechanisms will be important for predicting responses to changes in nutrient cycling and resource availability mediated by natural and anthropogenic habitat modifications, such as global climate change.

Review: Trait plasticity during plant-insect interactions: From molecular mechanisms to impact on community dynamics

Phenotypic plasticity, prevalent in all domains of life, enables organisms to cope with unpredictable or novel changes in their growing environment. Plants represent an interesting example of phenotypic plasticity which also directly represents and affects the dynamics of biological interactions occurring in a community. Insects, which interact with plants, manifest phenotypic plasticity in their developmental, physiological, morphological or behavioral traits in response to the various host plant defenses induced upon herbivory. However, plant-insect interactions are generally more complex and multidimensional because of their dynamic association with their respective microbiomes and macrobiomes. Moreover, these associations can alter plant and insect responses towards each other by modulating the degree of phenotypic plasticity in their various traits and studying them will provide insights into how plants and insects reciprocally affect each other's evolutionary trajectory. Further, we explore the consequences of phenotypic plasticity on relationships and interactions between plants and insects and its impact on their development, evolution, speciation and ecological organization. This overview, obtained after exploring and comparing data obtained from several inter-disciplinary studies, reveals how genetic and molecular mechanisms, underlying plasticity in traits, impact species interactions at the community level and also identifies mechanisms that could be exploited in breeding programs.