Metabolomic Differentiation of Nutritional Stress in an Aquatic Invertebrate

Abstract

Poor diet quality frequently constrains the growth and reproduction of primary consumers, altering their population dynamics, interactions in food webs, and contributions to ecosystem services such as nutrient cycling. The identification and measurement of an animal's nutritional state are thus central to studying the connections between diet and animal ecology. Here we show how the nutritional state of a freshwater invertebrate, Daphnia magna, can be determined by analyzing its endogenous metabolites using hydrogen nuclear magnetic resonance-based metabolomics. With a multivariate analysis, we observed the differentiation of the metabolite composition of animals grown under control conditions (good food and no environmental stress), raised on different diets (low quantity, nitrogen limited, and phosphorus limited), and exposed to two common environmental stressors (bacterial infection and salt stress). We identified 18 metabolites that were significantly different between control animals and at least one limiting food type or environmental stressor. The unique metabolite responses of animals caused by inadequate nutrition and environmental stress are reflective of dramatic and distinctive effects that each stressor has on animal metabolism. Our results suggest that dietary-specific induced changes in metabolite composition of animal consumers hold considerable promise as indicators of nutritional stress and will be invaluable to future studies of animal nutrition.

Bridging Ecological Stoichiometry and Nutritional Geometry with homeostasis concepts and integrative models of organism nutrition

“…; Wagner et al . ). We will outline how these molecular pathways can be conceptualized and thus integrated in mathematical models to examine individual‐level outcomes for physiology and fitness.…”

“…Complementary approaches using molecular techniques (e.g. transcriptomics and metabolomics) may provide insights of how nutrient limitation or excess induces changes in metabolism to maintain homeostasis (Jeyasingh et al 2011;Wagner et al 2015).…”

“…Besides halting growth, nutrient limited animals can modify many molecular processes to increase acquisition and use efficiency of the limiting nutrient, for example by altering gene expression to incorporate more of the limiting nutrient via increasing nutrient transporters (Boer et al 2003;Jeyasingh et al 2011). Nutrient limitation also causes changes in the metabolite profile (metabolome) of animals, for example by reducing metabolites containing the limiting nutrient (Boer et al 2010;Wagner et al 2015). We will outline how these molecular pathways can be conceptualized and thus integrated in mathematical models to examine individual-level outcomes for physiology and fitness.…”

Metabolomic responses to sublethal contaminant exposure in neonate and adult Daphnia magna

“…With the observed decreases in growth rate and glucose, and increases in many amino acid metabolites, we speculate that the metabolomic profile of D. magna exposed to propranolol may be attributed to protein degradation being used to fuel energetic demands . This general response of increased free amino acids and decreased growth rates is also observed under low food conditions , adding evidence that feeding rates may be decreased when daphnids are exposed to propranolol. Furthermore, increases in aromatic amino acids may indicate impairments to both immune function and the nervous system.…”

“…Mass specific growth rate (MSGR) determined by the equation: Where B2 is the final average mass per D. magna , B1 is the average initial neonate mass, and time is number of days of D. magna growth. Using mass specific growth rates, instead of mass or length accounts for the small variation in neonate initial size (1–2 μg) . Mass specific growth rate ranges between 0 and 1, with 1 indicating a doubling of mass per day, and 0 indicating no growth .…”