Dust you shall eat: Complex considerations underlying a simple diet

Animals assimilate macronutrients and mineral nutrients in specific
quantities and ratios to maximize fitness. To achieve this, animals must
ingest different foods that contain the needed nutrients or facilitate the
digestion of those nutrients. We explored how these multidimensional
considerations affect the desert isopods (Hemilepistus reaumuri) food
selection, using field and laboratory experiments. Wild isopods consumed
3-fold more macronutrient-poor biological soil crust (BSC) than plant
litter.  Isopods tightly regulated macronutrient and calcium
intake, but not phosphorus when eating the two natural foods and when
artificial calcium and phosphorus sources substituted the BSC. Despite the
equivalent calcium ingestion, isopods performed better when eating BSC
compared to artificial foods. Isopods that consumed BSC sterilized by
gamma-radiation ate more but grew slower than isopods that ate live BSC,
implying that ingested microorganisms facilitate litter digestion. Our
work highlights the need to reveal the multifaceted considerations that
affect food-selection when exploring trophic-interactions.