MEDI: Macronutrient Extraction and Determination from invertebrates, a rapid, cheap and streamlined protocol

Abstract

Macronutrients, comprising carbohydrates, proteins and lipids, underpin many ecological processes, but their quantification in ecological studies is often inaccurate and laborious, requiring large investments of time and bulk samples, which make individual‐level studies impossible. This study presents Macronutrient Extraction and Determination from Invertebrates (MEDI), a protocol for the direct, rapid and relatively low‐cost determination of macronutrient content from single small macroinvertebrates. Macronutrients were extracted by a sequential process of soaking in 1:12 chloroform:methanol solution to remove lipid and then solubilising tissue in 0.1 M NaOH. Proteins, carbohydrates and lipids were determined by colorimetric assays from the same individual specimens. The limits of detection of MEDI with the equipment and conditions used were 0.067, 0.065 and 0.006 mg/ml for proteins, carbohydrates and lipids respectively. Adjusting the volume of reagents used for extraction and determination can broaden the range of concentrations that can be detected. MEDI successfully identified taxonomic differences in macronutrient content between five insect species. Macronutrient Extraction and Determination from Invertebrates can directly and rapidly determine macronutrient content in tiny (dry mass ~3 mg) and much larger individual invertebrates. Using MEDI, the total macronutrient content of over 50 macroinvertebrates can be determined within around 3 days of collection at a cost of ~$1.35 per sample.

Impact of high larval density on the performance of Anastrepha ludens: Competition or feeding facilitation?

“…Body protein and lipids were determined according to Cheng et al, 2011 and Cuff et al (2021). Macronutrient extraction involved tissue solubilization (larva) using a 2:1 chloroform: methanol solution.…”

Larval nutritional effects on male and female survival and fecundity in Anastrepha ludens

“…(2010) and Cuff et al. (2021). Macronutrient extraction involved tissue solubilization (larva or adult) using a 2:1 chloroform: methanol solution.…”

“…Body protein and lipids were determined according to the methodology proposed by Cheng et al (2010) and Cuff et al (2021). Macronutrient extraction involved tissue solubilization (larva or adult) using a 2:1 chloroform: methanol solution.…”

Arthropod prey vary among orders in their nutrient and exoskeleton content

“…For example, some Orthoptera samples were only 1–2 individuals, while ant samples contained as many as 30 individuals, and some Hemiptera and Coleoptera contained biomass from individuals collected across all three sampling months. Macronutrient and exoskeleton content was measured according to established methods that were combined into a standardized protocol (Cuff et al, 2021 ), which are summarized here. We measured lipid content of arthropods using a gravimetric method with chloroform as a solvent.…”