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

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 MEDI (Macronutrient Extraction and Determination from Invertebrates), 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 solubilizing 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 mg ml-1, 0.065 mg ml-1 and 0.006 mg ml-1 for proteins, carbohydrates and lipids, respectively. Adjusting the volume of reagents used f...