DOI: 10.5061/dryad.qjq2bvqnj
title: Target for lipid to carbohydrate intake minimizes cost of growth

description: Many theoretical treatments of foraging use energy as currency, with
 carbohydrates and lipids considered interchangeable as energy sources.
 However, herbivores must often synthesize lipids from carbohydrates since
 they are in short supply in plants, theoretically increasing the cost of
 growth. We tested whether a generalist insect herbivore (Locusta
 migratoria) can improve their growth efficiency by consuming lipids, and
 whether these locusts have a preferred intake target caloric ratio of
 carbohydrate to lipid (C:L). Locusts fed pairs of isocaloric, isoprotein
 diets differing in C and L consistently selected a 2C:1L target. Locusts
 reared on isocaloric, isoprotein 3C:0L diets attained similar final body
 masses and lipid contents as locusts fed the 2C:1L diet but ate more and
 had a ~12% higher metabolic rate—indicating an energetic cost for
 lipogenesis. These results demonstrate that some animals can selectively
 regulate carbohydrate to lipid intake and that consumption of dietary
 lipid can improve growth efficiency.
description: To study whether locusts regulate their C:L energy intake during
 the 5<sup>th</sup> instare of migratory locust, we designed
 iso-caloric artificial diets. We supplied a pair of pre-weighed artificial
 diet dishes to each locust. Half the locusts were given a bowl of 3P:5C:1L
 (protein:carbohydrate:lipid ratio) diet and a bowl of 3P:1C:5L diet, and
 another half were provided bowls of 3P:5C:1L and 3P:2C:4L diets. For these
 diets, ratios refer to the relative proportion of all energy in that diet
 provided by that nutrient. In addition to artificial diets, we provided ad
 libitum water in a tube with a cotton plug. After three days, we replaced
 the diet dishes with new pre-weighed dishes. The consumption of each diet
 was measured as the difference between initial and final dry mass in each
 diet dish (following drying for 24h at 60°C). To test whether the specific
 lipid source affects how locusts regulate C:L consumption, we carried out
 this experiment three times using three different oil sources (canola,
 sunflower, grapeseed). To study how locusts perform on
 diets with and without lipids we measured developmental time, survival,
 energy consumption rates, and body lipid growth when locusts were confined
 to a single diet during 5<sup>th</sup> instar nymph
 development. We designed a new artificial diet, 3P:4C:2L, based on the
 self-selected C:L intake target ratio in the choice experiment, and
 compared it to developmental performance of nymphs that were reared on
 diets equivalent in protein and energy content, but with only
 carbohydrates as their non-protein energy source (3P:6C:0L). Pre-weighed
 diet dishes were inserted into each individual cage, replaced after three
 days with new fresh dishes, and removed at the end of the experiment when
 the locusts molted to adults. In addition, we measured CO2 production and
 oxygen consumption and calculated the RER (respiratory exchange ratio) for
 each of the diet treatment groups.
description: # Target for lipid to carbohydrate intake minimizes cost of growth
 [https://doi.org/10.5061/dryad.qjq2bvqnj](https://doi.org/10.5061/dryad.qjq2bvqnj) The data set contains locust consumption rates of different macronutrients, growth rates and developmental time in choice and non-choice experiments during 5th instar nymphs. In addition, it contains respirometry data of locusts that was confined to different diets. ## Description of the data and file structure This data set contains five excel files which represents several experiments. 1.Choice experiment - the excel files "Grape seed oil choice experiment; Canola oil choice experiment; Sunflower oil choice experiment" contain data from three different choice experiment in which the sources for lipids were different (grape seed oil, canola oil and sunflower oil). In each experiment, locusts were given different pairs of iso caloric diets - carb-biased and lipid-biased diets, varying in energy ratio content between different macronutrients. For each individual, we recorded initial mass (grams), end mass (grams), mass growth (grams), total energy consumption (kcal) and macronutrient-specific energy consumption (for carbohydrates and for lipids) (kcal). 2\. "Confined diets performance" - This excel file contains data from developmental performance experiments, where we compared developmental (initial mass, end mass, mass growth, lipid growth in grams; and developmental time for 5th instar, in days) and consumption data (caloric consumption during 5th instar in kcal) between individual locusts confined to no-lipid diet and individuals on diets containing lipids (optimal self-selected from the previous experiment). To compare body lipid content we corrected to dry body mass of each locusts (g/g dry mass). 3\. "Confined diets respirometry" - This excel file contains data from developmental performance experiments on different confined diets, where we measured oxygen consumption (ul/h/g), carbon dioxide production (ul/h/g) and calculated RER (respiratory exchange ratio, VCO2/VO2 unitless) for each individual.