Long-Chain Omega-3 Polyunsaturated Fatty Acids Have Developmental Effects on the Crop Pest, the Cabbage White Butterfly Pieris rapae

Rebecca H Hallett,Laurence Packer,Stefanie M Hixson,Kruti Shukla,Lesley Campbell,Michael Theodore Arts,Sandy M Smith

doi:10.32920/14639922

Abstract

Nutritional enhancement of crops using genetic engineering can potentially affect herbivorous pests. Recently, oilseed crops have been genetically engineered to produce the long-chain omega-3 polyunsaturated fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) at levels similar to that found in fish oil; to provide a more sustainable source of these compounds than is currently available from wild fish capture. We examined some of the growth and development impacts of adding EPA and DHA to an artificial diet of Pieris rapae, a common pest of Brassicaceae plants. We replaced 1% canola oil with EPA: DHA (11:7 ratio) in larval diets, and examined morphological traits and growth of larvae and ensuing adults across 5 dietary treatments. Diets containing increasing amounts of EPA and DHA did not affect developmental phenology, larval or pupal weight, food consumption, nor larval mortality. However, the addition of EPA and DHA in larval diets resulted in progressively heavier adults (F 4, 108 = 6.78; p = 0.011), with smaller wings (p < 0.05) and a higher frequency of wing deformities (R = 0.988; p = 0.001). We conclude that the presence of EPA and DHA in diets of larval P. rapae may alter adult mass and wing morphology; therefore, further research on the environmental impacts of EPA and DHA production on terrestrial biota is advisable.

Highlights

Fatty acids (FA) have multifaceted roles in metabolic energy storage, cell membrane structure, temperature acclimation, cell signalling, cognition, vision, and the immune system in both aquatic and terrestrial organisms [1–3]
Adult weight increased in a linear fashion with eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA) inclusion, whereby adults reared on the high EPA + DHA treatment were 20% heavier than those reared on the control treatment
We found that increasing the amount of EPA and DHA in larval diets resulted in a corresponding increase in the concentrations of these two FA in adult cabbage white butterflies upon emergence and directly correlated with changes in adult weight, and wing morphology

Summary

Introduction

Fatty acids (FA) have multifaceted roles in metabolic energy storage, cell membrane structure, temperature acclimation, cell signalling, cognition, vision, and the immune system in both aquatic and terrestrial organisms [1–3]. The 18-carbon omega-3 (n-3) and omega-6 (n-6) polyunsaturated fatty acids (PUFA), alpha-linolenic acid (ALA; 18:3n-3) and linoleic acid The long-chain n-3 polyunsaturated fatty acids (LC-PUFA), eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; 22:6n-3) are involved with key physiological functions in both aquatic invertebrates and vertebrates [3], yet most aquatic invertebrates and vertebrates cannot synthesize these two LC-PUFA at rates sufficient to maintain an optimal state [4]. EPA and DHA mainly originate in aquatic primary producers (algae) and are generally retained up the food chain via successive consumption by increasingly higher trophic level organisms [5]. EPA and DHA are novel to the terrestrial environment, as they are, for the most part, not produced by terrestrial plants and are not transferred through terrestrial food webs, unless consumed from aquatic resources or produced endogenously [6, 7]

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