Dietary eicosapentaenoic acid and docosahexaenoic acid are linearly retained by common insect crop pests (cabbage looper and bertha armyworm) and alter insect biomass

Abstract

The long-chain omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are prevalent in aquatic ecosystems and are not part of the natural diet of herbivorous, terrestrial insects, which generally consume alpha-linolenic acid (ALA) and linoleic acid (LNA). However, recent advances in genetic engineering have lead to the development of terrestrial crops that express the novel traits of EPA and DHA production. In the present study, we examine the effects of dietary EPA and DHA on the growth, development and fatty acid content of two crop pest insects: bertha armyworm and cabbage looper. Five experimental diets were formulated to include increasing amounts of pure EPA and DHA (in relation to the total diet lipid level), according to the ratios (EPA + DHA relative to a vegetable oil containing ALA and LNA): 0 (control), 0.25 : 0.75 (lowest), 0.5 : 0.5 (low), 0.75 : 0.25 (medium) and 1 : 0 (high). Dietary EPA and DHA had significant effects on development time, mass and fatty acid content in both species. Dietary treatment (interactive with time) had a significant effect on individual mass of both insects, indicating that, over time, EPA and DHA impacted growth. However, insect mass, development and morphology results are not linearly related with increasing dietary EPA and DHA. Both species retained EPA and DHA in adult form, and the body content of EPA and DHA was significantly, positively correlated with EPA and DHA diet treatments in both the bertha armyworm (r 2 = 91.3%) and cabbage looper (r 2 = 75.8%). Dietary EPA and DHA could have fitness consequences for these organisms and could be nutritionally transferred to higher consumers.

Pre-Treatment of Fish By-Products to Optimize Feeding of Tenebrio molitor L. Larvae

“…The intake of fish discards for periods longer than 7 days negatively affected the final body weight, except when the diet was administered as fresh ground fish, in which case the biomass obtained was doubled compared to any of the other treatments (Table 1). In cabbage looper (Tricoplusia ni Hübner) and the bertha armyworm (Mamestra configurata Walker) fed with a high content of EPA and DHA [49], similar results were described, showing an increase in weight in larvae fed with higher levels of EPA and DHA, but with lower levels of crude fat than seen in our experiment.…”

“…Despite the accumulation of EPA and DHA described by various authors [24,30,47], the percentage of accumulation is low regarding diet. In insects fed with oil rich in EPA and DHA, the percentage of retention is correlated with n-3 LCPUFA content of the diet, although levels were always relatively low, less than 20% in T. molitor and M. configurata [49] or 12.1% in H. illucens [30]. The natural diet of terrestrial insects is usually very specific and poor and, as suggested by Colombo et al [49], there has not been strong selection pressure to highly retain n−3 LCPUFAs, which results in low retention efficiencies.…”

“…In insects fed with oil rich in EPA and DHA, the percentage of retention is correlated with n-3 LCPUFA content of the diet, although levels were always relatively low, less than 20% in T. molitor and M. configurata [49] or 12.1% in H. illucens [30]. The natural diet of terrestrial insects is usually very specific and poor and, as suggested by Colombo et al [49], there has not been strong selection pressure to highly retain n−3 LCPUFAs, which results in low retention efficiencies. In H. illucens [30,47], an acceptable accumulation of n−3 LCPUFAs has been observed, especially for EPA, while the retention of DHA is low.…”