The Effect of Climate and Diet on Body Lipid Composition in the Oriental Hornet (Vespa orientalis)

Mika Volov,Levona Bodner,Eran Levin,Abraham Hefetz,Nitzan Cohen,Shahar Dubiner,Sofia Bouchebti

doi:10.3389/fevo.2021.755331

Abstract

Fatty acids (FA) are the primary metabolic fuel for many organisms and the fundamental component of membranes of all living organisms. FAs can be saturated (SFA), monounsaturated (MUFA), or polyunsaturated (PUFA). PUFA are not synthesized by most animals and are considered as essential nutrients. We examined the effect of climate on the saturation level of polar (mostly membranal) and neutral lipids in the body of the Oriental hornet (Vespa orientalis) from two extreme climatic zones: Mediterranean high elevation; and hot arid desert. In contrast to previous reports, the environmental temperature was shown to affect the hornet colonies’ thermal environments. The hornets nonetheless maintained their colony temperature within a narrow range. Analyses of the hornets’ unsaturation levels of polar and non-polar body lipids revealed caste differences: gynes and males contained less unsaturated lipids than workers. However, there were no differences in the respective castes between the two different climate zones tested. Experimentally manipulating the diet of queenless hornet colonies to a high Omega-3 diet (salmon) or a high Omega-6 diet (crickets) had only a minor effect on the worker-born males’ lipid composition. Although salmon-fed males had a higher Omega-3 content than cricket-fed ones, the proportion of these fatty acids was still low (below 1%). Cricket-fed males had significantly higher levels of Omega-6 than salmon-fed males. Our data show that the specific lipid composition of the hornet body is highly regulated and deficient in essential PUFA, even under different climates or high Omega-3 or Omega-6 PUFA diet. PUFA, especially Omega-3, is considered to have a beneficial effect on physiological processes. Our finding that these FA, when common in the diet, are almost absent in the body raises questions about how they affect animals’ physiology.

Highlights

Fatty acids (FA) are essential macronutrients, precursors in various biological processes, and key components in living cell membranes (De Carvalho and Caramujo, 2018; Hulbert, 2021)
We supplied the hornets with house crickets (Acheta domestica) rich in n-6 PUFA (Grapes et al, 1989), and in the second cage, we provided them with Atlantic salmon (Salmo salar), rich in n-3 PUFA (Sprague et al, 2016)
While the ambient temperature at the Dead Sea rose above 40◦C almost every day during summer, and surface temperature could reach 60◦C, colony temperatures in all nests never exceeded 37◦C

Summary

Introduction

Fatty acids (FA) are essential macronutrients, precursors in various biological processes, and key components in living cell membranes (De Carvalho and Caramujo, 2018; Hulbert, 2021). Omega-6 PUFA are common in plants and terrestrial animals; they are precursors of prostaglandins and are involved in mitigating the inflammatory process (De Carvalho and Caramujo, 2018). Most animals lack the respective desaturase enzymes commonly found in plants and microorganisms (but see Cripps et al, 1986). They must acquire both the n-6 and n-3 polyunsaturated FA from their diet or gut microbes (Hulbert et al, 2002). Various studies have suggested that the composition of animal body FA reflects their diet (McKenzie, 2001; Pierce et al, 2005; Lemieux et al, 2008; Levin et al, 2013; Lehtovaara et al, 2017; McWilliams et al, 2020)

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Results

Conclusion