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Hawkmoths use nectar sugar to reduce oxidative damage from flight

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Science  17 Feb 2017:
Vol. 355, Issue 6326, pp. 733-735
DOI: 10.1126/science.aah4634

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  • Nectar feeders take their vitamins
    • Paul A. Egan, Researcher, Swedish University of Agricultural Sciences
    • Other Contributors:
      • Leif Richardson, Researcher, University of Vermont
      • Philip C. Stevenson, Senior Research Leader / Professor, Royal Botanic Gardens, Kew / University of Greenwich

    The perception that nectar merely provides soluble sugar as a reward to consumers remains prevalent. Nectar in fact provides a remarkable diversity of metabolites linked to pollinator nutrition and health (1, 2), including the well-known antioxidant ascorbate (Vitamin C), which in plants also functions in the nectar redox cycle (3). The renowned antioxidant activity of many floral honeys can also be attributed in part to nectar phenolics.

    In a recent report in Science (4), Levin and colleagues report a novel mechanism by which the tobacco hawkmoth (Manduca sexta) channels nectar glucose to alleviate oxidative damage to flight muscles. We concur that the intense metabolic demand of certain flight behaviours (hovering, migration, etc.) may have encouraged this adaptation in many nectar feeders, including nectivorous birds and bats. However, we believe that hypotheses underpinning future research must critically decouple from their assertion that “antioxidants in nectar are scarce to non-existent” (4).

    Indeed, studies on hundreds of plant species contradict this statement (3, 5, 6). Coyote tobacco is also known to exhibit nectar redox cycling (7), and is an important nectar plant for hawkmoth and migrant hummingbird pollinators. It is thus likely these nectarivores consume antioxidants in nectar, supported by significant accumulation of ascorbate in M. sexta adults (8). Indeed, plant species pollinated by hovering moths are over twice as likely to contain antiox...

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    Competing Interests: None declared.