Abstract
BackgroundMany insects feed on pollen surface lipids and contents accessible through the germination pores. Pollen walls, however, are not broken down because they consist of sporopollenin and are highly resistant to physical and enzymatic damage. Here we report that certain Microlepidoptera chemically dissolve pollen grains with exudates from their mouthparts.Methodology/Principal FindingsField observations and experiments in tropical China revealed that two species of Deltophora (Gelechioidea) are the exclusive pollinators of two species of Phyllanthus (Phyllanthaceae) on which their larvae develop and from which the adults take pollen and nectar. DNA sequences placed the moths and plants phylogenetically and confirmed that larvae were those of the pollinating moths; molecular clock dating suggests that the moth clade is younger than the plant clade. Captive moths with pollen on their mouthparts after 2-3 days of starvation no longer carried intact grains, and SEM photographs showed exine fragments on their proboscises. GC-MS revealed cis-β-ocimene as the dominant volatile in leaves and flowers, but GC-MS analyses of proboscis extracts failed to reveal an obvious sporopollenin-dissolving compound. A candidate is ethanolamine, which occurs in insect hemolymphs and is used to dissolve sporopollenin by palynologists.Conclusions/SignificanceThis is the first report of any insect and indeed any animal chemically dissolving pollen.
Highlights
Obligate mutualisms are often supported by unique adaptations that facilitate specific interactions between the partners
Male and female moths carried pollen grains on their proboscises (Fig. 1F; Fig. 2F), and pollen grains under the microscope could unambiguously be identified as coming from the host plants
Cross-pollination is very effective as shown by the high fruit set in the dioecious species, P. cochinchinensis (Supporting Information S1)
Summary
Obligate mutualisms are often supported by unique adaptations that facilitate specific interactions between the partners. Examples include yucca flowers and yucca moths [1], senita cacti and senita moths [2], and Phyllantheae flowers and Epicephala moths [3,4]. In each of these mutualisms, special behaviors or mouthparts evolved, resulting in efficient transport of pollen to stigmas. None of these moths feed on pollen. We report that certain Microlepidoptera chemically dissolve pollen grains with exudates from their mouthparts
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