Feeding on ripening and over-ripening fruit: interactions between sugar, ethanol and polyphenol contents in a tropical butterfly

Abstract

In ripe fruit, energy mostly derives from sugar, while in over-ripe fruit, it also comes from ethanol. Such ripeness differences may alter the fitness benefits associated with frugivory if animals are unable to degrade ethanol when consuming over-ripe fruit. In the tropical butterfly Bicyclus anynana, we found that females consuming isocaloric solutions mimicking ripe (20% sucrose) and over-ripe fruit (10% sucrose, 7% ethanol) of the palm Astrocaryum standleyanum exhibited higher fecundity than females consuming a solution mimicking unripe fruit (10% sucrose). Moreover, relative to butterflies consuming a solution mimicking unripe fruit, survival was enhanced when butterflies consumed a solution mimicking either ripe fruit supplemented with polyphenols (fruit antioxidant compounds) or over-ripe fruit devoid of polyphenols. This suggests that (1) butterflies have evolved tolerance mechanisms to derive the same reproductive benefits from ethanol and sugar, and (2) polyphenols may regulate the allocation of sugar and ethanol to maintenance mechanisms. However, variation in fitness owing to the composition of feeding solutions was not paralleled by corresponding physiological changes (alcohol dehydrogenase activity, oxidative status) in butterflies. The fitness proxies and physiological parameters that we measured therefore appear to reflect distinct biological pathways. Overall, our results highlight that the energy content of fruit primarily affects the fecundity of B. anynana butterflies, while the effects of fruit consumption on survival are more complex and vary depending on ripening stage and polyphenol presence. The actual underlying physiological mechanisms linking fruit ripeness and fitness components remain to be clarified.

Honeybees show adaptive reactions to ethanol exposure

“…Our findings expand the range of knowledge regarding honeybees as models in alcohol research 1 , 2 . Similarly to other pollinators 35 – 37 , honeybees encounter ethanol in nature, in fermenting nectar, honey and fruits, although they digest it orally and in low percentages. Here, we chose vapour as the mode of delivery of ethanol, using a setup similar to that used by Ammons and Hunt 9 to investigate honeybee sensitivity to ethanol and its correlation with aggression.…”

Honey Bees (Apis mellifera) Show a Preference for the Consumption of Ethanol

“…Unlike the effect of EtOH on honey bees, fruit flies did not show increases in mortality when EtOH was added to food. Similarly, the addition of EtOH to a sucrose solution increased survival rates in the frugivorous butterfly, B. anynana (Beaulieu et al., ). The difference in survival of the fruit‐eating insects versus the nectar‐consuming honey bee may be due to a decreased ability not only to use EtOH as an energy source, but also to break down EtOH or its toxic metabolites.…”

Fruit-feeding in European cold season noctuid moths increases fecundity, but not longevity

“…In insects that specialize on rotting fruits, decomposition products, such as yeast amino acids, and the complex admixture of nutrients encountered in fruits are essential to achieve fitness benefits (Bauerfeind et al 2007;Geister et al 2008;Molleman et al 2008;Beaulieu et al 2017). To better locate their resources, specialist fruit-feeders also tend to be highly responsive to alcohols and other by-products of microbial decay of fruits (Ômura et al 2000;Dierks and Fischer 2008;Tang et al 2013).…”