Sex‐specific differences in emergence patterns of solitary, cavity‐nesting bee, Megachile rotundata

Abstract

Circadian rhythms play an important role in synchronizing biological processes. These rhythms are often influenced by semi‐predictable period cues, such as photoperiod or thermoperiod, often referred to as zeitgebers. The alfalfa leafcutting bee, Megachile rotundata, is a solitary, cavity‐nesting bee known to synchronize its emergence with thermoperiods as the dominant cue. Bees emerge as adults from brood cells. Brood cells are constructed by females with leaves and provisioned with pollen and nectar. One egg is laid in each brood cell, and a nest is composed of multiple brood cells in series in the cavity. Offspring go through all of juvenile development and metamorphosis in the cavity. It is unknown if certain variations in thermoperiod affects the timing of emergence. Because brood cells are built in series in the nest, adult offspring must emerge in a specific order to prevent bees placed at the back of the cavity from emerging before those in the front. If a bee in the back were to emerge first it would chew through its siblings' brood cells, potentially killing them, in order to exit the cavity. Thus, regulating emergence is important. On average, male M. rotundata are smaller than females, and often the brood cells at the front of cavities contain male offspring. Because of this, bee weight and sex are hypothesized to affect timing of emergence. To test this hypothesis, we disarticulated nests and placed individual brood cells in an apparatus that automatically records emergence time. We placed bees in various thermoperiods and recorded emergence time, sex, and dry weight of adult bees. It is well known that adult male offspring begin emerging days before females. In this study male offspring emerged earlier in the day than females which could be important for mating strategies. Understanding the roles sex and weight play in emergence and how these factors interact with different thermoperiods will help us to understand the maternal contribution to offspring development.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.