Influence of pollen deprivation on the fore wing asymmetry of honeybee workers and drones

Apidologie, Feb 2016

Environmental stress during development can be linked to changes in morphological traits of the organism such as increased fluctuating asymmetry. In suboptimal conditions, like food deprivation, developmental stability may be perturbed, because organisms are not able to buffer disturbances caused by stressors and, in effect, greater degrees of asymmetry can arise during development. In this study, honeybee workers and drones were reared in colonies with limited and unlimited access to pollen. The developmental instability of the workers and drones in these colonies was assessed using the asymmetry of their fore wing venation. Both workers and drones showed a similar directional asymmetry of size—in favour of the right wing—and significant, but dissimilar, differences of wing shape. Limited access to pollen caused some differences in the fluctuating asymmetry of size and shape in pollen-deprived workers and drones compared to the control bees. However, more pronounced differences were found due to replication than to pollen deprivation itself.

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Influence of pollen deprivation on the fore wing asymmetry of honeybee workers and drones

Influence of pollen deprivation on the fore wing asymmetry of honeybee workers and drones SZENTGYÖRGYI 0 Krystyn 0 CZEKOŃSKA 0 m TOFILSKI 0 0 Department of Pomology and Apiculture, University of Agriculture in Kraków , Al. 29. Listopada 54, 31-425, Kraków , Poland - Environmental stress during development can be linked to changes in morphological traits of the organism such as increased fluctuating asymmetry. In suboptimal conditions, like food deprivation, developmental stability may be perturbed, because organisms are not able to buffer disturbances caused by stressors and, in effect, greater degrees of asymmetry can arise during development. In this study, honeybee workers and drones were reared in colonies with limited and unlimited access to pollen. The developmental instability of the workers and drones in these colonies was assessed using the asymmetry of their fore wing venation. Both workers and drones showed a similar directional asymmetry of size-in favour of the right wing-and significant, but dissimilar, differences of wing shape. Limited access to pollen caused some differences in the fluctuating asymmetry of size and shape in pollen-deprived workers and drones compared to the control bees. However, more pronounced differences were found due to replication than to pollen deprivation itself. 1. INTRODUCTION Pollen is the main source of proteins, lipids, vitamins and minerals for both the developing brood and adult honeybees (Apis mellifera Linnaeus, 1758) (Brodschneider and Crailsheim 2010; Haydak 1970; Keller et al. 2005a, b) . Young worker larvae are fed with royal jelly, however, in older workers and drone larvae it is largely replaced with raw floral pollen (Haydak 1970; Hrassnigg and Crailsheim 2005) . The pollen is also consumed by adult drones in small amounts during the first few days after emergence (Free 1957; Haydak 1970; Szolderits and Crailsheim 1993; Schmickl and Crailsheim 2004) , while adult workers feed on pollen for a significantly longer period of time and consume much larger amounts of pollen (Szolderits and Crailsheim 1993; Hrassnigg and Crailsheim 2005) . In natural conditions, the availability of pollen changes seasonally because it depends on the diversity and abundance of flowering plants (Köppler et al. 2007; Odoux et al. 2012) . During dearth periods or unfavourable weather conditions, honeybees depend on pollen stores (Fewell and Winston 1992); however, occasionally these stores can be insufficient and bees can suffer from malnutrition. The quantity of pollen available in the hive during brood rearing can directly affect t he de ve l o pm e nt o f w or ke r s an d dr one s (Hrassnigg and Crailsheim 2005; Kunert and Crailsheim 1988; Mattila and Otis 2006a) . Workers suffering from pollen deprivation in most studies were found to live shorter (Janmaat and Winston 2000; Kunert and Crailsheim 1988; Mattila and Otis 2006b) , start foraging earlier (Rueppell et al. 2006; Schmickl and Crailsheim 2002) , have reduced hypopharyngeal glands (Crailsheim and Stolberg 1989) and ovaries (Pernal and Currie 2000) , less effective in flight (Brodschneider et al. 2009) and have lower levels of vitellogenin and transferrin expression (Di Pasquale et al. 2013) . Dwindling pollen stores during autumn is also a signal for bees to start rearing winter bees (Mattila and Otis 2007) . Among drones, limited access to pollen reduces their reproductive quality ( Czekońska et al. 2015 ) and mating success (Couvillon et al. 2010) . Pollen limitation can also affect bees’ susceptibility to Nosema spp. (Wang and Moeller 1970; Huang 2012; Di Pasquale et al. 2013) , Varroa destructor (Huang 2012; van Dooremalen et al. 2013) and other diseases (Brodschneider and Crailsheim 2010; de Grandi-Hoffman et al. 2010; Willard et al. 2011; Foley et al. 2012) . In extreme cases, pollen deprivation can lead to the cannibalism of young larvae in order to feed older larvae (Schmickl and Crailsheim 2004) or cessation of brood rearing completely, to avoid producing highly impaired individuals (Imdorf et al. 1998; Kunert and Crailsheim 1988; Crailsheim and Hrassnigg 1998; Boes 2010) . Malnutrition, as described above, is a strong exogenous stressor affecting development and can be linked to changes in various morphological traits. One of these traits is the body symmetry of an organism. It is assumed that in suboptimal conditions developmental stability may be perturbed, because organisms are not able to buffer disturbances caused by exogenous environmental stressors and, as an effect, greater degrees of randomly appearing asymmetry arise during development. Such asymmetry caused by suboptimal developmental conditions is called fluctuating asymmetry and is independent of body side (van Valen 1962) and can affect various body parts (Palmer and Strobeck 2003; Palmer 1994) . It should not be confused with directional asymmetry (van Valen 1962; Palmer 1994) which occu (...truncated)


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Hajnalka Szentgyörgyi, Krystyna Czekońska, Adam Tofilski. Influence of pollen deprivation on the fore wing asymmetry of honeybee workers and drones, Apidologie, 2016, pp. 653-662, Volume 47, Issue 5, DOI: 10.1007/s13592-015-0415-5