Learning performance and brain structure of artificially-reared honey bees fed with different quantities of food

Abstract

BackgroundArtificial rearing of honey bee larvae is an established method which enables to fully standardize the rearing environment and to manipulate the supplied diet to the brood. However, there are no studies which compare learning performance or neuroanatomic differences of artificially-reared (in-lab) bees in comparison with their in-hive reared counterparts.MethodsHere we tested how different quantities of food during larval development affect body size, brain morphology and learning ability of adult honey bees. We used in-lab rearing to be able to manipulate the total quantity of food consumed during larval development. After hatching, a subset of the bees was taken for which we made 3D reconstructions of the brains using confocal laser-scanning microscopy. Learning ability and memory formation of the remaining bees was tested in a differential olfactory conditioning experiment. Finally, we evaluated how bees reared with different quantities of artificial diet compared to in-hive reared bees.ResultsThorax and head size of in-lab reared honey bees, when fed the standard diet of 160 µl or less, were slightly smaller than hive bees. The brain structure analyses showed that artificially reared bees had smaller mushroom body (MB) lateral calyces than their in-hive counterparts, independently of the quantity of food they received. However, they showed the same total brain size and the same associative learning ability as in-hive reared bees. In terms of mid-term memory, but not early long-term memory, they performed even better than the in-hive control.DiscussionWe have demonstrated that bees that are reared artificially (according to the Aupinel protocol) and kept in lab-conditions perform the same or even better than their in-hive sisters in an olfactory conditioning experiment even though their lateral calyces were consistently smaller at emergence. The applied combination of experimental manipulation during the larval phase plus subsequent behavioral and neuro-anatomic analyses is a powerful tool for basic and applied honey bee research.

Transcriptome Analysis of Newly Emerged Honeybees Exposure to Sublethal Carbendazim During Larval Stage

“…Suitable carbendazim post-exposure risk evaluation samples were then prepared for RNA-Seq and qRT-PCR. Our previous in vitro larval-rearing revealed a 75 emergence rate, which was acceptable ( Brodschneider et al, 2009 ; Aupinel et al, 2010 ; Crailsheim et al, 2013 ; Wu et al, 2017 ), and demonstrated the reliability of the present results.…”

“…Rearing honeybee larvae in vitro is of great importance for research on pathogens and risk assessment ( Crailsheim et al, 2013 ). In the present study, honeybees were exposed to the fungicide carbendazim to assess and evaluate its sublethal effects.…”

“…The sublethal effects of carbendazim on honeybees were assessed using an artificial larva-rearing system modified from previous studies ( Crailsheim et al, 2013 ; Wu et al, 2017 ). Three honeybee colonies were selected for this experiment.…”

Queen Dominance May Reduce Worker Mushroom Body Size in a Social Bee

“…Another explanation for workers' smaller MB calyces, and whole brains as well, is that larval nutrition may influence neural development. Larval nutrition affects brain morphology in honeybees, with queens having larger and more rapidly growing brains in the larval stage (Moda et al , ), and reduced larval nutrition results in smaller MB calyces at emergence in workers (Steijven et al , ), but this has not been studied in primitively eusocial groups. Variation in larval nutrition can affect reproductive physiology and behavior in other sweat bee species (Richards and Packer, ; Brand and Chapuisat, ) as well as other species of primitively eusocial insects (Judd et al , ; Lawson et al , ; ; Kapheim, ).…”

Differences in pre-imaginal development of the honey bee Apis mellifera between in vitro and in-hive contexts

“…As a result, the in vitro rearing procedure (details in Sections 2.2 and 2.3) has been developed as a way to assess potential stressors during the development of bees under laboratory conditions (Becker and Keller 2016;Crailsheim et al 2013). Nevertheless, only a few studies have compared artificially reared brood with honey bees reared in the hive (Brodschneider et al 2009;De Souza et al 2015;Steijven et al 2017).…”