Scheiner Ricarda, Entler Brian V, Barron Andrew B, Scholl Christina, Thamm Markus
Behavioral Physiology and Sociobiology, Biocenter, University of WürzburgWürzburg, Germany.
Department of Biological Sciences, Macquarie UniversitySydney, NSW, Australia.
Front Syst Neurosci. 2017 Aug 8;11:55. doi: 10.3389/fnsys.2017.00055. eCollection 2017.
Division of labor is a hallmark of social insects. In the honeybee () each sterile female worker performs a series of social tasks. The most drastic changes in behavior occur when a nurse bee, who takes care of the brood and the queen in the hive, transitions to foraging behavior. Foragers provision the colony with pollen, nectar or water. Nurse bees and foragers differ in numerous behaviors, including responsiveness to gustatory stimuli. Differences in gustatory responsiveness, in turn, might be involved in regulating division of labor through differential sensory response thresholds. Biogenic amines are important modulators of behavior. Tyramine and octopamine have been shown to increase gustatory responsiveness in honeybees when injected into the thorax, thereby possibly triggering social organization. So far, most of the experiments investigating the role of amines on gustatory responsiveness have focused on the brain. The potential role of the fat body in regulating sensory responsiveness and division of labor has large been neglected. We here investigated the role of the fat body in modulating gustatory responsiveness through tyramine signaling in different social roles of honeybees. We quantified levels of tyramine, tyramine receptor gene expression and the effect of elevating fat body tyramine titers on gustatory responsiveness in both nurse bees and foragers. Our data suggest that elevating the tyramine titer in the fat body pharmacologically increases gustatory responsiveness in foragers, but not in nurse bees. This differential effect of tyramine on gustatory responsiveness correlates with a higher natural gustatory responsiveness of foragers, with a higher tyramine receptor () mRNA expression in fat bodies of foragers and with lower baseline tyramine titers in fat bodies of foragers compared to those of nurse bees. We suggest that differential tyramine signaling in the fat body has an important role in the plasticity of division of labor through changing gustatory responsiveness.
分工是群居昆虫的一个显著特征。在蜜蜂群体中，每只不育的雌性工蜂都会执行一系列社会任务。当一只在蜂巢中照顾幼虫和蜂王的保育蜂转变为觅食行为时，行为会发生最显著的变化。觅食蜂为蜂群提供花粉、花蜜或水。保育蜂和觅食蜂在许多行为上存在差异，包括对味觉刺激的反应。味觉反应的差异反过来可能通过不同的感官反应阈值参与调节分工。生物胺是行为的重要调节因子。已表明，将酪胺和章鱼胺注入蜜蜂胸部时，会增加其味觉反应，从而可能触发社会组织。到目前为止，大多数研究胺对味觉反应作用的实验都集中在大脑上。脂肪体在调节感官反应和分工方面的潜在作用在很大程度上被忽视了。我们在此研究了脂肪体在蜜蜂不同社会角色中通过酪胺信号调节味觉反应的作用。我们量化了酪胺水平、酪胺受体基因表达以及提高脂肪体酪胺滴度对保育蜂和觅食蜂味觉反应的影响。我们的数据表明，通过药理学方法提高脂肪体中的酪胺滴度会增加觅食蜂的味觉反应，但不会增加保育蜂的味觉反应。酪胺对味觉反应的这种差异效应与觅食蜂较高的天然味觉反应、觅食蜂脂肪体中较高的酪胺受体（）mRNA表达以及觅食蜂脂肪体中比保育蜂更低的基线酪胺滴度相关。我们认为，脂肪体中不同的酪胺信号通过改变味觉反应在分工可塑性中起重要作用。
