Department of Bioresource Science, Tamagawa University, Machida, Tokyo, Japan.
Honeybee Science Research Center, Tamagawa University, Machida, Tokyo, Japan.
PLoS One. 2020 Dec 17;15(12):e0244140. doi: 10.1371/journal.pone.0244140. eCollection 2020.
Caste polymorphism in eusocial insects is based on morphological plasticity and linked to physiological and behavioral characteristics. To test the possibility that dopamine production in the brain is associated with the caste-specific morphology and behavior in female honey bees, an intermediate caste was produced via artificial rearing using different amounts of diet, before quantifying the dopamine levels and conducting behavioral tests. In field colonies, individual traits such as mandibular shape, number of ovarioles, diameter of spermatheca, and dopamine levels in the brain differed significantly between workers and queens. Females given 1.5 times the amount of artificial diet that control worker receives during the larval stage in the laboratory had characteristics intermediate between castes. The dopamine levels in the brain were positively correlated with the mandibular shape indexes, number of ovarioles, and spermatheca diameter among artificially reared females. The dopamine levels were significantly higher in females with mandibular notches than those without. In fighting experiments with the intermediate caste females, the winners had significantly higher dopamine levels in the brain than the losers. Brain levels of tyrosine were positively correlated with those of catecholamines but not phenolamines, thereby suggesting a strong metabolic relationship between tyrosine and dopamine. Thus, the caste-specific characteristics of the honey bee are potentially continuous in the same manner as those in primitively eusocial species. Dopamine production in the brain is associated with the continuous caste-specific morphology, as well as being linked to the amount of tyrosine taken from food, and it supports the aggressive behavior of queen-type females.
社会性昆虫中的等级多态性基于形态可塑性，并与生理和行为特征相关联。为了测试大脑中多巴胺的产生是否与雌性蜜蜂特定等级的形态和行为有关，我们通过使用不同量的食物进行人工饲养来产生中间等级，然后定量测定多巴胺水平并进行行为测试。在野外群体中，个体特征，如下颌形状、卵巢管数量、精荚直径以及大脑中的多巴胺水平，在工蜂和蜂王之间存在显著差异。在实验室中，给予 1.5 倍于控制工蜂幼虫期接受的人工饮食量的雌性，其特征处于等级之间。大脑中的多巴胺水平与人工饲养的雌性的下颌形状指数、卵巢管数量和精荚直径呈正相关。具有下颌缺口的雌性的多巴胺水平明显高于没有下颌缺口的雌性。在与中间等级雌性的战斗实验中，胜利者的大脑中的多巴胺水平明显高于失败者。脑中酪氨酸的水平与儿茶酚胺呈正相关，但与苯乙胺无关，这表明酪氨酸和多巴胺之间存在很强的代谢关系。因此，蜜蜂的特定等级特征在某种程度上是连续的，与原始社会性物种中的特征相似。大脑中的多巴胺产生与连续的特定等级形态有关，同时与从食物中摄取的酪氨酸量有关，并支持蜂王型雌性的攻击性行为。
