Mizuta Hikaru, Morozumi Yutaro, Watanabe Michihito, Ohta Shinji, Ômura Hisashi
Graduate School of Integrated Sciences for Life, Hiroshima University, Higashihiroshima, Hiroshima 739-8528, Japan.
Graduate School of Biosphere Science, Hiroshima University, Higashihiroshima, Hiroshima 739-8528, Japan.
J Insect Physiol. 2023 Nov;150:104558. doi: 10.1016/j.jinsphys.2023.104558. Epub 2023 Aug 24.
Several myrmecophilous insects participate in symbiotic relationships with ants that receive sugar-rich food rewards. For instance, certain aphid species secrete honeydew containing high concentration of melezitose, which acts as a potent feeding-stimulant and attractant for ants. Lycaenid butterfly larvae possess dorsal nectary glands that secrete sugar-rich droplets for tending ants. However, the roles of sugar components in ant foraging and larva-tending activities are unknown. Lycaeides (Plebejus) argyrognomon are larvae that are frequently and facultatively attended by various ant species, including Formica japonica, on the host plant Indigofera pseudotinctoria. The larval secretions of this insect contained small amounts of trisaccharides, melezitose and maltotriose, which were not detected in the host plant's flower nectar, and larval secretions of two sympatric and myrmecophilous lycaenids, Zizeeria maha and Everes argiades. Melezitose and maltotriose, along with sucrose, were preferred by the worker ants. Of the four sugar mixture samples that mimicked I. pseudotinctoria floral nectar and the larval secretions of three lycaenids, respectively, the L. argyrognomon mimic was the most preferred by F. japonica ants. Moreover, the removal of trisaccharides from this mimic significantly reduced its stimulatory activity to ant feedings. These results indicated that the sugar composition of L. argyrognomon larval secretions is suited to the feeding preference of F. japonica ants, and that the trisaccharide components play a key role in increasing their preference. However, only half of the ants responded to the L. argyrognomon mimic even at the concentration corresponding to the maximum total sugar concentration in the collected larval secretions. The fact that the secretions of all L. argyrognomon larvae did not have sufficient sugar levels to stimulate ant feedings suggests that the production of sugar-rich secretions and trisaccharide components is metabolically costly for the larvae and that components other than sugars may be involved in ant attendance.
几种蚁栖昆虫与蚂蚁建立了共生关系，蚂蚁会给予它们富含糖分的食物作为回报。例如，某些蚜虫会分泌含有高浓度松三糖的蜜露，松三糖对蚂蚁来说是一种有效的取食刺激物和引诱剂。灰蝶科蝴蝶幼虫拥有背蜜腺，能分泌富含糖分的液滴以供蚂蚁照料。然而，糖分成分在蚂蚁觅食和照料幼虫活动中的作用尚不清楚。银灰蝶（Lycaeides (Plebejus) argyrognomon）的幼虫经常且偶尔会受到包括日本蚁（Formica japonica）在内的各种蚂蚁在寄主植物假靛蓝（Indigofera pseudotinctoria）上的照料。这种昆虫的幼虫分泌物中含有少量三糖，即松三糖和麦芽三糖，而在寄主植物花蜜以及两种同域分布且为蚁栖性的灰蝶——酢浆灰蝶（Zizeeria maha）和姬黄灰蝶（Everes argiades）的幼虫分泌物中均未检测到。松三糖、麦芽三糖以及蔗糖受到工蚁的偏爱。在分别模拟假靛蓝花蜜和三种灰蝶幼虫分泌物的四种糖混合物样本中，银灰蝶幼虫分泌物的模拟物最受日本蚁青睐。此外，从该模拟物中去除三糖会显著降低其对蚂蚁取食的刺激活性。这些结果表明，银灰蝶幼虫分泌物的糖分组成适合日本蚁的取食偏好，且三糖成分在增强它们的偏好方面起关键作用。然而，即使在对应于所收集幼虫分泌物中最大总糖浓度的浓度下，也只有一半的蚂蚁对银灰蝶幼虫分泌物模拟物有反应。所有银灰蝶幼虫的分泌物都没有足够的糖分水平来刺激蚂蚁取食，这一事实表明，产生富含糖分的分泌物和三糖成分对幼虫来说代谢成本很高，并且除了糖分之外的其他成分可能也参与了蚂蚁的照料行为。
