Insect Ecology Laboratory, Graduate School of Bioresources, Mie University, Tsu, Mie, Japan.
Graduate School of Agriculture, Tamagawa University, Machida, Tokyo, Japan.
J Insect Physiol. 2021 May-Jun;131:104223. doi: 10.1016/j.jinsphys.2021.104223. Epub 2021 Mar 10.
In the temperate paper wasp Polistes jokahamae, caste is influenced by photoperiod during the adult stage, but the mechanisms underlying the caste-fate determination system have been unclear. We measured the brain levels of monoamines and related substances in females kept isolated for two weeks under different photoperiods. Except for in the first-emerging group, the females developed ovaries under long-day conditions, whereas they stored lipids under short-day conditions. The levels of tyramine in the brain were significantly higher under long-day than under short-day conditions and positively correlated with maximum oocyte lengths. These results suggest that tyramine was produced in response to long daylength during the adult stage and associated with ovarian development, which is the principal characteristic of reproductive workers. There was also a significant positive correlation between dopamine levels in the brain and maximum oocyte length, independent of photoperiod, suggesting that dopamine is involved in reproductive function with tyramine resulting in the induction of reproductive workers. Meanwhile, higher levels of tryptophan in the brain were found in short-day conditions and positively correlated with lipid stores. However, serotonin synthesized from tryptophan and N-acetylserotonin were not associated with lipid stores without photoperiodic responses, suggesting that tryptophan is involved in the physiological changes toward gyne under short daylength, independently of serotonin signaling. In conclusion, tyramine and tryptophan are candidates for mediating photoperiod-dependent caste-fate determination in P. jokahamae: the former is involved in generating the worker caste while the latter is involved in generating the gyne caste.
在温带纸蜂 Polistes jokahamae 中，等级是由成虫阶段的光周期影响的，但等级命运决定系统的机制尚不清楚。我们测量了在不同光周期下隔离两周的雌性的大脑中单胺和相关物质的水平。除了第一批出现的组外，雌性在长日照条件下发育卵巢，而在短日照条件下储存脂质。脑中天冬氨酸的水平在长日照条件下显著高于短日照条件，与最大卵母细胞长度呈正相关。这些结果表明，天冬氨酸在成虫阶段对长日照产生反应，并与卵巢发育有关，这是生殖工蜂的主要特征。脑中天冬氨酸水平与最大卵母细胞长度之间也存在显著的正相关，与光周期无关，表明多巴胺参与生殖功能，天冬氨酸导致生殖工蜂的诱导。同时，在短日照条件下发现脑中天冬氨酸水平较高，并与脂质储存呈正相关。然而，由色氨酸合成的血清素和 N-乙酰血清素与脂质储存无关，没有光周期反应，表明色氨酸独立于血清素信号参与短日照下向雌蜂的生理变化。总之，天冬氨酸和色氨酸是介导 P. jokahamae 中光周期依赖性等级命运决定的候选物质：前者参与产生工蜂等级，后者参与产生雌蜂等级。
