Finnish Museum of Natural History, University of Helsinki, Helsinki, Finland.
Organismal and Evolutionary Biology Research Programme, Faculty of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland.
Sci Rep. 2019 Nov 13;9(1):16698. doi: 10.1038/s41598-019-53153-x.
Fungus-growing termites of the genus Macrotermes cultivate symbiotic fungi (Termitomyces) in their underground nest chambers to degrade plant matter collected from the environment. Although the general mechanism of food processing is relatively well-known, it has remained unclear whether the termites get their nutrition primarily from the fungal mycelium or from plant tissues partly decomposed by the fungus. To elucidate the flows of carbon and nitrogen in the complicated food-chains within the nests of fungus-growing termites, we determined the stable isotope signatures of different materials sampled from four Macrotermes colonies in southern Kenya. Stable isotopes of carbon revealed that the termite queen and the young larvae are largely sustained by the fungal mycelium. Conversely, all adult workers and soldiers seem to feed predominantly on plant and/or fungus comb material, demonstrating that the fungal symbiont plays a different nutritional role for different termite castes. Nitrogen stable isotopes indicated additional differences between castes and revealed intriguing patterns in colony nitrogen cycling. Nitrogen is effectively recycled within the colonies, but also a presently unspecified nitrogen source, most likely symbiotic nitrogen-fixing bacteria, seems to contribute to nitrogen supply. Our results indicate that the gut microbiota of the termite queen might be largely responsible for the proposed nitrogen fixation.
共生白蚁属的真菌培养白蚁在其地下巢穴室中培养共生真菌（Termitomyces），以降解从环境中收集的植物物质。尽管食物加工的一般机制相对较为清楚，但仍不清楚白蚁是主要从真菌菌丝体中获取营养，还是从真菌部分分解的植物组织中获取营养。为了阐明在真菌培养白蚁的巢穴内复杂食物链中的碳氮流动，我们确定了从肯尼亚南部四个共生白蚁属群体中采集的不同材料的稳定同位素特征。碳的稳定同位素表明，蚁后和幼幼虫主要由真菌菌丝体维持。相反，所有成年工蚁和兵蚁似乎主要以植物和/或真菌巢材料为食，这表明真菌共生体对不同的白蚁类群具有不同的营养作用。氮稳定同位素表明了不同类群之间的其他差异，并揭示了群体氮循环中的有趣模式。氮在群体内得到有效回收，但目前还不确定的氮源，很可能是共生固氮细菌，似乎有助于氮供应。我们的结果表明，蚁后的肠道微生物群可能在很大程度上负责提议的固氮作用。
