Termite-egg mimicry by a sclerotium-forming fungus
Termite-egg mimicry by a sclerotium-forming fungus
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DOI：
10.1098/rspb.2005.3434
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发表时间：
2006-05
期刊：
影响因子：
--
通讯作者：
K. Matsuura
中科院分区：
文献类型：
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作者：
K. Matsuura
模仿在广泛的有机体中进化，包括防御、觅食、授粉和社会寄生的不同策略。在这里，我要报告一个由真菌模仿卵子的特殊案例，真菌在白蚁巢中获得了没有竞争对手的栖息地。棕色真菌球，被称为白蚁球，经常在成堆的白蚁卵中发现。系统发育分析表明，分离自不同寄主的白蚁球状真菌均非常相似，不同寄主种类和地理位置的白蚁球状真菌分子水平无显著差异。我发现白蚁球对卵存活率没有显著影响。这种白蚁球状真菌很少在自然群体中杀死白蚁卵。即使是与这种真菌没有自然联系的白蚁物种(冲绳网蚁)，在实验中给白蚁提供白蚁球时，也会同时照看白蚁球和卵。利用玻璃微珠进行的假卵生物测定表明，形态伪装和化学伪装都是诱导白蚁趋化的必要条件。白蚁几乎只照顾直径与它们的卵大小完全匹配的白蚁球。此外，扫描电子显微镜观察显示，鸡蛋表面光滑的质地具有复杂的模仿性。这些结果提供了明确的证据，表明这种相互作用只对真菌有益，即寄生模仿白蚁卵的白蚁球。
Mimicry has evolved in a wide range of organisms and encompasses diverse tactics for defence, foraging, pollination and social parasitism. Here, I report an extraordinary case of egg mimicry by a fungus, whereby the fungus gains competitor-free habitat in termite nests. Brown fungal balls, called ‘termite balls’, are frequently found in egg piles of Reticulitermes termites. Phylogenetic analysis illustrated that termite-ball fungi isolated from different hosts (Reticulitermes speratus, Reticulitermes flavipes and Reticulitermes virginicus) were all very similar, with no significant molecular differences among host species or geographical locations. I found no significant effect of termite balls on egg survivorship. The termite-ball fungus rarely kills termite eggs in natural colonies. Even a termite species (Reticulitermes okinawanus) with no natural association with the fungus tended termite balls along with its eggs when it was experimentally provided with termite balls. Dummy-egg bioassays using glass beads showed that both morphological and chemical camouflage were necessary to induce tending by termites. Termites almost exclusively tended termite balls with diameters that exactly matched their egg size. Moreover, scanning electron microscopic observations revealed sophisticated mimicry of the smooth surface texture of eggs. These results provide clear evidence that this interaction is beneficial only for the fungus, i.e. termite balls parasitically mimic termite eggs.