仙女蜂(Megaphragma mymaripenne)確實(shí)微小,，如此之微小,，人們很難用肉眼看到它們,。當(dāng)跟阿米巴變形蟲和草履蟲一起放在載玻片上,，它是當(dāng)中最小的有機(jī)體,。正因?yàn)榇?，俄羅斯莫斯科國立大學(xué)的一個(gè)研究小組開始著手研究如此微小的昆蟲種神經(jīng)系統(tǒng)將如何運(yùn)轉(zhuǎn)。就像該小組在發(fā)表在Science Direct旗下雜志上的論文描述的那樣,，仙女峰,，昆蟲界第三小的生物，擁有大量沒有細(xì)胞核的神經(jīng)元,。
細(xì)胞核對于細(xì)胞而言通常非常重要,，畢竟那是儲存DNA的地方。它也是細(xì)胞發(fā)揮功能的一部分,，如更新蛋白從而讓細(xì)胞保持活性,。這當(dāng)然就讓研究人員好奇如果一個(gè)昆蟲的大多數(shù)神經(jīng)元沒有細(xì)胞核，它將如何能夠存活下來,。
研究小組發(fā)現(xiàn)秘密就在于該昆蟲如此小,，在蟲蛹階段發(fā)育的神經(jīng)元(帶有完整細(xì)胞核)明顯地制造出足夠多的蛋白來維持它成年時(shí)期的全部5天生活，因而就不再需要細(xì)胞核,，絕大部分細(xì)胞核通過爆裂的形式被摧毀,，以便使得細(xì)胞變得更小并為其他更加重要的細(xì)胞騰出空間。研究小組注意到這是首次記錄的在野外存在的無需細(xì)胞核的神經(jīng)元案例,。
研究小組還發(fā)現(xiàn)仙女蜂神經(jīng)系統(tǒng)是世界上最小神經(jīng)系統(tǒng)之一,，只有7400個(gè)神經(jīng)元，但是能夠飛行,、尋找食物和計(jì)算出在何處安置它的卵,；相比于另一種微小昆蟲的卵，它的卵長度不大于1微米,。它是通過將它的神經(jīng)系統(tǒng)幾乎全部只塞進(jìn)它的頭部來實(shí)現(xiàn)這一壯舉的,，因而才需要盡可能地縮小神經(jīng)元數(shù)目和降低細(xì)胞大小。
仙女蜂也有其他的變動之處從而允許能夠以尺寸小的狀態(tài)存活下來,。比如,，它擁有一個(gè)縮小的翅膀表面，這就意味著相比于其他較大的昆蟲運(yùn)動時(shí)產(chǎn)生的拍打,，它的翅膀簡直就是滄海之一粟,，只夠讓它隨著移動的空氣在四周飄移。（生物谷Bioon.com）
doi:10.1016/j.asd.2011.09.001
PMC:
PMID:
The smallest insects evolve anucleate neurons
Alexey A. Polilov
The smallest insects are comparable in size to unicellular organisms. Thus, their size affects their structure not only at the organ level, but also at the cellular level. Here we report the first finding of animals with an almost entirely anucleate nervous system. Adults of the smallest flying insects of the parasitic wasp genus Megaphragma (Hymenoptera: Trichogrammatidae) have only 339–372 nuclei in the central nervous system, i.e., their ganglia, including the brain, consist almost exclusively of processes of neurons. In contrast, their pupae have ganglia more typical of other insects, with about 7400 nuclei in the central nervous system. During the final phases of pupal development, most neuronal cell bodies lyse. As adults, these insects have many fewer nucleated neurons, a small number of cell bodies in different stages of lysis, and about 7000 anucleate cells. Although most neurons lack nuclei, these insects exhibit many important behaviors, including flight and searching for hosts.
