4月11日,，發(fā)表在Nature上的一項新研究,，推翻了人們之前所認為的“鴿子出色的導(dǎo)航技能應(yīng)當歸功于鴿子喙部上富含鐵質(zhì)的神經(jīng)細胞”的理論。
這項研究顯示,，鴿子喙部上富含鐵質(zhì)的細胞實際上是一種特定的白細胞，被稱為巨噬細胞。這項發(fā)現(xiàn)徹底顛覆了人們之前的觀念,，讓我們開始重新審視磁性細胞的問題。
“這一發(fā)現(xiàn)使得研究動物如何感應(yīng)磁場的道路變得更加迷霧重重,。” 該項研究的領(lǐng)導(dǎo)者David Keays博士說,。
Keays博士繼續(xù)說：“我們本希望找到磁性細胞，結(jié)果卻意外地發(fā)現(xiàn)了成千上萬個內(nèi)部充滿小鐵珠的巨噬細胞,。”
巨噬細胞是白細胞的一種,，在抵御機體感染和循環(huán)利用紅細胞中的鐵質(zhì)中發(fā)揮著舉足輕重的作用。他們不太可能參與磁感應(yīng),，因為它們并不是容易興奮的細胞且不可能像神經(jīng)細胞那樣能產(chǎn)生影響鴿子行為的電信號,。
這項研究由依托于維也納分子病理學(xué)研究所的Keays博士實驗室和來自西澳大學(xué)的Shaw博士、倫敦大學(xué)學(xué)院高級生物醫(yī)學(xué)成像中心的Lythgoe和Riegler博士共同完成,。
“我們運用了全球頂尖的成像技術(shù)來定位鴿子喙部充滿鐵質(zhì)的細胞,。” Mark Lythgoe博士說。
目前為止,，對科學(xué)家們來說,，候鳥和其他許多動物感應(yīng)地球磁場和實現(xiàn)“導(dǎo)航”的機制仍然是個難解之謎。
“我們也不清楚這個謎究竟有多難解,，但是至少,，這項研究為我們排除了一些不正確的解釋,。” Keays說。（生物谷Bioon.com）
doi:10.1038/nature11046
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Clusters of iron-rich cells in the upper beak of pigeons are macrophages not magnetosensitive neurons
Christoph Daniel Treiber, Marion Claudia Salzer, Johannes Riegler, Nathaniel Edelman, Cristina Sugar, Martin Breuss, Paul Pichler, Herve Cadiou, Martin Saunders, Mark Lythgoe, Jeremy Shaw & David Anthony Keays
Understanding the molecular and cellular mechanisms that mediate magnetosensation in vertebrates is a formidable scientific problem. One hypothesis is that magnetic information is transduced into neuronal impulses by using a magnetite-based magnetoreceptor. Previous studies claim to have identified a magnetic sense system in the pigeon, common to avian species, which consists of magnetite-containing trigeminal afferents located at six specific loci in the rostral subepidermis of the beak. These studies have been widely accepted in the field and heavily relied upon by both behavioural biologists and physicists. Here we show that clusters of iron-rich cells in the rostro-medial upper beak of the pigeon Columbia livia are macrophages, not magnetosensitive neurons. Our systematic characterization of the pigeon upper beak identified iron-rich cells in the stratum laxum of the subepidermis, the basal region of the respiratory epithelium and the apex of feather follicles. Using a three-dimensional blueprint of the pigeon beak created by magnetic resonance imaging and computed tomography, we mapped the location of iron-rich cells, revealing unexpected variation in their distribution and number—an observation that is inconsistent with a role in magnetic sensation. Ultrastructure analysis of these cells, which are not unique to the beak, showed that their subcellular architecture includes ferritin-like granules, siderosomes, haemosiderin and filopodia, characteristics of iron-rich macrophages. Our conclusion that these cells are macrophages and not magnetosensitive neurons is supported by immunohistological studies showing co-localization with the antigen-presenting molecule major histocompatibility complex class II. Our work necessitates a renewed search for the true magnetite-dependent magnetoreceptor in birds.
