大自然中也在上演“真人秀”：逆境生存，蛭形轮虫或许能够成为最后幸存的动物。这种微小的水生生物能从高辐射和多年干燥的环境中存活下来，并且它们已经无性生活了数百万年。
前不久，在线发表于《科学公共图书馆—遗传学》上的一项新研究揭示了蛭形轮虫是如何做到这些的。
科学家通过基因分析发现，蛭形轮虫大约10%的活跃基因是剽窃自其他物种的，例如真菌、细菌和植物。这些外源基因赋予蛭形轮虫其他动物没有的才能。这能解释为何蛭形轮虫能在极其恶劣的环境中生存。尤其是，这些外源基因让蛭形轮虫能一直独身生活——这通常能导致其他动物的灭绝。
蛭形轮虫是一种遗传嵌合体，它们到处获取DNA片段，就如同马赛克一样，英国剑桥大学分子生物学家Alan Tunnacliffe表示。像其他一些拥有“超能力”的生物一样，显微镜下的蛭形轮虫在恶劣的环境中快乐地生活着。
大约有400种蛭形轮虫生活在淡水和微咸水中。当它们的水家园突然消失不见时，蛭形轮虫也有大把的办法幸存下来，最长干燥存活纪录达9年。
从一个进化生物学家视角而言，蛭形轮虫更“超强”的能力是长期的无性生活。大约8000万年以来，所有的蛭形轮虫都是雌性，并稳定地进行着无性繁殖。
生物学家一直认为，有性繁殖带来基因变异，并让物种随着环境的变化而调整基因表达。并且人们普遍认为，动物放弃性，最终等于走向灭绝。但是，蛭形轮虫打破了这些传统观点。
之后，科学家排序了蛭形轮虫的DNA，发现它从超过500种不同的物种那里借来了DNA，最终蛭形轮虫成为了“超级英雄”。（生物谷Bioon.com）
doi:10.1371/journal.pgen.1003035
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Biochemical Diversification through Foreign Gene Expression in Bdelloid Rotifers
Chiara Boschetti, Adrian Carr, Alastair Crisp, Isobel Eyres, Yuan Wang-Koh, Esther Lubzens, Timothy G. Barraclough, Gos Micklem, Alan Tunnacliffe
Bdelloid rotifers are microinvertebrates with unique characteristics: they have survived tens of millions of years without sexual reproduction; they withstand extreme desiccation by undergoing anhydrobiosis; and they tolerate very high levels of ionizing radiation. Recent evidence suggests that subtelomeric regions of the bdelloid genome contain sequences originating from other organisms by horizontal gene transfer (HGT), of which some are known to be transcribed. However, the extent to which foreign gene expression plays a role in bdelloid physiology is unknown. We address this in the first large scale analysis of the transcriptome of the bdelloid Adineta ricciae: cDNA libraries from hydrated and desiccated bdelloids were subjected to massively parallel sequencing and assembled transcripts compared against the UniProtKB database by blastx to identify their putative products. Of ~29,000 matched transcripts, ~10% were inferred from blastx matches to be horizontally acquired, mainly from eubacteria but also from fungi, protists, and algae. After allowing for possible sources of error, the rate of HGT is at least 8%–9%, a level significantly higher than other invertebrates. We verified their foreign nature by phylogenetic analysis and by demonstrating linkage of foreign genes with metazoan genes in the bdelloid genome. Approximately 80% of horizontally acquired genes expressed in bdelloids code for enzymes, and these represent 39% of enzymes in identified pathways. Many enzymes encoded by foreign genes enhance biochemistry in bdelloids compared to other metazoans, for example, by potentiating toxin degradation or generation of antioxidants and key metabolites. They also supplement, and occasionally potentially replace, existing metazoan functions. Bdelloid rotifers therefore express horizontally acquired genes on a scale unprecedented in animals, and foreign genes make a profound contribution to their metabolism. This represents a potential mechanism for ancient asexuals to adapt rapidly to changing environments and thereby persist over long evolutionary time periods in the absence of sex.
