在没有氧的环境中生活一向被认为是细菌、病毒和单细胞生物的“专利”，但研究人员日前在地中海海底沉积物中发现3种能在无氧环境里终生生活的多细胞动物。
意大利和丹麦研究人员在新一期英国《BMC生物学》期刊上报告说，他们在地中海海底探寻未知生物时发现，在无氧和高盐度的海底沉积物中，生活着3种属于铠甲动物门的多细胞动物。它们只有1毫米长，在被发现时不仅保持着活跃的新陈代谢，其中一些个体还含有卵细胞，显示出这些动物在无氧环境中具有繁殖能力。
研究人员达诺瓦罗说，以前在海底无氧环境中只发现过多细胞动物的尸体，一般认为它们是沉到海底的，但这次却有证据证明一些多细胞动物可以一直在海底无氧环境中生存。这一发现拓宽了人们对动物生存能力的认识，揭示了自然界中奇特的生物多样性。
这项研究还显示，上述几种生物具有适应无氧环境的生理机制。通常如果动物依靠氧生存，那么其细胞内会有线粒体，线粒体可以通过氧化为细胞提供能量。一些在无氧环境中生存的单细胞生物则依靠“氢化酶体”这种细胞器来提供能量。而上述新发现物种的细胞内没有线粒体，为其提供能量的是与“氢化酶体”类似的细胞器。(生物谷Bioon.com)
延伸阅读
PNAS：细菌极端环境受迫生存机制
Science：南非金矿极端环境下发现新细菌
Science：氧气起源纷争再起
生物谷推荐原文出处：
BMC Biology DOI: 10.1186/1741-7007-8-30
The first metazoa living in permanently anoxic conditions
Roberto Danovaro , Antonio Dell'Anno , Antonio Pusceddu , Cristina Gambi , Iben Heiner and Reinhardt Mobjerg Kristensen
Background
Several unicellular organisms (prokaryotes and protozoa) can live under permanently anoxic conditions. Although a few metazoans can survive temporarily in the absence of oxygen, it is believed that multi-cellular organisms cannot spend their entire life cycle without free oxygen. Deep seas include some of the most extreme ecosystems on Earth, such as the deep hypersaline anoxic basins of the Mediterranean Sea. These are permanently anoxic systems inhabited by a huge and partly unexplored microbial biodiversity.
Results
During the last ten years three oceanographic expeditions were conducted to search for the presence of living fauna in the sediments of the deep anoxic hypersaline L'Atalante basin (Mediterranean Sea). We report here that the sediments of the L'Atalante basin are inhabited by three species of the animal phylum Loricifera (Spinoloricus nov. sp., Rugiloricus nov. sp. and Pliciloricus nov. sp.) new to science. Using radioactive tracers, biochemical analyses, quantitative X-ray microanalysis and infrared spectroscopy, scanning and transmission electron microscopy observations on ultra-sections, we provide evidence that these organisms are metabolically active and show specific adaptations to the extreme conditions of the deep basin, such as the lack of mitochondria, and a large number of hydrogenosome-like organelles, associated with endosymbiotic prokaryotes.
Conclusions
This is the first evidence of a metazoan life cycle that is spent entirely in permanently anoxic sediments. Our findings allow us also to conclude that these metazoans live under anoxic conditions through an obligate anaerobic metabolism that is similar to that demonstrated so far only for unicellular eukaryotes. The discovery of these life forms opens new perspectives for the study of metazoan life in habitats lacking molecular oxygen.
