Credit: R. Danovaro et al., BMC Biology
科学家们
首次发现了完全无氧环境中生存的多细胞动物。这一发现将改变人们
普遍认为氧气是生命存在的必要条件的观点,拓宽人类对生命存在、繁衍的认识,增进科学家对宇宙生命现象的研究和认知,扩展研究者对自然界及生物体系中能量
转化、吸收的理解。对于当今世界面临自然环境恶化、资源能源短缺、人口增长等严重威胁的情况下,这一发现必然引起很多人关注。
这一研究可预期地影响科学各领域的发展(Nature, Science等各大杂志都专门发表了评论),希望我国各界研究者解放思想,实事求是,与时俱进,科学发展,和谐合作,为推动科学和人类社会事业不断发展而努力奋斗!
Scientists
have found the first multicellular animals that apparently live
entirely without oxygen. The creatures reside deep in one of the
harshest environments on earth: the Mediterranean Ocean's L'Atalante
basin, which contains salt brine so dense that it doesn't mix with the
oxygen-containing waters above. Previous samples taken from the water
and sediments in the basin showed that single-celled life was present,
but a new studypublished this week in BMC Biology has
identified multi-cellular animals that apparently live and reproduce in
the sediments under the salt brine. Italian and Danish researchers
describe three new species of tiny animals called Loricifera. The
animals took up radioactively tagged leucine (an amino acid), and a
fluorescent probe that labels living cells, evidence that they were
alive when they were collected. The researchers also found examples of
individuals that contained eggs and evidence of apparent molting, which
led them to conclude that the animals spend their whole lives in the
harsh sediments. The creature's cells apparently lack mitochondria, the
organelles that use oxygen to power a cell. Instead they are rich in
what seem to be hydrogenosomes, organelles that can do a similar job in
anaerobic (or oxygen free) environments. The find could help scientists
understand what life might have looked like in the earth's early
oceans, which also had very little oxygen.
ScienceDaily (Apr. 7, 2010) —
Deep under the Mediterranean Sea, small animals have been discovered
that live their entire lives without oxygen and surrounded by
'poisonous' sulphides. Researchers writing in the open access journal BMC Biology report
the existence of multicellular organisms (new members of the group
Loricifera), showing that they are alive, metabolically active, and
apparently reproducing in spite of a complete absence of oxygen.
Roberto
Danovaro, from the Polytechnic University of Marche, Ancona, Italy,
worked with a team of researchers to retrieve sediment samples from a
deep hypersaline anoxic basin (DHABs)
of the Mediterranean Sea and studied them for signs of life. "These
extreme environments," said Danovaro, "have been thought to be
exclusively inhabited by viruses, Bacteria and Archaea. The bodies of
multicellular animals have previously been discovered, but were thought
to have sunk there from upper, oxygenated, waters. Our results indicate
that the animals we recovered were alive. Some, in fact, also contained
eggs."
Electronmicroscopy
shows that instead of aerobic mitochondria, these animals possess
organelles resembling the hydrogenosomes found previously in
unicellular organisms (protozoans) that inhabit anaerobic environments.
The
implications of this finding may reach far beyond the darker parts of
the Mediterranean Sea floor, according to Lisa Levin of the Scripps
Institution of Oceanography. In one of two commentaries accompanying
this piece of research, she said, "The finding by Danovaro et al.
offers the tantalizing promise of metazoan life in other anoxic
settings, for example in the subsurface ocean beneath hydrothermal
vents or subduction zones or in other anoxic basins."
In
the second commentary Marek Mentel and William Martin, from Comenius
and Dusseldorf Universities look at the incidence of anaerobic
mitochondria and hydrogenosomes in other organisms and focus on the
evolutionary significance of the new findings. "The discovery of
metazoan life in a permanently anoxic and sulfidic environment provides
a glimpse of what a good part of Earth's past ecology might have been
like in 'Canfield oceans', before the rise of deep marine oxygen levels
and the appearance of the first large animals in the fossil record
roughly 550-600 million years ago."