Abstract
Tiny marine animals that complete their life cycle in the total absence of light and oxygen are reported by Roberto Danovaro and colleagues in this issue of BMC Biology. These fascinating animals are new members of the phylum Loricifera and possess mitochondria that in electron micrographs look very much like hydrogenosomes, the H2-producing mitochondria found among several unicellular eukaryotic lineages. The discovery of metazoan life in a permanently anoxic and sulphidic 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. The findings underscore the evolutionary significance of anaerobic deep sea environments and the anaerobic lifestyle among mitochondrion-bearing cells. They also testify that a fuller understanding of eukaryotic and metazoan evolution will come from the study of modern anoxic and hypoxic habitats.
Highlights
Tiny marine animals that complete their life cycle in the total absence of light and oxygen are reported by Roberto Danovaro and colleagues in this issue of BMC Biology
Commentary The newly reported tiny marine animals that complete their life cycle in the total absence of light and oxygen are members of the phylum Loricifera, a phylum discovered less than 30 years ago, and they are less than a millimetre in size [1]
Facultative anaerobic mitochondria have been studied from various free living invertebrates, including the oyster Mytilus (Mollusca) [10], the peanut worm Sipunculus (Sipuncula) [11] or the polychaete worm Arenicola (Annelida) [12] and parasites like Fasciola (Platyhelminthes) [13] and Ascaris (Nematoda) [14]
Summary
Metazoan Life Without Oxygen London: Chapman and Hall, LondonBryant C 1991, 146-164. Origin of Mitochondria and Hydrogenosomes Berlin: SpringerVerlagMartin W, Müller M 2007, 85-104. Phil Trans Roy Soc London Series B 2008, 363:1435-1443
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