Like animals, plants, fungi and ameobas — but unlike bacteria — hemimastigotes have complex cells with mini-organs called organelles, making them part of the “domain” of organisms called eukaryotes rather than bacteria or archaea.
About 10 species of hemimastigotes have been described over more than 100 years. But up until now, no one had been able to do a genetic analysis to see how they were related to other living things. Emily Chung, “Rare microbes lead scientists to discover new branch on the tree of life” at CBC
Eglit watched carefully as it hunted. Hemimastix shoots little harpoons called extrusomes to attack prey such as Spumella, a relative of aquatic microbes called diatoms. It grasps its prey by curling its flagella around it, bringing it to a “mouth” on one end of the cell called a capitulum “as it presumably sucks its cytoplasm out,” Eglit said. Emily Chung, “Rare microbes lead scientists to discover new branch on the tree of life” at CBC
Note: “But Simpson noted that discoveries like this one are pretty rare: ‘It’ll be the one time in my lifetime that we find this sort of thing.’”
Just a minute here. The new organisms “were found in dirt collected on a whim” on a hike. Why should we assume that they are rare, as opposed to unsought? One can only wonder what new insights we would gain if there were less Darwin in our system and more open-minded exploration.
We are also told at CBC, “ … you’d have to go back a billion years — about 500 million years before the first animals arose — before you could find a common ancestor of hemimastigotes and any other known living things.”
Hmmm. Half a billion years is a long time. Why start by assuming that we even have a common ancestor?: Who decided that that should be our main focus just now when everything else has been a century-long mystery?
Two types of these organisms were found (and who knows how many others there may be?):
Opening sentences of the Letter to Nature Almost all eukaryote life forms have now been placed within one of five to eight supra-kingdom-level groups using molecular phylogenetics1–4. The ‘phylum’ Hemimastigophora is probably the most distinctive morphologically defined lineage that still awaits such a phylogenetic assignment. First observed in the nineteenth century, hemimastigotes are free-living predatory protists with two rows of flagella and a unique cell architecture5–7; to our knowledge, no molecular sequence data or cultures are currently available for this group. Here we report phylogenomic analyses based on high-coverage, cultivation-independent transcriptomics that place Hemimastigophora outside of all established eukaryote supergroups. They instead comprise an independent supra-kingdom-level lineage that most likely forms a sister clade to the ‘Diaphoretickes’ half of eukaryote diversity (that is, the ‘stramenopiles, alveolates and Rhizaria’ supergroup (Sar), Archaeplastida and Cryptista, as well as other major groups). The previous ranking of Hemimastigophora as a phylum understates the evolutionary distinctiveness of this group, which has considerable importance for investigations into the deep-level evolutionary history of eukaryotic life—ranging from understanding the origins of fundamental cell systems to placing the root of the tree. We have also established the first culture of a hemimastigote (Hemimastix kukwesjijk sp. nov.), which will facilitate future genomic and cell-biological investigations into eukaryote evolution and the last eukaryotic common ancestor. (open access) More.
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The story reminds some of us a bit of new findings about viruses.
See also: Virus expert highlights the conflict over whether viruses are alive In short, it is an open question. The question relates to the role viruses can play in evolution, among other things. Are they precursors of life, detritus of life, or something in between? Or all three? Keep the file open.
Viruses invent their own genes? Then what is left of Darwinism?
Why viruses are not considered to be alive
Another stab at whether viruses are alive
Phil Sci journal: Special section on understanding viruses
Should NASA look for viruses in space? Actually, it’s not clear that RNA came first. Nor is it clear that viruses precede life. A good case can doubtless be made for viruses being part of the scrap heap of existing life. But no matter. If you think you can find viruses in space, boldly go.
Why “evolution” is changing? Consider viruses
The Scientist asks, Should giant viruses be the fourth domain of life? Eukaryotes, prokaryotes, archaea… and viruses?
Are viruses nature’s perfect machine? Or alive?