Weird animal forms: a new domain of life (Introduction)

by David Turell , Friday, December 14, 2018, 19:30 (1953 days ago) @ David Turell

Ac whole new branch has turned up, and it is weird:

https://www.quantamagazine.org/what-a-newfound-kingdom-means-for-the-tree-of-life-20181...

"The tree of life just got another major branch. Researchers recently found a certain rare and mysterious microbe called a hemimastigote in a clump of Nova Scotian soil. Their subsequent analysis of its DNA revealed that it was neither animal, plant, fungus nor any recognized type of protozoan — that it in fact fell far outside any of the known large categories for classifying complex forms of life (eukaryotes). Instead, this flagella-waving oddball stands as the first member of its own “supra-kingdom” group, which probably peeled away from the other big branches of life at least a billion years ago.

***

"Hemimastigotes represent one of a handful of Rumsfeldian “known unknown” protist lineages — moderately well-described groups whose positions on the tree of life are not precisely known because they are difficult to culture in a lab and sequence. Protistologists have used peculiarities of hemimastigotes’ structure to infer their close relatives, but their guesses were “‘shotgunned’ all over the phylogeny,” Simpson said. Without molecular data, lineages like hemimastigotes remain orphans of unknown ancestry.

"But a new method called single-cell transcriptomics has revolutionized such studies. It enables researchers to sequence large numbers of genes from just one cell. Gordon Lax, another graduate student in the Simpson lab and an expert on this method, explained that for hard-to-study organisms like hemimastigotes, single-cell transcriptomics can produce genetic data of a quality previously reserved for more abundant cells, making deeper genomic comparisons finally possible.

***

"Finding a lineage as distinct as hemimastigotes is still relatively rare. But if you go down a level or two on the hierarchy, to the mere kingdom level — the one that encompasses, say, all animals — you find that new major lineages are popping up about once a year. “That rate isn’t slowing down,” said Simpson. “If anything, it might be speeding up.'”

Comment: The branch keeps enlarging.