Two newly cultivated eukaryotrophic flagellates represent distinct anaerobic lineages within Rhizaria
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Abstract
Endomyxans are a poorly sampled and incompletely resolved aggregate of Rhizarian lineages that fall outside Filosa and Retaria. Among them, “Novel Clade 12” (NC12; Bass et al. 2009) is an environmental clade comprised primarily of sequences derived from anoxic sediments, hitherto lacking a morphologically-characterised representative. We have cultivated a marine anaerobic eukaryotroph, SSF, that we identify as the first representative of NC12. SSF is a teardrop-shaped cell with two unequal flagella emerging a third of the way down the cell behind a distinctive row of refractile globules. The posterior end of the cell is filled with food vacuoles. There is a surface thickening discernible in light microscopy. We also describe another distinct anaerobe eukaryotrophic lineage, also cultivated from marine sediment: PG. It consists of large pyriform cells with a substantial trailing “tail” and two unequal flagella, the posterior exceptionally long. In small subunit ribosomal RNA gene phylogenies, it falls outside the characterised clades and forms a distinct novel rhizarian lineage in its own right. Together, SSF and PG represent two additional independent adaptations to anoxic conditions within Rhizaria.
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Organisms
This is really neat work highlighting incredible "new" organisms! Now that y'all have established methods for maintenance, will you be (or have you already) deposited these strains in a culture collection center? Thanks for doing this important work!
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Both organisms are presumed anaerobes and have documented eukaryotrophy on breviates.
Did y'all try to feed the organisms other prey? I'm curious if the same predation Step 1 methods would apply when other prey are encountered
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As with SSF, predation appears to occur in two decoupled steps, although PG may return and devour its prey only seconds following initial contact.
Amazing!!! How long is the gap between SSF predation steps if this one is only seconds?
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The breviates appear increasingly tattered and eventually round upon. Upon contact with a detached or partly rounded up cell, SSF (not necessarily the same cell as in the initial encounter) contacts it again and then phagocytoses it (Fig 1J, K)
Fascinating!!!! Did y'all ever see any tattered breviates that weren't contacted again? Does the initial contact kill them?
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Swimming cells have a snakey, ‘squishy’ movement.
These are really amazing cells! I'd love to see some dynamic videos to better understand this "snakey, 'squishy'" movement that y'all describe.
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Immediately next to the flagellar insertion site is the nucleus (Fig 1D).
Is this cell stained? I don't see any mention of dyes/stains but there seems to be some blue & pink colors in the cytoplasm of this cell. Just curious if this is real pigment being picked up by the DS10 camera.
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