Nov 122016

After studying amoeboid organisms for several decades–observing them in the field, publishing articles about them, and developing his wonderfully detailed website devoted to the little shapeshiftersFerry Siemensma now has an amoeba he can call his own. The organism, discovered by researchers in a small greenhouse pond at the university of Cologne, is Lecythium siemensmai, a cercozoan amoeboid that lives inside a flexible, secreted transparent “theca”. It looks like this:



The new species, is described, along with several others, in a complete revision of the genus Lecythium, recently published by Kenneth Dumack and two colleagues at Cologne. The genus itself is fairly old—it was erected by Richard Hertwig and E. Lesser in 1874—but it has been a very long time since taxonomists have paid any attention to its composition. Many organisms that properly belong in the group have been misplaced in other genera, such as Gromia, Trinema and Pamphagus. The latter has been recognized since 1915 as an invalid group (the name properly belongs to a genus of grasshoppers), but it is a mark of the neglect into which amoeboid taxonomy has fallen that a Google search on “pamphagus amoeba’’ turns up dozens of modern micrographs and videos of cells identified as belonging to a group that was formally abandoned over a hundred years ago. It is a tribute to the great amoebologists of the past that their work still casts such a long shadow. It is also a reminder that revisions like this one by Dumack et al. are urgently needed.

The paper, charmingly titled “A Bowl with Marbles” (a reference, presumably, to the glassy, round shape of the organism’s soft theca), uses molecular phylogeny to establish the genus as a well-defined clade within Tectofilosida (a rhizarian group whose organic shells lack the siliceous scales secreted by better-known filose amoebae like Euglypha and Assulina). In the section on taxonomy, the authors deftly untangle a few historic hairballs; for instance, tracing the relationship of their Lecythium spinosum to antecedents like Trinema spinosum, Plagiophrys armatus and Pamphagus armatus. Finally, they provide a visual key to the group, featuring clear illustrations and helpful diagnostic clues. For this genus, at least, they have built a convenient foot-bridge between phylogeny and field identification.

Congratulations to Ferry, and to the researchers at Cologne, all of whom are doing the kind of work that could coax future researchers back to the field.



• Dumack, Kenneth, Christina Baumann, and Michael Bonkowski. “A Bowl with Marbles: Revision of the Thecate Amoeba Genus Lecythium (Chlamydophryidae, Tectofilosida, Cercozoa, Rhizaria) Including a Description of Four New Species and an Identification Key.” Protist 167.5 (2016): 440-459.
• Hertwig, Richard, and E. Lesser. “Ueber Rhizopoden und denselben nahestehende Organismen.” Arch. Mikr. Anat 10.1874 (1874): 35-243.

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