Sphaeroforma arctica, is a unicellular eukaryote with a pivotal position in the tree of life. As member of the Ichthyosporea clade within the Teretosporea, it is an invaluable organism to understand the origin of animals. It was first isolated from the arctic marine amphipod Gammarus setosus. Like other ichthyosporeans such as Creolimax and Abeoforma, Sphaeroforma arctica are spherical cells characterized with their capacity to grow into multi-nucleated coenocytes (multi-nucleated cell). However, a unique feature of S. arctica, is that no obvious budding, hyphal, amoeboid, sporal or flagellated growth stages have been observed in laboratory growth conditions.
Indeed, Sphaeroforma arctica grows easily in Marine broth, with the particularity of growing synchronously. From a cell with 1 single nucleus, it can grow to reach a 128 nuclei cell before undergoing cellularization (the process by which the coenocytes split up to give new-born cells).
Moreover, it has been recently shown that S. arctica contains miRNA as well as the complex miRNA processing machinery. Taken together, Sphaeroforma arctica is a great model organism from both evolutionary and cell biology perspectives.
Sphaeroforma arctica confocal microscopy, stained with DAPI and tubulin. 3Dprojection
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