Vannella planctonica Van Wichelen & Vanormelingen, 2016

Van Wichelen, Jeroen, D’Hondt, Sofie, Claeys, Myriam, Vyverman, Wim, Berney, Cédric, Bass, David & Vanormelingen, Pieter, 2016, A Hotspot of Amoebae Diversity: 8 New Naked Amoebae Associated with the Planktonic Bloom-forming Cyanobacterium Microcystis, Acta Protozoologica 55 (2), pp. 61-87 : 80

Vannella planctonica Van Wichelen & Vanormelingen sp. n.

Diagnosis: Locomotive form fan-shaped. Cell length during locomotion 15–57 µm (mean 35), width 13–64 µm (33) and length/width ratio 0.4–2 (1.1). Vesicular nucleus 2–7 µm in diameter with one cen- trally located nucleolus. Floating form usually radial and symmetric with 5–11 pointed pseudopodia that are basally thickened. Cysts elliptical to ovoid, up to 32 µm in diameter.

Feeding behavior: Feeds voraciously on Microcystis aeruginosa cells (see Van Wichelen et al. 2012) although growth is also sustained on heterotrophic bacteria and pico-cyanobacteria (Van Wichelen, unpublished).

Type material: Strain A 2 FBB is designated as type strain. It is available from the NIES Microbial Culture Collection (NIES-3728). The 18S rDNA GenBank accession number is KP719193. Other strains are A4P- 4 ZHB, A2 SMB, A1 DVDPB, A2 DVDPB and A3 DVDPB (NIES-3765) .

Type locality: Strain A2 FBB was isolated from a Microcystis bloom sample from a ditch surrounding a moat (Fort Bornem, Belgium) ( Table1). Other strains were isolated from Microcystis blooms in fish ponds in Zonhoven and in De Panne and in a recreational lake (Schulensmeer, Lummen), all located in the Flemish part of Belgium.

Etymology: planctonica referring to its planktonic life style.

Differential diagnosis: V. lata cells are always fla- bellate and the hyaline area occupies a larger proportion of the cell (⅔) than in V. planctonica (40%). V. miroides is smaller (<35 µm), contains crystals in its cytoplasm and has a more extended hyaline area (> ½ body length) surrounding the whole cell ( Page 1988, Smirnov et al. 2007). V. simplex is much larger in size (on average 42–52 µm) and has usually fecal pellets adhered to the cell ( Page 1988, Smirnov et al. 2007), a feature never observed in V. planctonica . The 18S rDNA sequence distinguishes V. planctonica from all other Vannella species currently present in GenBank.