Vexillifera westveldii Van Wichelen &  Vanormelingen, 2016

 

Diagnosis: Locomotive amoebae acanthopodial with a triangular, spherical or slightly elongated shape. Pseudopodia often dactylopodial-like. Length without subpseudopodia 13–43 µm and width 5–24 µm. Usually one, rarely 2–3, small contractile vacuole(s) posteriorly. Vesicular nucleus 2–5 µm in diameter with one globular nucleolus. The cytoplasm always contains small, refractive spheroid granules. Floating amoebae slightly elongated, about 15 µm long with up to 17 sharply pointed pseudopodia. No cyst stage observed.

 

Ecology: Microcystis cells were observed inside food vacuoles, however the amoebae seem to grow better when only pico-cyanobacteria or heterotrophic bacteria were offered as food. No growth was observed with Acutodesmus as food source (Van Wichelen, unpublished data).
Type locality: Strain A18WVB was isolated from a Microcystis bloom sample from a small, eutrophied urban pond in Westveldpark, Sint-Amandsberg (Gent, Belgium). High densities of morphological very similar amoebae were found on Microcystis-colonies in samples (07/09/2013) from an eutrophied moat in Bazel (Belgium).

 

Differential diagnosis: Locomotive trophozoites of V. westveldii morphologically show strong similarities with V. multispinosa, V. bacillipedes, V. telma and V. displacata (Bovee 1985, Page 1988, Dyková et al. 2011). However, V. westveldii is slightly to much larger in size compared to V. telma (20–32 µm), V. multispinosa (10–20 µm), V. bacillipedes (8–24 µm) and V. displacata (7–12 µm). V. westveldii is distinguishable from V. telma by its irregular floating form with long radiating pseudopodia in contrast to the globular one of V. telma with only very small radiating pseudopodia. Moreover, V. westveldii is isolated from Microcystis blooms in contrast to the other species that were isolated from flowing water (V. displacata, V. bacillipedes) or fish organs (V. multispinosa, V. bacillipedes). The 18S rDNA sequence also distinguish V. westveldii from all other Vexillifera species currently present in GenBank.