Vexillifera westveldii 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 : 83

Vexillifera westveldii Van Wichelen & Vanormelingen sp. n.

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.

Feeding behavior: 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 No growth was observed with Acutodesmus as food source (Van Wichelen, unpublished data).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 material: Strain A18 WVB is available from the NIES Microbial Culture Collection (NIES-3729). The 18 S rDNA GenBank accession number is KP719187 .

Type locality: Strain A 18 WVB was isolated from a Microcystis bloom sample from a small, eutrophied urban pond in Westveldpark, Sint-Amandsberg (Gent, Belgium) (Tabel 1). High densities of morphological very similar amoebae were found on Microcystis -colonies in samples (07/09/2013) from an eutrophied moat in Bazel ( Belgium).

Etymology: westveld refers to the pond (Westveldpark) from where the strain was isolated.

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 18 S rDNA sequence also distinguish V. westveldii from all other Vexillifera species currently present in GenBank.

Acknowledgements. We are grateful for the provision of Microcystis bloom samples by associates of the Flemish Environment Agency ( VMM), by Peter Coene of the Flemish Union for Angling Clubs ( VVHV) and by Stina Drakare from the Swedish University of Agricultural Sciences. We thank Tine Verstraete for her help with the molecular analyses and Ellen Lambrecht and Julie Baré for their advice and help with the TEM analysis. P. V. is a postdoctoral research fellow with the Research Foundation – Flanders ( FWO). This research was financially supported by the BELSPO (Belgian Science Policy) project B-BLOOMS2. This paper is dedicated to Prof. Dr. Brian Moss (University of Liverpool), a shining example for 90 many of US, who passed away on May 27 th this year.