A Hotspot of Amoebae Diversity: 8 New Naked Amoebae Associated with the Planktonic Bloom-forming Cyanobacterium Microcystis Author Van Wichelen, Jeroen Author D’Hondt, Sofie Author Claeys, Myriam Author Vyverman, Wim Author Berney, Cédric Author Bass, David Author Vanormelingen, Pieter text Acta Protozoologica 2016 55 2 61 87 https://www.mendeley.com/catalogue/b604c599-ed8a-3422-8096-249caaf4697e/ journal article 10.4467/16890027AP.16.007.4942 1689-0027 Korotnovella pelagolacustris Van Wichelen & Vanormelingen sp. n. Diagnosis: Locomotive form dactylopodial with a length of 20–65 µm and a width of 6–32 µm. Vesicu- lar nucleus about 6 µm in diameter with one slightly eccentrically located nucleolus. Floating form radial, maximally 25 µm in diameter, with up to 20 point- ed pseudopodia. Scales elliptical, disk-shaped with a length of 260–391 nm and a width of 153–206 nm carrying a central spine 98–163 nm in length. Cyst formation rarely observed. Amoebae occasionally aggregate during cultivation. Feeding behavior: It feeds voraciously on Microcystis aeruginosa . No growth was observed when offering other Microcystis morphotypes ( M. viridis , M. wesenbergii ), heterotrophic bacteria and green algae ( Acutodesmus ) ( Van Wichelen et al . 2012 , Van Wichelen, unpublished). Type material: Strain A16 WVB is designated as the type strain. It is available from the NIES Microbial Culture Collection (NIES-3726). The 18 S rDNA GenBank accession number is HM017145 (see Van Wichelen et al . 2010 ) . Other strains are A8 WVB , A21 WVB , A54 WVB and A1 LMS . Type locality: Strain A16 WVB was isolated from a Microcystis bloom sample from a small, eutrophied urban pond in Westveldpark , Sint-Amandsberg ( Gent , Belgium ) . Other strains were isolated from the same locality and from a Microcystis bloom in Lake Mälaren (Ekoln, Sweden ) ( Table 1 ) . Very high densities of a morphological similar amoeba were found in Microcystis bloom samples ( 06/07/2015 ) from a fishpond in Zandhoven ( Belgium ) . Etymology: pélagos Gr. sea, pelagic; lacus Lat. pond, lake: referring to its habitat. Differential diagnosis: K. pelagolacustris closely resembles K. diskophora (Smirnov 1999) , the only described Korotnevella species so far with disc-like scales on its cell surface (basket or crown-like shaped or more than 1 scale type in all other Korotnevella spp. ). However, K. diskophora is smaller in size (16–34 µm, mean 23 µm) and has smaller spines (about 80 nm ) on its scales. Moreover, the floating form of K. pelagolacustris is globular with up to 20 radiating thin pseudopodia while the one described for K. diskophora is irregular with 1–4 long thin, tapering pseudopodia. Both species also differ in their ecology. K. diskophora was isolated from bottom sediments of the small freshwater Lake Leshevoe in North-Western Russia where it feeds on bacteria while K. pelagolacustris is isolated from Microcystis blooms in eutrophied water bodies where it specifically feeds on the cells of certain Microcystis colonies ( Van Wichelen et al . 2010 , Van Wichelen unpublished). K. jeppesenii , the other newly described species with the same ecology as K. pelagolacustris , is clearly smaller in size (max. 41 µm), has smaller (max. 327 nm ), relatively wider (mean L / W ratio 1.6) disc-like scales with shorter spines (max. 97 nm ) and differs in 18 S rDNA sequence.