Life history of Apocarchesium arndti Norf & Foissner, 2010 (Ciliophora, Peritrichia) including recognition of a novel type of zooid.

Apocarchesium rosettum and A. arndti were originally discovered in Japan (Lake Biwa) and Germany (River Rhine), respectively. We report the first record of A. arndti in the Danube and provide a detailed description of its colony development. Our findings support the theory of moderate endemicity and reveal a new, smaller zooid type in A. arndti. This zooid remains attached to the colony, connected to the stalk myoneme but lacks an aboral ciliary wreath. Unlike microzooids, it is incapable of leaving the colony. It exhibits a less spherical shape and arises from the fourth division of the colony-founder cell. Although its specific function is unknown, it is hypothesized to support the stalk dish. Our results have significant implications for understanding the systematics of vorticellids, suggesting their ancestral nature as colonial organisms characterized by a helically contracting stalk myoneme. Furthermore, the exclusive retention of the stalk myoneme by the parental cell after binary fission may serve as a synapomorphy for the Vorticellidae. We provide a descriptive analysis of the ecological environment and microhabitat of A. arndti in the Danube, revealing its preference for well-developed, detritus-rich biofilms during summer, absence in late winter and spring, emergence during peak summer, and subsequent decline until mid-winter.

Incidence and molecular diversity of Acanthamoeba species isolated from public baths in Hungary.

Hungary has a large number of thermal baths and spa facilities which attract hundreds of thousands of tourists annually. Until recently, however, the free-living amoebae were not of public health concern. Genotyping of Acanthamoeba species, potential agents of keratitis and granulomatous encephalitis, was carried out in 20 Hungarian public baths for the first time to assess the incidence and molecular diversity of the genus in the country. Our results show that 6.7% of the samples were positive for Acanthamoeba. Of these positive samples, 6.5 and 7% was from sterilized and unsterilized pools, respectively. The 18S rRNA gene investigation of the nine Acanthamoeba strains found reveals that seven belong to the hazardous T4 genotype. The remaining two samples were of the T15 type. All the strains kept growing at 36 °C. Our results underline the need to develop a control system for free-living amoebae and supervise the disinfection of Hungarian public baths.

Structure and seasonal dynamics of the protozoan community (heterotrophic flagellates, ciliates, amoeboid protozoa) in the plankton of a large river (River Danube, Hungary).

Seasonal dynamics of all major protozoan groups were investigated in the plankton of the River Danube, upstream of Budapest (Hungary), by bi-weekly sampling over a 1-year long period. Sixty-one heterotrophic flagellate, 14 naked amoeba, 50 testate amoeba, 4 heliozoan and 83 ciliate morphospecies were identified. The estimated abundance ranges of major groups throughout the year were as follows: heterotrophic flagellates, 0.27-7.8 x 10(6)ind.l(-1); naked amoebae, max. 3300ind.l(-1); testaceans, max. 1600ind.l(-1); heliozoans, max. 8500ind.l(-1); ciliates, 132-34,000ind.l(-1). In terms of biovolume, heterotrophic flagellates dominated throughout the year (max. 0.58mm(3)l(-1)), and ciliates only exceeded their biovolume in summer (max. 0.76mm(3)l(-1)). Naked amoeba and heliozoan biovolume was about one, and testacean biovolume 1-3, orders of magnitude lower than that of ciliates. In winter, flagellates, mainly chrysomonads, had the highest biomass, whilst ciliates were dominated by peritrichs. In 2005 from April to July a long spring/summer peak occurred for all protozoan groups. Beside chrysomonads typical flagellates were choanoflagellates, bicosoecids and abundant microflagellates (large chrysomonads and Collodictyon). Most abundant ciliates were oligotrichs, while Phascolodon, Urotricha, Vorticella, haptorids, Suctoria, Climacostomum and Stokesia also contributed significantly to biovolume during rapid succession processes. In October and November a second high protozoan peak occurred, with flagellate dominance, and slightly different taxonomic composition.