This study documents for the first time the presence of testate amoebae on glaciers. Three shallow firn cores of 10 m depth were obtained from the Mocho-Choshuenco and Osorno volcanoes, Southern Andes, Chile, in October and November, 2005. Euglyphid testate amoebae were detected in 28 samples that correspond to the spring-summer layers of the firn cores. Inspection of 454 collected individuals reveals the presence of four different taxa. Three of these taxa, Trinema lineare, Trinema enchelys and Puytoracia bergeri have previously been reported in ice-free environments. The fourth taxon corresponds to a new species Puytoracia jenswendti nov. sp. The observation of food content and reproductive activities in a significant fraction of specimens evidence that testate amoebae are competent to inhabit glaciers. The testate amoebae found in the firn cores display clear seasonal variations in abundance indicating that these records can provide a new and novel proxy as paleoindicator for firn/ice core dating and for estimation of past glacier mass balance.
 

Naked amoeba densities, sizes, biodiversity and carbon content were examined in relation to two particle size fractions (< 200 μm and > 200 μm) of suspended matter in the water column of the Hudson Estuary at a near-shore location south of the Tappan Zee, Palisades, New York. The densities varied markedly among the two particle fractions, and therefore the mean densities were not significantly different between the larger and smaller particle fractions. In contrast, the mean sizes and mean carbon content were statistically greater on larger size suspended particles compared to smaller size particles. There was a broader size range of amoebae on the larger particles, including very large Cochliopodium, Vannella, Mayorella, and Hartmannella species suggesting a larger biodiversity, also indicated by a larger diversity coefficient for the > 200-μm-particle fraction compared to the < 200-μm-particle fraction, 4.51 and 4.18, respectively. In conclusion, the size of suspended particulates in the water column of near-shore, estuarine habitats may have a significant influence on the composition of naked amoebae communities and their ecological roles, especially the organization of particle-associated microbial food webs.
 

Zebra mussels (Dreissena polymorpha) are bivalve mollusks that have invaded and altered the ecology of many North American lakes and rivers. To identify possible ecological effects of zebra mussels on naked amoebae, this study compared abundances of sediment and water column naked amoebae in shallow water zones of four lakes with and four lakes without zebra mussels. Additional data was collected on the density of macroflagellates. Although no statistically significant difference in naked amoebae density was found, higher ratios of sediment to water column naked amoebae abundances in zebra mussel lakes were observed due to increased naked amoebae abundances in the sediments. However, we did not observe a concomitant decrease in water column naked amoebae abundances. Flagellate abundances revealed no significant differences between the two lake types. Taken together, the data show that naked amoebae and flagellates thrive in shallow water zones of zebra mussel lakes and that the filter feeding activities of zebra mussels and reported reduced water column protists abundances may be offset by the flocculation of protists from the rich zebra mussel colonies.

Amoebae feed on attached bacteria within, and below, bacterial biofilms where they experience reduced oxygen levels. The implications of this were examined by comparing the migration (an index of growth) of thirteen strains of Acanthamoeba and five species of naked amoebae grown under microaerophilic and aerobic conditions. All amoebae replicated well under both conditions and twelve isolates migrated significantly faster under low oxygen. Only one isolate, Vannella sp., migrated further (presumably grew faster) under aerobic conditions. The data show most amoebae prefer low oxygen as befits the biofilm habitat. Interestingly, the eleven acanthamoeba strains that replicated faster under microaerophilic conditions were all T4 genotypes and included four strains isolated from patients with amoeba keratitis (AK) infections. This genotype is most frequently found in AK cases and it is suggested that strains of Acanthamoeba capable of rapid growth in a biofilm of a poorly cleansed contact lens may enable amoebae to multiply and provide an infective dos e when placed onthe cornea.

An amoeba was isolated from a soil sample collected at the edge of a fumarole of the volcano Ceboruco in the state of Nayarit, Mexico. The trophozoites of this new isolate have eruptive pseudopodes and do not transform into flagellates. The strain forms cysts that have a double wall. This thermophilic amoeba grows at temperatures up to 50°C. Molecular phylogenetic analysis of the small subunit ribosomal DNA (SSU rDNA) places the amoeba into the Heterolobosea. The closest relatives are Paravahlkampfia spp. Like some other heterolobosean species, this new isolate has a group I intron in the SSU rDNA. Because of its position in the molecular phylogenetic tree, and because there is no species found in the literature with similar morphological and physiological characteristics, this isolate is described as a new genus and a new species, Fumarolamoeba ceborucoi gen. nov., sp. nov.

Strains of the genus Acanthamoeba are usually assigned to sequence types or genotypes according to pair-wise similarity values of the nuclear gene for the small subunit of ribosomal RNA. This classification system was established by comparing full or nearly full gene sequences, > 2000 bp. For practical reasons, diagnostic fragments of smaller lengths have been identified and used for rapid and economic identification of large number of strains. While the use of these small fragments in diagnostics applications remains valid when and only if the reference full sequence-type is available, we contest their use to identify and describe new genotypes. We report herein the case of a new genotype described on the basis of solely a small partial sequence and discuss the poor reliability of this fragment to correctly infer phylogenetic relationships, and its limits in the description of new genotypes of Acanthamoeba.

Five amoeba strains isolated from organs of fish were selected by morphology as possible members of the genus Vexillifera Schaeffer, 1926. Phylogenetic analyses of SSU rDNA sequences revealed that four of these strains form a best supported clade together with Vexillifera minutissima (strain CCAP 1590/3) and V. bacillipedes (sequence of the type culture was newly generated in this study). Comparison of trophozoite morphology and SSU rDNA sequences identified one of the five fish-isolated strains as closely related to V. bacillipedes, and characteristics of another three strains allowed to establish three new species: Vexillifera multispinosa, V. fluvialis and V. tasmaniana. The enlargement of dataset of Vexillifera SSU rDNA sequences enables us to doubt the identification of ATCC strain 50883 designated as V. armata. Since sequence of this strain branched in our analysis in a distant phylogenetic position within Korotnevela and Neoparamoeba clade, the Vexillifera origin of this sequence is called in question. The same applies to the newly generated sequence of the type strain of V. expectata, previously characterised by its morphology only.
 

The ultrastructural characteristics of the sporogenesis of Myxobolus, which infect the brachial arches of Mugil cephalus, is presented. The prevalence of infection was 52.7%. The ultrastructural features of the Myxobolus species studied in general comply with known features of this genus. Based on the ultrastructural morphology and specificity to the host organ, we conclude that this species is Myxobolus ichkeulensis (Bahri and Marques 1996).