Andrew Rogerson

Variable Responses of acanthamoeba Strains to Three Multipurpose Lens Cleaning Solutions

Purpose. A novel method has been developed to compare Acanthamoeba strain differences by testing their susceptibility to multipurpose contact lens cleaning solutions (MPS). Methods. This method uses surface-attached amoebae that mimic cells attached to a contact lens. In brief, acanthamoebae were grown on non-nutrient agar plates with Escherichia coli prey. Blocks of agar with cysts or trophozoites (∼50 cells) were cut out and transferred to MPS [ReNu MultiPlus; (Bausch & Lomb, Rochester, NY), Complete (Allergan, Irvine, CA), and Opti-Free Express (Alcon, Ft. Worth, TX)] for up to 24 h treatment. After neutralizing in Dey Engley broth (Difco), blocks were washed in amoeba saline and reinoculated onto fresh prey bacteria. Positive growth was indicative of survival. Results. Testing showed that the efficacy of the three MPS was different. Opti-Free was the most effective against cysts, followed by ReNu while Complete was relatively ineffective. Not surprisingly, trophozoites were more susceptible than cysts. Conclusions. Findings for individual MPS complement previous work with other methods. This study has also identified that environmental strains vary in their sensitivity to disinfecting solutions. Overall, Acanthamoeba genotypes T3, T5, and T11 from the environment were more resistant than the T4 isolates from the cornea and beach. This resilience supports previous work on temperature tolerance, in which T3 and T5, and T11 acanthamoebae grew in temperatures up to 41°C. Investigators should therefore consider the strain genotype and its source before embarking on MPS sensitivity testing.

High Numbers of Naked Amoebae in the Planktonic Waters of a Mangrove Stand in Southern Florida, USA

Abstract This is the first study to examine the abundance of naked amoebae in the water column of a mangrove stand. A total of 37 different morphotypes was noted and at least 13 of these are probably new species. Over a one-year sampling interval, amoebae averaged 35,400 cells liter−1 (range 2,000–104,000) by an indirect enrichment cultivation method. Densities in the upper end of this range are the highest ever reported for any planktonic habitat. Variation between samples was related to the quantity of suspended aggregates (flocs) in the water column emphasizing that amoebae are usually floc-associated. The study also showed that it is essential to disrupt floc material prior to withdrawing sample aliquots for the indirect counting method since several amoebae can occupy the interstices of aggregates. There is concern that indirect enumeration methods that require organisms to be cultured in the laboratory seriously underestimate the true count. A direct counting method using acridine orange staining and epifluorescence microscopy was attempted to assess the possible magnitude of the error associated with indirect counting. While this direct method had limitations, notably the difficulty of unambiguously differentiating between small amoebae and nanoflagellates, the results suggested that the indirect method gave estimates that were close to the true count (within a factor of two). Mangrove waters are rich in heterotrophic protozoa (∼ 3 × 106 liter−1) and while the heterotrophic flagellates are by far the dominant group, naked amoebae outnumber ciliates some 20-fold. The ecological consequences of high numbers of amoebae, particularly the common small forms less than 10 μm in length, need to be examined for these important coastal sites.

Abundance of airborne heterotrophic protists in ground level air of South Dakota

Abstract The abundance of heterotrophic protists (as protozoan cysts) in the near-surface tropospheric air of Rapid City, SD, was determined using a filtration sampler capable of collecting particles in the 2.0 to 20.0 μm size range (sampling rate ca. 16 l min −1 ). The number of viable cysts collected on the filter was estimated after enrichment cultivation in soil extract medium. Samples were mainly collected in the spring, fall and winter of 1997 and abundances throughout the year ranged from below detection ( −3 ) to 1.08 cysts m −3 with an overall mean of 0.25 m −3 (SE=0.05). Not all of the isolates were identified to species but, over the study, 25 different morphotypes were found. Flagellates and naked amoebae were the commonest protozoa (as cysts) found; ciliates were rare. This reflects the abundance of these groups in soils, the likeliest source of most of the airborne protozoa in this study. The concentration of cysts generally increased as a function of the total particles in the atmosphere. The concentration of both particulates and cysts exhibited a wide range of variability, but highest values of both occurred on days with higher winds and lower relative humidity.

Platyamoeba pseudovannellida N. Sp., a Naked Amoeba With Wide Salt Tolerance Isolated from the Salton Sea, California

Abstract A new species of naked amoeba, Platyamoeba pseudovannellida n.sp., is described on the basis of light microscopic and fine structural features. The amoeba was isolated from the Salton Sea, California, from water at a salinity of ca. 44‰. Locomotive amoebae occasionally had a spatulate outline and floating cells had radiating pseudopodia, sometimes with pointed tips. Both these features are reminiscent of the genus Vannella. However, the surface coat (glycocalyx) as revealed by TEM indicates that this is a species of Platyamoeba. Although salinity was not used as a diagnostic feature, this species was found to have remarkable tolerance to fluctuating salinity levels, even when changes were rapid. Amoebae survived over the range 0‰ to 150‰ salt and grew within the range 0‰ to138‰ salt. The generation time of cells averaged 29 h and was not markedly affected by salt concentration. This is longer than expected for an amoeba of this size and suggests a high energetic cost of coping with salinity changes. The morphology of cells changed with increasing salinity: at 0‰ cells were flattened and active and at the other extreme (138‰) amoebae were wrinkled and domed and cell movement was very slow. At the ultrastructural level, the cytoplasm of cells grown at high salinity (98‰) was considerably denser than that of cells reared at 0‰.

The diet of two mud-shrimps, Calocaris macandreae and Upogebia stellata (Crustacea: Decapoda: Thalassinidea)

Abstract The monthly variations in the gut contents of Calocaris macandreae, principally a deposit feeder, and Upogebia stellata, principally a suspension feeder, were examined over the period of a year. The diet of both species consisted of a mixture of organic and fine inorganic fragments. The identifiable components of their respective diets included diatoms, dinoflagellates, algal and terrestrial plant fragments, and material of animal origin. The contribution of these different dietary components varied between the two species, and also over the year within each species. Using Strauss Linear Food Selection Index (L) it was found that U. stellata positively selected diatoms, dinoflagellates and plant and algal fragments whilst avoiding animal material. In contrast, C. marandreae showed little evidence of food selectivity, except in the case of algal material which was positively selected. In general, variations observed in the diet were related to changes in food abundance and availability within the...

Naked amoebae (Protozoa) of the Salton Sea, California

The Salton Sea is an inland lake in California with an average salinity of ca. 44 g l−1. This productive water body, which supports substantial fish and migratory bird populations, is under threat because of increasing salinity levels. The present study was the first to examine the naked amoeboid protozoa of the Salton Sea and provide a first estimate of their numerical importance. Over a six-month sampling period (June–December, 1999), 45 different morphospecies (considered to be species) of amoebae were isolated. Wherever possible, isolates were identified to species or genus using diagnostic features recognizable by light microscopy. For each isolate, illustrations and brief notes on the diagnostic characters used in the identifications are given. These will allow this paper to be used as an identification guide to amoebae of the Salton Sea in future studies. Of the 45 taxa, around 18 of the isolates (i.e. 40%) are probably new to Science. Preliminary counts, based on enrichment cultivation methods, showed that amoebae in shoreline waters ranged from 14u2009560 to 237u2009120 cells l−1 (mean 117u2009312 ± 86u2009075 S.D.). The ecological importance of high numbers and high diversity of amoebae is unknown. But it should be noted that several of the amoebae were actively grazing cyanobacterial and algal filaments and filaments of the bacterium Beggiatoa. Others were predominately associated with suspended particulates. As such, amoebae may be important in the cycling of carbon and nutrients in the Salton Sea.

A new species of Tetramitus in the benthos of a saline antarctic lake

A new amoeboflagellate, Tetramitus vestfoldii n. sp. was discovered in the microbial mat of Pendent Lake, Vestfold Hills, Eastern Antarctica. Isolates were examined using light microscopy, electron microscopy and molecular analysis of the small subunit ribosomal DNA (SSU rDNA). Microscopical observations revealed a markedly eruptive, limax amoeboid stage with a clear hyaline zone, whilst flagellates were tapered posteriorly with a cytostome and anterior rostrum from which 4 flagella of equal length arose. The SSU rDNA was sequenced. Alignment of the sequence with published sequences of some other amoeboflagellates revealed that this species is best placed within the Vahlkampfiidae. The T. vestfoldii SSU rDNA was found to show greatest similarity with that of T. rostratus , a species with which it also shares several structural characteristics. Inorganic nutrient measurements indicate that the benthos of Pendent Lake could be a favourable environment for a bacterivorous predator such as Tetramitus . Ice cover on Pendent Lake was seen throughout the study period and may have reduced light intensity in the microbial mat; a low light intensity would appear to be a requirement for this species. The new species is defined on the basis of a pronounced taper towards the posterior end in the flagellate stage, an intolerance to salt concentrations greater than 30 and phylogenetic resolution using SSU rDNA sequence comparisons.

Remarkable Salinity Tolerance of Seven Species of Naked Amoebae (gymnamoebae)

The salinity tolerance of naked amoebae collected from sites ranging from ca. 0‰ to 160‰ were compared in laboratory experiments. Amoebae were collected from hypersaline ponds around the perimeter of the Salton Sea, California, where salinities averaged 160‰, and directly from the shoreline waters of the Sea where salinities were generally between 44 and 48‰. Naked amoebae were also collected from the intertidal zone of a Florida beach, a habitat subject (on occasion) to salinity fluctuations within the range 6–85‰. From these combined sites, 6 clones of amoebae were isolated for salinity tolerance experiments (2 marine beach isolates, 2 Salton Sea isolates, and 2 hypersaline pond isolates). A seventh clone, Acanthamoeba polyphaga, a common freshwater/soil amoeba, was obtained from a Culture Collection. Laboratory experiments compared the effects of gradually changing culture salinity versus no salinity acclimatization. Growth rate and culture yield were used as indices of effect. Generally, amoebae were tolerant over a wide range of salinity conditions (in terms of growth and yield) and were not markedly influenced by pre-conditioning to salinity changes throughout the experiments. Overall, the freshwater amoeba Acanthamoeba grew between 0 and 12‰, the marine clones grew in the range of 2–120‰, and the Salton Sea clones reproduced between 0 and 138xa0‰. The hypersaline clones were the most resilient and grew between 0 and 270‰ salt. The survival and activity of large populations of naked amoebae in sites subject to salinity fluctuations suggest that they should be considered in future studies to better understand their, as yet, undefined ecological role.

Comparison of the mouthpart setal fringes of seven species of mud-shrimp (Crustacea: Decapoda: Thalassinidea)

A detailed description of the mouthpart morphology is provided for Axius stirhynchus Leach, Calocaris macandreae Bell, Upogebia deltaura (Leach) and U. pusilla Petagna. The distribution of setae on the mouthparts of three additional species of thalassinidean mud-shrimp, Callianassa subterranea (Montagu), Jaxea nocturna Nardo and U. stellata (Montagu), is also given. Particular attention was paid to the mouthpart setal fringes, where major differences were observed in setal type, inter-setal distances and inter-setule distances. The mouthparts of the three upogebiid species examined were characterized by plumed setae with very small intersetal distances. The mouthparts of the other four species of thalassinidean were dominated by more robust serrate setal types. The setal screens of the upogebiids were often made up of a single setal type, whereas those of Calocaris macandreae and Axius stirhynchus were often comprised of a number of different setal types. The observations made for Callianassa subterranea ...

Tolerance of naked amoebae to low oxygen levels with an emphasis on the genus Acanthamoeba

Published by and copyright of Jagiellonian University Press. The definitive version of this article is available at: http://www.ejournals.eu/Acta-Protozoologica/Tom-50(2011)/50/art/801/