On the morphology and life-history of Hemiurus luehei Odhner, 1905 (Digenea: Hemiuridae)

Previously undescribed cystophorous cercariae which develop in sporocyst germinal sacs in the tectibranch opisthobranch Philine denticulata (Adams) are shown to be cercariae of Hemiurus luehei Odhner, 1905 (Hemiuridae), a common stomach parasite of clupeid and salmonid fishes off the Atlantic coast of Europe, in the Baltic and the Mediterranean Sea. The free-swimming cercariae are seized by calanoid copepods. Temora longicornis (Müller) and Acartia tonsa Dana acted as suitable experimental intermediate hosts. Pressure by the copepod mouth appendages causes delivery tube eversion and the injection of the cercarcial body into the haemocoel. Sagitta sp. was found naturally infected with a metacercaria of H. luehei. The cystophorous cercaria and metacercaria are described using light and scanning electron microscopy. Adults from herring were examined under the stereoscan electron microscope.     

Examination of endopelic and epilithic algal community structure employing scanning electron microscopy

1. Biological community structure within a stream periphyton mat and sediment core was examined using scanning electron microscopy. Samples were fixed, freeze-fractured and viewed under normal conditions with a scanning electron microscope.
2. This technique enabled the analysis of orientation and spatial distribution of algal cells within the three-dimensional algal communities.
3. Fractured samples from a periphyton mat and sediment core at the Procter & Gamble Experimental Stream Facility showed layering of some dominant diatom species, such as Nitzschia dissipata , Melosira varians and Gyrosigma attenuatum . The spatial relationship of nematodes as potential algal predators was also revealed.
4. Advantages, disadvantages and potential future applications of this freeze fracture technique are discussed.     

Periphyton on nymphaeids: An evaluation of methods and separation techniques

The use of certain methods and techniques of periphyton research has been evaluated in connection with the study of periphyton on nymphaeid aquatic plants. Separation techniques explored are based on a combination of mechanical and chemical forces, on enzymatic action and on the chelating activity of EDTA. Mechanical separation by the application of superficial film is treated apart, because it is the only technique conserving the original pattern of periphyton. The means used to examine periphyton in situ consist of bleaching, epifluorescence and scanning electron microscopy.In the end, it is concluded that not one of the techniques is fully satisfactory. However, a combination of techniques may provide sufficient data to obtain an overall picture of species composition, microdistribution and architecture of a periphyton community.Contribution no. 30 of the nymphaeid project.Contribution no. 30 of the nymphaeid project.     

Scanning-beam electron microscopy of the conidia of the brown and albino filamentous varieties of Histoplasma capsulatum

Aspects of the surface appearance and external morphology of the conidial forms of the albino and brown filamentous varieties ofHistoplasma capsulatum as seen by scanning-beam electron microscopy are described and illustrated by electron micrographs. Septal areas between the hyphal cells of the supporting mycelium are seen as slightly elevated annular rings or ridges. The smooth micro- and macroconidia of the albino filamentous variety show a fine wrinkling and delicate irregularities of surface texture. Macroconidia of the brown filamentous variety are illustrated showing variations in numbers and respective length of the conspicuous wall projections or tubercles. The 3-dimensional perspective, unusual depth of focus, and high resolving power of the stereoscan technique permitted observations of external conidia morphology unattainable by other methods of study.     

Stereoscan studies of phylactolaemate bryozoan statoblasts including a key to the statoblasts of the British and European Phylactolaemata

The stereoscan electron microscope has been used to study morphological features of the statoblasts of nine phylactolacmate species. Pores present in the walls of annulus chambers of floating statoblasts are fully described for the first time. The taxonomic significance of surface patterning is assessed, and a key to the species found in Britain and Europe is included.     

Further observations on the scaled Chrysophycean and Synurophycean flora of the Ocala National Forest, Florida, U.S.A.

The distributions of silica-scaled chrysophytes in 30 freshwater ponds located in the Ocala National Forest, Florida, U.S.A., relative to chemical gradients are described. Phytoplankton, periphyton, and surface sediments from each of the 30 sites were collected in March of 2000 and later analyzed extensively with both scanning electron microscopy (SEM) and light microscopy (LM) for scaled chrysophytes. In addition, water samples were used to measure a suite of chemical characteristics, including specific conductance, pH, alkalinity, total phosphorus, total nitrogen, chlorophyll- a , chloride, sulfate and base cation concentrations. Overall, waterbodies included in this study are oligotrophic, dilute, poorly buffered and low in pH. Including six previously described species which are largely known only from the Ocala National Forest, we have identified forty-nine taxa of silica-scaled Chry-sophyceae and Synurophyceae, 23 of which were present in 5 or more waterbodies, indicating that lakes in this region are quite diverse and abundant in scaled chrysophytes. The most important species included Synura petersenii, S. echinulata and one recently reported new species from this region, Mallomonas wujekii , which was found in 73% of the lakes in this survey. The number of taxa found per lake ranged from 2 to 23 and observations include new records of several rarely reported species. Although the flora includes species commonly found in more northern regions, it also includes a group of taxa that appear to be endemic to the region and others commonly found in more tropical regions. Lastly, a new form found in ten ponds, Mallomonas transsylvanica f. curvata , is described.     

Temporal changes in periphyton standing crop during an unusually dry winter in streams of the Western Cascades,Oregon

The effects of light and discharge on standing crops of periphyton in adjacent shaded and open reaches of first to fourth order streams were examined during winter in three streams of the Western Cascades, Oregon. Standing crops were measured in terms of chlorophylla and periphyton biomass at each site on 8 occasions. Open sites supported higher standing crops of periphyton than shaded sites and increases in standing crop were shown to be related to light input at each site. Biomass increased throughout winter until scouring associated with an unusually late winter freshet reduced periphyton standing crops to their lowest observed levels. It is concluded that periphyton levels are affected by a combination of factors of which light levels, and the periodicity of storm events are of major importance.     

Interactions among nutrients, algae and invertebrates in a New Zealand mountain stream

SUMMARY. 1. Colonization of nutrient-diffusing substrata by periphyton and invertebrates was investigated at forested and open sites in a small, mountain stream and a spring in the South Island of New Zealand.
2. Substrata had colonization surfaces made from 100μm mesh plankton netting that enabled algal assemblages to be removed intact for scanning electron microscopy. They also allowed small volumes of solvent to be used for the extraction of photosynthetic pigments.
3. At all sites, periphyton assemblages were dominated by species of Achnanthes, Cocconeis and Gomphonema , and except in the forest in winter, periphyton biomass was always greater on enriched (N + P added) than control substrata.
4. Invertebrates colonizing diffusion substrata were principally larval Chironomidae (Orthocladiinac). No larvae were present in winter, but in three spring and summer trials mean larval densities were higher on nutrient-enriched than control substrata at all sites.
5. The inclusion of an insecticide Malathion in diffusion substrata, reduced insect colonization at open and forested sites. After 28 days, no concurrent increases in algal pigment concentration were observed on nutrienl-enriched or control substrata at the forested site. However, pigment concentrations were higher on substrata incorporating Malathion at the open site suggesting that algal standing crop was depressed by the activities of grazers.     

The insight into diatom diversity,ecology, and biogeography of an extreme cold ultraoligotrophic Lake Labynkyr at the Pole of Cold in the northern hemisphere

The freshwater ultraoligotrophic Lake Labynkyr is located near the Pole of Cold in the northern hemisphere (Yakutia, Russia). The lake is covered by ice during 240 days a year. We undertook several expeditions to the lake during the ice and open water periods for sampling ice fouling, plankton and periphyton that were then analyzed by means of scanning electron microscopy. As a result, we identified a high biodiversity of diatoms—123 species and intraspecific taxa from 53 genera, among them 3 species were new for Russia and 26 taxa were new for the algal flora of Yakutia. The oligo- and xenosaprobionts and their variations dominate—71 taxa. 18 Species were evaluated as tolerant to cold oligotrophic waters, 12 occurred on the ice bottom, and 62 in the water column under ice (0–25 m). 104 taxa were found during the open water period, 70 taxa were identified in the periphyton. We showed the diatom flora of Lake Labynkyr to be unique compared with other lakes of Yakutia and to share taxa with the diatom flora of Lake Baikal. The diatoms being indicators of the global climate changes and ecological status of lakes, our data can be used as an evidence of such changes as well as to be useful studies of biogeography and history of formation of flora in Arctic and Subarctic waters.

     

Scanning electron microscopy of the eggs of Ascaris lumbricoides, A. suum, Toxocara canis, and T. mystax.

Eggs of Ascaris lumbricoides, A. suum, Toxocara canis, and T. mystax were examined by scanning electron microscopy (SEM). All species under study exhibited pronounced surface ridges. The ridges formed distinctive patterns in T. canis and T. mystax. In the Ascaris species, the ridges are similar except that they are more pronounced in the eggs of A. suum. Operculumlike structures were observed only in Ascaris. Correlation of data from SEM with previously reported transmission electron microscopy suggests that the surface ridges seen in Ascaris eggs are formed by the chitinous layer of the shell.     

Pygidiopsis ardeae n. sp. (Digenea: Heterophyidae: Pygidiopsinae) in the grey heron Ardea cinerea L. from Denmark

A new species, Pygidiopsis ardeae (Heterophyidae, Pygidiopsinae), is described, using both light and stereoscan electron microscopy, from the grey heron Ardea cinerea L. (Ardeidae) from Denmark. The species has previously (as P. genata) been recorded in dogs fed on plaice and flounders from Danish waters. It developed experimentally in domestic chickens and pigeons. No species of Pygidiopsis Looss, 1907 has previously been described from birds in northern Europe. P. ardeae is very similar to the type-species, P. genata Looss, 1907, from Egypt, but the two species have different life-cycles. P. ardeae differs from P. piclaumoreli Dollfus & Capron, 1958 from Senegal in its size and the disposition of vitelline follicles. P. plana (Linton, 1928) Price, 1933, from a green heron from the eastern USA, is larger than P. ardeae and has a wide, sac-like prepharynx.     

Responses of Chironomidae (Diptera; Insecta) to the exclusion of shrimps and Ephemeroptera in a coastal forest stream, Rio de Janeiro, Brazil.

In a benthic community on a continuous flat granite substrate in a third-order coastal forest stream, the dominant chironomid (Cricotopus) increased in number when shrimps (Macrobrachium olfersi and Potimirim glabra) and baetid ephemeropterans were excluded by electricity. The response appeared to be mediated by an increase in periphyton and sediments, rather than a reduction of direct predation or interference. Chironomids, periphyton and sediments decreased significantly compared to the control when shrimps only were excluded. Baetid ephemeropteran appeared to be the most important determinants of periphyton and sediment mass; the density of chironomids appeared to follow the quantity of periphyton and sediments.     

Effects of desiccation duration on the community structure and nutrient retention of short and long-hydroperiod Everglades periphyton mats

Responses of periphyton communities to different relevant durations of dry down were assessed. Long-hydroperiod sites within Everglades National Park remain wet for greater than 8 months of the year while short-hydroperiod mats are wet for fewer than 4 months of the year. Dry down duration of long and short-hydroperiod Everglades periphyton was manipulated from 0 to 1, 3, or 8 months after which periphyton was rewetted 1 month and examined for algal species composition. The effects of desiccation and rewetting on periphyton nutrient retention were also assessed. Relative abundance of diatoms declined from an average of 47% in the long-hydroperiod community at the start of the experiment to 24% after 1 month of desiccation and only 12% after 8 months of desiccation. Short-hydroperiod periphyton contained a lower proportion of diatoms at the outset (3%), which declined to less than 1% after the 8-month desiccation treatment. A significant increase in the filamentous cyanobacteria Schizothrix calcicola occurred in long-hydroperiod periphyton mats during this same period, but not in short-hydroperiod mats. Long-hydroperiod periphyton communities had a greater response to desiccation overall, but short-hydroperiod community structure responded to desiccation more rapidly. Because short-hydroperiod communities dry frequently, they appear to cope better to desiccating conditions than long-hydroperiod periphyton communities. This is indicated by the dominance of desiccation resistant algal taxa such as the cyanobacterial filaments S. calcicola and Scytonema hofmanni. Long-hydroperiod periphyton mat communities converge compositionally to short-hydroperiod periphyton communities after prolonged desiccation. Desiccation and rewetting caused long-hydroperiod periphyton to flux greater concentrations of nutrients than short-hydroperiod periphyton. Significant increases in efflux occurred from 1 to 8 months for total phosphorus (TP) and from 1 to 3 and 8 months for total nitrogen (TN) and total organic carbon (TOC). Thus, changes in periphyton mat community structure and function with altered hydroperiod may have long-term ecosystem effects.     

Revision of the Family Spironemidae Doflein (Protista, Hemimastigophora), With Description of Two New Species, Spironema Terricola N. Sp. and Stereonema Geiseri N, G., N. Sp.

ABSTRACT. Two new hemimastigophoran flagellates are described using light and electron microscopy, and the family Spironemidae is revised. Spironema terricola n. sp. occurs in soil from the Grand Canyon (southwest USA). It moves in a conspicuously euglenoid manner and differs from S. multiciliatum Klebs by its vermiform shape and shorter kinetics. Spironema terricola is similar to Goodey's Spironema multiciliatum from soil in England. However, Goodey's vermiform species has a very elongate nucleus and is thus neither identical with S. terricola , which has a roundish nucleus, nor with Klebs' lanceolate S. multiciliatum ; we consider it a new species, Spironema goodeyi n. sp, Stereonema geiseri n. g., n. sp. was discovered in the Aufwuchs (periphyton) of a river in Bavaria, Germany. the new genus differs from Spironema by its a contractility, and from Hemimastix by its shorter kinetics and less plicate cortex. the fine structure of Spironema and Stereonema is very similar to that of Hemimastix Foissner et al., viz., the cortex is composed of two plates having diagonal symmetry and the flagellated basal bodies have associated a short and a long microtubular ribbon. All species have unique extrusomes of the same type. the main differences between the three genera and five species recognized are contractility, length of kinetics, body size, shape of cell and nucleus, and particulars of the cortex and extrusomes. the phylogenetic relationships of the Hemimastigophora are still uncertain. However, the diagonal symmetry of the cortical plates and the pronounced euglenoid movement of Spironema spp. suggest a common ancestor with euglenids.     

Changes in periphyton abundance and community structure with the dispersal of a caddisfly grazer, <Emphasis Type="Italic">Micrasema quadriloba</Emphasis>

We examined the larval population densities and biomass of a caddisfly grazer, Micrasema quadriloba, and the abundance and community structures of periphyton at a segment scale (7.4 km with four study sites), along a second-to fourth-order Japanese mountain stream throughout the grazer’s life cycle. In the uppermost riffle of the study segment (site 1), periphyton abundance was kept at low levels when the larvae occurred. The larval distribution spread downstream as larvae developed from first instars in May to fifth instars in January. We performed multiple regression analyses to test the effects of environmental variables and larval biomass on periphyton abundance in both the riffle of site 1 and the study segment; the results revealed that the larval biomass was significantly negatively correlated with periphyton abundance similarly in both the riffle and the study segment. In addition, both the correlation and community analyses showed that the larval biomass was significantly negatively correlated to the relative abundance of large and/or filamentous microalgae, which appeared in the uppermost layer of the periphyton mat, and that larval biomass was significantly positively correlated to the relative abundance of small diatoms, which strongly adhered to the substrate. Thus, the present study implied that the grazing of M. quadriloba larvae would regulate the abundance of periphyton in a riffle and also regulate the abundance and community structure of periphyton at the segment scale with the expansion of their longitudinal distribution.     

Number,biomass, and activity of bacteria in the water of overgrowths and periphyton on higher aquatic plants

The results of studies on the production-destruction processes in the water of overgrowths and periphyton of higher aquatic plants in the Volzhskii Reach of the Rybinsk Reservoir are presented. The studied aspects included the level of quantitative development and the activity of bacterioplankton of various ecological groups of macrophytes. It was revealed that the processes of destruction of organic matter under the impact of bacteria in the macrophyte periphyton prevail over the rate of primary production in algal periphyton. The production of periphyton and planktic bacteria per 1 m² of macrophyte overgrowth is calculated.     

Cellular and body scale morphology of Heterocapsa huensis sp. nov. (Peridiniales, Dinophyceae) found in Hue, Vietnam

Cellular and body scale structure of a new armored dinoflagellate Heterocapsa huensis , collected from Hue, Vietnam were investigated. Morphology of motile cell was observed by light, fluorescent and scanning electron microscopy, and body scale structure was examined by whole mounts of transmission electron microscopy. Cells of H. huensis were ellipsoid with a spherical nucleus located in the posterior and multiple pyrenoids located above the nucleus; this arrangement was similar to that of Heterocapsa pygmaea . Transmission electron microscopy revealed ultrastructure of the body scales consisted of a rounded triangular basal plate and three-dimensional ornaments. Structure of the basal plate resembles that of Heterocapsa illdefina ; however, the number of the peripheral spine is different from that of H. illdefina and this structure has never been reported from Heterocapsa species. A new Heterocapsa species, H. huensis Iwataki et Matsuoka sp. nov., is described based on positions of organelles and body scale ultrastructure.