Yuri A. Mazei 1 and Andrei N. Tsyganov 2
1 Department of Zoology and Ecology, Penza VG Belinsky State Pedagogical University, Penza, Russia
2 Department of Hydrobiology, Moscow MV Lomonosov State University, Moscow, Russia
Summary
An ecological study of the testate amoebae community in a sphagnum bog in the Middle Volga region (Russia)
during April-October 2004 revealed 63 taxa, belonging to 21 genera. Within the limits of the bog two types of
community differing by species composition are formed: (1) moss dwelling testate amoebae assemblage in sphagnum
quagmire and (2) detritus testate amoebae assemblage in bottom sediments of drain. In accordance with the
distributional pattern, it is possible to differentiate the following groups of species. Detritophilous group
(occurs in assemblages of quagmire margin and bottom sediments of drain) is represented by Arcella gibbosa,
A. vulgaris, A. hemisphaerica, A. discoides, A. intermedia, A. mitrata, Centropyxis aculeata sphagnicola, Cyclopyxis
kahli, Difflugia glans, Lesquereusia spiralis, Netzelia tuberculata and Phryganella hemisphaerica.
Stenotopic sphagnophilous species (inhabit typical sphagnum biotopes only) are Archerella flavum, Euglypha
cristata, Difflugia juzephiniensis, Cryptodifflugia compressa, Sphenoderia fissirostris and Nebela militaris.
Eurytopic sphagnophilous species (inhabit both typical sphagnum biotope and quagmire margin) are Nebela tenella,
N. tincta, Euglypha ciliata, Bullinularia indica, Assulina seminulum, A. muscorum, Hyalosphenia elegans, Difflugia
globulosa, D. parva and Centropyxis aculeata. Eurytopic species (occur in all biotopes) are Arcella
arenaria, Euglypha laevis, Trigonopyxis arcula, Hyalosphenia papilio and Trinema complanatum.
Within the sphagnum quagmire of the bog investigated, three types of testate amoebae communities in terms of
species structure were revealed: (i) xerophilous community (in hummocks with Polytrichum strictum, Sphagnum
papillosum and S. angustifolium) Assulina muscorum-A. seminulum-Cryptodifflugia compressa; (ii)
hygrophilous community (in lawns with Sphagnum palustre and S. magellanicum) Hyalosphenia
papilio-H. elegans-Heleopera sphagni-Nebela tenella; and (iii) hydrophilous community (in submerged Sphagnum
riparium) Cyclopyxis eurystoma-Phryganella hemisphaerica-Heleopera sphagni-Hyalosphenia papilio. The main
factor determining differences in community structure was depth to water table (moisture content). Community forming
at the edge of quagmire was the most specific. Assemblages in moist biotopes at the centre of quagmire were quite
homogenous, while in dry biotopes they were more different. Density of organisms was higher in moist habitats.
Thirty-five percent of the testate amoebae fauna was alive at the moment of sampling. The share of live organisms
was higher in moist habitats (36-45%) than in dry biotopes (22-27%).
We explored the patterns of testate amoebae distribution in macroscopically homogeneous Sphagnum
angustifolium carpet at the scale from 1 cm to 2 m. The spatial distribution analysis of populations of
different species showed that most of them combined into slightly marked aggregations with unclear bounds. So, these
aggregations probably resemble more or less expressed patches of different size smoothly passing into each other
rather than a distinct spatially constrained group. The size of agglomerations is species-specific and in some cases
(Assulina muscorum and A. seminulum) has positive correlations with amoebae shell size. Some species
produce aggregations of different size, the smallest patch reaching 1 cm. Degree of aggregation of species
distribution rises with increase of the study scale, but at the same time community heterogeneity grows too, i.e.
aggregations of different species of testate amoebae are not connected with each over in meter scale. Minimal size
of testate amoebae community (minimum-areal) does not exceed several centimeters.
The presence of a well-defined vertical structure of testate amoebae community in sphagnum biotopes was shown.
The species H. papilio, A. flavum, A. muscorum, A. seminulum, H. sphagni were characteristic of the upper
parts of Sphagnum stem, some of them (A. flavum, H. sphagni, H. papilio) were mixotrophs. In the upper
0-3 cm of sphagnum layer, species number and species diversity were minimal, whereas abundance was maximal. The
share of living organisms in the upper zone was significantly higher (about 75%) than in the lower one. Communities
forming under drier conditions have the most heterogeneous vertical structure. The opposite tendencies in
distribution of pair species H. papilio-H. elegans were noted. Mixotrophic species (H. papilio) dwells
in the upper sphagnum part while heterotro-phic species (H. elegans) lives in the lower one.
During vegetation season, from May to September, the species richness increased, while species diversity and
evenness remained at the same level with insignificant fluctuations. At the same time, species abundance could
increase, decrease or vary without well-defined directed tendencies. Characteristics of seasonal dynamics of
dominant species in different community variants were shown. In hygrophilous community species dominant in spring
H. papilio, N. tincta and H. sphagni, and in summer-autumn, N. tenella and H. elegans.
In xerophilous community the spring community was dominated by A. muscorum, N. tincta, H. sphagni, the summer
one, by N. tenella, A. seminulum, H. elegans, E. ciliata and the autumn community, by C. compressa, T.
arcula, A. seminulum. It was found that closely related species have opposite tendencies in seasonal
distribution. So, in pairs of species H. papilio-H. elegans, N. tincta-N. tenella, A. muscorum-A. seminulum
all the former species were characteristic of spring and the beginning of summer, while all the latter were mainly
found at the end of summer and in early autumn. A great share of empty tests of the genus Assulina is
accounted for, first of all, by low moisture content in biotopes where these species live (under these conditions
tests are better preserved) and, secondly , by r-strategy of these small organisms, whose population abundance
increases or decreases fast as a reaction to environment changes.
Key words: testate amoebae, sphagnum bog, community structure, Middle Volga Region, microscale
spatial distribution, vertical structure, patches, seasonal dynamics
Address for correspondence. Yuri A. Mazei. Department of Zoology and Ecology, Penza State Pedagogical University,
Lermontova str., 37, 440026 Penza, Russia. E-mail: yurimazei@mail.ru
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