Morphology and Biometry of Nebela tenella Penard, 1893 (Amoebozoa: Arcellinida)

Shell ultra-structure and morphometrical variability of Nebela tenella were investigated using scanning electron microscopy (SEM). N. tenella was isolated from two widely separated populations, one from Switzerland and another from Canada. The shell’s structural elements were similar to those of the other nebelids, but N. tenella has a characteristic peculiarity – always present depressions on the shell surface, which makes an uneven outline of the shell. Moreover, light microscopy and SEM study showed that the collar of the N. tenella represents a turned-over continuation of the neck, which is covered by the same idiosomes as on the shell body. The biometrical analysis showed that the majority of the basic characters of N. tenella vary moderately and give continuous series of transition forms. According to the shell depth and the ratio depth/width both populations were significantly different of each other. Variation coefficients showed that the variability of the characters differs in both populations and the Swiss population is more stable than the Canadian one. All new obtained data for N. tenella raise the question whether the shell’s size, cross section and ultramorphology are reliable enough as characters for the differentiation of N. tenella and N. griseola, and whether they are two distinct species or should just be considered as ecophenotypic variation within one species

Nebela golemanskyi sp. nov., a New Sphagnicolous Testate Amoeba from Bulgaria (Amoebozoa: Arcellinida, Nebelidae)

A new sphagnicolous species of the genus Nebela isolated from wet Sphagnum mosses gathered at Vitosha Mountain (Bulgaria) is described. Shell ultrastructure and morphological variability of Nebela golemanskyi sp. nov. are investigated using scanning electron microscopy. The newly described species is characterized by its almost uncompressed shell and by its large, rounded, voluminous and hollow structural elements (idiosomes). The analysis of the variation coefficients shows that the studied population is too homogeneous and all measured morphological characters are feebly variable (CV range from 3.28% to 5.02%). Size frequency distribution analysis indicates that N. golemanskyi is size-polymorphic species, characterized by not well-expressed main-size class in favour of many subsidiary classes. A biometrical and morphological comparison between N. golemanskyi and N. speciosa is made

On the morphology, biometry and biogeography of Lamtopyxis callistoma (Amoebozoa: Arcellinida)

The ultra-structure of the shell and the morphometric variability of soil inhabiting testate amoeba Lamtopyxis callistoma from Madagascar were studied by using light- and scanning electron microscopy. The biometrical characteristic of the species was made on the basis of 75 specimens measured. In addition to the diameter of the shell, six other shell characters were described biometrically for the first time. The analysis of the variation coefficients shows that the studied population of L. callistoma is comparatively homogeneous and almost all measured characters are weakly to moderate variable (CV less than 10%). Scanning electron microscopy (SEM) studies on the shell ultra-morphology show that it has a smooth apertural surface with a thick layer of porous and fibrous organic cement and a rough dorsal surface composed of bigger and angular pieces of quartz. The shell wall has a thickness of about 5-6 µm and is composed of three layers. Unlike the previously accepted opinion that species is characterized by the presence of four teeth, this study shows that population of L. callistoma from Madagascar is comprised of both, specimens with four teeth and specimens with three teeth, in ratio of about 60% to 40%. Taking into account the restricted geographical distribution, large sizes and characteristic apertural morphology of L. callistoma it is assumed that this species, like some bryophilic ‘Nebelas’ with circumaustral distribution (e.g. Apodera vas, Alocodera cockayni, Certesella certesi, Certesella martiali, etc.), can be used as an example that in free-living microbial eukaryotes ‘not everything is everywhere’

Sphagnum-Dwelling Testate Amoebae in Bulgaria

The aim of this atlas is to present summarised information and to illustrate comprehensively the shell morphology and structure of the majority of recorded Sphagnum-dwelling testate amoebae in Bulgaria (a total of 120 species, each of them illustrated with 9 LM and SEM photos). Since most of these species appear to be widely distributed in Europe, as well as in many other regions of the world, the atlas may be of interest to all researchers on testate amoebae and can also be used by specialists in ecology, hydrobiology, palaeoecology and environmental monitoring