Analysis of the community structure of abyssal kinetoplastids revealed similar communities at larger spatial scales.

Knowledge of the spatial scales of diversity is necessary to evaluate the mechanisms driving biodiversity and biogeography in the vast but poorly understood deep sea. The community structure of kinetoplastids, an important group of microbial eukaryotes belonging to the Euglenozoa, from all abyssal plains of the South Atlantic and two areas of the eastern Mediterranean was studied using partial small subunit ribosomal DNA gene clone libraries. A total of 1364 clones from 10 different regions were retrieved. The analysis revealed statistically not distinguishable communities from both the South-East Atlantic (Angola and Guinea Basin) and the South-West Atlantic (Angola and Brazil Basin) at spatial scales of 1000-3000 km, whereas all other communities were significantly differentiated from one another. It seems likely that multiple processes operate at the same time to shape communities of deep-sea kinetoplastids. Nevertheless, constant and homogenous environmental conditions over large spatial scales at abyssal depths, together with high dispersal capabilities of microbial eukaryotes, maintain best the results of statistically indistinguishable communities at larger spatial scales.

WITHDRAWN: Wide distribution ranges of several microbial eukaryotes of nanofaunal size at abyssal depths of the South-East Atlantic and the Mediterranean.

This article has been withdrawn.

Electron microscopy of Paramecium (Ciliata).

Paramecium may be the best known single-celled organism in existence (Hausmann et al., 2003). Today its image often appears on television programs where the producers use it to illustrate a stereotypic microorganism, be it pathogenic or nonpathogenic, prokaryotic or eukaryotic. Paramecium was probably one of the first single-celled organisms observed with a light microscope by the Dutch cloth vendor and amateur lens maker Antoni van Leuwenhoek (1632-1723) (Dobell, 1932), and it is still being investigated in the 21st century in the days of the modern electron microscopes.

Large-scale patterns in biodiversity of microbial eukaryotes from the abyssal sea floor.

Eukaryotic microbial life at abyssal depths remains "uncharted territory" in eukaryotic microbiology. No phylogenetic surveys have focused on the largest benthic environment on this planet, the abyssal plains. Moreover, knowledge of the spatial patterns of deep-sea community structure is scanty, and what little is known originates primarily from morphology-based studies of foraminiferans. Here we report on the great phylogenetic diversity of microbial eukaryotic communities of all 3 abyssal plains of the southeastern Atlantic Ocean--the Angola, Cape, and Guinea Abyssal Plains--from depths of 5,000 m. A high percentage of retrieved clones had no close representatives in genetic databases. Many clones were affiliated with parasitic species. Furthermore, differences between the communities of the Cape Abyssal Plain and the other 2 abyssal plains point to environmental gradients apparently shaping community structure at the landscape level. On a regional scale, local species diversity showed much less variation. Our study provides insight into the community composition of microbial eukaryotes on larger scales from the wide abyssal sea floor realm and marks a direction for more detailed future studies aimed at improving our understanding of deep-sea microbes at the community and ecosystem levels, as well as the ecological principles at play.

Description and phylogenetic relationships of Spumochlamys perforata n. sp. and Spumochlamys bryora n. sp. (Amoebozoa, Arcellinida).

Spumochlamys perforata n. sp. and Spumochlamys bryora n. sp. were isolated and described from dry epiphytic moss. The morphology and ultrastructure of both species clearly demonstrate that they belong to the genus Spumochlamys (family Microchlamyiidae). They differ from its only described member, Spumochlamys iliensis (as well as from species of Microchlamys), in the relief of the dorsal surface of the test, revealed by scanning electron microscopy, which can represent a good characteristic for species identification. They also differ in the structure of the dorsal part of the test wall (especially S. perforata). Small subunit ribosomal DNA-based molecular phylogenetic analyses show that Spumochlamys is a deeply branching lineage of the Arcellinida, without any close affinities. Actin gene sequence analysis places this genus within the Tubulinea, close to two other arcellinid lineages but without forming a monophyletic group with them. These data together strongly suggest that the lack of resolution in the arcellinid molecular phylogenies is due to serious undersampling of taxa, a limited number of sequence data, and high divergence rates in most of the species.

Spumochlamys iliensis n.g. n. sp. (Testacealobosia, Microchlamyiidae) from Central Asia, with notes on the diversity of Microchlamys-like testate amoebae.

Spumochlamys iliensis n. g., n. sp. was isolated from a mineral pond in an arid, semi-desert region in Kazakhstan (Central Asia). This amoeba is covered with a plate-shaped, flexible organic spongious test. The thin membranous margin of this test extends ventrally to surround a flexible ventral aperture. In its morphological features and behaviour this amoeba is very similar to Microchlamys patella (Claparède and Lachmann, 1859) Cockerell, 1911, but differs from this species and from M. sylvatica Golemansky, Skarlato and Todorov, 1987 in the lack of an additional membrane separating the cell body from the test, a feature that can only be detected using electron microscopy. The presence of this membrane is considered to be a principal characteristic of the genus Microchlamys and family Microchlamyiidae; however, this conclusion was reached from the study of only two species. The data presented show a higher diversity of Microchlamys-like testate amoebae; we therefore suggest that the described species should be included in the family Microchlamyiidae with emendation of its diagnosis, but that a separate genus within this family should be established to accommodate it.