José L. Olmo

Biodiversity of terrestrial protozoa appears homogeneous across local and global spatial scales.

Free-living microbes are by far the most abundant group of organisms in the biosphere, yet estimates of global species richness remain nebulous, and there is no consensus regarding the likely geographical distribution of species. Both uncertainties are addressed by the suggestion that the vast abundance of microbes may drive their ubiquitous random dispersal; for this would also make it likely that global species richness is relatively low. Here we test the idea of ubiquitous dispersal of testate amoebae and ciliates living in soil. We analysed their abundance and species richness in 150 soil samples collected from the one-hectare grassland site at Sourhope in Scotland, and in comparable published data from 1500 soil samples collected worldwide. Following taxonomic revision and removal of synonyms, there remained a total of 186 taxa (91 testate and 95 ciliate) recorded from both Sourhope and other places in the world. A fundamental pattern of random spatial distribution of species was revealed in species that are relatively rare. This probably arises from random dispersal, for when localised population growth occurs, the distributions become aggregated, as in virtually all metazoan species. We find no evidence for geographically-restricted protozoan morphospecies at spatial scales of 4 m2, 10,000 m2, or worldwide. Species that are locally rare or abundant are similarly rare or abundant on a global scale. Approximately one third of the global diversity of soil protozoa was found at the one-hectare grassland site in Scotland, but this is a minimum figure, for recorded species richness is proportional to sampling effort, as shown here.

Ciliated protozoa from a volcanic crater-lake in Victoria, Australia

We have investigated the ciliated protozoa living in the crater-lake of an extinct volcano in Australia. Our principal objective was to discover if such a habitat— geographically distant and isolated from Europe (the latter having provided most of the diversity on which ciliate taxonomy is based)— could yield species that were unusual, and perhaps new to science. Numerous samples were taken from the superficial layer of lake sediment, and examined fresh in the laboratory. Thereafter, the samples were manipulated to encourage growth of rare and cryptic ciliate species. Eighty-five species of ciliated protozoa were identified. None of these was new, all having been found previously in fresh-or brackish water, sea water, or soil. All, apart from one (Oxytricha salmastra), are already known from Europe. In order to test our ability to discover new ciliate species, we examined a variety of water samples from other lakes, including those known to harbour endemic algae. One new ciliate species (Lembadion curvatum) was discovered in a lake in Western Tasmania. We conclude that the ciliate fauna of Australia is remarkably similar to that in Europe and other parts of the world. This is supported by the example of those ‘endemic’ ciliate species described in the literature which have, in response to additional sampling, been found elsewhere in the world.

Cristigera pleuronemoides Roux, 1901: a cosmopolitan ciliate that embraces at least three nominal species

Summary We have investigated the morphology of the ciliate Cristigera pleuronemoides from life, and we describe the pattern of its infraciliature using silver-impregnation techniques. It is now apparent that C. pleuronemoides embraces four nominal species described in the international literature. We conclude that three of these are synonyms and that this ciliate (like most ciliate species) probably has a cosmopolitan distribution.

Redescription of Psilotricha acuminata Stein, 1859 and Revisions of the Genera Psilotricha and Urospinula (Ciliophora, Hypotrichida)

Abstract Psilotricha acuminata was described by Stein in 1859 as the type species of the ciliate genus Psilotricha Stein, 1859. The ciliate has rarely been found since, and its infraciliature has never been described with the aid of silver-impregnation techniques. We have found P. acuminata Stein, 1859 in soil samples from upland grassland in Scotland (U.K.). Living and healthy organisms of P. acuminata are oblong in outline, and dorso-ventrally compressed. They closely resemble ciliates of the genus Euplotes. The main morphological features used for identification of P. acuminata are the very long and sparse cirri, and the two macronuclei. When the ciliate crawls, the cirri appear stiff and directed backwards. Specimens observed from the ventral side have a protruding anterior end, a rounded or acuminate posterior pole, and a “beak-like” projection to the left side of the posterior end. The ciliate shares characters with the Euplotidae (body shape and reduced ciliature) and with the Oxytrichidae (marginal rows, macronuclei, reduced number of transverse cirri). Because the arrangement of the silver-impregnated infraciliature was unknown, and as the only description of the ciliate was that of Stein (1859a, b), the genus Psilotricha became confused with other hypotrich genera, especially Urospinula Corliss, 1960. Here we provide a full redescription of P. acuminata based on living and silver-impregnated specimens, and a revision of the genera Psilotricha Stein, 1859 and Urospinula Corliss, 1960. We resurrect the genus Urospinula, and give an emended diagnosis for both genera. The species now included within the genus Psilotricha are P. acuminata Stein, 1859 (type species); Psilotricha viridis (Penard, 1922) Kahl, 1932; and Psilotricha geleii (Gelei, 1954) Stiller, 1974. Psilotricha viridis sensu Kahl, 1932 and Psilotricha dragescoi Grolière, 1975 are considered incertae sedis.

New records of the ectoparasitic flagellate Colpodella gonderi on non-Colpoda ciliates

Colpodella gonderi is the only ectoparasitic flagellate of ciliated protozoa described thus far. This investigation reveals new records of C. gonderi retrieved from soil samples in southern Scotland, UK. Of fourteen ciliates species identified in one single occasion, three of them, Colpoda steinii, Pseudoplatyophrya nana and Grossglockneria acuta, were infested with the parasite. These results provide further evidence that C. gonderi is not host-specific of the ciliate genus Colpoda.

Morphology and morphogenesis of Uroleptus lepisma (Wenzel, 1953) Foissner, 1998 (Ciliophora, Hypotrichida)

Summary Uroleptus is a difficult genus comprising more than 30 species. One of these species is Uroleptus lepisma. The morphology and morphogenesis of one Spanish and one Scottish population of U. lepisma were investigated using living and protargol-impregnated specimens. The morphogenesis of U. lepisma shows two unique characteristics within the family Urostylidae: 1) the parental adorai zone of membranelies is maintained during the whole morphogenesis; 2) the majority of cirri from the midventral row are retained until after cytokinesis.

Cinetozona pyriformis n. g., n. sp.: a Relative of the Ciliate Genera Urozona and Cinetochilum (Ciliophora, Scuticociliatida)

Cinetozona pyriformis n. g., n. sp. is a very small scuticociliate recently found in a freshwater artificial pond in Madrid, Spain. This new ciliate is here described using silver impregnation techniques. C. pyriformis bears a girdle of cilia near the equator ot the cell, similar to the genus Urozona Schewiakoff, 1889, while the oral structures resemble those in the genus Cinetochilum Perty, 1852. The ciliates systematic position is discussed, and its inclusion in the family Cinetochilidae is proposed.

New aspects of the morphology and morphogenesis of Gonostomum strenuaEngelmann, 1862 (ciliophora, hypotrichida)

Summary The morphology and morphogenesis of a population of the hypotrichous ciliate Gonostomum strenua, found in moss samples from emergent stones collected in the Guadarrama River (Central Spain) is described. This population shows slight variations in morphology compared to the Chinese population studied by Song , (1990). The main differences between the European and Asian population appear in the first stages of morphogenesis. New data on infra-ciliature and cysts are also shown.