Wilhelm Foissner

Basic light and scanning electron microscopic methods for taxonomic studies of ciliated protozoa

The following methods for taxonomic studies of ciliated protozoa are described in detail: live observation, supravital staining with methyl green-pyronin, dry silver nitrate impregnation, wet silver nitrate impregnation, silver carbonate impregnation, protargol impregnation (three procedures), and scanning electron microscopy. Familiarity with these methods (or modifications) is an absolute prerequisite for successful taxonomic work. No staining method is equally appropriate to all kinds of ciliates. A table is provided which indicates those procedures which work best for certain groups of ciliates. A second table relates to the structures revealed by the procedures. Good descriptions usually demand at least live observation, silver nitrate and protargol or silver carbonate impregnation. Some instructions are provided for distinguishing mono- and dikinetids as well as ciliated and non-ciliated basal bodies in silvered ciliates. The brilliancy of the silver preparations has unfortunately recently tempted some taxonomists to neglect live observation. However, many important species characters cannot be seen or are changed in silvered specimens. I thus consider all species descriptions based exclusively on silver slides as incomplete and of doubtful value for both α-taxonomists and ecologists. Especially the latter are usually not trained to correlate the silvered structures with the live appearance of the cell.

Protist diversity and distribution: some basic considerations

This essay discusses protist species number and geographic distribution, both heavily influenced by undersampling and human introductions. The features of the ubiquity model and the moderate endemicity model are compared. I recognize five main flaws of the ubiquity model, viz., the ignorance of the extraordinary possibilities protists have to speciate due to their short generation time and the likelihood that many persisted over geological time scales; that all protist species have high abundances; that their small size is a main reason for global distribution; the ignorance of human introductions; and the rejection of literature evidence on the occurrence of flagship species with restricted distribution in a wide variety of protists. Thus, the data available support the moderate endemicity model which proposes about 300,000 extant, free-living protist species, of which one third might have a restricted distribution, i.e., is not cosmopolitan in spite of suitable habitats. To sum up, the distribution of protists, flowering plants, and larger animals has much in common, but protists usually have wider ranges and thus a higher proportion of cosmopolites. Future research should reconcile morphologic, genetic, and ecological species concepts because this is crucial for determining the number of protist species. Further, greatly intensified research is required on morphospecies in heterotrophic protists because their diversity has never been investigated in large areas of the earth.

Diversity and geographic distribution of ciliates (Protista: Ciliophora)

About 4,500 free-living ciliate morphospecies have been described, applying an average synonymy rate of 20%. We estimate that 83–89% of the ciliate diversity is still undescribed, using the following probabilities: detailed habitat studies suggest that the described number of morphospecies must be doubled: 4,500 → 9,000; this figure has to be increased by about 50% due to species with similar interphase morphology but different resting cysts: 9,000 → 13,500; the genetic and molecular data suggest that this value must be doubled or trebled: 13,500 → 27,000 to 40,000 free-living, biological ciliate species. The knowledge on geographic distribution of ciliates heavily depends on flagship species and statistical analyses because reliable faunistic studies are rare and molecular data are still in its infancy. We present a list of 52 ciliate flagship species as a testable hypothesis, i.e., the hypothesis of restricted distribution of certain ciliate species must be refused when a considerable number of them is found in all or most biogeographic regions. Flagship species and statistical analyses consistently show Gondwanan and Laurasian ciliate communities, suggesting that the split of Pangaea deeply influenced ciliate distribution and rare species play a key role in geographic differentiation. However, there is also substantial evidence for continental, regional, and local endemism of free-living ciliates. The molecular studies usually show a high level of genetic diversity underlying ciliate morphospecies, suggesting that morphologic and molecular evolution may be decoupled in many ciliate species. Molecular studies on ciliate biogeography are at variance, possibly because most are still focusing on single molecular markers. In sum, the data indicate that ciliate biogeography is similar to that of plants and animals, but with an increased proportion of cosmopolites, favouring the moderate endemicity model.

An updated compilation of world soil ciliates (Protozoa, Ciliophora), with ecological notes, new records, and descriptions of new species

Summary This review compiles and analyses the taxonomic and biogeographical information available on soil ciliates. Key literature (257 references) is tabulated for each species. Furthermore, about 500 new records are reported from hundreds of samples collected world-wide, and four new species are described from Kenyan soils, including the new genus Apobryophyllum; Metopus ovalis Kahl, 1927 is redescribed. 643 ciliate species were originally described or reliably recorded from about 1000 soil samples world-wide, 49 (7.6%) of them were later recognized as junior synonyms, and 78 (13.2%) have been poorly described, leaving a total of 516 well-known species. However, the studied samples contained about 700 new species, most of which (about 500) have not yet been described. Thus, the total number of soil ciliates amounts to at least 1000 species. The overwhelming portion of soil ciliates belongs to three systematic assemblages, viz. the hypotrichs (39%), gymnostomatids (26%) and colpodids (13%) if the undescribed species are taken into account. Most soil ciliates feed on bacteria (39%) or are predatory (34%) or omnivorous (20%). Some are strictly mycophagous and highly characteristic for terrestrial habitats; and a few (mainly metopids) are anaerobic. Only about one fourth of the soil ciliate species has been reliably reported from freshwater habitats and from more than three out of five main biogeographical regions, indicating a high specificity of the soil ciliate biota and a limited distribution of at least some species. This is supported by the observation that some very conspicuous species, such as Krassniggia auxiliaris and Bresslauides discoideus , have so far been found only in Gondwanan, respectively, Laurasian soils.

Phylogeny of the Stichotrichia (Ciliophora; Spirotrichea) Reconstructed with Nuclear Small Subunit rRNA Gene Sequences: Discrepancies and Accordances with Morphological Data

ABSTRACT. The Stichotrichia, known as an especially various and taxonomically difficult group, were intensely studied with morphological, morphogenetic, and molecular methods in the last years. Nevertheless, a consistent classification is lacking and several important questions about the phylogenetic relationships within this group remain unsolved. In order to gain deeper insights into these relationships, the nuclear small subunit rRNA genes of seven species of the Stichotrichia, representatives of the families Oxytrichidae, Amphisiellidae, and Pseudourostylidae, were phylogenetically analysed. Although our analyses resulted in a poor resolution of the phylogenetic relationships, some conclusions can be drawn. Firstly, following the current classification systems the Oxytrichidae as well as their subfamilies seem to be paraphyletic and the basic 18 FVT cirral pattern has been modified several times independently. Secondly, sequence analyses of several Oxytricha species resulted in a high molecular diversity, which does not support monophyly of this genus. Thirdly, several families of the order Urostylida (Urostylidae, Pseudokeronopsidae, and Pseudourostylidae) also do not form monophyletic groups.

Cladistic relationships and generic characterization of oxytrichid hypotrichs (protozoa, ciliophora)

Summary The relationships of 13 common oxytrichid genera were analysed using cladistic methods (Hennig, PAUP). Twenty-three characters in four groups were selected, viz. the morphology of the oral apparatus (three characters), infraciliature of ventral and dorsal side (ten characters), cortical features (two characters), and ontogenetic particulars (eight characters). All characters and character states are described and discussed using published and original data. Half of the characters originated independently in several genera at least twice, making it very difficult to follow oxytrichid evolution. The autapomorphies of the family Oxytrichidae are 18 characteristically arranged fronto-ventral-transverse cirri and the fragmentation of at least one dorsal kinety. The cladograms show two major branches, termed subfamily Oxytrichinae Jankowski and subfamily Stylonychinae n. subfam. The Oxytrichinae have a unique synapomorphy, viz. the participation of cirrus V/3 in primordia formation. This subfamily contains the genera Cyrtohymena, Gonostomum, Notohymena, Onychodromopsis, Oxythcha, Tachysoma, Urosoma, Urosomoida and, very likely, Australocirrus, Parurosoma and Pseudostrombidium . The Stylonychinae have three synapomorphies, viz. the rigid body, an oral apparatus of more than 40% of body length, and the lack of cortical granules. This subfamily comprises Coniculostomum, Histriculus, Steinia, Sterkiella, Stylonychia and, very likely, Parastylonychia and Pleurotricha . The family Oxytrichidae, its subfamilies, and the genera included are characterized and keyed. An unambiguous terminology is established for oxytrichid hypotrichs, and synonymy and nomenclature of genera are discussed.

The Fine Structure of Fuscheria terricolaBerger et al., 1983 and a Proposed New Classification of the Subclass Haptoria Corliss, 1974 (Ciliophora, Litostomatea)

Summary The general fine structure of Fuscheria terricola Berger, Foissner and Adam , 1983 is very similar to that of other haptorid ciliates. However, a tela corticalis and parasomal sacs are absent. Fuscheria terricola has doughnutshaped mucocysts and unique nail-shaped toxicysts. Their nail-like appearance is due to a conspicuous posterior thickening of a fibro-granular material surrounding the rod-shaped center which is very similar to the pexicysts of Acropisthium and Didinium. The somatic kinetids are monokinetids with the classical haptorian fibrillar associates. In addition, the upper 4 to 7 somatic kinetids in each kinety possess nematodesmal bundles. At the base of the oral cone there is a circumoral kinety composed of typical haptorian dikinetids. Their nematodesmal bundles and those from the upper somatic kinetids form a highly characteristic irregular rhabdos. Acropisthium and Actinorhabdos show the same oral organization as Fuscheria. Hence, these 3 genera are united in the new family Acropisthiidae nov. fam. The rhabdos of most members of the subclass Haptoria is built up of 3 microtubular components: a) the transverse microtubular ribbons which originate from the nonciliated kinetosomes of oral dikinetids or from ciliated or nonciliated oralized somatic kinetids and turn to the center of the oral bulge, where they plunge inwards to support the cytopharynx; b) the nematodesmal bundles which form an “outer rhabdos”; and c) the vertically oriented bulge microtubules which are distributed rather regularly in the marginal area of the oral bulge and grouped in nematodesmata-like bundles in the lower oral region, where they form a more or less pronounced “inner rhabdos”. Exceptions from this pattern are the Cyclotrichina which lack nematodesmata and the Archistomatida which lack bulge microtubules, probably because of the absence of toxicysts. The term “oralized somatic kinetids” is suggested for such kinetids which lie within somatic kineties, but bear nematodesmal bundles contributing to the rhabdos. Such kinetids may be monokinetids or dikinetids; they may or may not be associated with normal haptorid oral dikinetids; and they may be ciliated or nonciliated. The different kinds of kinetids which contribute to the rhabdos and the dorsal brush (presence/absence) are the clue characters for a revised classification of the Haptoria. The following new higher taxa are erected: Enchelyina nov. subord. (with nonciliated oralized somatic monokinetids), Acropisthiina nov. subord. (with oral dikinetids and ciliated oralized somatic monokinetids), Spathidiida nov. ord. (with oral dikinetids only), Litonotina nov. subord. (right oral kinety associated with somatic monokinetids), Pseudoholophryida nov. ord. and Pseudoholophryina nov. subord. (dorsal brush absent or highly aberrant), Helicoprorodontina nov. subord. (oralized somatic dikinetids, dorsal brush probably absent).

A Fossilized Microcenosis In Triassic Amber

ABSTRACT Detailed data on bacterial and protistan microfossils are presented from a 0.003 mm3 piece of Triassic amber (Schlierseerit, Upper Triassic period, 220‐230 million years old). This microcenosis, which actually existed as such within a very small, probably semiaquatic habitat, included the remains of about two bacteria species, four fungi (Palaeodikaryomyces baueri, Pithomyces‐like conidia, capillitium‐like hyphae, yeast cells) two euglenoids, two chlamydomonas (Chlamydomonas sp., Chloromonas sp.), two coccal green microalgae (Chlorella sp., Choricystis‐like cells), one zooflagellate, three testate amoebae (Centropyxis aculeata var. oblonga‐like, Cyclopyxis eurystoma‐like, Hyalosphenia baueri n. sp.), seven ciliates (Pseudoplaryophrya nana‐like, Mykophagophrys terricola‐like, Cyrtolophosis mucicola‐like, Paracondylostoma sp., Bryometopus triquetrus‐like. Tetrahymena rostrata‐like, Paramecium triassicum n. sp.) the microfossils correspond to or diverge from extant species only slightly.

Endemic ciliates (Protozoa, Ciliophora) from tank bromeliads (Bromeliaceae): a combined morphological, molecular, and ecological study

Bromeliads are mainly epiphytic rosette plants occurring only in Central and South America. They collect rain water and particulate materials in tanks (cisterns) formed by the coalescing leaf axils. These tanks form an extensive, highly compartmentalized water and humus body above the ground and are inhabited by many ordinary and endemic organisms. We discovered at least 10 new ciliate species in the tanks of about 15 bromelian species from the Dominican Republic, Ecuador, and Brazil. Since there are 2000–3000 bromelian species with very different lifestyles, they are likely to contain hundreds of novel ciliate species. Two of the new species described here are real “flagships”, that is, they have such a large size that they would have been found in Europe, if they were there. Consequently, these species must have a restricted geographical distribution, disproving the old hypothesis that microscopic organisms are cosmopolitan. Also the smaller ciliates described here represent new genera and families, arguing for a long-lasting, independent evolution driven by ecological constraints and spatial isolation. Almost half of the new species can switch from bacteriophagous, microstome morphs to a predatory, macrostome lifestyle, likely due to the strong competition in these peculiar habitats. The high morphological and ecological diversity of tank bromeliad ciliates is only partially recovered by small-subunit (18S) ribosomal RNA (rRNA) gene sequences.

Morphologic and Biometric Characterization of Twenty-four Soil Testate Amoebae (Protozoa, Rhizopoda)

Summary 24 soil dwelling testate amoebae, belonging to 34 populations, are described and biometrically characterized. An “ideal individual” for each of the investigated species is constructed by means of the biometric data. Species separation in the Nebela tincta-parvula-bohemica-collaris group is discussed in detail. In Plagiopyxis declivis, idiosomes of euglyphids occur between the xenosomes of the shell. The analysis of the coefficients of variation of all species shows the lowest variation for the length of the shell and the highest values for its aperture. In general, the Testaceafilosa and shells composed of idiosomes have wider ranges of variation as compared with the Testacealobosa and species covered with xenosomes. This indicates that the Testaceafilosa evolve faster or are evolutionary younger than the Testacealobosa. Pseudodifflugia fascicularis, Euglypha strigosa and Difflugia lucida have only 1 central nucleolus, which contrasts with earlier data from literature. Significant differences between populations of the same species were found and indicate the existence of several geographical races which differ only in their size.