Wilfried Schonborn

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.

Adaptive polymorphism in soil-inhabiting testate amoebae (Rhizopoda): its importance for delimitation and evolution of asexual species

Summary The varieties of the soil-inhabiting testate species Trinema complanatum Penard, 1890, and Euglypha laevis Perty, 1849 (including Euglypha rotunda Wailes & Penard, 1911) are shown to be adaptive morphs of an extreme polymorphism. The morphs represent adaptations in the (upper) litter and the underlying humus horizon in raw humus soils. The morphs of the litter horizon also occur in Sphagnum where the microhabitat structure is similar to that of litter. In clonal cultures the features of the morphs remain relatively constant. Nevertheless, over the course of several months other morphs occur. The morphs could be transformed into each other by selection. In nature these species have a high ability to manoeuvre ecologically. With the help of known genetic mechanisms this paper proposes a genetic interpretation of the polymorphism of asexual protozoan species, which simultaneously gives understanding of the delimitation and evolution of asexual species.

Population dynamics and production biology of testate amoebae (Rhizopoda, Testacea) in raw humus of two coniferous forest soils

Summary In raw humus (two spruce forest soils) near the village of Plothen (GDR, Thuringia) the population dynamics and annual production (including its parameters) of Testacea were investigated. Thirty-two testacean species were found. The annual production of individuals in the needle layer (litter layer) was 19 and 11 times higher respectively than in the underlying humus layer. The produced biomass in both layers was less different, caused by the large species in the humus layer. The average biomass production amounted to 650 kJ · m −2 · yr −1 . The relationship between habitat structure, adaptation and production biology was described. Length of generation time and rate of mortality showed an inverse relationship independent of the height of production. The generation times are shorter in the humus layer than in the needle layer; but the rate of mortality increases from needle layer to underlying layer. In the more extreme site 2, production and turnover were higher than in site 1. The curve of resting stages oscillated throughout the year and often accounted for 50 % of the populations. The decomposition of empty shells in raw humus was essentially slower than in mull and moder. The half-time of decomposition amounted to 51 d. The occurrence of accompanied microfauna (zooflagellates, amoebae, ciliates, rotifers, and nematodes) was noticed. Interpretation of the needle preference of ciliates was given. Some comparisons between testacean production and its parameters in raw humus and mull have been carried out. The average consumption of Testacea in raw humus amounted to 1420 kJ · m −2 · yr −1 and reached nearly the amount of consumption of all arthropods or “worms” in beech forest soils.

Comparative Studies on the Production Biology of Protozoan Communities in Freshwater and Soil Ecosystems

Abstract The hitherto known values of annual production of gymnamoebae, testate amoebae, and ciliates are presented comparatively and analysed. Advantages and disadvantages of the methods applied depend largely on the dynamics of populations. The P/B-quotient in protozoan communities is determined not only by the absolute amount of production but also by the production pattern and the production-mortality-abundance (PMA)-type. Both ciliates in bodies of water and Testacea in soils have high and comparable production values. Testacea and loricate ciliates in rivers showed a relatively low production. The 4 PMA-types are presented again, and general laws on the relationships between generation times, number of generations, rates of mortality, distribution of mortality in course of the population growth and production have been derived. The mortality in most protozoan communities averages 5-10 %/d. Generation times, consumption, respiration, and egestion are influenced synchronously by external and population dynamic factors with reference in each case to the sizes of the energy budget. Details of the energy budget are analysed comparatively. As far as secondary production is concerned, protozoa hold second place behind bacteria in the element cycle of many ecosystems. Among the invertebrates the protozoa have a major part in the element cycle, amounting to 50 % and more. It reaches 5-50 % of that of bacteria. In soils this proportion is shifted in favour of bacteria. The predation effect of protozoa on bacteria and the function in the energy flow are analysed. In benthic and terrestrial habitats short (circuited) cycles seem to occur more frequently. Productivity, habitat sutructure, and phylogenetic adaptation are correlated.

Biometric Studies on Species, Races, Ecophenotypes and Individual Variations of Soil-inhabiting Testacea (Protozoa, Rhizopoda), Including Trigonopyxis minuta nspand Corythion asperulum nsp.

Summary In a raw humus soil, (GDR, Thuringia) the testacean genera of Trigonopyxis, Assulina, Valkanovia and Corythion were investigated biometricallyThe analyses referred essentially to measurements of shells and quantitative features of the shape of shells. With the help of significance tests and the analysis of size frequency distributions, two new species, Trigonopyxis minuta and Corythion asperulum were discovered as well as the presence of Assulina collaris Kufferath, which until now had been overlooked(Corythion asperulum is also qualitatively characterized by fine spines.) Comparisons of biometric analyses between geographically separated populations led to distinction of geographic races in Trigonopyxis arcula and Corythion dubium (statistically significant differences). In addition to geographic races ecological variations were also examinedSoil-inhabiting populations of Euglypha ciliata have shorter spines than lake-inhabiting individualsThis variation, however, is reversible (modification) and has an adaptive value: ecophenotypesFurthermore, the analyses showed that there are size-monomorphic and size-polymorphic TestaceaBetween these extremes exist many transitionsThe biometric method, however, permits separation of new species or geographic races only within monomorphic genera. It could be shown that even slight genetic shifts within the range of a monomorphic character can lead to a new shell type (at the height of aperture of Trinema lineare). Directives on analyses and classifications of quantitative variations are given (3.4)Individual variations are: insignificant differences, all forms of feature spectrum of polymorphic species and also quantitative and qualitative aberrations found only a few timesInstead of naming these variations it may be better to put together a phenospectrum of the population examined (Fig6C). The genetic causes of the various variations are discussed.

Testate amoebae from a Cretaceous forest floor microbiocoenosis of France

ABSTRACT. Amber‐preserved shells of testate amoebae often provide as many diagnostic features as the tests of modern taxa. Most of these well‐preserved microfossils are morphologically assignable to modern species indicating either evolutionary stasis or convergent evolution. Here we describe two Lower Cretaceous testate amoebae that are clearly distinguishable from modern species. Centropyxis perforata n. sp. and Leptochlamys galippei n. sp. possessed perforate shells that were previously unknown in these genera. They are preserved in highly fossiliferous amber pieces from the Upper Albian (ca. 100 million years old) of Archingeay/Les Nouillers (Charente‐Maritime, southwestern France). Syninclusions of soil and litter dwelling arthropods and microorganisms indicate a limnetic‐terrestrial microhabitat at the floor of a coastal conifer forest.

Tracking the autochthonous carbon transfer in stream biofilm food webs

Food webs in the rhithral zone rely mainly on allochthonous carbon from the riparian vegetation. However, autochthonous carbon might be more important in open canopy streams. In streams, most of the microbial activity occurs in biofilms, associated with the streambed. We followed the autochthonous carbon transfer toward bacteria and grazing protozoa within a stream biofilm food web. Biofilms that developed in a second-order stream (Thuringia, Germany) were incubated in flow channels under climate-controlled conditions. Six-week-old biofilms received either ¹³C- or ¹²C-labeled CO₂, and uptake into phospholipid fatty acids was followed. The dissolved inorganic carbon of the flow channel water became immediately labeled. In biofilms grown under 8-h light/16-h dark conditions, more than 50% of the labeled carbon was incorporated in biofilm algae, mainly filamentous cyanobacteria, pennate diatoms, and nonfilamentous green algae. A mean of 29% of the labeled carbon reached protozoan grazer. The testate amoeba Pseudodifflugia horrida was highly abundant in biofilms and seemed to be the most important grazer on biofilm bacteria and algae. Hence, stream biofilms dominated by cyanobacteria and algae seem to play an important role in the uptake of CO₂ and transfer of autochthonous carbon through the microbial food web.

Periphyton and sphagnicolous protists of dystrophic bog lakes (Brandenburg, Germany): II. Characteristic species and trophy of the lakes

Abstract Glass-slides were exposed in four different bog lakes located in great forest areas in Northern Germany, about 100 km north of Berlin, in order to examine the protist community of these dystrophic, acid lakes. Species composition and succession of the periphyton were studied during one year. The four investigated bog lakes exhibit similar species compositions, most of the species were present in each of the four lakes. The periphyton was composed of a great variety of protist species. Specimens of all major flagellated protists and of most of the ciliate taxa were found on the slides. Many of these species are ubiquitous. Some species, however, like the flagellates Spongomonas sacculus, Rhipidodendron huxleyi, Cyathobodo sp., and Pseudodendromonas vlkii as well as the ciliates Ophrydium hyalinum, Leptopharynx costatus, Uroleptus caudatus , and Platyophrya sphagni are found more frequently in acid waters. A regular and common occurrence of these species partly characterizes the acid Sphagnum bogs. Besides that, common species like Bodo spp., Cryptomonas spp., Goniomonas truncata, Chilodonella uncinata, Vorticella sp., and Cyrtolophosis mucicola are represented in the periphyton. Examinations of the testate amoebae in the Sphagnum mats show a very different species composition compared to earlier studies. The investigated bog lakes revealed mesotrophic conditions. In the upper regions of the Sphagnum mats and in the center of the larger bog lakes, oligotrophic conditions still prevail. The lower regions of the Sphagnum mat and the smaller lakes, however, are influenced by the partly degradation of plants and the run-off water from surrounding land. In comparison to earlier studies, the species composition indicates a beginning eutrophication of the bog lakes. A direct anthropogenic impact can be excluded.

Observations on the morphology and ecology of the soil-inhabiting testate Amoeba Schoenbornia humicola (Schönborn, 1964) Decloitre, 1964 (protozoa, rhizopoda)

Summary Six geographically widely separated populations of Schoenbornia humicola were investigated. The shell, analyzed by scanning electron microscopy and silver staining, consists of shell platelets (idiosomes) of euglyphids, angular quartz, and amorphous siliceous elements. The foreign idiosomes are picked up from the soil and incorporated. They are not obtained by predation of other testaceans. A comparative biometric analysis of the shells yielded a statistically significant difference in the length of one population. This may be an indication for geographic races in S. humicola . The protoplasm shows a clear zonation as in euglyphids and Nebela species. The nucleus is spherical and has a central nucleolus. The pseudopodium is a very long endolobopodium, used to crawl (as “crawling-pseudopodium”) and to feed (as “furcate-pseudopodium”). Extension of the pseudopodium is very rare. Resting stages are cysts and precysts (Kapselstadien). The more frequent resting stages are precysts. During very dry periods a bubble can form between the pseudostome plug and the retracted cytoplasm. On the basis of these observations the genus Schoenbornia can be classified within the family Hyalosphenudae Schulze , subfamily Nebelinae Cash & Hopkinson . Schoenbornia humicola has certain feeding phases. During optimal periods the cell collects humus particles and stores them just outside the pseudostome as a so-called “food-bundle”. Humus particles from the food-bundle are continually taken into the cytoplasm; this can take place also during suboptimal periods. This feeding strategy is interpreted as an adaptation to the often quickly changing environmental conditions in the soil. Schoenbornia humicola mainly inhabits the humus layers of the soil and is essentially confined to acid humus. It is an indicator species for moder and raw humus. Its percentage of the entire testacean community amounted maximally to 39.5 %. Schoenbornia humicola is slightly stimulated by fertilizers and depressed by lime, if liming causes an excessive increase of the pH of its habitat.

Phagotrophic Protist Diversity in the Groundwater of a Karstified Aquifer – Morphological and Molecular Analysis

To clarify the structure of microbial food webs in groundwater, knowledge about the protist diversity and feeding strategies is essential. We applied cultivation‐dependent approaches and molecular methods for further understanding of protist diversity in groundwater. Groundwater was sampled from a karstified aquifer located in the Thuringian Basin (Thuringia, Germany). Cultivable protist abundance estimated up to 8,000 cells/L. Eleven flagellates, 10 naked amoebae, and one ciliate morpho‐species were detected in groundwater enrichment cultures. Most of the flagellates morpho‐species, typically < 10 μm, were sessile or free swimming suspension feeders, e.g., Spumella spp., Monosiga spp., and mobile, surface‐associated forms that grasp biofilms, e.g., Bodo spp. Naked amoebae, typically < 35 μm, that grasp biofilms were represented by, e.g., Vahlkampfia spp., Vannella spp., and Hartmanella spp. The largest fraction of the 18S rRNA gene sequences was affiliated with Spumella‐like Stramenopiles. Besides, also sequences affiliated with fungi and metazoan grazers were detected in clone libraries of the groundwater. We hypothesize that small sized protist species take refuge in the structured surface of the fractures and fissures of the karstified aquifer and mainly feed on biofilm‐associated or suspended bacteria.