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.     

Trichomonas gallinae in wintering Common Wood Pigeons Columba palumbus in Spain

We studied the prevalence and potential subclinical effects of infestation by Trichomonas gallinae in 91 hunter-harvested Common Wood Pigeons Columba palumbus from northern ( n  = 30) and southern ( n  = 61) Spain during the winter period. All animals were measured, sexed, aged, necropsied and their organs were weighed. Infestation with T. gallinae was diagnosed using three different methods: direct inspection for the presence of lesions, direct microscopic observation and culture. Of the sampled birds, 34.2% were positive for the presence of T. gallinae . Prevalence was significantly higher in adult Wood Pigeons than in the juvenile group, and prevalence was significantly lower in birds sampled from the north. No significant differences in prevalence were found between males and females. Culture was significantly more sensitive than the other methods of diagnosis. Parasitized birds were in poorer body condition, as revealed by their lower body mass and fat reserves. No significant variation could be detected in heart or spleen weight between parasitized and healthy birds. However, juvenile Wood Pigeons in which T. gallinae was detected had a significantly larger bursa of Fabricius. Variations in the prevalence of T. gallinae in Wood Pigeons could be related to migration as well as increased exposure through shared feed and water where these are artificially provided. We also discuss the potential effect of T. gallinae on body condition and the eventual risk for endangered predators through increased exposure to infected prey.     

Comparative Ultrastructure and Physiology of Chromatophores, with Emphasis on Changes Associated with Intracellular Transport

Recent advances in our understanding of the mechanism of intracellulartransport in unicellular chromatophores are reviewed. Emphasisis placed on the possible role(s) of the three major cytoskeletalcomponents microtubules, intermediate filaments, and actin filaments.A comparative analysis of different chromatophore types suggeststhat these cytoskeletal fiber systems may play different roles,or at least seem to be involved to a varying degree, in intracellularpigment translocation. Ultrastructure, transport characteristics,and responses to pharmacological agents of a wide variety ofvertebrate and invertebrate chromatophores do show sufficientvariation to make one consider the possibility that the underlyingmechanisms also vary to some extent. It is hoped that the increaseduse of new methodological approaches, including microinjectionof single cells and the development of reactivatable cell models,will greatly aid us in our exploration of the physical-chemicalbasis of chromatophore motility.     

The Effects of Winter Exposure to Acid Soil Conditions on the Subsequent Survival and Growth of Herbaceous, Forest Perennials: a Preliminary Investigation

For many plant species, growth is limited in acid soils, whichare characterized by high levels of potentially-toxic elementsand low nutrient availability. Although plant-soil interactionsare traditionally studied during the growing season, the highestconcentrations of toxic elements in the soil may occur duringthe winter months. The present study investigated the effectsof a 3-month exposure to either an acid or a reference soil,at temperatures fluctuating around freezing point, on subsequentsurvival and growth of eight herbs (Brachypodium sylvaticum,Carex pilulifera, Geum urbanum, Luzula pilosa, Mycelis muralis,Silene dioica, Stellaria nemorum, Veronica officinalis).Theplants were exposed to ambient weather conditions from Decemberto March, after which they were replanted in fresh referencesoil and transferred to a glasshouse. Their biomass was measured5 weeks later. The plant species differed in their responsesto the soils, in a manner reflecting their natural field distributions.All plants of the most acid-tolerant species survived in bothtreatments, whereas the more sensitive species showed lowersurvival rates after growth in the acid than in the referencesoil. Similar results were found for the regrowth:C. piluliferaandL.pilosa, the most acid-tolerant species, were unaffected by thesoil treatments (ratios between biomass in acid compared toreference soils were 0.8 and 1.1, respectively), whereasG. urbanum,M. muralis, S. nemorumandV. officinaliswere negatively affected(ratios 0.3–0.5). Effects on above- and below-ground biomasswere broadly similar. This preliminary evidence indicates thatsoil chemistry during the winter can be important for both survivaland growth during the vegetative period that follows.Copyright1998 Annals of Botany Company. Acids soils, toxicity, vascular plants, winter exposure.     

Circadian rhythms in the blowfly, Phormia terraenovae: control of phase within the range of entrainment

ABSTRACT Locomotor activity of individual blowflies, Phormia (= Protophormia) terraenovae R.D. (Diptera, Calliphoridae) was recorded by means of running wheels. A few days after emergence, adult flies were placed in the wheels and exposed to at least two of four light-dark cycles (LD) differing in cycle duration T (LD 11:11, 12:12, 13:13 and 14:14 h). The intensity of illumination was 400 lux in L and 2 lux in D. From the actograms, phase-angle differences were read off between onset of activity and light-on (ψ/_onset), and between end of activity and light-off (ψend)- Within the range of entrainment, ψ changed systematically from negative values in T =22 h to positive values in T =28 h: the mean change in ψ per hour change in T , expressed in degree of the full circadian cycles, was 20^o. Standard deviations of ψ around its mean were computed for ten-cycle intervals; in ψ_onset and in ψ_end standard deviation was minimal when 4ψ was close to zero, and increased steadily with increasing negative or positive ψ -values.     

A Cover of Glass: First Report of Biomineralized Silicon in a Ciliate, Maryna umbrellata (Ciliophora: Colpodea)

ABSTRACT. Using hydrofluoric acid, scanning electron microscope-assisted X-ray microanalysis, and energy-filtered transmission electron microscopy, we present the first definite proof of biomineralized silicon [(SiO₂)] _n in a ciliophoran protist, Maryna umbrellata , a common inhabitant of ephemeral pools. In the trophic specimen, the amorphic silicon (glass) granules are accumulated in the anterior half of the body. When entering the dormant stage, most glass granules are excreted to form the surface cover of the globular resting cyst. Most likely, the silicon granules are synthesized in vesicles of the Golgi apparatus. First, nanospheres with a size of 20–40 nm are formed in a fibrous matrix; they grow to be spongious complexes, eventually becoming amorphous glass granules with an average size of 819 nm × 630 nm. In the transmission electron microscope, the silicon granules show the characteristic fracture pattern of glass known from many other silicon-bearing organisms. A literature survey suggests that silicon is very rare in ciliates. The fine structure and genesis of silicon granules in M. umbrellata are very similar to those of other organisms, including vascular plants and animals, indicating a common mechanism. Light perception and protection against mechanical stress and predators might be functions of the silicon granules in M. umbrellata . The palaeontological significance of glass cysts in ciliates is also discussed.     

Circadian rhythms in the blowfly, Phormia terraenovae: the period in constant light

ABSTRACT. Locomotor activity of individual blowflies, Phormia (=Protophormia) terraenovae R.D. (Diptera, Calliphoridae), was recorded by means of running wheels made of Perspex (plexiglass). At various intervals after hatching, flies were placed in the wheel in continuous light (120 lx). The period of the free-running rhythm was often shorter than 24 h initially, but lengthened later and stabilized after 15–20 days at values around or above 25 h. The mean period was independent of age in both sexes. Within a range from 2 to 2000lx the period did not depend in a systematic way on intensity of illumination; no activity could be recorded below 1 lx.