Amoeboflagellate Transformations and the Gibbs-Donnan Ratio*

SYNOPSIS. A number of protozoa may have amoeboid, flagellated, or intergrade forms. At the present time several mechanisms have been proposed for inducing the formation of each of the above forms, but a definite triggering mechanism has not been elucidated. However, some change in the environment precedes the transformation of the cell from one form to another. Jahn (1962) and Czarska (1964), respectively, correlated ciliary reversal and water expulsion vesicle activity with alterations in the ionic environment. In both cases the processes involved are correlated with changes in the Gibbs-Donnan (G-D) relationship rather than direct ratios or molarities. It seems reasonable to assume that additional environmentally induced phenomena may also be based on changes in the relationship. The assumption is here made that an amoeboid cell, possessing the necessary genetic and physiologic potentials, can respond to certain changes in its environment by enflagellation. The following hypothesis is being considered: a change in the environment that increases the relative concentration of associated divalent cations is perhaps one of the main triggers for amoeba-to-flagellate transformations. Thus, in accordance with the G-D theory, this transformation would be expected to occur when a given ionic environment is diluted. In addition, the transformation is discussed in relation to pH, population density, and other environmental parameters that alter the Gibbs-Donnan ratio.     

Certain Aspects of the Sexuality of Two Species of Chlamydomonas

SUMMARY. When older cultures (18 days old) of Chlamydomonas eugametos were mated, zygote formation occurred under conditions similar to those devised for C. moewusii. Young (6 days old) cultures of the former did not mate when the nitrogen concentration of the medium was high (0.03% NH₄NO₃). In confirmation of the work of Sager and Granick, it was found that low nitrogen concentrations, produced by decreasing the concentration of NH₄NO₃ in the original medium, by increasing the intensity of the illumination, or by using old cultures, enhanced gametogenesis in C. eugametos. It has also been demonstrated that the two species are compatible with one another, even under conditions which are unfavorable for gametogenesis in C. eugametos alone.     

Proteomic analysis of β-aminobutyric acid priming and abscisic acid – induction of drought resistance in crabapple (Malus pumila): effect on general metabolism, the phenylpropanoid pathway and cell wall enzymes

In a variety of herbaceous, model and crop plants, DL- β -aminobutyric acid (BABA), has been shown to enhance both biotic and abiotic stress resistance by potentiating rather than inducing resistance responses but studies in woody plants are lacking. In the present study, two-dimensional difference in-gel electrophoresis (DIGE) was used to quantify differences in protein abundance in leaf tissue from BABA-treated, abscisic acid (ABA)-treated and untreated (control) plants during a 10 d drought stress. ABA-treated seedlings were most resistant to water loss followed by BABA-treated seedlings and then untreated seedlings. Although some similarity was observed in the proteome of ABA- and BABA-treated seedlings, a dramatic shift in the proteome occurred earlier in ABA-treated seedlings. Some proteins showed almost identical patterns of increase or decrease in abundance in both BABA- and ABA-treated seedlings, supporting the concept that BABA-induced abiotic stress resistance in plants is achieved by potentiating an ABA-regulated pathway. Some proteins, however, were induced or suppressed only in BABA-primed plants, indicating that BABA may also mediate resistance via some ABA-independent pathways. Based on the putative function of the identified proteins, we propose that changes in cell wall enzymes and a suppression of lignin biosynthesis may play a specific role in BABA-primed drought resistance.     

Epizootiology of Amblyospora connecticus (Microsporida) in Field Populations of the Saltmarsh Mosquito, Aedes cantator, and the Cyclopoid Copepod, Acanthocyclops vernalis

The natural ecology of a heterosporous microsporidium, Amblyospora connecticus was investigated at three different salt marsh habitats during 1986–1989. The parasite has a well-defined seasonal transmission cycle that occurs regularly each year and intimately involves the primary mosquito host, Aedes cantator, and the intermediate copepod host, Acanthocyclops vernalis. In the spring, the microsporidium is horizontally transmitted from the copepod, where it appears to overwinter, to the mosquito via the ingestion of haploid spores produced in the copepod. Mosquitoes develop a benign infection, and females transmit the microsporidium transovarially to their progeny via infected eggs. Oviposition occurs during the summer and infected eggs hatch synchronously in the fall causing widespread epizootics. Infected larvae die, and the cycle is completed when meiospores are released into the pool and subsequently are eaten by A. vernalis, which reappears in the fall and early winter. Amblyospora connecticus thereby persists by surviving in one of two living hosts throughout most of its life cycle rather than in the extra-corporeal environment. This represents an important survival strategy for A. connecticus as results show the salt marsh habitat to be a relatively unstable environment that is subject to periodic flooding and drying. The adaptive significance of utilizing an intermediate host in the life cycle is discussed as it directly facilitates transmission and enhances survival of the microsporidium.     

Osmotic Homeostasis in Dictyostelium Discoideum: Excretion of Amino Acids and Ingested Solutes

ABSTRACT. The response to osmotic stress in axenically cultured Dictyostelium discoideum was examined. Hypoosmotic buffers elicited two changes in the large (-50 mM) cytosolic pool of amino acids: a) the total size of the pool diminished, while b) about half of the initial pool was excreted. Hyperosmotic stress had the opposite effect. Among the predominant amino acids in the pool were glycine, alanine and proline. Putrescine, the major diamine, was neither excreted nor modulated. Recently ingested radioactive amino acids were excreded in preference to those in the cytoplasm, suggesting that the endocytic pathway might be involved in water excretion. Furthermore, hypoosmotic stresss strimulated the selective exretion of small, membrane-impermeable fluorescent dyes which had been ingested into endocytic vacuoles. Caffeine inhibited the excretion of the fluorophores but not the amino acids. We conclude that the response of Dictyostelium to osmotic stress is complex and includes both modulation of the cytoplasmic amino acid pool and the excretion of amino acids and other small solutes from the endocytic pathway.     

Eocene handfishes from Monte Bolca,with description of a new genus and species,and a phylogeny of the family Brachionichthyidae (Teleostei: Lophiiformes)

The family Brachionichthyidae, commonly known as the handfishes, is a small group of lophiiform fishes, the living species of which are restricted in distribution mostly to shallow temperate and subtropical waters of Tasmania and southern and eastern Australia. Despite their narrow present‐day distribution, and the extreme rarity of lophiiforms in the fossil record, handfishes are well represented in the Eocene of Monte Bolca, Italy. A revision of the known fossil material shows the presence of two fossil species in two monotypic genera, ?Histionotophorus and ? Orrichthys gen. nov. Diagnoses of the family Brachionichthyidae, the two fossil genera, as well as two recognized extant genera Brachionichthys and Sympterichthys are provided. An osteological analysis of ?Histionotophorus bassani revealed many new features as well as reinterpretations of some previously described skeletal parts. A phylogenetic analysis of brachionichthyid genera and representatives of the antennarioid families Antennariidae, Tetrabrachiidae, and Lophichthyidae, using 36 morphological characters, strongly supported monophyly of brachionichthyids and antennarioids, the former taxon representing the sister group of the other families of the latter. Within the Brachionichthyidae, the two extant genera Brachionichthys and Sympterichthys form a species pair, as do the extinct genera ?Histionotophorus and ? Orrichthys gen. nov. Biogeographical considerations suggest that the present geographical range of handfishes can be considered a residual distribution of a temporally and spatially dynamic range shift. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 160 , 621–647.     

Anodal Contraction of Paramecium Protoplasm*

SYNOPSIS. Paramecia immobilized on an agar surface were stimulated with pulses of 2–8 mamps/cm² with intervals ranging from 1.0 to 1000 msec. High speed cine films (1500-6000 frames per second) of the animals' responses were analyzed to determine changes in body length and the effects on cilia and trichocysts. At current densities in the range of 1.0 mamp/cm², rapid ciliary reversal occurred. Above this value the paramecia shortened. This body contraction can be very rapid, resulting in shortening to 95% of the body length in 0.95 msec. At all levels of stimulation, contraction of the body length occurred 1st anodally, then cathodally. Extensive trichocyst extrusion occurred 1st at the anode and later at the cathode at current densities greater than 5 mamp/cm² in the agar. Results of this study indicate that the protoplasm of paramecia is capable of very fast contraction in response to electric stimulation and that the initial response is always anodal.     

Serotypic Variation Among Isolates of Ichthyophthirius multifiliis Based on Immobilization

Efforts have been made to determine whether surface antigens could be used as biochemical markers to define strain differences in the parasitic ciliate Ichthyophthirius multifiliis. In previous studies, a wild-type isolate designated G1 was found to have surface proteins analogous to the immobilization antigens of Paramecium and Tetrahymena; rabbit antiserum against this strain immobilizes homologous cells in vitro. It has now been shown for two additional Ichthyophthirius isolates (designated G1.1 and G2) that immobilization antigens are both present and serologically distinct. Proteins of similar size, which cross-react in Western blots with rabbit antisera against immobilization antigens of the G1 strain, are nevertheless found in the G1.1 and G2 isolates. As shown by Southern blotting analysis, the G1.1 and G2 strains also contain genomic DNA sequences which hybridize with an immobilization antigen cDNA from G1 when probed under conditions of reduced stringency. The serotypic differences in immobilization between I. multifiliis isolates appear to be stable over time and provide a means of discriminating strains. In addition to providing a basis for comparative studies, the work described here has implications for the development of vaccines against this important fish parasite.