Non-indigenous insect species in Israel and adjacent areas

Non-indigenous species cause great damage worldwide. Non-indigenous insects are known as harmful in many regions, but few comprehensive works have investigated non-indigenous insects as a group. We compiled a comprehensive database of established non-indigenous (ENI) insects in Israel and adjacent regions to investigate how they arrived, their biological characteristics, and the attributes of areas they invade. Of 218 species of ENI insects in this region, 124 are widespread. Most species came as stowaways, but 38 were brought intentionally for biological control. Most ENI insects in this region are in the Coleoptera, Diptera, Hymenoptera, Lepidoptera, and Homoptera. Species from various orders differ in their tendency to be localized or widespread, and in biogeographic origins. The distribution of species among orders differs between native and ENI insects. The Coastal Plain houses the most ENI insect species and the Negev and Judean deserts the fewest. Most ENI insects spread from the Coastal Plain to other regions. Absence of roads, settlements and presence of nature reserves are negatively correlated with occurrence of ENI species. Seventy-nine species are categorized as pests that damage produce, merchandise, forestry, etc. Despite a general dearth of knowledge on impacts of ENI insects on natural systems, 42 species are known to feed on native plants, some of conservation concern. Biological control agents are usually more limited in their distribution than other ENI insects. Further research, legislation, and enforcement are required to minimize effects of these species on agriculture and natural habitats.     

Neocentromeres Form Efficiently at Multiple Possible Loci in Candida albicans

Centromeres are critically important for chromosome stability and integrity. Most eukaryotes have regional centromeres that include long tracts of repetitive DNA packaged into pericentric heterochromatin. Neocentromeres, new sites of functional kinetochore assembly, can form at ectopic loci because no DNA sequence is strictly required for assembly of a functional kinetochore. In humans, neocentromeres often arise in cells with gross chromosome rearrangements that rescue an acentric chromosome. Here, we studied the properties of centromeres in Candida albicans, the most prevalent fungal pathogen of humans, which has small regional centromeres that lack pericentric heterochromatin. We functionally delimited centromere DNA on Chromosome 5 (CEN5) and then replaced the entire region with the counter-selectable URA3 gene or other marker genes. All of the resulting cen5Δ::URA3 transformants stably retained both copies of Chr5, indicating that a functional neocentromere had assembled efficiently on the homolog lacking CEN5 DNA. Strains selected to maintain only the cen5Δ::URA3 homolog and no wild-type Chr5 homolog also grew well, indicating that neocentromere function is independent of the presence of any wild-type CEN5 DNA. Two classes of neocentromere (neoCEN) strains were distinguishable: “proximal neoCEN” and “distal neoCEN” strains. Neocentromeres in the distal neoCEN strains formed at loci about 200–450 kb from cen5Δ::URA3 on either chromosome arm, as detected by massively parallel sequencing of DNA isolated by CENP-A^Cse4p chromatin immunoprecipitation (ChIP). In the proximal neoCEN strains, the neocentromeres formed directly adjacent to cen5Δ::URA3 and moved onto the URA3 DNA, resulting in silencing of its expression. Functional neocentromeres form efficiently at several possible loci that share properties of low gene density and flanking repeated DNA sequences. Subsequently, neocentromeres can move locally, which can be detected by silencing of an adjacent URA3 gene, or can relocate to entirely different regions of the chromosome. The ability to select for neocentromere formation and movement in C. albicans permits mechanistic analysis of the assembly and maintenance of a regional centromere.     

Carbon:chlorophyll <Emphasis Type=Italic>a</Emphasis> ratio,assimilation numbers and turnover times of Lake Kinneret phytoplankton

Carbon to chlorophyll a (C:Chl) ratios, assimilation numbers (A.N.) and turnover times of natural populations of individual species and taxonomic groups were extracted from a long-term database of phytoplankton wet-weight biomass, chlorophyll a concentrations, and primary production in Lake Kinneret, Israel. From a database spanning more than a decade, we selected data for samples dominated by a single species or taxonomic group. The overall average of C:Chl was highest for cyanophytes and lowest for diatoms, while chlorophytes and dinoflagellates showed intermediate values. When converting chlorophyll a to algal cellular carbon this variability should be taken into account. The variability in C:Chl within each phylum and species (when data were available) was high and the variability at any particular sampling date tended to be greater than the temporal variability. The average chlorophyll a-normalized rate of photosynthetic activity of cyanophytes was higher and that of the dinoflagellates lower than that of other phyla. Turnover time of phytoplankton, calculated using primary productivity data at the depth of maximal photosynthetic rate, was longest in dinoflagellates and shortest in cyanophytes, with diatoms and chlorophytes showing intermediate values. The more extreme C:Chl and turnover times of dinoflagellates and cyanobacteria in comparison with chlorophytes and diatoms should be taken into consideration when employed in ecological modeling.     

Population genetics and reproductive strategies of two Notostraca (Crustacea) species from winter ponds in Israel

Fluorescent-amplified fragment length polymorphism (FAFLP) fingerprinting assay was used to compare the genetic diversity within and between tadpole shrimps (Notostraca) populations of Lepidurus apus (n=7) and Triops cancriformis (n=2) from rain pools in Israel. Each ephemeral water body has revealed a unique fingerprint pattern with an entailed genetic drift between nearby ponds. High similarity of genotypic diversity within each geographic area led to three clusters of water bodies, north, south and center of Israel. FAFLP assays on several newly hatched individuals of T. cancriformis revealed high identity amongst kin, as compared to L. apus where newly hatched from the same maternal source showed high diversity. Results indicate that T. cancriformis populations from Israel are probably parthenogenetic as indicated by clonal structures. The higher genetic variability in the L. apus populations and in laboratory-hatched specimens indicates the existence of sexual reproduction.     

Effects of Cr(VI) long-term and low-dose action on mammalian antioxidant enzymes (an in vitro study)

In order to investigate the low-dose long-term Cr(VI) action on antioxidant enzymes in cultured mammalian cells we estimated the activity of glutathione dependent antioxidant enzymes, catalase and superoxide dismutase (SOD) under various chromium concentrations in human epithelial-like L-41 cells. The long-term action of 20 microM causes the toxicity that results in losing of the cell viability by activating the apoptotic process, as identified by morphological analysis, the activation of caspase-3, and DNA fragmentation. The toxic chromium concentration totally destroys glutathione antioxidant system, and diminishes the activity of catalase and cytosolic Cu, ZnSOD. The non-toxic concentration (2 microM) causes the activation of the antioxidant defense systems, and they neutralize the oxidative impact.     

Reversible hypercondensation and decondensation of mitotic chromosomes studied using combined chemical-micromechanical techniques

We show that the chromatin in mitotic chromosomes can be drastically overcompacted or unfolded by temporary shifts in ion concentrations. By locally 'microspraying' reactants from micron-size pipettes, while simultaneously monitoring the size of and tension in single chromosomes, we are able to quantitatively study the dynamics of these reactions. The tension in a chromosome is monitored through observation and calibration of bending of the glass pipettes used to manipulate the chromosomes. For concentrations > 500 mM of NaCl and > 200 mM of MgCl2, we find that the initially applied tensions of approximately 500 pN relax to zero and that mitotic chromatin temporarily disperses in agreement with previous work (Maniotis et al. [1997] J. Cell. Biochem. 65:114-130). This unfolding occurs in about 1 s, and is reversible once the charge density is returned to physiological levels, if the exposure is not longer than approximately 1 min. Low concentrations of NaCl (< 30 mM) also induces a decrease in tension and increase in size. We observe this swelling to be isotropic in experiments on chromosomes under zero tension, a behavior inconsistent with the existence of a well-defined central chromosome 'scaffold'. By contrast 10 mM of divalent cations (MgCl2 and CaCl2) induces an extremely rapid and reversible increase in tension and a reduction in the size of mitotic chromosomes. Hexaminecobalt trichloride (trivalent cation) has the same effect as MgCl2 and CaCl2, except the magnitude of force increase and size change are much larger. Hexaminecobalt trichloride reduces mitotic chromosomes to 65% of their original volume, indicating that at least 1/3 of their apparent volume is aqueous solution. These results indicate that chromatin inside mitotic chromatids has a large amount of conformational freedom allowing dynamic unfolding and refolding and that charge interactions play a central role in maintaining mitotic chromosome structure.     

How to move with no rigid skeleton? The octopus has the answers

The octopus is amazingly flexible and shows exceptional control and coordination in all its movements. It seems remarkable to us skeletal creatures that the octopus achieves all this without a single bone.