The comparison of mechanically stimulated and spontaneous firings in traps of aquatic carnivorous Utricularia species

Firing and resetting of traps in aquatic Utricularia species are associated with water flows and trap volume changes. In this study, trap thickness was used as a measure of water flow and was monitored automatically using an electronic position sensor. Isolated traps from three aquatic Utricularia species were monitored over the course of 1-2 days to verify spontaneous firings (without any mechanical stimulation) and describe their basic characteristics. Isolated traps of three Utricularia species were initially fired by mechanical stimulation and allowed to naturally reset within a period of 24-48 h. Within this resting period, spontaneous firings were found in the traps of all species and in two trap age categories of U. vulgaris. The timing of spontaneous firings was found to be irregular. Spontaneous firings ranged between 0.29 and 2.4 during the 24-h resting period and the mean time between two spontaneous firings was highly variable within each species (319-891 min). There was no quantitative difference between spontaneous and mechanically stimulated firings of the traps. Spontaneous firings could explain how phytoplankton or detritus enters traps even when no prey species are present.     

Immersed in situ microcosms: A tool for the assessment of pollution impact on phytoplankton

In situ phytoplankton microcosms were developed and characterized for use in toxicity testing. The microcosms contained 225 μm filtered seawater maintained in 1 liter glass bottles attached to a plastic frame and immersed at 3 m under the sea surface. Synechococcus and picoeukaryote population dynamics in microcosms and the surrounding water were compared. A bloom-like behaviour observed for Synechococcus in these phytoplankton microcosms was avoided when 10% of the culture volume was replaced, every two days, by filtered seawater. After 2 weeks, no significant difference in Synechococcus and picoeukaryotes cell counts was observed in microcosms compared to the surrounding free seawater. Synechococcus fluorescence at 545 nm (phycoerythrobilin) fluctuated with a similar pattern in such microcosms and in free seawater and were shown to be correlated to light intensity fluctuations over a two week experiment. The in situ microcosms were used to study the impact of low copper additions. Synechococcus populations were dramatically decreased by copper addition, while picoeukaryote populations were increased simultaneously. Our data show that drastic changes in species composition can occur at copper concentrations encountered in polluted coastal areas.     

Interconversion of ketoprofen recognition in firefly luciferase-catalyzed enantioselective thioesterification reaction using from Pylocoeria miyako (PmL) and Hotaria parvura (HpL) just by mutating two amino acid residues

We identified the critical amino acid residues for substrate recognition using two firefly luciferases from Pylocoeria miyako (PmL) and Hotaria parvura (HpL), as these two luciferase enzymes exhibit different activities toward ketoprofen. Specifically, PmL can catalyze the apparent enantioselective thioesterification reaction, while HpL cannot. By comparing the amino acid sequences around the active site, we identified two residues (I350 and M397 in PmL and F351 and S398 in HpL) that were different between the two enzymes, and the replacement of these amino acids resulted in changing the ketoprofen recognition pattern. The inactive HpL was converted to the active enzyme toward ketoprofen and vice versa for PmL. These residues also affected the enantioselectivity toward ketoprofen; however, the bioluminescent color was not affected. In addition, using molecular dynamics calculations, the replacement of these two amino acids induced changes in the state of hydrogen bonding between ketoprofen and the S349 side chain through the active site water. As S349 is not considered to influence color tuning, these changes specifically caused the differences in ketoprofen recognition in the enzyme.     

An experimental test of the effects of variation in recruitment intensity on intertidal community composition

The rocky intertidal has been a model system for experimentally testing hypotheses regarding the factors that structure natural communities. Many ecologists have proposed that changes in the intensity of recruitment of individuals into a community should influence community structure. Past work investigating this hypothesis has primarily been surveys of recruitment and community structure across large spatial scales. Surprisingly, no researchers to date have manipulated recruitment into a rocky intertidal community to assess the response of interactions of the whole community to variation in recruitment intensity. We manipulated the densities of Balanus glandula and Chthamalus spp. recruits across a four-fold difference at two sites spanning the Monterey Bay, California, USA, to experimentally test if differences in recruitment intensity influenced initial changes in community composition and if these changes persisted through time. The results of this work indicate that differences in recruitment influence community composition initially, but that these changes can be short-lived.     

Trypanosoma evansi: Hematologic changes in experimentally infected cats

This study aimed at evaluating hemogram and erythropoietic changes in cats experimentally infected with Trypanosoma evansi. Thirteen adult female non-breeding Felix catus were separated into two groups: seven animals were infected with 10⁸ trypomastigotes each, and six animals were used as negative controls. Animals were kept in air-conditioned rooms and blood smears were performed daily for 49 days. Blood samples were collected from the jugular vein at days 0, 7, 21, 35 and 49 and stored in blood-collecting tubes containing anticoagulant. Bone marrow was collected from the proximal epiphysis of the right femur at days 14 and 42 post-inoculation (PI). Total erythrocyte count, hematocrit and hemoglobin showed statistical differences among groups from the seventh day PI onwards (P < 0.05). The mean corpuscular volume and the mean corpuscular hemoglobin concentration remained normal, characterizing a normocytic-normochromic anemia. Reticulocyte count increased in the infected group from the 21st day onwards, but remained near normal values suggesting a mild regenerative anemia. Moreover, the myeloid:erythroid ratio significantly reduced at day 42 PI, evidencing a bone marrow hematopoietic response. Based on these results we conclude that cats infected with T. evansi have normocytic, normochromic, regenerative anemia.     

盐胁迫对2种栎树苗期生长和根系生长发育的影响

以低浓度(50 mmol/L)和高浓度(150 mmol/L)NaCl处理弗吉尼亚栎(Quercus virginiana)和麻栎(Quercus acutissima)1年生幼苗,研究了2种栎树在盐胁迫下的生长、对盐分的敏感性和耐受性及其根系形态学参数变化以及根系对盐离子的吸收与积累。结果表明,高浓度盐胁迫明显抑制了2种栎树地上部生物量的积累(P0.05),而低浓度盐胁迫对弗吉尼亚栎地上部干重的影响不明显,但显著抑制了麻栎地上部干重(P0.05);2种栎树的根冠比在盐胁迫下呈增加趋势,特别是在高浓度盐胁迫下,2种栎树的根冠比明显增加(P0.05),盐胁迫下增加生物量在根部的分配是植物应对盐胁迫的方式之一。2种栎树根部生物量积累在盐胁迫下变化不明显,但2种栎树根系形态学参数在盐胁迫下的响应不同,弗吉尼亚栎根系总长度、总表面积和总体积在盐胁迫下均有不同程度增加,特别是在低浓度盐胁迫下,根系形态学参数明显增加(P0.05),但麻栎根系形态学参数有下降趋势,但与对照相比变化不明显;通过对不同径级根系总长的分析发现,弗吉尼亚栎根系总长度的增加主要是由于直径小于2 mm的细根总长的增加,细根长度的增加对于植物吸收水分和营养物质具有重要意义;通过对Na+和Cl-在根系的含量分析表明,盐胁迫下2种栎树根系盐离子的积累均有明显增加,但弗吉尼亚栎根系盐离子的含量在低浓度和高浓度盐胁迫下的差异不明显,而麻栎在高浓度盐胁迫下根系盐离子的含量明显高于弗吉尼亚栎。综合2种栎树盐胁迫下的生物量分配策略和根系形态学响应以及盐离子的积累规律,证明2种栎树尽管在生物量分配策略方面具有相同的特点,但根系的响应策略截然不同,弗吉尼亚栎在盐胁迫下能够扩大根系吸收范围,维持较高的K+/Na+比值,而麻栎在盐胁迫下根系由于吸收过多的盐离子,导致根系的生长发育受到抑制,影响了根系在逆境中的分布范围,从而在一定程度上避免了进一步的盐害。     

Pressure dependence of activity and stability of dihydrofolate reductases of the deep-sea bacterium Moritella profunda and Escherichia coli

To understand the pressure-adaptation mechanism of deep-sea enzymes, we studied the effects of pressure on the enzyme activity and structural stability of dihydrofolate reductase (DHFR) of the deep-sea bacterium Moritella profunda (mpDHFR) in comparison with those of Escherichia coli (ecDHFR). mpDHFR exhibited optimal enzyme activity at 50 MPa whereas ecDHFR was monotonically inactivated by pressure, suggesting inherent pressure-adaptation mechanisms in mpDHFR. The secondary structure of apo-mpDHFR was stable up to 80 °C, as revealed by circular dichroism spectra. The free energy changes due to pressure and urea unfolding of apo-mpDHFR, determined by fluorescence spectroscopy, were smaller than those of ecDHFR, indicating the unstable structure of mpDHFR against pressure and urea despite the three-dimensional crystal structures of both DHFRs being almost the same. The respective volume changes due to pressure and urea unfolding were − 45 and − 53 ml/mol at 25 °C for mpDHFR, which were smaller (less negative) than the corresponding values of − 77 and − 85 ml/mol for ecDHFR. These volume changes can be ascribed to the difference in internal cavity and surface hydration of each DHFR. From these results, we assume that the native structure of mpDHFR is loosely packed and highly hydrated compared with that of ecDHFR in solution.     

The systems approach to the prespore-specific activation of sigma factor SigF in Bacillus subtilis

The prespore-specific activation of sigma factor SigF (σ^F) in Bacillus subtilis has been explained mainly by two factors, i.e., the transient genetic asymmetry and the volume difference between the mother cell and the prespore. Here, we systematically surveyed the effect of these two factors on sporulation using a quantitative modeling and simulation architecture named hybrid functional Petri net with extension (HFPNe). Considering the fact that the transient genetic asymmetry and the volume difference in sporulation of B. subtilis finally bring about the concentration difference in two proteins SpoIIAB (AB) and SpoIIAA (AA) between the mother cell and the prespore, we have surveyed the effect of AB and AA concentration on the prespore-specific activation of σ^F occurring in the early stage of sporulation. Our results show that the prespore-specific activation of σ^F could be governed by the ratio of AA to AB rather than their concentrations themselves. Our model also suggests that B. subtilis could maximize the ratio of AA to AB in the prespore and minimize it in the mother cell by employing both the transient genetic asymmetry and the volume difference simultaneously. This might give a good explanation to the co-occurrence of the transient asymmetry and the volume difference during sporulation of B. subtilis. In addition, we suggest for the first time that the σ^F activation in the prespore might be switched off by the decrease in the ratio of AA to AB after the transient genetic asymmetry is to an end by completion of DNA translocation into the prespore.     

Behavior,Parasitism, Morphology,and Biochemistry of Criconemella xenoplax and C. ornata on Peach

Host-parasite relationships of Criconemella xenoplax and C. ornata on Nemaguard peach and common bermudagrass were determined in the greenhouse. Criconemella xenoplax reproduced on peach and reduced root volume, height, and dry stem weight after 6 months, compared with the noninfested check. Numbers of C. ornata did not increase on peach or influence peach growth, but they did reduce dry top weight and root volume of common bermudagrass, compared with C. xenoplax. Criconemella xenoplax and C. ornata produced the enzyme β-glucosidase and were capable of metabolizing prunasin, but only C. xenoplax produced β-cyanoalanine synthase to detoxify the cyanide released from prunasin. The apparent inability of C. ornata to detoxify cyanide is one explanation why numbers of this species did not increase on peach. Criconemella xenoplax and C. ornata can be distinguished by using stylet length, vaginal configuration, and shape of the anterior head region.     

Extensive Divergence Between Mating-Type Chromosomes of the Anther-Smut Fungus

Genomic regions that determine mating compatibility are subject to distinct evolutionary forces that can lead to a cessation of meiotic recombination and the accumulation of structural changes between members of the homologous chromosome pair. The relatively recent discovery of dimorphic mating-type chromosomes in fungi can aid the understanding of sex chromosome evolution that is common to dioecious plants and animals. For the anther-smut fungus, Microbotryum lychnidis-dioicae (= M. violaceum isolated from Silene latifolia), the extent of recombination cessation on the dimorphic mating-type chromosomes has been conflictingly reported. Comparison of restriction digest optical maps for the two mating-type chromosomes shows that divergence extends over 90% of the chromosome lengths, flanked at either end by two pseudoautosomal regions. Evidence to support the expansion of recombination cessation in stages from the mating-type locus toward the pseudoautosomal regions was not found, but evidence of such expansion could be obscured by ongoing processes that affect genome structure. This study encourages the comparison of forces that may drive large-scale recombination suppression in fungi and other eukaryotes characterized by dimorphic chromosome pairs associated with sexual life cycles.     

Non-destructive species identification of Drosophila obscura and D. subobscura (Diptera) using near-infrared spectroscopy

The vinegar flies Drosophila subobscura and D. obscura frequently serve as study organisms for evolutionary biology. Their high morphological similarity renders traditional species determination difficult, especially when living specimens for setting up laboratory populations need to be identified. Here we test the usefulness of cuticular chemical profiles collected via the non-invasive method near-infrared spectroscopy for discriminating live individuals of the two species. We find a classification success for wild-caught specimens of 85%. The species specificity of the chemical profiles persists in laboratory offspring (87–92% success). Thus, we conclude that the cuticular chemistry is genetically determined, despite changes in the cuticular fingerprints, which we interpret as due to laboratory adaptation, genetic drift and/or diet changes. However, because of these changes, laboratory-reared specimens should not be used to predict the species-membership of wild-caught individuals, and vice versa. Finally, we demonstrate that by applying an appropriate cut-off value for interpreting the prediction values, the classification success can be immensely improved (to up to 99%), albeit at the cost of excluding a considerable portion of specimens from identification.     

Reproduction of Virulent Isolates of Meloidogyne incognita on Susceptible and Mi-resistant Tomato

The reproductive potential of natural and laboratory-selected Meloidogyne incognita isolates virulent against the tomato Mi resistance gene, all derived from a single egg-mass, were compared when the nematodes were inoculated on susceptible and resistant tomato. Fewer second-stage juveniles (P = 0.01) of the two virulent populations selected under laboratory conditions matured to females on the resistant tomato compared to the susceptible cultivar. In contrast, no differences were found between the number of egg masses produced on the resistant versus the susceptible tomato by the two natural virulent isolates. No clear general trends concerning the fecundity of the females could be inferred from the comparative analysis of the numbers of eggs per egg mass x tomato cultivar combination. These observations suggested that the genetic changes induced under environmentally controlled nematode growth might be different from those occurring in natural Mi-resistance breaking biotypes grown without environmental control.     

Host specificity of microsporidia pathogenic to the gypsy moth, Lymantria dispar (L.): Field studies in Slovakia

Several species of microsporidia are important chronic pathogens of Lymantria dispar in Europe but have never been recovered from North American gypsy moth populations. The major issue for their introduction into North American L. dispar populations is concern about their safety to native non-target insects. In this study, we evaluated the susceptibility of sympatric non-target Lepidoptera to two species of microsporidia, Nosema lymantriae and Vairimorpha disparis, isolated from European populations of L. dispar and applied in field plots in Slovakia. Application of ultra low volume sprays of the microsporidia maximized coverage of infective spores in a complex natural environment and, thus, exposure of non-target species to the pathogens. Of 653 non-target larvae collected from plots treated with V. disparis in 2002, 18 individual larvae representing nine species in four families were infected. These plots were monitored for two subsequent seasons and V. disparis was not recovered from non-target species. Of 2571 non-target larvae collected in N. lymantriae-treated sites, one larva was found to be infected. Both species of microsporidia, particularly N. lymantriae, appear to have a very narrow host range in the field, even when an inundative technique is used for their introduction. V. disparis infections in L. dispar exceeded 40% of recovered larvae in the treated study sites; infection rates were lower in sites sprayed with N. lymantriae. Several naturally-occurring pathogens were recorded from the non-target species. The most common pathogen, isolated from 21 species in eight families, was a microsporidium in the genus Cystosporogenes.     

Optimal Release Rates for Attracting Meloidogyne incognita,Rotylenchulus reniformis,and Other Nematodes to Carbon Dioxide in Sand

Movement of vermiform stages of Meloidogyne incognita, Rotylenchulus reniformis, Ditylenchus phyllobius, Steinernema glaseri, and Caenorhabditis elegans in response to carbon dioxide was studied in 40- and 72-mm-long cylinders of moist sand inside 38-mm-d acrylic tubes. Meloidogyne incognita, R. reniformis, and S. glaseri were attracted to CO₂ when placed on a linear gradient of 0.2%/cm at a mean CO₂ concentration of 1.2%. When CO₂ was delivered into the sand through a syringe needle at flow rates between 2 and 130 μl/minute, the optimal flow rate for attracting M. incognita and R. reniformis was 15 μl/minute, and maximal attraction of the two species from a distance of 52 mm was achieved after 29 and 40 hours, respectively. After 24 hours, a total CO₂ volume of 20 cm³ was sufficient to induce 96% of all M. incognita introduced to move into the half of the cylinder into which CO₂ was delivered and more than 75 % to accumulate in the 9 cm³ of sand volume nearest the source. Results indicate it may be possible to use a chemical or biological source of CO₂ to attract nematodes to nematicide granules or biocontrol agents.     

A new classification of marginal resin ducts improves understanding of hard pine (Pinaceae) diversity in Taiwan

Resin ducts provide important characters for classifying the Pinaceae. Here we study Pinus massoniana and P. taiwanensis and show that the generally-used term marginal (=external) resin duct, applied to ducts in needle leaves, needs to be further differentiated into marginal (strongly attaching to the dermal tissue, and lacking the complete ring structure formed by the sheath cells) and submarginal ducts (adjacent to hypodermal cells, with a complete ring structure formed by the sheath cells). On this basis P. massoniana and P. taiwanensis, which are nearly indistinguishable based on external morphology, are clearly differentiated. Their similar morphology has led to a long standing debate on where P. massoniana occurs in Taiwan. Based on this new classification of resin ducts, we examined old herbarium specimens previously identified as P. massoniana, surveyed current hard pines in Taiwan, and checked historical documents. Needle leaves of these two taxa were studied and compared with the material of P. massoniana from mainland China as a reference. Pinus massoniana shows almost exclusively marginal resin ducts, with extremely rare changes along the length of the duct to submarginal positions. In contrast, P. taiwanensis shows a mixture of medial, submarginal, septal, and rarely endonal ducts, with occasional changes of the duct between various types. Re-identification of specimens showed that only 5 specimens are possible native P. massoniana collected from northern Taiwan and the others are all P. taiwanensis. The hard pine of Junjianyan is unexpectedly found to be the only currently known P. massoniana in Taiwan, which is likely a relic of historical afforestation. The hard pine from Huoyansan and the Coastal Range, which is widely accepted as P. massoniana, is not this species. In addition to the taxonomic value of the new definition applied to these two studied taxa, we expect that this approach can generally be applied distinguishing the respective characters in the genus Pinus and in other conifers.     

Temporal analysis of gene expression in a field population of the Scleractinian coral Montastraea faveolata

Organisms maintain homeostasis and abate cellular damage by altering gene expression. Coral colonies have been shown to produce unique gene expression patterns in response to different environmental stimuli. In order to understand these induced changes, the natural variation in expression of genetic biomarkers needs to be determined. In this study, an array of genes isolated from Scleractinian coral was used to track changes in gene expression within a population of Montastraea faveolata from April to October 2001 in the Florida Keys. The profiles of genes observed in this study can be divided into two groups based on expression over this time period. In spring and early summer, May through July, most of the genes show little deviation from their average level of expression. In August and September, several genes show large deviations from their average level of expression. The physiological and environmental triggers for the observed changes in gene expression have not yet been identified, but the results show that our coral stress gene array can be used to track temporal changes in gene expression in a natural coral population.     

Monogamy and polygamy in two species of mirid bugs: a functional-based approach

Multiple mating in females is widespread among insects in spite of the risk of predation, disease acquisition and/or physical injury that may occur. One common consequence of female polyandry is competition among sperm from two or more males within the female to fertilize the ova. This competition is an evolutionary driving force that determines a series of adaptations in both males and females. In this work, we examine some behavioral, morphological and physiological characteristics of males and females of two Heteropteran species that are related to their monoandrous/polyandrous mating behavior. Females of Macrolophus pygmaeus (Het. Miridae), the monoandrous species, were coy about accepting a male partner, spent a short time in copula, and received only a small volume of ejaculate. Even so, with only one mating event, they received enough sperm to fertilize most of their ova (21 days after mating all females were still fertile). In contrast, females of Nesidiocoris tenuis (Het. Miridae), the polyandrous species, readily accepted any mating partner, spent a long time in copula and received a large volume of ejaculate. However, these latter females soon ran out of sperm and needed to mate periodically in order to maintain a sufficient sperm supply to fertilize their eggs. As predicted, based on current theory (Simmons, 2001b), an increased investment in spermatogenesis was detected in N. tenuis with relation to M. pygmaeus. The males of the polyandrous species had larger accessory reproductive glands, seminal vesicles, testes and sperm cells than those of the monoandrous species.     

Stimulation of the biosynthesis of carotenes by oxidative stress in Blakeslea trispora induced by elevated dissolved oxygen levels in the culture medium

The adaptive response of the fungus Blakeslea trispora to the oxidative stress induced by elevated dissolved oxygen concentrations during carotene production was investigated by measuring the specific activities of catalase (CAT) and superoxide dismutase (SOD) and the micromorphology of the fungus using a computerized image analysis system. Changes in the ratio of the volume of air (V_a) over the medium and the volume of medium (V_m) in the flask caused changes of the morphology of microorganism from clumps to pellets and increases in the specific activities of CAT and SOD. The oxidative stress in B. trispora resulted in a significant increase in carotene production, and a maximum proportion of β-carotene (60%), γ-carotene (50%), and lycopene (10%) (as percentages of total carotenes) was observed at a ratio V_a/V_m of 15.7, 4.0 and 1.5, respectively. The highest concentration of carotenes (115.0 mg/g dry biomass) was obtained in V_a/V_m ratio of 9.0.