Mechanisms of interspecific competition that result in successful control of Pacific mites following inoculations of Willamette mites on grapevines

We have successfully reduced populations of economically damaging Pacific mites by introducing another economically unimportant herbivorous mite to grapevines. Although this technique has proven successful in greenhouse and commercial applications, we had a poor understanding of why it worked. Experiments were conducted in a Zinfandel vineyard to assess the relative importance of different forms of competition between these two species and the importance of the timing of the introduction. The early season release of Willamette mites that occurred as shoots were first elongating reduced populations of Pacific mites, indicating that some form of competition occurred in this experiment. However, introductions of Willamette mites 4 weeks later did not reduce populations of Pacific mites. An early season release is essential for control. Control shoots did not receive additions of Willamette mites and had high population densities of Pacific mites. In contrast to this, Pacific mite populations were reduced on treatments with Willamette mites, regardless of whether the two species overlapped spatially or were separated by a barrier. This indicated that physical interference was not responsible, that induced resistance was involved, and that the effect was systemic throughout the shoot.     

Studies on light absorption and photochemical activity changes in chloroplast suspensions and leaves due to light scattering and light filtration across chloroplast and vegetation layers

An experimental analysis is presented concerning the effect on relative light absorption by the two photosystems caused by (a) a highly light scattering environment (the detour effect) and (b) light filtration across successive chloroplast layers (the light attenuation effect). Both suspensions of isolated chloroplasts and leaves were employed.It is concluded that within a single spinach leaf these phenomena are likely to lead to only rather small increases in relative photosystem I absorption and activity with respect to photosystem II and will thus not exert a significant effect on non cyclic electron transport. On the contrary when light is filtrated across successive vegetation layers (shade light) significant increases in the relative PSI absorption and activity may be encountered.It is determined that the detour effect in mature leaves from a variety of plants increases overall photosynthetically useful light absorption by 35–40%.Abbreviations F_M maximal fluorescence - LHCP₂ light-harvesting chlorophyl a/b protein complex II - Q_A-primary quinone acceptor of photosystem II     

Contamination of Passenger Trains with Dermatophagoides (Acari: Pyroglyphidae) Mite Antigen in Japan

Passenger trains were surveyed for contamination with Dermatophagoides farinae Hughes and Dermatophagoides pteronyssinus (Trouesart) mites in Japan. A total of 492 dust samples were collected from upholstered seats in six commuter trains, one long-distance express train and three night trains in October, 1996 and January, April, and July, 1997. Mite antigen levels contained in fine dust fractions of these samples were measured by an enzyme- linked immunosorbent assay. Most samples obtained from commuter trains showed relatively high mite antigen levels of >10gm^–2 (corresponding to >100 mites). Express and night trains showed lower antigen levels per square meter, but higher mite antigen levels per gram of fine dust than commuter trains, indicating relatively high mite antigen densities. Seasonal comparisons indicated that commuter trains showed the highest mean antigen level per square meter in winter (January), whereas the highest antigen level per gram of fine dust was observed in summer (July) in express and night trains.     

Characterization of catecholamine uptake2 in isolated cardiac myocytes

Extraneuronal catecholamine uptake was investigated in isolated quiescent rat myocardial cells. By administration of (³H-)(–)noradrenaline concentration of 22 nmol/l up to 1000 mol/l the following data were obtained: (1) The K_M of the uptake process amounted to 260 mol/l, the V_max to 4.24 nmol/(10 min × mg Protein) corresponding to 179 nmol/(min × g_WWt)(WWT = Wet Weight). (2) The uptake was largely inhibited by the uptake₂-inhibitors corticosterone (100 mol/l), isoprenaline (IC so = 30.6 mol/l), and O-methylisoprenaline (IC₅₀ = 2.1 pmol/l), but not by the uptake₁-inhibitors cocaine (100 mol/l) and desipramine (10 mol/l). (3) The affinity-values K_M and IC₅₀ closely agreed with those already known, but the V_max-value was higher than those obtained in whole rat hearts by a factor of at least 1.79. This is caused presumably by the voltage dependence of the uptake mechanism and the resulting inhibition of uptake 2 during the periods of depolarisation in beating hearts of other studies.     

Negative interactions between Willamette mites and Pacific mites: possible management strategies for grapes

Willamette mites and Pacific mites are often negatively associated on grape vines. In particular, vineyards with early season infestations of the less damaging Willamette mite rarely develop high populations of the economically important Pacific mite. We report that Willamette mites had a negative effect on Pacific mite populations in both the greenhouse and field. In some experiments, the negative effect was more pronounced when vines had been damaged by previous feeding of Willamette mites and in other experiments concurrent feeding by both mite species was necessary to demonstrate a negative effect. Therefore, we cannot conclude if the mechanism of the response involves induced resistance against Pacific mites, more conventional interspecific competition, or both. Since predators were uncommon in our experiments, predator build up on Willamette mites did not cause the low Pacific mite population that we observed, although this mechanism may be important in many vineyards. Further, larger scale experiments are necesary to determine if growers can introduce Willamette mites to help control Pacific mites.

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Résumé E. willametti et T. pacificus sont souvent antagonistes dans les vignobles. En particulier, dans les vignobles contaminés tôt dans la saison par E. willametti,-dont les dégâts sont moins conséquents-, on observe rarement des populations élevées de T. pacificus, dont les dégâts sont économiquement importants. Nous avons constaté que E. Willametti a réduit les populations de T. pacificus, tant en serres qu'à l'extérieur. Dans quelques cas, l'effet antagoniste était plus marqué quand les vignes avaient été préalablement endommagées par l'alimentation de E. willametti. Dans d'autres expériences, la compétition alimentaire entre les deux espèces d'acariens était nécessaire pour produire un effet antagoniste. Cependant, nous ne pouvons pas en conclure que la réponse implique une résistance induite contre T. pacificus, ou une compétition interspécifique plus classique, ou les deux à la fois. Puisque les prédateurs étaient rares dans nos expériences, une explosion des prédateurs sur E. willametti n'a pu provoquer le faible niveau de population observé avec T. pacificus, bien qu'un tel méchanisme puisse être important dans certains vignobles. Quoi qu'il en soit, des expériences à plus grande échelle sont nécessaires pour déterminer si les vignerons peuvent introduire Eotetranychus willametti afin de limiter les populations de Tetranychus pacificus.

     

Recovery kinetics of radiation-induced chromosome aberrations in human G0 lymphocytes

Summary Declining yields of radiation-induced dicentric chromosomes in human G⁰ lymphocytes were observed in split-dose experiments with time intervals varied up to 8 h. In agreement with microdosimetric intratrack-intertrack interaction models, only the dose-squared yield component was reduced and approached an asymptotic value equal to one half of the corresponding single exposure yield. For 150 kV X-rays and 13 MeV electrons, at total doses up to 6 Gy, the time constant of the approximately exponential decline was practically dose- and quality-independent within a range of 100–180 min. For 10 kV X-rays, in the presence of a dominant linear yield component, only a small split-dose effect, but with a consistent-value, was observed for a total dose of 5 Gy. Since can be interpreted as the mean life time of primary lesions in chromatin fibres, its independence from absorbed dose and radiation quality means that radiation damage of the split-dose recovery mechanism can be excluded for doses up to 6 Gy. By correlating the observed split-dose reduction of the acentric fragment yield to the reduction of the dicentric yield, (1.64 ± 0.03) acentrics/dicentric for 150 kV X-rays and (1.51 ± 0.11) acentrics/dicentric for 13 MeV electrons were obtained. Acentrics formed in the course of dicentric formation as well as in other binary interactions of primary lesions are represented in these ratios. Post-irradiation recovery during time intervals between irradiation and cell stimulation up to 24 h did not occur. The relations to comparable results in cell lethality experiments are discussed, and a hypothesis of fast and slow binary interactions of primary lesions is put forward.Dedicated to Prof. Dr. H. Muth on the occasion of his 65th birthdayThis work was supported by the Bundesministerium des Innern, Bonn, FRG     

Dispersal of the glasshouse red spider mite Tetranychus urticae Koch (Acarina, Tetranychidae)

Under glass Tetranychus urticae Koch spreads by (a) migration of teneral females to oviposition sites (b) migration of mites from heavily infested plants by falling without the usual silken parachutes normally used by Tetranychid mites and (c) movement over the soil surface in accordance with the plane of polarized light.It is postulated that the effect of this combination of dispersal mechanisms is to restrict mite populations to one portion of a glasshouse from season to season with relatively slow lateral spread from these centres during each growing season.

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Zusammenfassung Bewegung auf der Wirtspflanze ist auf negativ geotaktisches Wandern der jungen Weibchen beschränkt, während Abwanderung nur stattfindet, wenn die Wirtspflanze so sehr zu Schaden gekommen ist, daß an den obersten Teilen der Pflanze keine frischen Blätter mehr vorhanden sind.Experimente haben gezeigt, daß — ungleich anderen Tetranychiden — Milben dieser Art nicht an seidenen Fallschirmen in der Luft treiben können, sondern zwangsläufig von seidenen Fäden zu Boden fallen, die sie als pendelnde Taue an stark befallenen Pflanzen bilden. Am Boden reagieren die Milben auf die Ebene des polarisierten Lichtes.Es wird daraus geschlossen, daß in Gurkenhäusern die Ausbreitung von den Überwinterungs-plätzen oder stark befallenen Pflanzen aus seitwärts nur in beschränktem Ausmaße erfolgt, so daß die Kolonien von Jahr zu Jahr in den gleichen Teilen des Gewächshauses auftreten.

     

Distortion of the spermathecae of phytoseiid mites (Acari: Phytoseiidae) in slide preparation

The shape and dimensions of the spermathecae are taxonomically important characteristics in phytoseiid mites. In experiments with Neoseiulus californicus (McGregor) and Typhlodromus pyri Scheuten, the shape of the cervix of the spermatheca changed considerably and its diameter was increased by 42–49% when mites were flattened, compared to being mounted with 140m spacers underneath the coverslips. Dimensions of the dorsal shield were also affected by flattening, increasing by 3–5%.     

Cold storage of Halotydeus destructor (Acari: Penthaleidae) for use in experiments

Survival of medium sized nymphal stages of redlegged earth mite Halotydeus destructor (Tucker) (mainly tritonymphs and deutonymphs) stored under low temperature (1.5°C) in sealed plastic boxes remained more than 50% after 12 days of storage, with some mites surviving for up to eight weeks. Adding fresh subclover leaves into the storage box increased the survival rate of mites from 12% to 28%, 19 days after the storage started. Mites stored for two weeks at low temperatures showed feeding activity in a screening experiment similar to mites collected directly from the field. This indicated that cold storage of redlegged earth mite can be used to build up mite numbers for large screening experiments, or to extend the period of availability of mites collected from the field. However, their reproductive ability was greatly reduced after three weeks at low temperature. Thus, care should be taken when using mites for experiments measuring reproduction. The implications of low temperatures for reducing field populations of mites in midwinter are also discussed.     

Differential induction of β-galactosidase and phospho-β-galactosidase activities in the fermentation of whey permeate by Clostridium acetobutylicum

Summary Strains of Clostridium acetobutylicum were tested for the presence of -galactosidase and phospho--galactosidase activities when grown on lactose. All strains, except C. acetobutylicum ATCC 824, showed both enzyme activities. Only phospho--galactosidase activity was detected with C. acetobutylicum ATCC 824. C. acetobutylicum strains P262 and ATCC 824 showed no detectable -galactosidase or phospho--galactosidase activities when grown on glucose. In the fermentation of whey permeate C. acetobutylicum P262 showed an early induction of phospho--galactosidase associated with the acidogenic phase. The -galactosidase activity peaked at a later stage of the fermentation (22 h) coinciding with the solvent production phase. Similar induction of phospho--galactosidase at the early stages (13 h) of fermentation of whey permeate by C. acetobutylicum ATCC 824 was also shown. No -galactosidase activity was detected during the entire course of fermentation by strain ATCC 824.     

Ultrastructure and behaviour of the spindle pole body of the aphid-pathogenic fungusErynia neoaphidis

Summary A detailed account of the ultrastructure and behaviour of the spindle pole body (SPB) of the entomophthoraceous fungusErynia neoaphidis is presented for the first time.The SPB consists of extranuclear (ENC) and intranuclear (INC) components. The ENC is a saucepan-shaped structure which lies in a pocket of the nuclear envelope. It is composed of a forked, fibrillar handle and a shallow, cylindrical pan. The pan has a wall of two layers, both of which are thickened with a regular periodicity so that they appear to be beaded. It is postulated that the pan is formed from rough endoplasmic reticulum and that it synthesizes the amorphous, electron-dense material coating the ENC.The INC is a saucer-shaped, electron-dense plaque in which the ends of the spindle microtubules terminate. During metaphase, a clear zone separates the INC from the nuclear envelope and persists until telophase. The roles of the amorphous, electron-dense material and the clear zone as well as the method of SPB replication are discussed.     

Isolation and identification of plant growth inhibitors as candidate(s) for allelopathic substance(s), from aqueous leachate from mesquite (Prosopis juliflora (Sw.) DC.) leaves

As candidate(s) for allelopathic substance(s), two plant growthinhibitors were isolated from aqueous leachate of leaves of mesquite, whichshowa strong allelopathy, and which were identified as syringin and(–)-lariciresinol by their spectral analyses. Syringin inhibited root andshoot growth of lettuce seedlings at concentrations greater than 0.8M, and root and shoot growth of barnyard grass seedlings atconcentrations greater than 2.7 and 26.9 M, respectively. Onthe other hand, (–)-lariciresinol inhibited root and shoot growth oflettuce seedlings at concentrations greater than 2.8 and 0.8M,and root and shoot growth of barnyard grass seedling at concentrations greaterthan 0.8 and 2.8 M, respectively. The contents of syringin and(–)-lariciresinol in the rhizosphere soil of mesquite were 0.34 and 0.38g/g soil, respectively. These results indicate that syringinand (–)-lariciresinol are allelopathic substance(s), and may play rolesinthe allelopathy of mesquite.     

A Cytogenetic Study of the Leaf Beetle Genus Cyrtonus (Coleoptera, Chrysomelidae)

The chromosomes of ten species of Cyrtonus and the genome sizes of six are surveyed. Among the total of 15 chromosomally studied species, 11 have 2n=28 chromosomes and a 13+Xy_p male meioformula, three have 2n=40 and 19+Xy_p and one 2n=46 and 22+Xy_p. All but one species with 28 chromosomes show only metacentric or submetacentric chromosomes, whereas the species with 40 and 46 chromosomes display some telocentrics or subtelocentrics, that are probably derived from the former by centric fissions. However, since the number of major chromosome arms is strikingly higher in these latter species (NF=70 and 78) than in the 28-chromosome species (mostly NF=56), other chromosomal rearrangements such as pericentric inversions or heterochromatin accretions could also be involved. The genome sizes display a narrow range, from 1C=0.6–1.22pg, and they are not significantly correlated with the chromosome numbers. Some possible factors implied in the rough chromosomal evolution of Cyrtonus are discussed in relation to a few other genera of the subfamily Chrysomelinae.     

Two cystic fibrosis patients with the genotype G542X/G551D

Two adult sisters affected by cystic fibrosis were both shown to carry two different alterations within exon 11 of the CFTR gene, the nonsense mutation G542X and the missense mutation G551D. Both patients exhibit a relatively benign clinical course. In the described patients, G542X functions as a mild allele and is, in this respect, dominant to the severe G551D.     

Hexagonally ordered “rosettes” of particles in the plasma membrane ofMicrasterias denticulata Bréb. and their significance for microfibril formation and orientation

Summary Cells ofMicrasterias denticulata Bréb. at the stage of secondary wall formation have been studied by freeze-etching. It was found that the plasma membrane exhibits oval areas in which arrays of membrane particles occur. These particles form rosettes which are arranged in a hexagonally ordered lattice with a center to center spacing of 25 nm. Nearly the same periodicities can be found between microfibrils. It is concluded that the rosettes probably together with the thickened area of the plasma membrane below them represent the apparatus for the production and orientation of microfibrils. The hypothesis suggesting the incorporation of membrane templates functional in microfibril formation, originally advanced byKiermayer andDobberstein (1973) has received further support.     

Comparative susceptibility and possible detoxification mechanisms for selected miticides in banks grass mite and two-spotted spider mite (Acari: Tetranychidae)

The susceptibility and possible detoxification mechanisms of the Banks grass mite (BGM), Oligonychus pratensis (Banks), and the two-spotted spider mite (TSM), Tetranychus urticae Koch, to selected miticides were evaluated with and without synergists. BGM was 112-fold more susceptible to the organophosphate dimethoate, and 24-fold more susceptible to both the pyrethroids bifenthrin and -cyhalothrin than TSM. The synergist triphenyl phosphate (TPP) enhanced the toxicities of bifenthrin and -cyhalothrin against BGM by 3.0- and 4.2-fold, respectively, and enhanced the toxicities of bifenthrin, -cyhalothrin, and dimethoate against TSM by 6.2-, 1.9-, and 1.7-fold, respectively. The synergist diethyl maleate (DEM) enhanced the toxicities of bifenthrin and -cyhalothrin against BGM by 2.2- and 2.9- fold, respectively, and enhanced the toxicity of bifenthrin against TSM by 4.1-fold. On the other hand, the synergist piperonyl butoxide (PBO) increased the toxicities of bifenthrin and -cyhalothrin by 6.0- and 2.6-fold, respectively, against BGM, and by 4.5- and 1.9-fold, respectively, against TSM. The significant synergism with these pyrethroids of all three tested synergists (except for DEM with -cyhalothrin against TSM) suggests that esterases, glutathione S-transferases, and cytochrome P450 monooxygenases all play important roles in their detoxification. However, the toxicity of dimethoate was not enhanced by these synergists in either mite species (except for TPP against TSM). Apparently, these metabolic enzymes play less of a role in detoxification of this organophosphate in these mites.     

Diel Movements of Bat Rays, Myliobatis californica, in Tomales Bay, California: Evidence for Behavioral Thermoregulation?

We used ultrasonic telemetry to examine movement patterns of 11 bat rays, Myliobatis californica, in Tomales Bay, California. Tomales Bay is long (20km) and narrow (1.4km), and is hydrographically separated into outer and inner bay regions. The outer bay (the outermost 8km) is characterized by oceanic conditions while the shallow inner bay (the innermost 12km) features wide seasonal temperature shifts. Five rays were tracked monthly from October 1990 to November 1991 and six rays (four of which carried temperature-sensing transmitters) were tracked daily from 30 June to 16 July 1992. Mean bat ray movement rate was 8.84mmin^–1 (range 4.49 to 13.40mmin^–1) and was not significantly affected by size (p=0.592), tidal stage (p=0.610), or time of day (p=0.327). Movement direction was unrelated to tidal stage (p=0.472) but showed a highly significant diel pattern (p<0.001). From 2:50–14:50h, rays moved toward the warmer and shallower inner bay, while from 14:50–2:50h they moved toward the cooler and deeper outer bay. These telemetry data, along with known bat ray foraging patterns and respiratory temperature-sensitivity, argue for behavioral thermoregulation as the primary influence on this movement pattern.     

Attachment Sites and Frequency Distribution of Erythraeid Mites, Leptus Indianensis (Acari: Prostigmata), Ectoparasitic on Harvestmen, Leiobunum Formosum (Opiliones)

Host attachment sites and frequency distribution of parasitism were investigated for the larval erythraeid mite Leptus indianensis parasitising a sample of 500 harvestmen, Leiobunum formosum in Tennessee, USA. A significant difference was found in the number of mites attached to different body segments of the harvestmen with the greatest number of mites attached to femurs I–IV. Scanning electron microscopy revealed that the mites attached to smooth areas of the host integument between rows of stout setae. The frequency distribution of mites parasitising the harvestman population was highly clumped (Coefficient of Dispersion=3.34) with a relatively small number of hosts being parasitised by most of the mites.     

Purification and immunocytochemical localization of kafirins inSorghum bicolor (L. Moench) endosperm

Summary Kafirins are the storage proteins of sorghum and are found in protein bodies in the seed endosperm. They have been classified as -, -, and -kafirins according to differences in molecular weight, solubility, and structure. The kafirins were purified, amino acid composition was determined, and immunolocalization methods were used to determine the organization of the protein bodies and distribution of kafirins throughout the endosperm. All three groups of kafirins were low in lysine. -Kafirins and -kafirins were relatively high in cysteine, and -kafirins were relatively high in methionine. Transmission electron microscopy showed that protein bodies in the peripheral endosperm were spheroid with concentric rings and few darkly stained inclusions. In contrast, protein bodies of the central endosperm were irregularly shaped with a higher proportion of darkly stained material. The light staining regions of the protein bodies are composed primarily of -kafirins with minor portions of - and -kafirins. The dark staining regions, however, are composed primarily of - and -kafirins. Immunoelectron microscopy showed that protein bodies in the peripheral endosperm contain predominantly a-kafirin with minor amounts of - and -kafirin. Central endosperm protein bodies are also predominantly -kafirin, but have a higher proportion of -kafirin and -kafirin than the peripheral endosperm protein bodies.Abbreviations GAR-HRP Goat anti-rabbit horseradish peroxidase - IgG immunoglobulin G - 2-ME 2-mercaptoethanol - SDS-PAGE sodium dodecyl sulfate polyacrylamide gel electrophoresis - TBS Tris buffer saline - TBS-T Tris buffer saline with Tween - TBS-T-B Tris buffer saline with Tween and bovine serum albumin - TCA trichloroacetic acid - UV ultraviolet     

Lateral hydrodynamic effects of rotating filaments

On the basis of the filament rotation model that was elaborated for interpretations in cell motility, the lateral hydrodynamic effects of rotating filaments have been investigated by large-scale model experiments. Helices were rotated by small electric motors in a medium of high viscosity (honey or polyethyleneglycol). The observed effects, hitherto not investigated in detail by hydrodynamics, show some features that were attributed to the indefinable formative power or vital force of the past. The main effects generated by the rotating filaments are (1) flows and flow patterns with impact zones where flows collide, (2) regions of excessive pressure and negative pressure (corner effect) along a wall, (3) grooves and smoothly shaped ridges on a free fluid surface, and (4) rolling motions of freely hanging filaments. All effects and flow patterns depend on the appropriate distribution of rotating and counterrotating filaments. Each change of the rotational direction means a dramatic alteration. The application of the observed effects explains largely the function of the microtubule/microfilament hoops or helices during the cytokinesis of a plant cell. Interpretations or simulations are described for events as the formation of secondary wall thickenings, the orientation of their microfibrils, the motion of the preprophase band microtubules, the formation of the phragmosome, the migration, stationary position and shape of the preprophase nucleus, the girdle-, septum- and H-piece formation of cell walls in algae and some events of morphogenesis inMicrasterias. Further interpretations are related to the lateral flows and to invaginations of free cell membranes, to lateral filament motions, to the right-left problem, to the selfintertwining of filaments, to the rotation of a cell body by its flagellum, to the repulsion of chromatids during meiosis and to the tetragonal and hexagonal arrangement of filaments.Dedicated to Prof. DrLothar Geitler on the occasion of the 90th anniversary of his birthday.