Fine Structure of the Schizont and Merozoite of Isospora sp. (Sporozoa: Eimeriidae) Parasitic in Gehyra variegata (Dumeril and Bibron, 1836) (Reptilia: Gekkonidae)

SYNOPSIS. A study was made of the fine structure of some stages in the life cycle of an undesignated species of Isospora parasitic in a gecko. The merozoites which lay within a membrane-bound periparasitic vacuole in the host epithelial cell, had a striking similarity to Plasmodium, Lankesterella, Toxoplasma, Besnoitia, Sarcocystis, Eimeria and the M-organism. Each merozoite was invested with a triple-layered pellicle, the outer membrane of which was loosely applied. At the anterior end of the merozoite were conoid and apical rings; microtubules terminated in the posterior apical ring. Other organelles included nucleus, endoplasmic reticulum, mitochondria, micropyle, paired organelle, toxonemes and a variety of vacuoles. Although the sequence of development of the merozoite was not completely followed, some events in this process were recorded. The evidence suggests that anterior ends are formed early and that merozoites develop subsequently by a process of budding. The merozoite pellicle appears to be continuous with, altho structurally different from, the investing membrane of the parent cell.     

Multi‐species distribution modelling highlights the Adelaide Geosyncline,South Australia,as an important continental‐scale arid‐zone refugium

The mainland portion of the Adelaide Geosyncline (Mount Lofty and Flinders Ranges) has been postulated as an important arid‐zone climate refugium for Australia. To test the sensitivity of this putative Australian arid biome refugium to contemporary climate change, we compared Generalized Additive Modelling and MaxEnt distribution models for 20 vascular plant species. We aimed to identify shared patterns to inform priority areas for management. Models based on current climate were projected onto a hypothetical 2050 climate with a 1.5°C increase in temperature and 8% decrease in rainfall. Individual comparisons and combined outputs of logistic models for all 20 species showed range contraction to shared refugia in the Flinders Ranges and southern Mount Lofty Ranges. Modelling suggests the Flinders Ranges will experience species turnover while suitable climatic habitat will be retained in the Mount Lofty Ranges for the current suite of species. Fragmentation of the southern Mount Lofty Ranges poses management challenges for conserving species diversity with warming and drying. Although projected models must be interpreted carefully, they suggest the region will remain an important but threatened refugium for mesic species at a continental scale.     

Lanzia berggrenii及其相关种的系统发育地位(英文)

系统发育分析结果表明,尽管Lanzia berggrenii能在寄主中形成基物子座,但与膜盘菌属的核心种关系较近,而与蜡盘菌科成员关系较远,应该归属于膜盘菌属。在广义的膜盘菌属的系统树中该种及在新西兰发现的4个新种构成一个单系群,分别命名为Hymenoscyphus haasticus,H. kiko,H.ohakune和H.waikaia。它们的共同特征:基物均为南青冈叶片,侧丝顶端分枝形成类似囊层被的结构,覆盖于子实层上部。Lanzia berggrenii var.metrosideri应为膜盘菌属中一个独立的种,即Hymenoscyphus metrosideri。     

Alternative oxidase impacts the plant response to biotic stress by influencing the mitochondrial generation of reactive oxygen species

Previously, we showed that inoculation of tobacco with Pseudomonas syringae incompatible pv. maculicola results in a rapid and persistent burst of superoxide (O₂^‐) from mitochondria, no change in amount of mitochondrial alternative oxidase (AOX) and induction of the hypersensitive response (HR). However, inoculation with incompatible pv. phaseolicola resulted in increased AOX, no O₂^‐ burst and no HR. Here, we show that in transgenic plants unable to induce AOX in response to pv. phaseolicola, there is now a strong mitochondrial O₂^‐ burst, similar to that normally seen only with pv. maculicola. This interaction did not however result in a HR. This indicates that AOX amount is a key determinant of the mitochondrial O₂^‐ burst but also that the burst itself is not sufficient to induce the HR. Surprisingly, the O₂^‐ burst normally seen towards pv. maculicola is delayed in plants lacking AOX. This delay is associated with a delayed HR, suggesting that the burst does promote the HR. A O₂^‐ burst can also be induced by the complex III inhibitor antimycin A (AA), but is again delayed in plants lacking AOX. The similar mitochondrial response induced by pv. maculicola and AA suggests that electron transport is a target during HR‐inducing biotic interactions.     

Biological Control of Take-all Disease of Wheat Caused by Gaeumannomyces graminis var. tritici Under Field Conditions Using a Phialophora sp.

A Phialophora sp. (isolate I-52), originally isolated from soil in a wheat field exhibiting suppression of take-all disease caused by Gaeumannomyces graminis var. tritici , was tested under field conditions for its ability to suppress this disease in winter and spring wheat. I-52 was grown on a variety of autoclaved organic substrates, including oat, millet and canola seed. All of these gave significant disease control when added to the seed furrow with inoculum of the take-all fungus. W hole seed of I-52 substrate was as effective as particles < 0.5 mm in diameter. Placing I-52 in powdered form directly on to wheat seed was ineffective in controlling take-all. Rates as low as 2 g of I-52/3.3 m of row added with the seed provided some control of take-all, and nearly complete control in winter wheat was obtained using 15 g/3.3 m. The winter wheat host cultivar did not influence the degree of control of take-all by I-52.     

Initiation of flight muscle apoptosis and wing casting in the red imported fire ant Solenopsis invicta

Abstract Newly‐mated Solenopsis invicta flight queens cast (shed) their wings within 24 h. An examination of their flight muscle cells reveals numerous apoptotic (terminal deoxynucleotidyl transferase mediated dUTP nick end labelling positive) nuclei. By contrast, flight muscle cells of mature alate virgin (MAV) females removed 24 h earlier from a managed laboratory colony exhibit neither wing casting nor the presence of apoptotic nuclei. Using MAV‐females, the initiation of flight muscle apoptosis and wing casting is compared with artificial mating using seminal fluid with sperm, seminal fluid with no sperm, saline as a negative control, the mating flight as simulated in the laboratory, elevated CO₂ exposure, application of methoprene (a juvenile hormone analogue), or injection of 20‐hydroxyecdysone. Numerous apoptotic nuclei are revealed in the flight muscle cells of mated dealate females 24 h after a natural mating flight but not in MAV‐females controls. Only artificial mating of MAV‐females reveals a similar pattern of apoptotic nuclei flight muscle 24 h after insemination. None of the other factors tested induces flight muscle cell apoptosis in MAV‐females. Methoprene dissolved in methyl ethyl ketone, at a concentration of 0.44 ng per μL per ant, stimulates 90% of MAV‐females to shed their wings within 24 h, as opposed to 10% or less wing shedding for the methyl ethyl ketone control and all other treatments.     

Rampant drift in artificially fragmented populations of the endangered tidewater goby (Eucyclogobius newberryi)

Habitat fragmentation and its genetic consequences are a critically important issue in evaluating the evolutionary penalties of human habitat modification. Here, we examine the genetic structure and diversity in naturally subdivided and artificially fragmented populations of the endangered tidewater goby (Eucyclogobius newberryi), a small fish restricted to discrete coastal lagoons and estuaries in California, USA. We use five naturally fragmented coastal populations from a 300‐ km spatial scale as a standard to assess migration and drift relative to eight artificially fragmented bay populations from a 30‐ km spatial scale. Using nine microsatellite loci in 621 individuals, and a 522‐base fragment of mitochondrial DNA control region from 103 individuals, we found striking differences in the relative influences of migration and drift on genetic variation at these two scales. Overall, the artificially fragmented populations exhibited a consistent pattern of higher genetic differentiation and significantly lower genetic diversity relative to the naturally fragmented populations. Thus, even in a species characterized by habitat isolation and subdivision, further artificial fragmentation appears to result in substantial population genetic consequences and may not be sustainable.