Dispersal Behavior of Tetranychus evansi and T. urticae on Tomato at Several Spatial Scales and Densities: Implications for Integrated Pest Management

Studying distribution is necessary to understand and manage the dynamics of species with spatially structured populations. Here we studied the distribution in Tetranychus evansi and T. urticae, two mite pests of tomato, in the scope of evaluating factors that can influence the effectiveness of Integrated Pest Management strategies. We found greater positive density-dependent distribution with T. evansi than T. urticae when assayed on single, detached tomato leaves. Indeed, T. evansi distribution among leaflets increased with initial population density while it was high even at low T. urticae densities. Intensity and rate of damage to whole plants was higher with T. evansi than T. urticae. We further studied the circadian migration of T. evansi within plant. When T. evansi density was high the distribution behavior peaked between 8 am and 3 pm and between 8 pm and 3 am local time of Kenya. Over 24 h the total number of mites ascending and descending was always similar and close to the total population size. The gregarious behavior of T. evansi combined with its rapid population growth rate, may explain why few tomato plants can be severely damaged by T. evansi and how suddenly all the crop can be highly infested. However the localisation and elimination of the first infested plants damaged by T. evansi could reduce the risk of outbreaks in the entire crop. These findings suggest also that an acaricide treated net placed on the first infested plants could be very effective to control T. evansi. Moreover circadian migration would therefore accentuate the efficiency of an acaricide treated net covering the infested plants.     

Age- and density-dependent growth within populations of the ectoparasitic digenean Transversotrema patialense on the fish host

Mills C. A. 1980. Age- and density-dependent growth within populations of the ectoparasitic digenean Transversotrema patialense on the fish host. Internationaljournal for Parasitology, 10: 287–291. Growth of the adult ectoparasitic digenean Transversotrema patialense on the fish host Brachydanio rerio is shown to be age-dependent, ceasing 15–20 days post infection. The vitelline glands expand greatly in size after infection from 1.25 % of cercarial area to 20.7 % of that of the mature adult. There is an increase in the occurrence of reproductive abnormalities in old parasites but this alone fails to account for the decline in egg production found as populations of T. patialense age. Growth of adult T. patialense is density-dependent with reduced growth at high initial parasite densities per host.     

The effect of host plants on Tetranychus evansi, Tetranychus urticae (Acari: Tetranychidae) and on their fungal pathogen Neozygites floridana (Entomophthorales: Neozygitaceae)

In a series of tritrophic-level interaction experiments, the effect of selected host plants of the spider mites, Tetranychus evansi and Tetranychus urticae, on Neozygites floridana was studied by evaluating the attachment of capilliconidia, presence of hyphal bodies in the infected mites, mortality from fungal infection, mummification and sporulation from fungus-killed mite cadavers. Host plants tested for T. evansi were tomato, cherry tomato, eggplant, nightshade, and pepper while host plants tested for T. urticae were strawberry, jack bean, cotton and Gerbera. Oviposition rate of the mites on each plant was determined to infer host plant suitability while host-switching determined antibiosis effect on fungal activity. T. evansi had a high oviposition on eggplant, tomato and nightshade but not on cherry tomato and pepper. T. urticae on jack bean resulted in a higher oviposition than on strawberry, cotton and Gerbera. Attachment of capilliconidia to the T. evansi body, presence of hyphal bodies in infected T. evansi and mortality from fungal infection were significantly higher on pepper, nightshade and tomato. The highest level of T. evansi mummification was observed on tomato. T. evansi cadavers from tomato and eggplant produced more primary conidia than those from cherry tomato, nightshade and pepper. Switching N. floridana infected T. evansi from one of five Solanaceous host plants to tomato had no prominent effect on N. floridana performance. For T. urticae, strawberry and jack bean provided the best N. floridana performance when considering all measured parameters. Strawberry also had the highest primary conidia production. This study shows that performance of N. floridana can vary with host plants and may be an important factor for the development of N. floridana epizootics.     

Mitochondria Contribute to NADPH Generation in Mouse Rod Photoreceptors

NADPH is the primary source of reducing equivalents in the cytosol. Its major source is considered to be the pentose phosphate pathway, but cytosolic NADP⁺-dependent dehydrogenases using intermediates of mitochondrial pathways for substrates have been known to contribute. Photoreceptors, a nonproliferating cell type, provide a unique model for measuring the functional utilization of NADPH at the single cell level. In these cells, NADPH availability can be monitored from the reduction of the all-trans-retinal generated by light to all-trans-retinol using single cell fluorescence imaging. We have used mouse rod photoreceptors to investigate the generation of NADPH by different metabolic pathways. In the absence of extracellular metabolic substrates, NADPH generation was severely compromised. Extracellular glutamine supported NADPH generation to levels comparable to those of glucose, but pyruvate and lactate were relatively ineffective. At low extracellular substrate concentrations, partial inhibition of ATP synthesis lowered, whereas suppression of ATP consumption augmented NADPH availability. Blocking pyruvate transport into mitochondria decreased NADPH availability, and addition of glutamine restored it. Our findings demonstrate that in a nonproliferating cell type, mitochondria-linked pathways can generate substantial amounts of NADPH and do so even when the pentose phosphate pathway is operational. Competing demands for ATP and NADPH at low metabolic substrate concentrations indicate a vulnerability to nutrient shortages. By supporting substantial NADPH generation, mitochondria provide alternative metabolic pathways that may support cell function and maintain viability under transient nutrient shortages. Such pathways may play an important role in protecting against retinal degeneration.     

Density-Dependent Multiplication and Survival Rates in Heterodera glycines

Seasonal multiplication and overwinter survival are density-dependent in Heterodera glycines. At low to moderate population densities, the nematode is capable of large population increases on susceptible soybean cultivars and high rates of oversummer or overwinter survival in the absence of a host. To improve estimates of H. glycines multiplication and survival rates, egg densities were monitored for 12 cropping sequences across 10 years. Log-linear regression analysis was used to describe and compare density-dependent relationships. Growing-season change in H. glycines egg densities was density-dependent for all crops (susceptible soybean, resistant soybean, and nonhost), with slope estimates for the density-dependent relationship greater for susceptible soybean compared with a non-host crop. Overwinter population change also was density-dependent, with similar declines in survival rates observed for all crops as population densities increased. Survival was greater following susceptible soybean compared with resistant soybean, with an intermediate rate of survival associated with non-host crops. Survival estimates greater than 100% frequently were obtained at low population densities, despite attempts to account for sampling error. Rates of growing-season multiplication and survival, when standardized for population density, declined with year of the study. Standardized overwinter survival rates were inversely related to average daily minimum temperature and monthly snow cover.     

Pyridine nucleotide levels as a function of growth in normal and transformed 3T3 cells.

The levels of NAD (NAD⁺ + NADH) and NADP (NADP⁺ + NADPH) and their redox states were measured as a function of growth in 3T3 mouse fibroblasts which exhibit density-dependent inhibition of growth and SV40 (simian virus #40)-transformed 3T3 cells (SVT2) which have lost this property. The levels were related to cell numbers, protein content, and rates of DNA synthesis. At corresponding cell densities, 3T3 cells contain approximately twice as much total protein as SVT2 cells. The levels of NAD relative to total cellular protein are density dependent in both 3T3 and SVT2, increasing with increasing cell density. Over a 30-fold range of cell densities, the NAD levels in 3T3 increase 2.4-fold, while the levels in SVT2 increase 1.6-fold. The levels of NAD are very similar in dividing 3T3 and SVT2 cells at corresponding cell densities; however, a marked increase in the levels of NAD is observed in 3T3 cells, but not in SVT2 cells, at cell densities just prior to where 3T3 cells enter density-dependent inhibition of growth. This increase in NAD levels is correlated with the cessation of DNA synthesis. The NAD pools are 15–25% NADH for 3T3 and 5–15% NADH for SVT2. NADP levels relative to protein in 3T3 and SVT2 are less density dependent, with overall increases of 1.3- and 1.2-fold, respectively, observed over the range of cell densities examined. NADP levels relative to protein are nearly twice as high in SVT2 cells as in 3T3 cells of corresponding cell densities. The NADP pools are approximately 70–80% NADPH in both cell types.     

Regulation and control of intracellular algae (= zooxanthellae) in hard corals

To examine algal (= zooxanthellae) regulation and control, and the factors determining algal densities in hard corals, the zooxanthellae mitotic index and release rates were regularly determined in branch tips from a colony of a staghorn coral, Acropora formosa, recovering from a coral ''bleaching'' event (the stress-related dissociation of the coral–algal symbiosis). Mathematical models based upon density-dependent decreases in the algal division frequency and increases in algal release rates during the post-bleaching recovery period accurately predict the observed recovery period (ca. 20 weeks). The models suggest that (i) the colony recovered its algal population from the division of the remaining zooxanthellae, and (ii) the continual loss of zooxanthellae significantly slowed the recovery of the coral. Possible reasons for the ''paradoxical'' loss of healthy zooxanthellae from the bleached coral are discussed in terms of endodermal processes occurring in the recovering coral and the redistribution of newly formed zooxanthellae to aposymbiotic host cells. At a steady-state algal density of 2.1 x 10⁶ zooxanthellae cm^-2 at the end of the recovery period, the zooxanthellae would have to form a double layer of cells in the coral tissues, consistent with microscopic observations. Neighbouring colonies of A. formosa with inherently higher algal densities possess proportionately smaller zooxanthellae. Results suggest that space availability and the size of the algal symbionts determines the algal densities in the coral colonies. The large increases in the algal densities reported in corals exposed to elevated nutrient concentrations (i.e between a two- and five-fold increase in the algal standing stock) are not consistent with this theory. We suggest that increases of this magnitude are a product of the experimental conditions: reasons for this statement are discussed. We propose that the stability of the coral–algal symbiosis under non-stress conditions, and the constancy of zooxanthellae densities in corals reported across growth form, depth and geographic range, are related to space availability limiting algal densities. However, at these densities, zooxanthellae have attributes consistent with nutrient limitation.     

Testing for reproductive interference in the population dynamics of two congeneric species of herbivorous mites

When phylogenetically close, two competing species may reproductively interfere, and thereby affect their population dynamics. We tested for reproductive interference (RI) between two congeneric haplo-diploid spider mites, Tetranychus evansi and Tetranychus urticae, by investigating their interspecific mating and their population dynamics when they competed on the same plants. They are both pests of tomato, but differ in the host plant defences that they suppress or induce. To reduce the effect of plant-mediated interaction, we used a mutant tomato plant lacking jasmonate-mediated anti-herbivore defences in the competition experiment. In addition, to manipulate the effect of RI, we introduced founder females already mated with conspecific males in mild RI treatments or founder, virgin females in strong RI treatments (in either case together with heterospecific and conspecific males). As females show first-male sperm precedence, RI should occur especially in the founder generation under strong RI treatments. We found that T. urticae outcompeted T. evansi in mild, but not in strong RI treatments. Thus, T. evansi interfered reproductively with T. urticae. This result was supported by crossing experiments showing frequent interspecific copulations, strong postmating reproductive isolation and a preference of T. evansi males to mate with T. urticae (instead of conspecific) females, whereas T. urticae males preferred conspecific females. We conclude that interspecific mating comes at a cost due to asymmetric mate preferences of males. Because RI by T. evansi can improve its competitiveness to T. urticae, we propose that RI partly explains why T. evansi became invasive in Europe where T. urticae is endemic.     

Review of the invasion of Tetranychus evansi: biology, colonization pathways, potential expansion and prospects for biological control

In the last two decades the subtropical red tomato spider mite, Tetranychus evansi, has expanded its geographical distribution and emerged as a major invasive agricultural pest. The mite is considered to be native to South America. Since its first report from north-eastern Brazil in 1952, it has been reported from different continents. This paper reviews literature on several aspects of the biology of T. evansi related to its status as an invasive species. It addresses taxonomical issues, occurrences, life history traits, host-plant interactions, genetic diversity of geographical isolates and worldwide colonisation pathways. It also presents updated data which allowed the assessment of the actual worldwide distribution of this species, from its discovery to the latest reports. As T. evansi is considered an emerging agricultural pest, we also present data based on modelling of the potential of T. evansi to colonize new geographical areas. In addition, this review presents past and current research on natural enemies of T. evansi potentially useful for its biological control. While summarizing the knowledge on T. evansi, the review emphasizes research possibilities that are worth pursuing, mainly concerning the ability of T. evansi to establish new populations and to detect new promising natural enemies.     

Genome and Phylogenetic Analyses of Trypanosoma evansi Reveal Extensive Similarity to T. brucei and Multiple Independent Origins for Dyskinetoplasty

Two key biological features distinguish Trypanosoma evansi from the T. brucei group: independence from the tsetse fly as obligatory vector, and independence from the need for functional mitochondrial DNA (kinetoplast or kDNA). In an effort to better understand the molecular causes and consequences of these differences, we sequenced the genome of an akinetoplastic T. evansi strain from China and compared it to the T. b. brucei reference strain. The annotated T. evansi genome shows extensive similarity to the reference, with 94.9% of the predicted T. b. brucei coding sequences (CDS) having an ortholog in T. evansi, and 94.6% of the non-repetitive orthologs having a nucleotide identity of 95% or greater. Interestingly, several procyclin-associated genes (PAGs) were disrupted or not found in this T. evansi strain, suggesting a selective loss of function in the absence of the insect life-cycle stage. Surprisingly, orthologous sequences were found in T. evansi for all 978 nuclear CDS predicted to represent the mitochondrial proteome in T. brucei, although a small number of these may have lost functionality. Consistent with previous results, the F₁F_O-ATP synthase γ subunit was found to have an A281 deletion, which is involved in generation of a mitochondrial membrane potential in the absence of kDNA. Candidates for CDS that are absent from the reference genome were identified in supplementary de novo assemblies of T. evansi reads. Phylogenetic analyses show that the sequenced strain belongs to a dominant group of clonal T. evansi strains with worldwide distribution that also includes isolates classified as T. equiperdum. At least three other types of T. evansi or T. equiperdum have emerged independently. Overall, the elucidation of the T. evansi genome sequence reveals extensive similarity of T. brucei and supports the contention that T. evansi should be classified as a subspecies of T. brucei.     

Exploitation of auxotrophies and metabolic defects in Toxoplasma as therapeutic approaches

Like any obligate intracellular pathogen, the parasite Toxoplasma gondii has lost its capacity for living independently of another organism. Toxoplasma lacks many genes that encode for entire metabolic pathways and has, in return, expanded genes that promote nutrient scavenging to meet its basic metabolic requirements. Although sequestrated in a parasitophorous vacuole and thus insulated from the nutrient-rich host cytosol and organelles by a membrane, T. gondii has evolved efficient strategies to acquire essential metabolites from mammalian cells. This review explores the natural auxotrophies and nutrient scavenging activities of the parasite, emphasising unique transport systems and salvage pathways. We describe the mechanisms deployed by Toxoplasma to modify its parasitophorous vacuole to gain access to host cytosolic molecules and to hijack host organelles to retrieve their nutrient content. From a therapeutic perspective, we survey the different possibilities to starve T. gondii by nutrient depletion or disruption of salvage pathways.     

Characterization of the Pivotal Carbon Metabolism of Streptococcus suis Serotype 2 under ex Vivo and Chemically Defined in Vitro Conditions by Isotopologue Profiling

Streptococcus suis is a neglected zoonotic pathogen that has to adapt to the nutritional requirements in the different host niches encountered during infection and establishment of invasive diseases. To dissect the central metabolic activity of S. suis under different conditions of nutrient availability, we performed labeling experiments starting from [¹³C]glucose specimens and analyzed the resulting isotopologue patterns in amino acids of S. suis grown under in vitro and ex vivo conditions. In combination with classical growth experiments, we found that S. suis is auxotrophic for Arg, Gln/Glu, His, Leu, and Trp in chemically defined medium. De novo biosynthesis was shown for Ala, Asp, Ser, and Thr at high rates and for Gly, Lys, Phe, Tyr, and Val at moderate or low rates, respectively. Glucose degradation occurred mainly by glycolysis and to a minor extent by the pentose phosphate pathway. Furthermore, the exclusive formation of oxaloacetate by phosphoenolpyruvate (PEP) carboxylation became evident from the patterns in de novo synthesized amino acids. Labeling experiments with S. suis grown ex vivo in blood or cerebrospinal fluid reflected the metabolic adaptation to these host niches with different nutrient availability; however, similar key metabolic activities were identified under these conditions. This points at the robustness of the core metabolic pathways in S. suis during the infection process. The crucial role of PEP carboxylation for growth of S. suis in the host was supported by experiments with a PEP carboxylase-deficient mutant strain in blood and cerebrospinal fluid.     

Trypanosoma evansi: Levels of copper, iron and zinc in the bloodstream of infected cats

The aim of this study was to evaluate the concentrations of copper, iron and zinc in blood serum of cats experimentally infected with Trypanosoma evansi. Animals were divided into two groups: control and infected with T. evansi. The animals were infected with 10⁸ trypomastigotes each and parasitemia was estimated daily for 56 days by microscopic examination of smears. Hematological and biochemical parameters were evaluated for monitoring of the disease. Serum metal levels were determined in blood samples collected at days 7, 28 and 56 of the experiment. Inductively coupled plasma optical emission spectrometry was used to measure the levels of copper, iron and zinc. Significant differences were observed among groups (P < 0.05). Increased levels of copper and decreased iron and zinc levels were observed. A decrease in the number of red blood cells was also observed 7 days after inoculation. Biochemical parameters were not altered. Therefore, the infection by T. evansi might alter the serum metal levels, causing metabolic disturbances in cats.     

First identification of Trypanosoma vivax among camels (Camelus dromedarius) in Yazd,central Iran,jointly with Trypanosoma evansi

Trypanosomes are protozoan parasites of class Kinetoplastida. Trypanosoma vivax is one of the organisms that can cause Nagana and Trypanosoma evansi can cause Surra. In Africa, Trypanosoma vivax is mainly transmitted by Glossina spp. (tsetse fly) but it can be transmitted mechanically by other blood-feeding dipters. Trypanosoma evansi is transmitted mechanically and non-dependent to tsetse fly. In this research, T. vivax and T. evansi among camels (Camelus dromedarius) in Yazd, Iran were identified by microscopy and molecular examinations but the sensitivity of microscopy was lower than molecular examinations. Trypanosoma vivax and T. evansi were observed in 4 out of 134 blood film samples (2.98%). The prevalence of Trypanosoma spp. among 134 male camels (C. dromedarius) based on molecular examinations was 30.6% (22.76–38.44% with 95% confidence interval), 25 out of 134 (18.65%) had co-infection of T. evansi and T. vivax, and 16 out of 134 (11.94%) had an infection of T. vivax alone. We provided the first confirmation of infection with T. vivax among camels in Iran, and also in Asia, which has important implications on our knowledge of the occurrence and possible spread of this pathogen at the global level. Investigations in other species such as cattle and sheep are strongly recommended.     

Assessing Anti-fungal Activity of Isolated Alveolar Macrophages by Confocal Microscopy

The lung is an interface where host cells are routinely exposed to microbes and microbial products. Alveolar macrophages are the first-line phagocytic cells that encounter inhaled fungi and other microbes. Macrophages and other immune cells recognize Aspergillus motifs by pathogen recognition receptors and initiate downstream inflammatory responses. The phagocyte NADPH oxidase generates reactive oxygen intermediates (ROIs) and is critical for host defense. Although NADPH oxidase is critical for neutrophil-mediated host defense^1-3, the importance of NADPH oxidase in macrophages is not well defined. The goal of this study was to delineate the specific role of NADPH oxidase in macrophages in mediating host defense against A. fumigatus. We found that NADPH oxidase in alveolar macrophages controls the growth of phagocytosed A. fumigatus spores⁴. Here, we describe a method for assessing the ability of mouse alveolar macrophages (AMs) to control the growth of phagocytosed Aspergillus spores (conidia). Alveolar macrophages are stained in vivo and ten days later isolated from mice by bronchoalveolar lavage (BAL). Macrophages are plated onto glass coverslips, then seeded with green fluorescent protein (GFP)-expressing A. fumigatus spores. At specified times, cells are fixed and the number of intact macrophages with phagocytosed spores is assessed by confocal microscopy.     

Metabolic Network Analysis of Streptomyces tenebrarius, a Streptomyces Species with an Active Entner-Doudoroff Pathway

Streptomyces tenebrarius is an industrially important microorganism, producing an antibiotic complex that mainly consists of the aminoglycosides apramycin, tobramycin carbamate, and kanamycin B carbamate. When S. tenebrarius is used for industrial tobramycin production, kanamycin B carbamate is an unwanted by-product. The two compounds differ only by one hydroxyl group, which is present in kanamycin carbamate but is reduced during biosynthesis of tobramycin. ¹³C metabolic flux analysis was used for elucidating connections between the primary carbon metabolism and the composition of the antibiotic complex. Metabolic flux maps were constructed for the cells grown on minimal medium with glucose or with a glucose-glycerol mixture as the carbon source. The addition of glycerol, which is more reduced than glucose, led to a three-times-greater reduction of the kanamycin portion of the antibiotic complex. The labeling indicated an active Entner-Doudoroff (ED) pathway, which was previously considered to be nonfunctional in Streptomyces. The activity of the pentose phosphate (PP) pathway was low (10 to 20% of the glucose uptake rate). The fluxes through Embden-Meyerhof-Parnas (EMP) and ED pathways were almost evenly distributed during the exponential growth on glucose. During the transition from growth phase to production phase, a metabolic shift was observed, characterized by a decreased flux through the ED pathway and increased fluxes through the EMP and PP pathways. Higher specific NADH and NADPH production rates were calculated in the cultivation on glucose-glycerol, which was associated with a lower percentage of nonreduced antibiotic kanamycin B carbamate.     

Characterizing Roles for the Glutathione Reductase,Thioredoxin Reductase and Thioredoxin Peroxidase-Encoding Genes of Magnaporthe oryzae during Rice Blast Disease

Understanding how pathogenic fungi adapt to host plant cells is of major concern to securing global food production. The hemibiotrophic rice blast fungus Magnaporthe oryzae, cause of the most serious disease of cultivated rice, colonizes leaf cells asymptomatically as a biotroph for 4–5 days in susceptible rice cultivars before entering its destructive necrotrophic phase. During the biotrophic growth stage, M. oryzae remains undetected in the plant while acquiring nutrients and growing cell-to-cell. Which fungal processes facilitate in planta growth and development are still being elucidated. Here, we used gene functional analysis to show how components of the NADPH-requiring glutathione and thioredoxin antioxidation systems of M. oryzae contribute to disease. Loss of glutathione reductase, thioredoxin reductase and thioredoxin peroxidase-encoding genes resulted in strains severely attenuated in their ability to grow in rice cells and that failed to produce spreading necrotic lesions on the leaf surface. Glutathione reductase, but not thioredoxin reductase or thioredoxin peroxidase, was shown to be required for neutralizing plant generated reactive oxygen species (ROS). The thioredoxin proteins, but not glutathione reductase, were shown to contribute to cell-wall integrity. Furthermore, glutathione and thioredoxin gene expression, under axenic growth conditions, was dependent on both the presence of glucose and the M. oryzae sugar/ NADPH sensor Tps1, thereby suggesting how glucose availability, NADPH production and antioxidation might be connected. Taken together, this work identifies components of the fungal glutathione and thioredoxin antioxidation systems as determinants of rice blast disease that act to facilitate biotrophic colonization of host cells by M. oryzae.     

Host plant resistance among tomato accessions to the spider mite <Emphasis Type="Italic">Tetranychus evansi</Emphasis> in Kenya

The spider mite Tetranychus evansi has a broad range of host plants. Control of T. evansi has been a big challenge to tomato farmers due to its fast rate of reproduction, development of resistance to chemical pesticides and its ability to use weeds as alternative hosts when the tomato plants are not available. The aim of the current study was to determine the host plant acceptance and the relative contributions of trichomes in the control of the red spider mite by comparing the survival, development and oviposition rates of the red spider mite on eight tomato accessions. Leaflets from eight tomato varieties were assayed with the spider mites to determine the egg laying capacity and developmental time of the spider mites on the tomato accessions as well as the trichome densities. Densities of trichome types I, IV, V and VI varied among the tomato accessions. Variation in types I, IV and VI accounted for most of the variation in mite responses. The varieties with high densities of types IV and VI had the highest fecundity and mite development did not go beyond the larval stage. The developmental time varied significantly among the tomato accessions. The results indicated that the higher the density of trichome type I the lower the adult survival. The findings indicated possible resistance of some of the tested tomato accessions against T. evansi which is partially associated with trichomes types and density.     

<Emphasis Type="Italic">Trypanosoma brucei</Emphasis> Plimmer &amp; Bradford, 1899 is a synonym of <Emphasis Type="Italic">T. evansi</Emphasis> (Steel, 1885) according to current knowledge and by application of nomenclature rules

Proper application of the principles of biological nomenclature is fundamental for scientific and technical communication about organisms. As other scientific disciplines, taxonomy inherently is open to change, thus species names cannot be final and immutable. Nevertheless, altering the names of organisms of high economical, medical, or veterinary importance can become a complex challenge between the scientific need to have correct classifications, and the practical ideal of having fixed classifications. Trypanosoma evansi (Steel, 1885), T. brucei Plimmer & Bradford, 1899 and T. equiperdum Doflein, 1901 are important parasites of mammals. According to current knowledge, the three names are synonyms of a single trypanosome species, the valid name of which should be T. evansi by the mandatory application of the Principle of Priority of zoological nomenclature. Subspecies known as T. brucei brucei Plimmer & Bradford, 1899, T. b. gambiense Dutton, 1902 and T. b. rhodesiense Stephens & Fantham, 1910 should be referred to respectively as T. evansi evansi (Steel, 1885), T. e. gambiense and T. e. rhodesiense. The polyphyletic groupings so far known as T. evansi and T. equiperdum should be referred respectively to as surra- and dourine-causing strains of T. e. evansi. Likewise, trypanosomes so far known as T. b. brucei should be referred to as nagana-causing strains of T. e. evansi. Though it modifies the scientific names of flagship human and animal parasites, the amended nomenclature proposed herein should be adopted because it reflects phylogenetic and biological advancements, fixes errors, and is simpler than the existing classificatory system.     

The invasive spider mite Tetranychus evansi (Acari: Tetranychidae) alters community composition and host-plant use of native relatives

The tomato spider mite Tetranychus evansi Baker and Pritchard (Acari: Tetranychidae), is a worldwide pest of solanaceous crops that has recently invaded many parts of the world. In the present study we examined the ecological impact of its arrival in the Mediterranean region. The spider mite and phytoseiid mite assemblages in various crop and non-crop plants in three areas of Valencia (Spain) were studied a few months before and 10 years after the invasion of T. evansi. According to rarefaction analyses, the invasion of T. evansi did not affect neither the total number of species in the mite community examined (spider mite and phytoseiid species) nor the number of species when the two communities were examined separately. However, after the invasion, the absolute and relative abundance of the native Tetranychus species was significantly reduced. Before the invasion, T. urticae and T. turkestani were the most abundant spider mites, accounting for 62.9 and 22.8 % of the specimens. After the invasion, T. evansi became the most abundant species, representing 60 % of the total spider mites recorded, whereas the abundance of T. urticae was significantly reduced (23 %). This reduction took place principally on non-crop plants, where native species were replaced by the invader. Null model analyses provided evidence for competition structuring the spider mite community on non-crop plants after the invasion of T. evansi. Resistance to acaricides, the absence of efficient native natural enemies, manipulation of the plant defenses and the web type produced by T. evansi are discussed as possible causes for the competitive displacement.