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B A Croft - One of the best experts on this subject based on the ideXlab platform.

  • intra and interspecific predation by adult female Metaseiulus occidentalis and typhlodromus pyri acari phytoseiidae when provisioned with varying densities and ratios of tetranychus urticae acari tetranychidae and phytoseiid larvae
    Experimental and Applied Acarology, 1997
    Co-Authors: Ian V Macrae, B A Croft
    Abstract:

    The phytoseiid mites Metaseiulus occidentalis (Nesbitt) and Typhlodromus pyri Schueten are used together and alone as biological control agents against tetranychid pest mites of apple. Their effectiveness as control agents may be impacted by intraguild predation. The effects of prey species and prey density on the rates of inter- and intraspecific predation and oviposition by these two predators were investigated through a series of experiments. Adult female predators were given prey as mixed populations of phytoseiid larvae and larvae of a more preferred species, the spider mite, Tetranychus urticae Koch, at different densities and ratios. Typhlodromus pyri, more of a generalist predator, showed higher rates of predation and cannibalism on phytoseiid immatures at most prey densities and ratios. Manly preference indices indicated that T. pyri switched to feed on phytoseiid larvae at higher prey levels and ratios of T. urticae than M. occidentalis. This greater ability to use phytoseiid larvae as prey may help stabilize T. pyri populations when more preferred prey is unavailable. This may, in part, explain the observed persistence of T. pyri populations when M. occidentalis populations were decreasing in orchard test plots.

  • Intra- and interspecific predation on four life stage groups by the adult females of Metaseiulus occidentalis, Typhlodromus pyri, Neoseiulus fallacis and Amblyseius andersoni
    Experimental & Applied Acarology, 1996
    Co-Authors: B A Croft
    Abstract:

    Do adult females of oligophagous species such as Neoseiulus fallacis (Garman) and Metaseiulus occidentalis (Nesbitt) show less intra- and interspecific predation on phytoseiids when other foods are scarce than polyphagous species such as Amblyseius andersoni Chant and Typhlodromus pyri Scheuten? We caged single adult females of each species without food with ten of their own eggs or larvae, with ten eggs or larvae of the other species or with ten nymphs or adult females of M. occidentalis ( T. pyri for M. occidentalis ). We assessed the ambulatory activity, survival time, egg levels and prey loss in each test. Polyphages (in particular T. pyri ) lived longer than oligophages (in particular N. fallacis ) without food. The small T. pyri detected its own stages and benefited most by feeding on small active stages of other species. Amblyseius andersoni , the largest mite, fed and gained the most of any species when held with nymphs and female adults. Metaseiulus occidentalis fed on eggs of all four species to enhance survival. The large hyperactive N. fallacis gained the least from these behaviours. Each mite seemed uniquely adapted to survive conditions of scarce prey and these behaviours may explain their roles in phytoseiid mite complexes. Overall, oligophagous adult females fed less and gained less by feeding on phytoseiids than did polyphagous adult females.

  • differential impact of egg predation by zetzellia mali acari stigmaeidae on Metaseiulus occidentalis and typhlodromus pyri acari phytoseiidae
    Experimental and Applied Acarology, 1996
    Co-Authors: Ian V Macrae, B A Croft
    Abstract:

    The differential impact of Zetzellia mali on the phytoseiids Metaseiulus occidentalis and Typhlodromus pyri was studied in the laboratory and by analysis of population from orchard plots that contained either phytoseiid, similar numbers of prey mites and high or low densities of Z. mali. Five hypotheses were evaluated to explain why Z. mali had more impact on M. occidentalis in the field than on T. pyri. Given equal opportunity, Z. mali adult females did not consume more M. occidentalis eggs than T. pyri eggs nor did adult females of either phytoseiid inflict greater mortality on Z. mali eggs or larvae through attack or consumption. There was no difference in the within-tree association of Z. mali adult females with eggs of either phytoseiid species nor were there differences in the way prey mites (all life stages) were spatially partitioned between adult female Z. mali as compared with adults and deutonymphs (combined) of either phytoseiid. The foraging area of adult female Z. mali and the oviposition locations of the two phytoseiids from both field and laboratory data were compared using spatial statistics. Metaseiulus occidentalis laid significantly more eggs in the primary foraging area of adult female Z. mali than T. pyri. This was the only factor identified which may explain the greater impact of Z. mali on M. occidentalis. The impact of these interspecific effects on the persistence of predatory mite guilds and biological control are discussed.

  • Walking, feeding and intraspecific interaction of larvae of Metaseiulus occidentalis, Typhlodromus pyri, Neoseiulus fallacis and Amblyseius andersoni held with and without eggs of Tetranychus urticae
    Experimental & Applied Acarology, 1994
    Co-Authors: B A Croft, Z.-q. Zhang
    Abstract:

    Larvae of Metaseiulus occidentalis (Nesbitt), Typhlodromus pyri Scheuten, Neoseiulus fallacis (Garman) and Amblyseius andersoni Chant exhibited different activity levels when held on apple leaf or on tile arenas and given or not given eggs of Tetranychus urticae Koch and water (tiles only). M. occidentalis larvae held without prey exhibited high levels of walking (includes searching) during 24 hours of evaluation, whereas M. occidentalis larvae held with prey fed quickly and then became less active. Fed larvae of M. occidentalis were less active on leaves than tile. Larvae of T. pyri on leaves had a very low frequency of walking, almost never fed and quickly assumed a resting position during development. While much less active than M. occidentalis , fed and unfed T. pyri larvae walked more on tiles than leaves before resting. Larvae of N. fallacis and A. andersoni fed at low rates and were similarly active on tiles and leaves. Free water increased walking by M. occidentalis, A. andersoni and T. pyri on tile but not N. fallacis. M. occidentalis larvae interacted 5–7 times more often than larvae of the other three species. Cannibalism or scavenging was rarely seen and then only for M. occidentalis larvae. Larvae of all four mites walked, fed and interacted much more in the first 12 hours than the second 12 hours of tests, except unfed M. occidentalis . Unfed M. occidentalis larvae did not molt to protonymphs but unfed larvae of the other three species did. Unfed and fed protonymphs of all four species walked more at 4 hours after molting than larvae at 12–24 hours. Unfed and fed protonymphs of T. pyri or A. andersoni had similar walking frequencies, but unfed protonymphs of N. fallacis were more active than fed ones. Trends in larval activities are discussed relative to the life history of each species.

  • larval survival and feeding by immature Metaseiulus occidentalis neoseiulus fallacis amblyseius andersoni and typhlodromus pyri on life stage groups of tetranychus urticae koch and phytoseiid larvae
    Experimental and Applied Acarology, 1993
    Co-Authors: B A Croft, M B Croft
    Abstract:

    When 20 newly hatched larvae either of Metaseiulus occidentalis (Nesbitt), Neoseiulus fallacis (Garman), Amblyseius andersoni Chant or Typhlodromus pyri Scheuten were held in arenas without food at 95% RH and 20°C, the percentages of mites surviving to protonymphs were 5.0, 81.3, 86.3, and 83.8%, respectively. Unfed M. occidentalis larvae starved within 2–3 days, while immatures of the other three species lived up to 12–14 days, with some becoming adults by cannibalizing and/or scavenging. Phytosciid larvae given eggs, larvae/protochrysalis/protonymphs (L/P), deutochrysalis/deutonymphs (D) or teleiochrysalis/female adult (T/A) of Tetranychus urticae Koch, fed at different incidences during 6 h tests. Larvae of T. pyri never fed, but almost all larvae of M. occidentalis fed on eggs and L/Ps and 60–70% of M. occidentalis larvae fed on Ds and T/As. N. fallacis and A. andersoni larvae fed at incidences from 20–75% depending on the stage of spider mite given. Larvae fed more commonly on eggs and L/Ps than Ds and T/As for M. occidentalis and N. fallacis but not A. andersoni. Protonymphs and deutonymphs of all four species, readily fed on T/As after 3 h of exposure, but incidences were higher for A. andersoni and T. pyri. Feeding on phytoseiid larvae by protonymphs and deutonymphs also was more common for A. andersoni and T. pyri. Except for M. occidentalis, deutonymphs fed more than protonymphs on phytoseiid larvae. Results are discussed in relation to individual species ‘life histories and the value of these traits in predicting a species’ role in a biological control system.

Ke Wu - One of the best experts on this subject based on the ideXlab platform.

  • The Glutathione-S-Transferase, Cytochrome P450 and Carboxyl/Cholinesterase Gene Superfamilies in Predatory Mite Metaseiulus occidentalis
    PLOS ONE, 2016
    Co-Authors: Ke Wu
    Abstract:

    : Pesticide-resistant populations of the predatory mite Metaseiulus (= Typhlodromus or Galendromus) occidentalis (Arthropoda: Chelicerata: Acari: Phytoseiidae) have been used in the biological control of pest mites such as phytophagous Tetranychus urticae. However, the pesticide resistance mechanisms in M. occidentalis remain largely unknown. In other arthropods, members of the glutathione-S-transferase (GST), cytochrome P450 (CYP) and carboxyl/cholinesterase (CCE) gene superfamilies are involved in the diverse biological pathways such as the metabolism of xenobiotics (e.g. pesticides) in addition to hormonal and chemosensory processes. In the current study, we report the identification and initial characterization of 123 genes in the GST, CYP and CCE superfamilies in the recently sequenced M. occidentalis genome. The gene count represents a reduction of 35% compared to T. urticae. The distribution of genes in the GST and CCE superfamilies in M. occidentalis differs significantly from those of insects and resembles that of T. urticae. Specifically, we report the presence of the Mu class GSTs, and the J' and J" clade CCEs that, within the Arthropoda, appear unique to Acari. Interestingly, the majority of CCEs in the J' and J" clades contain a catalytic triad, suggesting that they are catalytically active. They likely represent two Acari-specific CCE clades that may participate in detoxification of xenobiotics. The current study of genes in these superfamilies provides preliminary insights into the potential molecular components that may be involved in pesticide metabolism as well as hormonal/chemosensory processes in the agriculturally important M. occidentalis.

  • the glutathione s transferase cytochrome p450 and carboxyl cholinesterase gene superfamilies in predatory mite Metaseiulus occidentalis
    PLOS ONE, 2016
    Co-Authors: Ke Wu
    Abstract:

    : Pesticide-resistant populations of the predatory mite Metaseiulus (= Typhlodromus or Galendromus) occidentalis (Arthropoda: Chelicerata: Acari: Phytoseiidae) have been used in the biological control of pest mites such as phytophagous Tetranychus urticae. However, the pesticide resistance mechanisms in M. occidentalis remain largely unknown. In other arthropods, members of the glutathione-S-transferase (GST), cytochrome P450 (CYP) and carboxyl/cholinesterase (CCE) gene superfamilies are involved in the diverse biological pathways such as the metabolism of xenobiotics (e.g. pesticides) in addition to hormonal and chemosensory processes. In the current study, we report the identification and initial characterization of 123 genes in the GST, CYP and CCE superfamilies in the recently sequenced M. occidentalis genome. The gene count represents a reduction of 35% compared to T. urticae. The distribution of genes in the GST and CCE superfamilies in M. occidentalis differs significantly from those of insects and resembles that of T. urticae. Specifically, we report the presence of the Mu class GSTs, and the J' and J" clade CCEs that, within the Arthropoda, appear unique to Acari. Interestingly, the majority of CCEs in the J' and J" clades contain a catalytic triad, suggesting that they are catalytically active. They likely represent two Acari-specific CCE clades that may participate in detoxification of xenobiotics. The current study of genes in these superfamilies provides preliminary insights into the potential molecular components that may be involved in pesticide metabolism as well as hormonal/chemosensory processes in the agriculturally important M. occidentalis.

  • genome sequencing of the phytoseiid predatory mite Metaseiulus occidentalis reveals completely atomized hox genes and superdynamic intron evolution
    Genome Biology and Evolution, 2016
    Co-Authors: Robert M Waterhouse, Ke Wu, Aaron Pomerantz, Alden S Estep, Panagiotis Ioannidis, William J Palmer, Felipe A Simao, Jainy Thomas
    Abstract:

    Metaseiulus occidentalis is an eyeless phytoseiid predatory mite employed for the biological control of agricultural pests including spider mites. Despite appearances, these predator and prey mites are separated by some 400 Myr of evolution and radically different lifestyles. We present a 152-Mb draft assembly of the M. occidentalis genome: Larger than that of its favored prey, Tetranychus urticae, but considerably smaller than those of many other chelicerates, enabling an extremely contiguous and complete assembly to be built-the best arachnid to date. Aided by transcriptome data, genome annotation cataloged 18,338 protein-coding genes and identified large numbers of Helitron transposable elements. Comparisons with other arthropods revealed a particularly dynamic and turbulent genomic evolutionary history. Its genes exhibit elevated molecular evolution, with strikingly high numbers of intron gains and losses, in stark contrast to the deer tick Ixodes scapularis Uniquely among examined arthropods, this predatory mite's Hox genes are completely atomized, dispersed across the genome, and it encodes five copies of the normally single-copy RNA processing Dicer-2 gene. Examining gene families linked to characteristic biological traits of this tiny predator provides initial insights into processes of sex determination, development, immune defense, and how it detects, disables, and digests its prey. As the first reference genome for the Phytoseiidae, and for any species with the rare sex determination system of parahaploidy, the genome of the western orchard predatory mite improves genomic sampling of chelicerates and provides invaluable new resources for functional genomic analyses of this family of agriculturally important mites.

  • cloning and functional characterization of two btb genes in the predatory mite Metaseiulus occidentalis
    PLOS ONE, 2015
    Co-Authors: Ke Wu
    Abstract:

    Proteins containing the BTB (Bric-a-brac, tramtrack, and Broad Complex) domain typically share low sequence similarities and are involved in a wide range of cellular functions. We previously identified two putative and closely related BTB genes, BTB1 and BTB2, in the genome of the predatory mite Metaseiulus occidentalis. In the current study, full-length BTB1 and BTB2 cDNAs were cloned and sequenced. BTB1 and BTB2 encode proteins of 380 and 401 amino acids, respectively. BTB1 and BTB2 proteins each contain an N-terminal BTB domain and no other identifiable domains. Thus, they belong to a large category of BTB-domain proteins that are widely distributed in eukaryotes, yet with largely unknown function(s). BTB1 and BTB2 gene knockdowns in M. occidentalis females using RNAi reduced their fecundity by approximately 40% and 73%, respectively, whereas knockdown had no impact on their survival or the development of their offspring. These findings suggest these two proteins may be involved in processes related to egg production in this predatory mite, expanding the list of functions attributed to these diverse proteins.

  • clathrin heavy chain is important for viability oviposition embryogenesis and possibly systemic rnai response in the predatory mite Metaseiulus occidentalis
    PLOS ONE, 2014
    Co-Authors: Ke Wu
    Abstract:

    Clathrin heavy chain has been shown to be important for viability, embryogenesis, and RNA interference (RNAi) in arthropods such as Drosophila melanogaster. However, the functional roles of clathrin heavy chain in chelicerate arthropods, such as the predatory mite Metaseiulus occidentalis, remain unknown. We previously showed that dsRNA ingestion, followed by feeding on spider mites, induced systemic and robust RNAi in M. occidentalis females. In the current study, we performed a loss-of-function analysis of the clathrin heavy chain gene in M. occidentalis using RNAi. We showed that ingestion of clathrin heavy chain dsRNA by M. occidentalis females resulted in gene knockdown and reduced longevity. In addition, clathrin heavy chain dsRNA treatment almost completely abolished oviposition by M. occidentalis females and the few eggs produced did not hatch. Finally, we demonstrated that clathrin heavy chain gene knockdown in M. occidentalis females significantly reduced a subsequent RNAi response induced by ingestion of cathepsin L dsRNA. The last finding suggests that clathrin heavy chain may be involved in systemic RNAi responses mediated by orally delivered dsRNAs in M. occidentalis.

Ayyamperumal Jeyaprakash - One of the best experts on this subject based on the ideXlab platform.

  • transcriptome sequencing and annotation of the predatory mite Metaseiulus occidentalis acari phytoseiidae a cautionary tale about possible contamination by prey sequences
    Experimental and Applied Acarology, 2013
    Co-Authors: Fahong Yu, Ayyamperumal Jeyaprakash, Jason M Meyer, Oscar A Tarazona, Ke Wu
    Abstract:

    Next-generation sequencing was applied to the transcriptome of the phytoseiid Metaseiulus occidentalis to characterize gene expression in all life stages reared under different conditions to optimize the recovery of as many genes as possible. One production and one titration run produced a total of 862,069 reads (average size: 314.87 bp), which generated 255.6 Mbp of sequences on the GS-FLX Titanium sequencing platform. After removal of putative prey sequences 850,543 reads were used in NewBler and PTA assemblies to produce 74,172 non-redundant sequences, including 30,691 contigs and 43,481 singlets with 11,994 contigs consisting of more than 500 bp and 37,278 sequences >300 bp, constituting 48.7 % of all sequences. There were 25,888 hits with the NCBI non-redundant database and 15,376 unique transcripts. There were 26,225 hits with the Ixodes scapularis genome and 6,634 unique transcripts. There were 22,225 hits with the RefSeq of Homo sapiens with 6,465 unique transcripts, and 23,656 hits with the RefSeq of Drosophila melanogaster with 9,216 unique transcripts. Selected ESTs corresponding to genes of interest were analyzed including those related to transposable elements, GPCRs, Sox transcription factors, diapause and foraging behavior, and pesticide resistances. Novel and important genes appear to have been discovered that provide insight into the evolution, biology, and physiology of this important predator of pest mites in agriculture and will be useful in analyzing complete genome sequences of this natural enemy.

  • real time pcr reveals endosymbiont titer fluctuations in Metaseiulus occidentalis acari phytoseiidae colonies held at different temperatures
    Florida Entomologist, 2010
    Co-Authors: Ayyamperumal Jeyaprakash
    Abstract:

    Real-time PCR (Polymerase Chain Reaction) can estimate Wolbachia endosymbiont population density in mosquitoes (Wiwatanaratanabutr & Kittayapong 2009). The COS (?arbaryl-OP-Sul fur resistant) colony of the phytoseiid Metaseiulus (=Typhlodromus or Gcdendromus) occidentalis (Nesbitt) harbors several endosymbionts, includ ing Cardinium, Wolbachia, Enterobacter, and Bacteroidetes in their gut and reproductive tis sues (Johanowicz & Hoy 1996; Hoy & Jeyaprakash 2005). Johanowicz & Hoy (1998) ob served mating incompatibility when females from a heat-treated (33?C) COS colony (a treatment presumed to eliminate Wolbachia) was crossed with males from a room-temperature (23?C) COS colony containing Wolbachia, resulting in the pro duction of shriveled eggs that did not hatch. It was not clear whether the Wolbachia population was reduced or completely eliminated from the heat-treated mites because a standard PCR pro tocol was used, which is relatively insensitive compared to high-fidelity PCR (Jeyaprakash & Hoy 2000). In this paper, we estimate the endo symbiont population density in COS colonies of M. occidentalis held under different tempera tures in the laboratory using real-time PCR. One colony of M. occidentalis was maintained at room-temperature (23-25?C) and 2 colonies ini tiated from this line were maintained at 32 and 34?C for More than 1 year in growth chambers prior to experiments. Female mites (100) were isolated from each colony and their genomic DNA extracted by Puregene and QIAGEN methods (Jeyaprakash & Hoy 2007), and resuspended in 50 pL of sterile water. Four different plasmids carrying endosymbiont 16S rRNA sequences; pAJ233 (Cardinium), pAJ234 (Bacteroidetes), pAJ235 (Wolbachia) and pAJ239 (Enterobacter), were extracted and their yield estimated with a BioPhotometer Plus (Eppendorf AG, Hamburg, Germany). Species-specific primers were de signed with Primer 3 software (http:// frodo.wi.mit.edu/primer3/) and a probe was de signed with Primer X software (Applied Biosys tems, Foster City, CA) from the variable regions for each species (Table 1). Real-time PCR was per formed in a 20-pL reaction volume containing ge nomic DNA from 2 females (1 pL) or serially-di luted plasmid DNA (100 pg to 1 fg) or a no DNA control (1 pL), forward and reverse primers (400 pM), probe (100 pM) and TaqMan master mix (10 pL). Two linked profiles: (1) one cycle of 50?C for 2 min and 95?C for 10 min, and (2) 60 cycles consist ing of denaturation at 95?C for 15 s, annealing at 59?C (Cardinium) or 57?C (Wolbachia or Entero bacter or Bacteroidetes) for 30 s and extension at 72?C for 30 s, were used. Each treatment was rep l cated 3 times. The starting copy number of all plasmid DNA dilutions used in the real-time PCR was obtained with an open-source software (http:/

  • The nuclear genome of the phytoseiid Metaseiulus occidentalis (Acari: Phytoseiidae) is among the smallest known in arthropods
    Experimental and Applied Acarology, 2009
    Co-Authors: Ayyamperumal Jeyaprakash
    Abstract:

    The genome size of the phytoseiid Metaseiulus (= Typhlodromus or Galendromus ) occidentalis (Nesbitt) needs to be estimated before the whole nuclear genome can be sequenced. Two different procedures were used to estimate the genome size of M. occidentalis ; (1) flow cytometry (Marescalchi et al. in Genome 33:789–793, 1990 ) and (2) quantitative real-time PCR (qRT-PCR) (Wilhelm et al. in Nucleic Acids Res 31:e56, 2003 ). Fluorescence intensity of propidium iodide-stained nuclei of M. occidentalis was measured by flow cytometry using females, males, and eggs. Only the eggs yielded peaks, which ranged in size from 35 to 160 Mb, with a tall peak of 140 Mb in 1-day-old eggs and 65 Mb in 2-day-old eggs, respectively. However, the peaks are broad and do not provide an accurate estimate. The qRT-PCR procedure required single-copy nuclear gene sequences from this phytoseiid. This was accomplished by designing degenerate primers, amplifying the Actin and EF1α sequences from M. occidentalis , and then designing M. occidentalis -specific primers that amplified a unique sequence. The standard qRT-PCR protocol was inefficient and amplification failed frequently, so we developed a high-fidelity qRT-PCR protocol, which utilizes a mix of two DNA polymerases ( Taq and a proof-reading Tgo or ACCUZYME) to consistently amplify sequences. This allowed us to estimate the nuclear genome size of M. occidentalis as 88–90 ± 5 Mb. When compared to other arthropod genomes, this appears to be very small.

  • symbionts including pathogens of the predatory mite Metaseiulus occidentalis current and future analysis methods
    Experimental and Applied Acarology, 2008
    Co-Authors: Ayyamperumal Jeyaprakash
    Abstract:

    Metaseiulus (= Typhlodromus or Galendromus) occidentalis (Nesbitt) (Acari: Phytoseiidae) is an effective natural enemy of pest mites in a variety of crops around the world, although it is considered to be endemic in the western USA. A broad understanding of much of its biology, ecology, behavior, and genetics has been obtained over the past 60 years, but the role(s) symbionts play, which includes pathogens and other microorganisms, remains to be resolved fully. Until molecular tools became available, analysis methods were limited primarily to microscopic observations; some viruses and rickettsia-like organisms were observed infecting ‘diseased’ M. occidentalis, but it is not clear which one(s) was the causal agent(s) of the disease(s). Subsequent to the development of the polymerase chain reaction (PCR) and genome sequencing, we identified putative gut symbionts and reproductive tract symbionts in M. occidentalis, as well as a microsporidian pathogen. A new phylogenetic analysis of the Bacteroidetes-Flavobacterium group suggests the unnamed Bacteroidetes in M. occidentalis is associated with the digestive tract. However, much of our current information about the role these microorganisms play in the biology of M. occidentalis is based on correlation, lacking the strength of fulfilling Koch’s postulates. We also currently lack any knowledge of the importance of these microorganisms under field conditions. In the future, it should be possible to learn what role(s) these organisms play in the biology of this important predator using metagenomics approaches to analyze the transcriptome and to determine their relative abundance within their hosts with the quantitative PCR. We have just begun to resolve these relationships.

  • the mitochondrial genome of the predatory mite Metaseiulus occidentalis arthropoda chelicerata acari phytoseiidae is unexpectedly large and contains several novel features
    Gene, 2007
    Co-Authors: Ayyamperumal Jeyaprakash
    Abstract:

    Abstract The complete mitochondrial genome of the phytoseiid Metaseiulus occidentalis (Arthropoda: Chelicerata: Acari: Phytoseiidae) has been sequenced. It is 24,961 bp in length and contains a 14,695-bp unique region, a 345-bp triplicated region, and a 9921-bp duplicated region, in that order. The A+T content of the unique region is 76.9% and contains 11 protein coding ( COI–III ; ATP6–8 ; CytB ; ND1 , 2 , 4 , 5 and 4L ), two ribosomal RNA ( srRNA and lrRNA ), 22 transfer RNA ( tRNA ) genes, and two copies of D-loop control sequence. Two genes ( ND3 and 6 ) appear to be missing, but there is a large intergenic spacer (390 bp) present, which could contain ND3 if a different codon usage is employed. The gene order is completely different from the pattern in all other known chelicerates, including the horseshoe crab Limulus polyphemus [Lavrov et al., Mol. Biol. Evol., 2000; 17:813–824]. All the inferred tRNA genes are missing the TΨC arm, but this arm has fused with the variable arm to generate a TV replacement loop. The duplicated region (9921 bp) contains 18 genes in the same order as in the unique region from CytB to tRNA-His , plus one copy of D-loop control sequence (311 bp) and a partial tRNA-Leu2 sequence (34 bp). The small triplicated region (345 bp) contains a D-loop control sequence (311 bp) and a partial tRNA-Leu2 sequence (34 bp). Because of these anomalies, amplifying sequences posed technical difficulties, but were accomplished by using a primer-walking strategy and increasing the AT content to 75% in the high-fidelity PCR dNTP mix. This is the first phytoseiid mitochondrial genome to be completely sequenced and the largest (25 kb) detected from the Chelicerata.

Ian V Macrae - One of the best experts on this subject based on the ideXlab platform.

  • intra and interspecific predation by adult female Metaseiulus occidentalis and typhlodromus pyri acari phytoseiidae when provisioned with varying densities and ratios of tetranychus urticae acari tetranychidae and phytoseiid larvae
    Experimental and Applied Acarology, 1997
    Co-Authors: Ian V Macrae, B A Croft
    Abstract:

    The phytoseiid mites Metaseiulus occidentalis (Nesbitt) and Typhlodromus pyri Schueten are used together and alone as biological control agents against tetranychid pest mites of apple. Their effectiveness as control agents may be impacted by intraguild predation. The effects of prey species and prey density on the rates of inter- and intraspecific predation and oviposition by these two predators were investigated through a series of experiments. Adult female predators were given prey as mixed populations of phytoseiid larvae and larvae of a more preferred species, the spider mite, Tetranychus urticae Koch, at different densities and ratios. Typhlodromus pyri, more of a generalist predator, showed higher rates of predation and cannibalism on phytoseiid immatures at most prey densities and ratios. Manly preference indices indicated that T. pyri switched to feed on phytoseiid larvae at higher prey levels and ratios of T. urticae than M. occidentalis. This greater ability to use phytoseiid larvae as prey may help stabilize T. pyri populations when more preferred prey is unavailable. This may, in part, explain the observed persistence of T. pyri populations when M. occidentalis populations were decreasing in orchard test plots.

  • differential impact of egg predation by zetzellia mali acari stigmaeidae on Metaseiulus occidentalis and typhlodromus pyri acari phytoseiidae
    Experimental and Applied Acarology, 1996
    Co-Authors: Ian V Macrae, B A Croft
    Abstract:

    The differential impact of Zetzellia mali on the phytoseiids Metaseiulus occidentalis and Typhlodromus pyri was studied in the laboratory and by analysis of population from orchard plots that contained either phytoseiid, similar numbers of prey mites and high or low densities of Z. mali. Five hypotheses were evaluated to explain why Z. mali had more impact on M. occidentalis in the field than on T. pyri. Given equal opportunity, Z. mali adult females did not consume more M. occidentalis eggs than T. pyri eggs nor did adult females of either phytoseiid inflict greater mortality on Z. mali eggs or larvae through attack or consumption. There was no difference in the within-tree association of Z. mali adult females with eggs of either phytoseiid species nor were there differences in the way prey mites (all life stages) were spatially partitioned between adult female Z. mali as compared with adults and deutonymphs (combined) of either phytoseiid. The foraging area of adult female Z. mali and the oviposition locations of the two phytoseiids from both field and laboratory data were compared using spatial statistics. Metaseiulus occidentalis laid significantly more eggs in the primary foraging area of adult female Z. mali than T. pyri. This was the only factor identified which may explain the greater impact of Z. mali on M. occidentalis. The impact of these interspecific effects on the persistence of predatory mite guilds and biological control are discussed.

  • influence of temperature on interspecific predation and cannibalism by Metaseiulus occidentalis and typhlodromus pyri acarina phytoseiidae
    Environmental Entomology, 1993
    Co-Authors: Ian V Macrae, B A Croft
    Abstract:

    Interspecific predation and cannibalism and associated rates of oviposition were assessed for adult female Metaseiulus occidentalis (Nesbitt) and Typhlodromus pyri Scheuten when provided nonlimiting amounts of either eggs, larvae, protonymphs, or deutonymphs. Tests with all four stages of phytoseiids and larvae of Tetranychus urticae Koch were carried out at 25°C. At 15 and 12.5°C, only larvae of phytoseiids and larvae of T. urticae were prey items. Predation by T. pyri was higher than by M. occidentalis at 12.5 and 15°C but more similar at 25°C. M. occidentalis did not feed appreciably on phytoseiid larvae at 15 and 12.5°C. Neither phytoseiid oviposited at 12.5°C when fed phytoseiid larvae, but T. pyri did at 15°C. We concluded that T. pyri was a more active predator at low temperatures. Early-season predation on M. occidentalis immatures by T. pyri could contribute to displacement of M. occidentalis from apple orchards in western Oregon.

  • biological control of apple mites impact of zetzellia mali acari stigmaeidae on typhlodromus pyri and Metaseiulus occidentalis acari phytoseiidae
    Environmental Entomology, 1993
    Co-Authors: B A Croft, Ian V Macrae
    Abstract:

    Zetzellia mali (Ewing) feeds on and is fed upon by Typhlodromus pyri Scheuten and Metaseiulus occidentalis (Nesbitt), especially when phytophagous mites are scarce on apple foliage. These mites interact indirectly through competition for prey. Probably because of both indirect and direct effects, T. pyri was less dense and M. occidentalis was much less dense in plots with Z. mali than in plots where Z. mali was suppressed by endosulfan. M. occidentalis also had less effect on Z. mali than T. pyri . Biological control of Panonychus ulmi (Koch) and Aculus schlechtendali Nalepa was effective where Z. mali occurred alone at high levels or with either or both phytoseiids. Plots that received mixed T. pyri–M. occidentalis had effective control of pest mites with or without Z. mali. Z. mali displaced M. occidentalis and controlled pest mites in plots with M. occidentalis only. In plots with T. pyri only, dominance of T. pyri or Z. mali was mixed—most often near equal levels occurred, but sometimes one or the other dominated. In mixed plots T. pyri displaced M. occidentalis in 1991, but interactions between T. pyri and Z. mali in 1992 were like those in plots with T. pyri only. Releases of 25–50 M. occidentalis and 200–300 P. ulmi into trees with many Z. mali did not allow for establishment of M. occidentalis , but establishment readily occurred where few Z. mali were present. Management of M. occidentalis, T. pyri, Z. mali , and pest mites is discussed in relation to long-term biological control.

  • persistence of typhlodromus pyri and Metaseiulus occidentalis acari phytoseiidae on apple after inoculative release and competition with zetzellia mali acari stigmaeidae
    Environmental Entomology, 1992
    Co-Authors: B A Croft, Ian V Macrae
    Abstract:

    Biological control of European red mite, Panonychus ulmi (Koch), and apple rust mite, Aculus schlechtendali (Nalepa), varied in 1991 in 20 prey-predator treatment plots after Single and mixed releases of Metaseiulus occidentalis (Nesbitt) and Typhlodromus pyri Scheuten were made in 1990. Control of spider mites in 1991 was better in mixed-species than in single-species release plots. M. occidentalis was the dominant phytoseiid in mixed-species release plots in 1990, but T. pyri was more common in 1991. In fall, eggs of M. occidentalis disappeared before eggs of T. pyri did. In spring, eggs of T. pyri appeared first. Oviposition by M. occidentalis may have been slowed by cool weather and limited use of pollen as food. With few prey present, competition favored T. pyri , and M. occidentalis eventually disappeared from mixed-, but not from single-species plots. M. occidentalis was more affected by Zetzellia mali (Ewing) than was T. pyri , but T. pyri had more impact on populations of this stigmaeid mite. Competition by Z. mali with the phytoseiids may cause negative and pOSitiveeffects on biological control. The two phytoseiids have complementary traits that allow them to control pest mites together, but their management may be complicated by interspecific competition.

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  • evaluation of proxies for quality of Metaseiulus occidentalis acari phytoseiidae reared on different stages of tetranychus urticae acari tetranychidae
    Biological Control, 2013
    Co-Authors: Rana Akyazi
    Abstract:

    Abstract Experiments were conducted to determine if two different methods for assessing quality of the predatory mite Metaseiulus (= Galendromus or Typhlodromus ) occidentalis (Nesbitt) (Acari: Phytoseiidae) could be used instead of the more-lengthy and tedious life-history assessment method. First, an experiment was conducted to confirm it was possible to develop females of confirmed different quality by rearing immatures on two diets (eggs only or actives only of Tetranychus urticae Koch (Acari: Tetranychidae). Metaseiulus occidentalis females had a higher total fecundity (15.6 vs. 8.5 eggs female −1 ), a higher daily fecundity (2.2 vs. 1.4 eggs female −1 day −1 ), a higher survival rate (100% vs. 56.7%) over 7 days of evaluation, and a higher rate of developmental success of their progeny (96.4% vs. 69.5%) when fed eggs only rather than actives only, respectively. The results confirmed adult females of known different quality could be produced for evaluating potential quality-control assessment methods. Two potential quality-control metrics were investigated using these females: survival time of females when held without food and water, and size (length and width) of their dorsal shields. Starvation time and body size were influenced significantly by both diet type and mating status, but the differences obtained were insufficient to use as proxies for evaluating the quality of the M . occidentalis females of known different quality.