Motile Stages Research Articles

Integrated biological control of Diaspis echinocacti (Bouché) on Opuntia ficus-indica (L.) Mill (Cactaceae) using predatory ladybirds and fungal pathogens

Diaspis echinocacti (Bouché) (Hemiptera: Diaspididae) causes severe damage to Opuntia spp. (Cactaceae) worldwide, necessitating effective control measures. In this study, we tested the single and combined use of predatory ladybirds and a fungal pathogen on D. echinocacti infesting Opuntia ficus-indica (L.) Mill. Plants under screenhouse conditions (mean 26.32 °C, 55.1% RH.). The treatments were: untreated control, 0.003% Tween 80 (TW), Chilocorus bipustulatus (Coleoptera: Coccinellidae) (CB) alone, Exochomus nigripennis (Coleoptera: Coccinellidae) (EN) alone, entomopathogenic fungi Alternaria murispora (AM) alone, AM + CB, AM + EN, and mineral oil (MO) (positive control). Treatment efficacy was evaluated weekly for five weeks. AM + EN and AM + CB treatments significantly reduced egg counts to 4.89 and 2.44 by week 5, respectively. For motile stages, the AM + CB and AM + EN treatments were most effective, reducing counts to 6.89 and 9.56 by week 5. AM alone resulted in the highest number of mummies (D. echinocacti killed by A. murispora) (29.67) by week 5. For predator densities, C. bipustulatus peaked at 36.11 individuals per cladode by week 3 in the CB-only treatment, while E. nigripennis peaked at 32.33 individuals per cladode by week 3 in the EN-only treatment. Both CB and EN densities were higher in single treatments compared to the combined treatments throughout the study. Combining A. murispora with C. bipustulatus or E. nigripennis significantly reduced D. echinocacti infestations on O. ficus-indica without affecting plant quality (visual score >9 by week 5). Prolonged exposure enhanced efficacy, showing promise for effective non-chemical pest management.

SPARK regulates AGC kinases central to the Toxoplasma gondii asexual cycle.

Apicomplexan parasites balance proliferation, persistence, and spread in their metazoan hosts. AGC kinases, such as PKG, PKA, and the PDK1 ortholog SPARK, integrate environmental signals to toggle parasites between replicative and motile life stages. Recent studies have cataloged pathways downstream of apicomplexan PKG and PKA; however, less is known about the global integration of AGC kinase signaling cascades. Here, conditional genetics coupled to unbiased proteomics demonstrates that SPARK complexes with an elongin-like protein to regulate the stability of PKA and PKG in the model apicomplexan Toxoplasma gondii. Defects attributed to SPARK depletion develop after PKG and PKA are down-regulated. Parasites lacking SPARK differentiate into the chronic form of infection, which may arise from reduced activity of a coccidian-specific PKA ortholog. This work delineates the signaling topology of AGC kinases that together control transitions within the asexual cycle of this important family of parasites.

Grass-Endophyte Interactions and Their Associated Alkaloids as a Potential Management Strategy for Plant Parasitic Nematodes.

Claviceptaceous endophytic fungi in the genus Epichloë mostly form a symbiotic relationship with cool-season grasses. Epichloë spp. are capable of producing bioactive alkaloids such as peramines, lolines, ergot alkaloids, and indole-diterpenes, which protect the host plant from herbivory by animals, insects, and nematodes. The host also benefits from enhanced tolerance to abiotic stresses, such as salt, drought, waterlogging, cold, heavy metals, and low nitrogen stress. The bioactive alkaloids produced can have both direct and indirect effects towards plant parasitic nematodes. Direct interaction with nematodes' motile stages can cause paralysis (nematostatic effect) or death (nematicidal effect). Indirectly, the metabolites may induce host immunity which inhibits feeding and subsequent nematode development. This review highlights the different mechanisms through which this interaction and the metabolites produced have been explored in the suppression of plant parasitic nematodes and also how the specific interactions between different grass genotypes and endophyte strains result in variable suppression of different nematode species. An understanding of the different grass-endophyte interactions and their successes and failures in suppressing various nematode species is essential to enable the proper selection of grass-endophyte combinations to identify the alkaloids produced, concentrations required, and determine which nematodes are sensitive to which specific alkaloids.

Are predatory mites effective as biological control agents to suppress Oligonychus ilicis (Acari: Tetranychidae) in blueberry plantings?

Southern red mite, Oligonychus ilicis McGregor (Acari: Tetranychidae), is an important polyphagous spider mite pest that causes economic damage to many ornamentals, coffee, and fruit crops. Blueberry growers in the Southeastern United States, including Florida and Georgia, have experienced severe losses due to outbreaks of O. ilicis. Predatory mites are an important management tool used for controlling spider mites; however, predators have not been studied and successfully evaluated in blueberry systems. Amblyseius swirskii Athias-Henriot, Phytoseiulus persimilis Athias-Henriot, and Neoseiulus californicus (McGregor) (Acari: Phytoseiidae) are among the most economically important arthropod agents used in augmentative biological control worldwide. To evaluate the potential of these 3 commercially available predatory mites for use in blueberry plantings, we conducted experiments under controlled laboratory conditions and in the greenhouse. In preliminary laboratory experiments, P. persimilis and N. californicus significantly reduced the number of O. ilicis motile stages below those found in the untreated control, indicating the potential for these 2 predatory mite species to suppress O. ilicis populations. Amblyseius swirskii did not perform well controlling O. ilicis motiles in the laboratory. Under greenhouse conditions, N. californicus and P. persimilis significantly reduced the number of eggs after 7 days of release and the number of motile stages after 14 days of release. This is the first report of using phytoseiid mites to suppress O. ilicis in blueberry systems in the United States. Further studies on predator behavior, feeding preferences, and acaricide compatibility with predators are required to investigate the possibility of using P. persimilis, and N. californicus as biological control agents of O. ilicis in blueberry systems.

Combined application of entomopathogenic fungi and predatory mites for biological control of Tetranychus urticae on chrysanthemum.

Most studies on efficacy of fungal pathogens and predatory mites against Tetranychus urticae have been done on individual species in the laboratory. We evaluated fungi and predatory mites separately and together against glasshouse populations of T. urticae on chrysanthemum plants. First, effectiveness of the fungal pathogens Beauveria bassiana (Bb88) and Metarhizium anisopliae (Ma129) was compared; then, effectiveness of the predatory mites Phytoseiulus persimilis and Neoseiulus californicus. Based on the results, N. californicus and isolate Ma129 were selected and evaluated in combination. In all experiments, treatment effects were assessed for eggs and motile stages of T. urticae. The first experiment showed no significant effect of either fungal isolate on T. urticae populations, except on plants initially infested with 20 mites, where more eggs were found in the control compared to the fungal treatments. In the second experiment, both predatory mites were equally effective at reducing T. urticae populations compared with the control, regardless of initial T. urticae population density. The last experiment demonstrated that populations of T. urticae were reduced most when M. anisopliae (Ma129) and N. californicus were applied together, compared with the control and when each natural enemy was applied separately. Metarhizium anisopliae (Ma129) and B. bassiana (Bb88) isolates did not have a significant effect on reducing T. urticae populations. Both predatory mites reduced T. urticae populations, regardless of T. urticae density. Combined application of M. anisopliae (Ma129) and N. californicus were more effective against T. urticae than the control or when each agent was applied separately. © 2024 Society of Chemical Industry.

Larval swimming in the sea anemone Nematostella vectensis is sensitive to a broad light spectrum and exhibits a wavelength-dependent behavioral switch.

In nearly all animals, light-sensing mediated by opsin visual pigments is important for survival and reproduction. Eyeless light-sensing systems, though vital for many animals, have received relatively less attention than forms with charismatic or complex eyes. Despite no single light-sensing organ, the sea anemone Nematostella vectensis has 29 opsin genes and multiple light-mediated behaviors throughout development and reproduction, suggesting a deceptively complex light-sensing system. To characterize one aspect of this light-sensing system, we analyzed larval swimming behavior at high wavelength resolution across the ultraviolet and visual spectrum. N. vectensis larvae respond to light at least from 315 to 650 nm, which is a broad sensitivity range even compared to many animals with complex eyes. Planktonic swimming is induced by ultraviolet (UV) and violet wavelengths until 420 nm. Between 420 and 430 nm a behavioral switch occurs where at wavelengths longer than 430 nm, larvae respond to light by swimming down. Swimming down toward the substrate is distinct from light avoidance, as animals do not exhibit positive or negative phototaxis at any wavelength tested. At wavelengths longer than 575 nm, animals in the water column take increasingly longer to respond and this behavior is more variable until 650 nm where larval response is no different from the dark, suggesting these longer wavelengths lie outside of their sensitivity range. Larval swimming is the only motile stage in the life history of N. vectensis, and increased planktonic swimming could lead to greater dispersal range in potentially damaging shallow environments with short-wavelength light exposure. Longer wavelength environments may indicate more suitable substrates for metamorphosis into the polyp stage, where the individual will remain for the rest of its life. Future work will test whether this robust behavior is mediated by multiple opsins.

Dual nomenclature in organic-walled dinoflagellate cysts II: Spiniferites elongatus and S. membranaceus, and their equivalent non-fossil species Gonyaulax ovum comb. nov. and G. lewisiae sp. nov.

The cyst-defined extant Spiniferites elongatus Reid 1974 and Spiniferites membranaceus (Rossignol 1964) Sarjeant 1970 are environmentally significant fossil-species of the Quaternary, the former often dominating polar and subpolar assemblages. Following cyst incubation experiments and the establishment of cultures, these species were emended to incorporate information on their motile stages, and transferred to the non-fossil genus Gonyaulax Diesing 1866, as Gonyaulax elongata (Reid 1974) Ellegaard et al. 2003 and Gonyaulax membranacea (Rossignol 1964) Ellegaard et al. 2003. This unified approach to dinoflagellate nomenclature severs an important link with the fossil-genus Spiniferites Mantell 1850. We have applied dual nomenclature, as sanctioned by the International Code of Nomenclature for algae, fungi and plants, in returning these species to their previous assignments as Spiniferites elongatus and Spiniferites membranaceus, and we propose Gonyaulax ovum (Gaarder 1954) comb. nov., emend. and Gonyaulax lewisiae sp. nov., respectively, as their equivalent non-fossil species. A distinctive morphotype initially described as Rottnestia amphicavata var. amphicavata Dobell & Norris in Harland et al. 1980 is proposed as Spiniferites elongatus forma amphicavata stat. nov.

Molecular and cellular basis of life cycle transition provides new insights into ecological adaptation in jellyfish

<p>Jellyfish are renowned for their complex life cycles and important ecological and evolutionary position. The unique transition from the sessile polyp to motile medusa stages is a key process determining a switch in jellyfish behaviour and regulating the formation of jellyfish blooms. Here, we presented a comprehensive cell atlas spanning four successive life cycle stages during the polyp-to-medusa transition in the scyphozoan jellyfish <i>Aurelia</i> <i>coerulea</i>. Moreover, we characterised the variation in cell composition and gene expression patterns during the phase transition, especially in the neuromuscular system. We found several previously unreported cell types that potentially underpin the complex swimming behaviour of jellyfish. Furthermore, we discovered the pivotal role of <i>HOX1</i> in modulating the genesis of striated muscles in <i>A</i>. <i>coerulea</i>. Collectively, this study provides valuable insights into the cellular and molecular mechanisms underlying the complex life cycle transition and helps to advance our understanding of ecological adaptation in jellyfish.</p>

Life history of the two predacious mites species, Amblyseius swirskii, and Neoseiulus cucumeris (Acari: Phytoseiidae), as biological control agents of the date palm mite, Oligonychus afrasiaticus (Acari: Tetranychidae).

The date palm mite, Oligonychus afrasiaticus (McGregor) (Acari: Tetranychidae), is a serious pest of dates in the Middle East and North Africa, inflicting severe economic damage if not controlled early. As predaceous mites are known to be potential biocontrol agents against several pests, so predation capacity, life table, reproduction, and survival of Amblyseius swirskii Athias-Henriot and Neoseiulus cucumeris (Oudemans) (Acari: Phytoseiidae), collected from date palm farms in Qassim Saudi Arabia, were studied under laboratory conditions (25 °C, 30 °C, 35 °C and 50 ± 5% RH) against all motile stages of O. afrasiaticus. For both predators, mean developmental time, oviposition period, and longevity were inversely related to temperature from 25 to 35 °C. Various parameters were studied for A. swirskii and N. cucumeris at 25 °C, 30 °C and 35 °C, i.e. the female developmental time, 9.37, 7.29, 5.56, and 10.67, 8.38, 6.45 d; oviposition period, 19.77, 16.18, 13.94 and 15.90, 13.84, 10.64 d; longevity, 29.39, 24.79, 20.64 and 25.42, 21.94, 17.39 d; fecundity, 31.91, 37.10, 42.16 and 21.75, 26.84, 30.56 eggs per female, respectively. The maximum daily predation rate for both the predators was recorded at 35 °C during the oviposition period. The total predation of A. swirskii and N. cucumeris female was 370.86, 387.54, 405.83, 232.14, 263.32, 248.85 preys at 25 °C, 30 °C and 35 °C respectively. The maximum reproduction rate of A. swirskii and N. cucumeris (3.02, 2.87 eggs/♀/day) was recorded at 35 °C while the minimum (2.00, 1.36 eggs/♀/day) was recorded at 25 °C. The life table parameters were estimated as net reproductive rate (Ro) 21.68, 25.94, 29.52 and 18.95, 20.25, 22.78; the mean generation time (T) 24.92, 21.82, 18.24 and 26.30, 23.60, 20.56 d; the intrinsic rate of increase (rm) 0.181, 0.232, 0.248 and 0.170, 0.185, 0.196; the finite rate of increase (λ) 1.365, 1.551, 1.706 and 1.126, 1.324, 1.428 for A. swirskii and N. cucumeris at 25 °C, 30 °C and 35 °C respectively. The results of this study suggested that the two phytoseiid species are promising biological control agents of O. afrasiaticus at a wide range of temperatures.

Circadian rhythms and circadian clock gene homologs of complex alga Chromera velia.

Most organisms on Earth are affected by periodic changes in their environment. The circadian clock is an endogenous device that synchronizes behavior, physiology, or biochemical processes to an approximately 24-hour cycle, allowing organisms to anticipate the periodic changes of day and night. Although circadian clocks are widespread in organisms, the actual molecular components differ remarkably among the clocks of plants, animals, fungi, and prokaryotes. Chromera velia is the closest known photosynthetic relative of apicomplexan parasites. Formation of its motile stage, zoospores, has been described as associated with the light part of the day. We examined the effects on the periodic release of the zoospores under different light conditions and investigated the influence of the spectral composition on zoosporogenesis. We performed a genomic search for homologs of known circadian clock genes. Our results demonstrate the presence of an almost 24-hour free-running cycle of zoosporogenesis. We also identified the blue light spectra as the essential compound for zoosporogenesis. Further, we developed a new and effective method for zoospore separation from the culture and estimated the average motility speed and lifespan of the C. velia zoospores. Our genomic search identified six cryptochrome-like genes, two genes possibly related to Arabidopsis thaliana CCA/LHY, whereas no homolog of an animal, cyanobacterial, or fungal circadian clock gene was found. Our results suggest that C. velia has a functional circadian clock, probably based mainly on a yet undefined mechanism.

Phosphate starvation decouples cell differentiation from DNA replication control in the dimorphic bacterium Caulobacter crescentus.

Upon nutrient depletion, bacteria stop proliferating and undergo physiological and morphological changes to ensure their survival. Yet, how these processes are coordinated in response to distinct starvation conditions is poorly understood. Here we compare the cellular responses of Caulobacter crescentus to carbon (C), nitrogen (N) and phosphorus (P) starvation conditions. We find that DNA replication initiation and abundance of the replication initiator DnaA are, under all three starvation conditions, regulated by a common mechanism involving the inhibition of DnaA translation. By contrast, cell differentiation from a motile swarmer cell to a sessile stalked cell is regulated differently under the three starvation conditions. During C and N starvation, production of the signaling molecules (p)ppGpp is required to arrest cell development in the motile swarmer stage. By contrast, our data suggest that low (p)ppGpp levels under P starvation allow P-starved swarmer cells to differentiate into sessile stalked cells. Further, we show that limited DnaA availability, and consequently absence of DNA replication initiation, is the main reason that prevents P-starved stalked cells from completing the cell cycle. Together, our findings demonstrate that C. crescentus decouples cell differentiation from DNA replication initiation under certain starvation conditions, two otherwise intimately coupled processes. We hypothesize that arresting the developmental program either as motile swarmer cells or as sessile stalked cells improves the chances of survival of C. crescentus during the different starvation conditions.

Characteristics of a sea louse (Caligus clemensi) epizootic in wild Pacific herring (Clupea pallasii)

We characterized a natural sea louse epizootic of Caligus clemensi and the effects of parasitism on Pacific herring Clupea pallasii in Port Angeles Harbor, WA, USA. Infestation prevalence on newly metamorphosed age 0 Pacific herring reached 100% prevalence by mid-August. At this time, the mean louse intensity was 4.6 lice/fish, and a positive correlation occurred between louse intensity and herring body length. The epizootic then waned, with infestation prevalence decreasing to less than 25% and the mean parasite intensity falling below 1 louse. While skin injuries were not detected, motile lice preferentially aggregated around head and anterior dorsal areas. However, louse tropism became evenly distributed over the body as the parasite intensity increased. Louse-induced mortality in herring was negligible in controlled experiments. These results indicate that Caligus clemensi epizootics reach high prevalence, but also fade from mid-summer to early fall. Due to the predominant presence of motile copepod stages, we suggest that the epizootic fades because lice complete their life cycle and dislodge from the host; however, multiple explanations for epidemic fading are possible.

The role of photobehaviour in sponge larval dispersal and settlement.

Deciphering the behavioural ecology of adult (sessile) sponges is challenging. However, their motile larval stages afford opportunities to investigate how behaviour contributes to dispersal and selection of habitat. Light is a fundamental cue contributing to larval sponge dispersal where photoreceptive cells contribute to this process. But how universal is light as a cue to sponge larval dispersal and settlement? Behavioural choice experiments were used to test the effect of light on dispersal and settlement behaviours. Larvae of the tropical sponge species Coscinoderma mathewsi, Luffariella variabilis, Ircinia microconnulosa, and Haliclona sp., from deep (12-15 m) and shallower-water habitats (2-5 m), were used in experiments. Dispersal experiments provided a light-gradient-choice where light represented light attenuation with depth. Light treatments included white light and the spectral components of red and blue light. Settlement experiments comprised a choice between illuminated and shaded treatments. Fluorescence microscopy was used to establish the presence of fluorescent proteins associated with posterior locomotory cilia. Deeper-water species, C. mathewsi and I. microconnulosa discriminate light spectral signatures. Both species changed dispersal behaviour to light spectra as larvae aged. For C. mathewsi positive phototaxis to blue light changed to photophobic responses (all light treatments) after six hours and behaviours in I. microconnulosa changed from positive to negative phototaxis (white light) after six hours. L. variabilis, also a deeper-water species, was negatively phototactic to all light treatments. Larvae from the shallow-water species, Haliclona sp., moved towards all light wavelengths tested. There was no effect of light on settlement of the shallow-water Haliclona sp., but larvae in all three deeper-water species showed significantly higher settlement in shaded treatments. Fluorescence microscopy showed discrete fluorescent bands contiguous to posterior tufted cilia in all four species. These fluorescent bands may play a contributory role in larval photobehaviour.

Mechanism of small molecule inhibition of Plasmodium falciparum myosin A informs antimalarial drug design

Malaria results in more than 500,000 deaths per year and the causative Plasmodium parasites continue to develop resistance to all known agents, including different antimalarial combinations. The class XIV myosin motor PfMyoA is part of a core macromolecular complex called the glideosome, essential for Plasmodium parasite mobility and therefore an attractive drug target. Here, we characterize the interaction of a small molecule (KNX-002) with PfMyoA. KNX-002 inhibits PfMyoA ATPase activity in vitro and blocks asexual blood stage growth of merozoites, one of three motile Plasmodium life-cycle stages. Combining biochemical assays and X-ray crystallography, we demonstrate that KNX-002 inhibits PfMyoA using a previously undescribed binding mode, sequestering it in a post-rigor state detached from actin. KNX-002 binding prevents efficient ATP hydrolysis and priming of the lever arm, thus inhibiting motor activity. This small-molecule inhibitor of PfMyoA paves the way for the development of alternative antimalarial treatments.

(258–260) Proposals to eliminate contradiction between Articles 11.7 and 11.8 and to equate non‐fossil with fossil names of dinophytes for purposes of priority

(258–260) Proposals to eliminate contradiction between Articles 11.7 and 11.8 and to equate non‐fossil with fossil names of dinophytes for purposes of priority

Proximity-Dependent Biotinylation and Identification of Flagellar Proteins in Trypanosoma cruzi.

The flagellated kinetoplastid protozoan and causative agent of human Chagas disease, Trypanosoma cruzi, inhabits both invertebrate and mammalian hosts over the course of its complex life cycle. In these disparate environments, T. cruzi uses its single flagellum to propel motile life stages and, in some instances, to establish intimate contact with the host. Beyond its role in motility, the functional capabilities of the T. cruzi flagellum have not been defined. Moreover, the lack of proteomic information for this organelle, in any parasite life stage, has limited functional investigation. In this study, we employed a proximity-dependent biotinylation approach based on the differential targeting of the biotin ligase TurboID to the flagellum or cytosol in replicative stages of T. cruzi to identify proteins that are enriched in the flagellum by mass spectrometry. Proteomic analysis of the resulting biotinylated protein fractions yielded 218 candidate flagellar proteins in T. cruzi epimastigotes (insect stage) and 99 proteins in intracellular amastigotes (mammalian stage). Forty of these enriched flagellar proteins were common to both parasite life stages and included orthologs of known flagellar proteins in other trypanosomatid species, proteins specific to the T. cruzi lineage and hypothetical proteins. With the validation of flagellar localization for several of the identified candidates, our results demonstrate that TurboID-based proximity proteomics is an effective tool for probing subcellular compartments in T. cruzi. The proteomic data sets generated in this work offer a valuable resource to facilitate functional investigation of the understudied T. cruzi flagellum. IMPORTANCE Trypanosoma cruzi is a protozoan parasite that causes Chagas disease, which causes substantial morbidity and mortality in South and Central America. Throughout its life cycle, T. cruzi interacts with insect and mammalian hosts via its single flagellum, establishing intimate contact with host membranes. Currently, few flagellar proteins have been identified in T. cruzi that could provide insight into the mechanisms involved in mediating physical and biochemical interactions with the host. Here, we set out to identify flagellar proteins in the main replicative stages of T. cruzi using a proximity-labeling approach coupled with mass spectrometry. The >200 candidate flagellar proteins identified represent the first large-scale identification of candidate flagellar proteins in T. cruzi with preliminary validation. These data offer new avenues to investigate the biology of T. cruzi-host interactions, a promising area for development of new strategies aimed at the control of this pathogen.

The Skp1-Cullin1-FBXO1 complex is a pleiotropic regulator required for the formation of gametes and motile forms in Plasmodium berghei

Malaria-causing parasites of the Plasmodium genus undergo multiple developmental phases in the human and the mosquito hosts, regulated by various post-translational modifications. While ubiquitination by multi-component E3 ligases is key to regulate a wide range of cellular processes in eukaryotes, little is known about its role in Plasmodium. Here we show that Plasmodium berghei expresses a conserved SKP1/Cullin1/FBXO1 (SCFFBXO1) complex showing tightly regulated expression and localisation across multiple developmental stages. It is key to cell division for nuclear segregation during schizogony and centrosome partitioning during microgametogenesis. It is additionally required for parasite-specific processes including gamete egress from the host erythrocyte, as well as integrity of the apical and the inner membrane complexes (IMC) in merozoite and ookinete, two structures essential for the dissemination of these motile stages. Ubiquitinomic surveys reveal a large set of proteins ubiquitinated in a FBXO1-dependent manner including proteins important for egress and IMC organisation. We additionally demonstrate an interplay between FBXO1-dependent ubiquitination and phosphorylation via calcium-dependent protein kinase 1. Altogether we show that Plasmodium SCFFBXO1 plays conserved roles in cell division and is also important for parasite-specific processes in the mammalian and mosquito hosts.

Paleontological Evidence for Dinoflagellates and Ciliates as Early Eukaryotes

Molecular trees and geochemical markers suggest the divergence of dinoflagellates as early eukaryotes (~650 million years ago), but the traditional fossil record of cysts (dinocysts) starts during the Triassic (~230 million years ago). A re-evaluation of the pre-Triassic record shows that many acritarchs (microfossils of uncertain affinities) are dinocysts representing “missing” fossil evidence. Traditional diagnostic criteria for dinocysts, based on morphologic comparisons with motile stages, are biased towards thecate species. The approach proposed here, based on the more natural comparison with living cysts, includes athecate species. Many living cysts of athecate species would be “acritarchs” if found as fossils, and many earlier acritarchs would be accepted as dinoflagellate cysts if found living. The earliest acritarchs represent an innovation with profound implications for evolution: a cell wall of sporopollenin-like material enabling survival from microbial attack, in a then microbial-dominated world. Related cell wall material most likely evolved as protection for crucial stages in sexual reproduction (e.g., cysts in ciliates and dinoflagellates, and spores and pollen in algae and plants). Ciliates and dinoflagellates may have evolved in response to extreme climatic conditions in the Cryogenian, where a robust resting cyst would be advantageous. Thecate dinoflagellates most likely evolved from athecate forms, possibly in response to predatory pressure.

Management of Panonychus ulmi with Various Miticides and Insecticides and Their Toxicity to Predatory Mites Conserved for Biological Mite Control in Eastern U.S. Apple Orchards

Panonychus ulmi (Koch) (Acari: Tetranychidae), commonly known as European red mite, is a polyphagous pest of various tree and small fruit crops, including apples. A field study was conducted to evaluate different pesticide options available for the management of P. ulmi, and their impact on the population of non-target predatory mite species complex consisting of Neoseiulus fallacis, Typhlodromus pyri, and Zetzellia mali in apple orchards. Pesticides were applied using a commercial airblast sprayer at the 3-5 mite/leaf recommended economic Integrated Pest Management (IPM) threshold or prophylactically in the spring ignoring IPM practices such as monitoring, reliance on biological control and economic thresholds. Effects on the motile and egg stages of P. ulmi were evaluated as were effects on the populations of predatory mites through frequent leaf counts during the season. We also recorded the subsequent overwintering eggs of P. ulmi from each pesticide treatment. The two prophylactic treatments containing a mixture of zeta-cypermethrin + avermectin B1 + 1% horticultural oil and abamectin + 1% horticultural oil provided effective control of P. ulmi population throughout the season without reducing predatory mite populations. In contrast, eight treatments applied at the recommended economic threshold of 3-5 mites/leaf were not effective in suppressing P. ulmi populations and most reduced predatory mites. Etoxazole had significantly higher number of overwintering P. ulmi eggs compared to all other treatments.

The Intracellular Amastigote of Trypanosoma cruzi Maintains an Actively Beating Flagellum.

Throughout its complex life cycle, the uniflagellate parasitic protist, Trypanosoma cruzi, adapts to different host environments by transitioning between elongated motile extracellular stages and a nonmotile intracellular amastigote stage that replicates in the cytoplasm of mammalian host cells. Intracellular T. cruzi amastigotes retain a short flagellum that extends beyond the opening of the flagellar pocket with access to the extracellular milieu. Contrary to the long-held view that the T. cruzi amastigote flagellum is inert, we report that this organelle is motile and displays quasiperiodic beating inside mammalian host cells. Kymograph analysis determined an average flagellar beat frequency of ~0.7 Hz for intracellular amastigotes and similar beat frequencies for extracellular amastigotes following their isolation from host cells. Inhibitor studies reveal that flagellar motility in T. cruzi amastigotes is critically dependent on parasite mitochondrial oxidative phosphorylation. These novel observations reveal that flagellar motility is an intrinsic property of T. cruzi amastigotes and suggest that this organelle may play an active role in the parasite infection process. IMPORTANCE Understanding the interplay between intracellular pathogens and their hosts is vital to the development of new treatments and preventive strategies. The intracellular "amastigote" stage of the Chagas disease parasite, Trypanosoma cruzi, is a critical but understudied parasitic life stage. Previous work established that cytosolically localized T. cruzi amastigotes engage physically and selectively with host mitochondria using their short, single flagellum. The current study was initiated to examine the dynamics of the parasite flagellum-host mitochondrial interaction through live confocal imaging and led to the unexpected discovery that the T. cruzi amastigote flagellum is motile.