Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Microbial interactions in the fish gut
    Giatsis, Christos - \ 2016
    Wageningen University. Promotor(en): Johan Verreth, co-promotor(en): Marc Verdegem; Detmer Sipkema. - Wageningen : Wageningen University - ISBN 9789462578777 - 196
    fishes - tilapia - larvae - microbial interactions - intestinal microorganisms - intestines - dynamics - fish feeding - probiotics - fish culture - aquaculture - vissen - tilapia - larven - microbiële interacties - darmmicro-organismen - darmen - dynamica - visvoeding - probiotica - visteelt - aquacultuur

    Aquaculture has realized considerable growth over the past years while the world demand on seafood has been increasing. As aquaculture intensifies, the production sector needs to tackle major bottlenecks such as suboptimal growth and high and unpredictable mortality, especially in larval cultures. Fish-microbe interactions are closely related to overall fish health. To obtain a healthy and resilient microbial community (MC), it is important to understand the underlying mechanisms of microbial colonization in the fish gut.

    The goal of this thesis was to investigate the role of water and feed microbial communities on shaping gut communities during early development of Nile tilapia.

    To determine the contribution of stochasticity to overall variation, we first characterized the spatio-temporal variation in MC composition between individuals reared within the same or in replicate recirculating or active suspension systems (RAS vs. AS). Highly similar MCs developed in the gut when larvae shared the same water and diet. Rearing larvae in replicate production systems resulted in significantly different gut communities indicating that compositional replication of the MCs of an ecosystem is not fully predictable. We found that mainly water MCs, and to a lesser degree feed MCs, were associated with changes in MCs. Thus, we could conclude that steering gut MCs can be possible through water MC management tailored on the specifications of the rearing system in use.

    Next, the possibility of early life steering of gut communities via microbial manipulations of feed MCs was explored. We hypothesized that gut microbial composition is strongly shaped by selective pressures in the gut and by the MCs present in the water. Thus similar MCs should develop between treatments regardless of the dietary treatments. Fish larvae were fed either a control feed or the control feed containing MCs derived from aerobic, methanogenic or denitrifying sludge reactors. We found that gut microbiota shared a much higher number of operational taxonomic units (OTUs) with microbiota in sludge-based feeds than with water, resulting in distinct gut MCs between treatments. Our findings suggest that Nile tilapia gut MC has a certain plasticity, which makes it amenable to interventions through proper feed microbial management.

    Subsequently, we tested the imprinting effect of early exposure to the probiotic Bacillus subtilis on shaping gut MC composition even after the administration of the probiotic discontinues. For this, we constrained the initial contact with microbes from the environment by producing axenic tilapia larvae, which were then exposed to normal husbandry conditions. Early life probiotic exposure affected gut MC composition during B. subtilis administration but also within the first two weeks after its administration stopped, thus indicating that early exposure to the probiotic strain via the water had a sustained impact on gut MC composition.

    Finally, overall conclusions and practical implications of our results for aquaculture production were presented. A meta-analysis was also performed to examine (1) the phylogenetic similarity among gut MCs of the same and different fish species reared in different habitats, fed different diets and at different developmental stages and (2) the factors primarily shaping gut MCs. We showed that the selective pressure responsible in shaping gut MC composition highly depends on the host as gut communities clustered primarily together by host and to a lesser extent reflected differences in habitat and diet. The phylogenetic analysis of gut communities revealed a clear clustering by study thus indicating that manipulation of gut communities is conceivable. Study-to-study variation could be attributed to the methodology used for MC analysis highlighting also the importance of methodological uniformity when comparisons between studies are made.

    Overall, this thesis provided fundamental knowledge on MC composition and development in aquaculture rearing systems. Although the insights generated by this thesis are still premature to fully explain, predict or steer MC composition, and though additional studies are needed, we believe that, in the long run, this approach will facilitate the development of safe and effective methods for manipulating gut microbial composition to promote fish health in aquaculture rearing systems.

    Duurzame aanpak engerlingen: ken de vijand!
    Rozen, K. van; Wolters, Ria ; Olijve, A.J. - \ 2015
    St. Veldleeuwerik - 9
    scarabaeidae - larven - duurzame landbouw - biologische bestrijding - geïntegreerde plagenbestrijding - grasveld - scarabaeidae - larvae - sustainable agriculture - biological control - integrated pest management - grass sward
    Uit recent onderzoek blijkt dat bepaalde cultuurmaatregelen engerlingen afdoden ( Rapport Bestrijding van engerlingen in grasland ). Uit een deskundigendag bleek dat goed beheerd grasland minder gevoelig is voor sc hade door engerlingen. Het is onduidelijk welke aanpak en onder welke omstandigheden een effectieve bijdrage levert aan de schadebeperking. Hoe effectief kunnen deze maatregelen worden ingezet? Kan op basis van kennis een gerichte en daarmee goedkopere bio logische bestrijding met bijvoorbeeld insectparasitaire nematoden worden ingezet? Bij welke soorten en aantallen engerlingen levert het een aceptable beheersing op? Uit gesprekken met landbouwers bleek dat er ook andere ideeën. Pagina 2 van 11 leven om het engerlingenprobl eem aan te pakken. Dit praktijknetwerk heeft het omgaan met engerlingen een nieuwe impuls gegeven. Kennisuitwisseling via dit netwerk heeft tot goede discissies geleidt en nieuwe inzichten zijn opgedaan. Een duurzame oplossing lijkt mogelijk.
    Het uitzetten van macrofauna als beekherstelmaatregel
    Verdonschot, R.C.M. ; Verdonschot, P.F.M. - \ 2015
    H2O online (2015)3 oktober.
    herstelbeheer - waterlopen - macrofauna - ecologisch herstel - waterbeheer - evaluatie - larven - veluwe - restoration management - streams - macrofauna - ecological restoration - water management - evaluation - larvae - veluwe
    In het voorjaar van 2014 zijn in de herstelde middenloop van de Heelsumse beek op de Veluwe enkele duizenden larven van de voor laaglandbeken karakteristieke kokerjuffer Lepidostoma basale uitgezet. De reden om de natuur een handje te helpen is dat veel beekinsecten zich slecht verspreiden. Soorten die van nature in zo’n beek thuishoren lijken veel door beekherstelmaatregelen geschikt gemaakte beken niet te kunnen bereiken. In dit artikel wordt de situatie een jaar na het uitzetten van dieren besproken. Was het project succesvol en welke consequenties heeft dit voor de evaluatie van beekherstelprojecten?
    Tweede jaar op rij een recordaantal teken gevangen
    Vliet, A.J.H. van; Bron, W.A. ; Takken, W. - \ 2015
    Nature Today (2015).
    borrelia burgdorferi - lyme-ziekte - tekenbeten - nimfen - larven - tekenbesmettingen - gegevens verzamelen - vangen van dieren - onderzoek - vangmethoden - borrelia burgdorferi - lyme disease - tick bites - nymphs - larvae - tick infestations - data collection - capture of animals - research - trapping
    Voor het tweede jaar op rij is er door vrijwilligers een recordaantal teken gevangen op 12 vaste tekenvanglocaties. In totaal zijn er 17.400 teken gevangen. Vorig jaar waren dat er 16.800. Van de drie levensstadia namen vooral de larven sterk in aantal toe, terwijl het aantal gevangen nimfen juist lager lag dan in 2013. In combinatie met het grote aantal muizen afgelopen jaar, de belangrijkste gastheer van de teek, kan dit jaar juist het aantal nimfen hoog uitkomen. Nimfen veroorzaken de meeste tekenbeten.
    Effect of pile-driving sound on the survival of fish larvae.
    Bolle, L.J. ; Jong, C.A.F. ; Blom, E. ; Wessels, P.W. ; Damme, C.J.G. van; Winter, H.V. - \ 2014
    IJmuiden : IMARES (Report / IMARES Wageningen UR C182/14) - 33
    larven - vissen - geluidshinder - onderwaterakoestiek - offshore - constructie - windmolenpark - nederland - dierenwelzijn - larvae - fishes - noise pollution - underwater acoustics - offshore - construction - wind farms - netherlands - animal welfare
    Er bestaat zorg over de mogelijk schadelijk effecten van onderwatergeluid gegenereerd gedurende het heien bij de aanleg van offshore windparken. Harde impulsgeluiden zoals heigeluid kunnen dodelijke verwondingen veroorzaken bij vissen. Tot voor kort was er weinig bekend over de geluidsniveaus waarbij fysieke schade optreedt. Wij hebben letale effecten van blootstelling aan heigeluid onderzocht in verschillende larvale stadia van drie vissoorten (tong Solea solea, zeebaars Dicentrarchus labrax en haring Clupea harengus). De experimenten zijn uitgevoerd met de ‘larvaebrator’, een apparaat dat ontwikkeld is om larven bloot te kunnen stellen aan heigeluid in het laboratorium.
    Herring larvae surveys 2012 - 2013: Survey reports and results
    Damme, C.J.G. van; Bakker, C. - \ 2014
    IJmuiden : IMARES (Report / IMARES Wageningen UR 14.001) - 36
    haringen - larven - aquatische ecosystemen - monitoring - populatie-ecologie - noordzee - herrings - larvae - aquatic ecosystems - monitoring - population ecology - north sea
    The international herring larvae surveys (IHLS) are carried out to sample larvae of the North Sea autumn and winter spawning herring populations. The abundance of larvae is used as an index for the estimation of North Sea herring spawning stock biomass. These surveys are performed within the statutory research tasks within the framework of EZ-programs (WOT).
    Later zaaien voorkomt emeltschade
    Rozen, K. van; Raaijmakers, E. - \ 2014
    Boerderij 99 (2014)25. - ISSN 0006-5617 - p. 63 - 63.
    suikerbieten - tipulidae - larven - zaaitijd - gewasbescherming - ziektebestrijdende teeltmaatregelen - plantenplagen - insectenplagen - akkerbouw - sugarbeet - tipulidae - larvae - sowing date - plant protection - cultural control - plant pests - insect pests - arable farming
    Emelten, de larven van de langpootmug, kunnen in bieten flinke schade geven. Later zaaien kan in sommige gevallen de schade beperken.
    Eggsposed : impact of maternally transferred POPs on fish early life development
    Foekema, E.M. - \ 2013
    Wageningen University. Promotor(en): Tinka Murk. - S.l. : s.n. - ISBN 9789461736659 - 208
    vissen - persistente organische verontreinigende stoffen - maternale effecten - visseneieren - larven - biologische ontwikkeling - overleving - marien milieu - verontreiniging - ecotoxicologie - fishes - persistent organic pollutants - maternal effects - fish eggs - larvae - biological development - survival - marine environment - pollution - ecotoxicology

    Persistent organic pollutants (POP), with well-known representatives as polychlorinated biphenyls (PCBs), dioxins, and brominated flame retardants as polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecanes (HBCD), are still globally present in the marine environment, This despite the substantial reduction of application and emission that was achieved during the last decades. Apart from their persistency these compounds share low water solubility and a high lipophilicity which make that the highest concentrations in the aquatic environment are found in the organic matrix of sediments and in biota. Dissolved water concentrations are low. Hence, intake of contaminated food items forms the major source for POPs exposure of aquatic organisms, and through biomagnification the highest concentrations can be found in the tissue of top predators. POPs have the potency to cause a variety of toxic effects, among which endocrine disruption and teratogenic effects that especially apply to early life stages. As the early life stages of most fish species develop suspended in the water column, exposure to POPs may be considered relatively low, at least until the larvae start feeding after yolk absorption. However, POPs accumulated in the tissue of the mother are transferred to the eggs. The research presented in this thesis aims at the determination of the impact of such maternally transferred POPs on development and survival of fish early life stages, in order to assess if this exposure route can significantly impact the development of a fish population at current environmental concentrations, especially in combination with high fishing pressure.

    For this purpose a bioassay was developed with the common sole (Solea solea). The advantages for this research of this new bioassay above standard fish early life stage (ELS) tests are that sole is a native West European species that as all flatfishes undergoes an obvious metamorphosis. The test set-up includes this metamorphosis that is thyroid hormone mediated and therefore expected to be easily disrupted by POPs, based on research with amphibians. The prolonged Early Life Stage test (p-ELS) with sole is presented in chapter 2. Early life stages were exposed to a concentration series of the dioxin-like PCB 126 (3,3',4,4',5-pentachlorobiphenyl) in seawater until 4, 8,10 and 15 days post fertilisation (dpf). Subsequently the development of the larvae was registered under further unexposed conditions. The LC50s at the start of the free-feeding stage (12 dpf) ranged between 39 and 83 ng PCB 126/l depending on exposure duration. After the fish had completed the metamorphosis, the LC50 values ranged between 1.7 and 3.7 ng PCB 126/l for the groups exposed for 4, 8 and 10 dpf respectively. Thus exposure for only 4 days, covering only the egg stage, was sufficient to cause adverse effects during a critical developmental phase two weeks later. This study indicates that ELS fish tests that are terminated shortly after the fish becomes free-feeding underestimate the toxic potential of compounds with low acute toxicity such as PCBs. The internal dosages of these larvae at the end of the exposure, determined by means of an in-vitro gene reporter assays as dioxin-equivalent values (TEQ), revealed an internal lethal concentration, ILC50 of 1 ng TEQ/g lipid, which is within the same order of magnitude as TEQ levels found in fish from highly polluted areas. This suggests that larval survival of fish populations at contaminated sites can be affected by persistent compounds that are accumulated by the female fish and passed on to the eggs.

    Based on these first results the p-ELS test procedure was improved to reach a better control performance. The exposure period was terminated when all larvae had hatched (6 dpf), this in order to mimic exposure through maternal transfer as good as possible without exposing parent fish or manipulation the eggs. In a second test (Chapter 3) the eggs were exposed to a concentration series of methyltriclosan (MTCS), a metabolite of triclosan (TCS) that is commonly used as bactericide in a wide variety of human care products. MTCS and TCS are discharged with waste water, bioaccumulate in fish tissue, and are known to have the potency to disrupt the thyroid hormone system. Mortality occurred in the higher treatment levels until 20 dpf. Indications for thyroid hormone disruption were not observed; all surviving larvae completed metamorphoses without problems. Internal effect concentrations, reached in larvae at the end of the exposure (6 dpf), were 5.8 mg/g lipid weight (lw) and 2.1 mg/g lw for ILC50 and ILC10 respectively. These internal effect concentrations are at least 200 times higher than concentrations that due to maternally transfer can be expected in the eggs of highly exposed fish in a field situation. Our results thus do not indicate a high risk from maternally transferred MTCS for fish at the current field concentrations.

    In order to get more insight in the fate of the POPs in the larvae, in Chapter 4 the existing bioaccumulation model OMEGA was adjusted for sole early life stages and validated with experimental data with PCBs. This study revealed, that tissue concentrations of compounds with log Kow>6, peak in the tissues of developing sole at the end of the yolk-sac stage, when lipid reserves are depleted. As a result, just before the larvae become free feeding, the peak tissue concentrations of the pollutants in the larvae exceed that of the adult fish. This also explains at least partly, the delayed effects that were observed in Chapter 2 (and 5).

    Chapter 5 assesses the likelihood that early life development of fish from contaminated areas is affected by maternally transferred POPs. Following the p-ELS test protocol, effects on sole larvae were determined for the dioxin-like PCB 126, the technical PCB-mixture Arochlor 1254, PBDEs and HBCDs, for an artificial mixture of PCBs and PBDEs, and for ‘field mixtures’ extracted from sole collected from the North Sea and in the contaminated Western Scheldt estuary. As was earlier observed with PCB126 and MTCS, exposure to PCBs, PBDEs and the artificial and field mixtures caused mortality that started to occur shortly after the larvae became free-feeding and continued to increase until the onset of metamorphoses. The effects induced by the field mixtures correlated well with the ∑PCB concentrations in the tissue of the exposed larvae. No indications were found for synergistic effects or for substantial contribution of other (unknown) substances in the field mixtures. HBCD did not induce toxic effects. POP levels in sole from Western Scheldt estuary are about 20 times lower than the ILC50, the larval tissue concentration that produced 50% early life stage mortality. Levels in North Sea sole are an order of a magnitude lower.

    Chapter 6 describes a risk assessment for toxicant induced larval survival for European eel (Anguilla anguilla). Eels are considered sensitive for the effect of POPs that can accumulate to high levels in their lipid rich tissue. During spawning migration without feeding high lipophilic dioxin-like POPs in the eel’s tissue were estimated to increase 1.33 or 2 fold, due to weight loss. As no toxicity data are available for eel larvae, the critical egg concentrations for larval survival was estimated from a sensitivity distribution based on literature data of other species. It was assumed that eel larvae belong to the 5% or 1% most sensitive teleost fish species. Given concentrations of dioxin-like pollutants as reported for European eel, and following the worst case scenarios with respect to sensitivity of the larvae and bio amplification during migration, it can be expected that larvae of eel from highly contaminated locations in The Netherlands and Belgium will experience more than 50% mortality due to maternally transferred dioxin-like toxicants.

    Chapter 7 explores the potential impact of (toxicant induced) early life stage mortality on the population development of sole by application of a simple age structured matrix model. The model is used to explore the population response to a combination of (toxicant induced) larval mortality and fishing-related mortality of mature fish. The results indicate that the impact of larval mortality that occurs before metamorphosis is very low, even in population subject to high fishing pressure. This is the result of the combination of a high fecundity and the fact that the larval mortality occurs before the moment when the number of recruits is limited by the carrying capacity of the nursery areas. When colonising the nursery areas the, until than pelagic sole larvae metamorphose into flatfishes with a benthic life style. The individuals hence concentrate from the three dimensional pelagic environment to a two dimensional benthic environment, which caused density dependent mortality. This concentration of early life stages is typical for flatfish. Mortality that occurs after the nursery areas are populated will have a more pronounced impact on population development. The results further imply that population development of pelagic fish species that do not concentrate in nursery areas, and species with low fecundity is more vulnerable for disturbance through mortality of early life stages.

    Chapter 8 synthesises and discusses the outcome of the research. It is stressed that short term fish tests, often covering only the embryonic development, will underestimate the real risk of lipophilic substances. Toxicity of these substances will peak after yolk sac absorption when these tests have already been ended. When the characteristics of the test substance are known this risk is predictable with for instance the ELS-OMEGA model. However, especially when mixtures of unknown composition (effluents, sediment extracts) are being tested one must realise that the contribution of lipophilic substances may be underestimated in test that are terminated before, or too soon after the fish larvae are free feeding.

    The absence of effects on metamorphosis in our P-ELS test is explained by the prediction of the ELS-OMEGA model that the POPs concentrations in the larvae, had reached too low concentrations at the moment of metamorphoses to disrupt the thyroid hormone system. This was due to passive excretion (for substances with log Kow<6) and growth dilution.

    It must be realised that the experimental set-up that was followed to mimic the effects of maternally transferred POPs does not include potential effects of maternally transferred metabolites of these POPs that can be formed by the parent fish and that are often more toxic than the mother compounds. Also effects of the mother’s condition on the quality of the eggs and epigenetic effects were not included. This implies that the results of the tests as performed in some cases might underestimate the actual effects of these substances.

    The species most vulnerable to the effects of maternally transferred POPs share a high exposure, low fecundity and the absence of density dependent mortality of early life stages. According to these criteria sharks and especially the Greenland shark (Somniosus microcephalus) that is highly exposed to POPs can be considered as highly vulnerable. It is therefore recommended to investigate the actual sensitivity of this species, in order to get more insight in the potential vulnerability of the populations.

    Swim-training affects zebrafish development: from molecules to function
    Fiaz, A.W. - \ 2013
    Wageningen University. Promotor(en): Johan van Leeuwen; Stefan Schulte-Merker, co-promotor(en): Sander Kranenbarg. - S.l. : s.n. - ISBN 9789461736468 - 156
    danio rerio - larven - biologische ontwikkeling - zwemmen - africhten van dieren - kinematica - biomechanica - genexpressie - moleculaire biologie - morfogenese - zoölogie - danio rerio - larvae - biological development - swimming - training of animals - kinematics - biomechanics - gene expression - molecular biology - morphogenesis - zoology

    In the last decades, it became clear that not only molecular signals but also mechanical forces are crucial regulators of developmental processes. The molecular mechanisms via which mechanical forces mediate their control of developmental processes have been extensively investigated via in vitro studies. However, the full range of molecular signals and mechanical forces that regulate development in vivo cannot be covered with only in vitro studies. In vivo studies have just started to reveal the molecular link between mechanical forces and development.

    To help fill this gap, we subjected zebrafish larvae to swim-training, which presumably increases mechanical load, and investigated the effect thereof on a molecular, morphological and kinematic level during development. The zebrafish is an established model for vertebrate development and has a reproduction cycle of only three months, transparent embryos and starts to swim as early as 2 days post fertilization. A wide range of genetic analyses and tools to investigate developmental processes at various stages (embryo, larval, juvenile, adult) and levels (e.g. molecular, cellular and organ level) are available for the zebrafish.

    To investigate the effect of the applied flow on the swimming kinematics of larval zebrafish, we performed a detailed analysis of the swimming kinematics of zebrafish larvae in varying flow conditions at 10 days post fertilization (dpf). We used a two camera set-up (obtaining recordings from the lateral and bottom side of the tube) and a new in-house developed 3D tracker program which allowed us to take pitch and roll angles into account and to accurately track the motion of the center of mass, the lateral bending of the body and motion of the tail fin. Furthermore, our study is the first which calculated the actual swimming speed of larval fish subjected to flow by determining the ambient flow velocity near the position of the fish via particle image velocimetry and computational fluid dynamics analysis of the flow in the tube. The analysis of the swimming kinematics showed that fish subjected to flow had a higher tail beat frequency and swam faster and longer. In addition, normalized maximum curvatures during an individual swimming burst (a forward movement consisting of several tail beats) and averaged over the first three half beats were higher in the caudal fin in fish subjected to flow. These data indicate that the applied flow increased the swimming intensity during a swimming burst and time spent on swimming.

    Subsequently, we investigated the effect of swim-training on chondrogenesis and osteogenesis of the cranial, axial and appendicular skeleton during early larval development (5-14 dpf). Swim-training prioritized the development of cartilage and bone structures in the head and in the median fins. We furthermore demonstrated that swim-training can increase growth depending on the feeding regime, training regime and stocking density of fish in a tube during zebrafish larval development. Furthermore, swim-training increased burst frequency which indicates that swim-training not only increased swimming intensity but also swimming activity.

    To investigate the effect of swim-training on the gene expression during zebrafish larval development, we performed transcriptome analysis of zebrafish larvae subjected to training and control fish at 10 dpf on a quantitative and spatial gene expression level. We chose this stage because the first ossified structures (hypurals and finrays) appear in the caudal fin around 10 dpf. This analysis demonstrated that swim-training led to molecular changes in the brain, muscle and gastrointestinal system during zebrafish larval development. In addition, we investigated if swim-training affected the expression of genes involved in muscle growth and structure with quantitative real-time PCR in trained and control fish at 5 and 14 dpf. The expression of slow fiber markers was increased after ten days of swim-training, indicating that muscle can already shift towards a slower aerobic phenotype during zebrafish larval development.

    Furthermore, since swim-training prioritized the onset of skeletal elements in (among others) the caudal fin and fish subjected to flow had higher normalized maximum curvatures in the caudal fin, we explored the molecular link between an increased swimming activity and caudal fin development. Fish were subjected to swim-training from 5-10 dpf and we performed a whole genome microarray analysis on the caudal fins of fish at 10 dpf. From this analysis, we identified two muscle specific genes, aste1 (asteroid homolog 1) and zgc:65811, which showed an increased expression exclusively in the caudal fin. The gene aste1 contains an XPG coding domain and might be involved in DNA repair in muscle fibers. Since DNA repair plays an important role during cell division, this suggests that this gene might be implicated in cell division in muscle fibers. The gene zgc:65811 contains a domain which encodes for the CD-9 large extracellular loop region. The protein CD-9 belongs to the family of tetraspanin transmembrane proteins and is possibly involved in muscle fiber differentiation.

    Our study demonstrated that swim-training can increase growth and lead to morphological and molecular changes during zebrafish larval development. We furthermore showed that the applied flow generated larger peak curvatures in the caudal fin and that swim-training led to specific morphological and molecular changes in the caudal fin. Our work suggests that the zebrafish is an interesting model species to elucidate the in vivo molecular link between functional performance and morphological development.

    Nog geen oplossing tegen larven van lyprauta : vooral lastig probleem bij phalaenopsis
    Pijnakker, J. ; Leman, A. ; Arkesteijn, M. - \ 2013
    Onder Glas 10 (2013)6/7. - p. 25 - 25.
    orchidaceae - phalaenopsis - plantenplagen - potplanten - insectenplagen - larven - organismen ingezet bij biologische bestrijding - roofmijten - glastuinbouw - orchidaceae - phalaenopsis - plant pests - pot plants - insect pests - larvae - biological control agents - predatory mites - greenhouse horticulture
    In potgrond en andere teeltsubstraten komen allerlei muggenlarven voor. Het meest talrijk zijn rouwmuglarven. In phalaenopsis en andere potorchideeën treden de laatste tien jaar problemen op met een andere type muggenlarven van het geslacht Lyprauta, die men in de wandelgangen ‘potwormen’ noemt. De schade in phalaenopsis door deze muggenlarven bedraagt naar schatting 17% van de omzet.
    Bestrijding van engerlingen in grasland : screening van middelen in lab- en veldproeven ter bestrijding van engerlingen (mei- en rozenkevers) in grasland 2010-2011
    Rozen, K. van; Huiting, H.F. - \ 2012
    Lelystad : Praktijkonderzoek Plant & Omgeving Wageningen UR, Business Unit PPO-agv - 67
    graslanden - coleoptera - larven - insectenplagen - schade - bestrijdingsmethoden - insecticiden - proeven - laboratoriumproeven - nederland - veldproeven - grasslands - coleoptera - larvae - insect pests - damage - control methods - insecticides - trials - laboratory tests - netherlands - field tests
    In 2009 werd de veehouderijsector geconfronteerd met sc hade door engerlingen in grasland. Engerlingen van de meikever en de rozenkever vreten aan de wortels van de grasplanten waarbij het contact van de resterende wortels met de ondergrond minder wordt. Bij droog weer verdroogt de zode en sterft de grasmat af, wat de primaire schade wordt genoemd. Het is echter voornamelijk de secundaire schade die zichtbaar wordt, veroorzaakt door zoogdieren en vogels op zoek naar de voedzame engerlingen. Een effectieve manier van bestrijding is het scheuren van de graszode in de nazomer en het najaar, waarna opnieuw gezaaid kan worden. Vanwege uitspoeling mag scheuren op zandgronden alleen in de periode van 1 februari t/m 10 mei. Een vrijstellingsregeling was noodzakelijk om in het najaar te mogen scheuren. Daarnaast brengt het herinzaaien van percelen extra kosten mee voor de veehouder. Dit resulteerde a ansluitend in een onderzoekswens om engerlingen te bestrijden met insecticiden. Op basis van oriënterend labonderzoek, toelatingskansen en overleg met de producthouders kwa men twee insecticiden in aanmerking voor het veldonderzoek. Daarnaast zijn enkele middelen op basis van kruidenextracten en etherische oliën geselecteerd voor proefveldonderzoek die op de particuliere markt en sportvelden worden toegepast tegen engerlingen . Eén middel zit nog in de testfase. In 2010 en 2011 zijn in totaal vier proeven aangelegd op percelen met een populatie engerlingen onder de graszode waaraan schade werd geconstateerd. In het eerste jaar lag de nadruk op het volvelds en bovengronds toepas sen. In het tweede jaar lag de nadruk op het injecteren van de middelen in de bodem. Alle niet toegelaten middelen zijn gecodeerd weergegeven .
    Herring larvae surveys 2011 - 2012: Survey reports and results
    Damme, C.J.G. van; Bakker, C. - \ 2012
    IJmuiden : IMARES (Rapport / IMARES Wageningen UR C099.12) - 34
    visstand - inventarisaties - haringen - larven - noordzee - fish stocks - inventories - herrings - larvae - north sea
    In the period September 2011 to January 2012 three herring larvae surveys were carried out by ‘RV Tridens’. In September, the Buchan area and Central North Sea were sampled and in December and January the southern North Sea and the Eastern channel. The weather conditions during the September and December surveys were mostly good and all planned stations could be sampled. In January due to bad weather conditions and engine problems some stations could not be sampled. During all surveys good coverage of the entire sampling area was achieved.
    Meikeverengerlingen zijn nog niet te verslaan
    Elberse, I.A.M. ; Vlug, H. ; Tol, R.W.H.M. van - \ 2012
    De Boomkwekerij 25 (2012)12. - ISSN 0923-2443 - p. 18 - 19.
    houtachtige planten - plantenplagen - melolontha melolontha - larven - bestrijdingsmethoden - teeltsystemen - insectenplagen - landbouwkundig onderzoek - woody plants - plant pests - melolontha melolontha - larvae - control methods - cropping systems - insect pests - agricultural research
    De problemen door meikever zijn nijpend, vooral in het oosten en zuiden van het land. Een projectteam van PPO , PRI Insect Consultancy ging in opdracht van het Productschap Tuinbouw met een nieuwe aanpak het probleem te lijf. De meikeverengerlingen bleken zich echter nog niet gewonnen te geven.
    The baculovirus per os infectivity complex
    Peng, K. - \ 2012
    Wageningen University. Promotor(en): Just Vlak, co-promotor(en): Monique van Oers; Jan van Lent. - S.l. : s.n. - ISBN 9789461732187 - 138
    baculovirus - dierenvirussen - ongewervelde dieren - insecten - larven - infectiviteit - mond - middendarm - eiwit-eiwit interacties - baculovirus - animal viruses - invertebrates - insects - larvae - infectivity - mouth - midgut - protein-protein interactions

    Insect larvae are orally infected by baculoviruses through ingestion of proteinaceous occlusion bodies (OB) containing the so-called occlusion derived viruses (ODV). OBs disintegrate in the alkaline environment of the insect midgut releasing the ODV, which then bind and fuse with the microvillar membrane of epithelial cells thereby initiating infection. After replication and spread through the larval body, ODVs are assembled and occluded into OBs. In this thesis the protein structure of ODVs and their entry into microvillar cells were studied from the perspective of protein-protein interactions. A number a novel interactions were identified among ODV structural proteins shedding light on the spatial and temporal mechanism of ODV assembly. Furthermore, a group of highly conserved viral per os infectivity factors (PIF) was shown to form a complex on the ODV envelope. These PIF proteins are essential for oral infectivity of ODVs and the complex may play a pivotal role in binding and fusion of ODV with the microvillar membrane. It was further found that in the OB structure a host derived alkaline protease was tightly associated with ODVs and cleaved one of the PIF proteins (P74). Proteolytic processing of PIF proteins may be necessary to trigger conformational changes in the complex to facilitate its function in binding and fusion with the host cell membrane. This thesis provided not only novel insights on the mechanism of ODV entry and assembly and the role of individual ODV proteins, but also triggered new questions to direct future investigations.

    Report of the Workshop on the identification of clupeoid, flatfish, gadoids and other fish larvae (WKIDFL)
    Imares, - \ 2011
    IJmuiden : IMARES (ICES WKIDFL report 2011)
    conferenties - larven - vis - dieridentificatiesystemen - dieridentificatie - identificatie - overeenkomsten - pleuronectiformes - conferences - larvae - fish - animal identification systems - animal identification - identification - agreements - pleuronectiformes
    The Workshop on the Identification of clupeoid, flatfish, gadoid and other fish larvae (WKIDFL) met from 5 to 9 September 2011 in IJmuiden, The Netherlands, to calibrate fish larvae identification. The meeting was chaired by Cindy van Damme, The Neth-erlands, and Matthias Kloppmann, Germany. In total 17 persons representing 10 in-stitutes from 8 countries participated in the workshop. The majority of the time at the workshop was spent identifying fish larvae. The re-sults promoted discussion and highlighted specific problem areas. These discussions led to the further development of standard keys and larval identification characteris-tic tables.
    Biologische grondontsmetting bij de teelt van trekheesters: Implementatie van een alternatieve ontsmettingsmerhode in de praktijk
    Ludeking, D.J.W. ; Hamelink, R. ; Bloemhard, C.M.J. ; Slooten, M.A. van - \ 2011
    Bleiswijk : Wageningen UR Glastuinbouw (Rapporten GTB 1135) - 46
    biologische grondontsmetting - syringa - viburnum - verticillium dahliae - meloidogyne incognita - scarabaeidae - larven - veldproeven - nederland - biological soil sterilization - syringa - viburnum - verticillium dahliae - meloidogyne incognita - scarabaeidae - larvae - field tests - netherlands
    This report is about biological soil disinfestation with an organic product named Herbie 7022. The effect has been investigated against Verticillium dahliae, Meloidogyne incognita and larvae of Serica brunnea. All larvae of Serica brunnea are killed after application of a period of anaerobic conditions. Against Meloidogyne incognita the method of biological soil disinfestation with Herbie 7022 is less effective. No effect of adding Herbie 7022 on a depth of 20 cm is determined compared with only coverage of the soil with plastic foil and adding no extra products. An effect Herbie 7022 is visible against Meloidogyne incognita on a level of 50 cm depth. The same conclusions can be drawn for Verticillium dahliae. After 8 weeks of anaerobic conditions there is no significant difference between the application of Herbie 7022, compared with a treatment of only coverage of the soil with plastic foil. In deeper layers adding of Herbie 7022 shows an effect in this experiment. The knowledge produced in this project is applicable for growers of Syringa and Viburnum in the Aalsmeer region in The Netherlands. For them chemical or physic soil disinfestation is not optional and therefore biological soil disinfestation might help them to suppress high levels of pathogens and pests in their peaty soils.
    Hatchery manual for broodstock management and larval production of tubrot (Psetta maxima)
    Rurangwa, E. ; Poelman, M. - \ 2011
    Yerseke : IMARES (Report / IMARES Wageningen UR C150/11) - 52
    tarbot - larven - broeddieren - bedrijfsvoering - visproductie - dierhouderij - voortplanting - broedinstallaties - kuitschieten - visziekten - visteelt - aquacultuur - turbot - larvae - broodstock - management - fish production - animal husbandry - reproduction - hatcheries - spawning - fish diseases - fish culture - aquaculture
    This hatchery manual is intended to provide detailed information from available published work and grey literature on turbot broodstock management and larval production. In reviewing larviculture techniques for turbot, it is notable that the major initial zoo technical advances were made in the 1980s. Subsequent refinements have been industry-led and are subject to commercial confidentiality. Some actors in the sector that have been approached either did not provide requested information or denied access to their sources of information. This manuscript therefore considers those aspects of commercial rearing techniques that are in the public domain, together with the applied scientific literature and information collected from different experts. With the aim to cover all aspects related to the production of turbot juveniles in Dutch farms from egg to fish of 10-15 g, the manual describes in details different steps. These have been grouped around the broodstock management, the hatchery/nursery period, the on growing and the grow out periods. A list of common diseases in turbot has been added at the end. The manual provides a link to the most update information available on live prey production and enrichment.
    Beheersing meikeverengerlingen
    Elberse, I.A.M. ; Rijkers, D. - \ 2011
    melolontha melolontha - larven - boomteelt - plagenbestrijding - plantenplagen - kerstbomen - picea abies - lokgewassen - gewasbescherming - melolontha melolontha - larvae - arboriculture - pest control - plant pests - christmas trees - picea abies - trap crops - plant protection
    Poster met onderzoeksinformatie. Meikeverengerlingen zorgen in boomkwekerijen in vooral de Achterhoek en Twente voor enorme schade. Geprobeerd werd om door het stapelen van diverse maatregelen in verschillende fasen van de teelt en verschillende levensstadia van de meikever, een succesvolle kerstbomenteelt (Picea abies) mogelijk te maken.
    Shorlist Masterplan Wind. Evaluation of the sampling grid of the year-round ichthyoplankton survey
    Bolle, L.J. ; Beek, J.K.L. van - \ 2011
    IJmuiden : IMARES (Report / IMARES Wageningen UR C026/11) - 34
    zoöplankton - kuitschieten - bemonsteren - monitoring - methodologie - visseneieren - larven - vissen - het kanaal (english channel) - noordzee - zooplankton - spawning - sampling - monitoring - methodology - fish eggs - larvae - fishes - english channel - north sea
    Within the research programme 'Shortlist Masterplan Wind' a year-round ichthyoplankton survey is being carried out. The sampling area is based on known spawning concentrations and prevailing currents.
    Shortlist masterplan wind Effect of pilling noise on the survival of fish larvae (pilot study)
    Bolle, L.J. ; Jong, C.A.F. ; Bierman, S.M. ; Haan, D. de; Huijer, T. ; Kaptein, D. ; Lohman, M. ; Tribuhl, S.V. ; Beek, F.A. van; Damme, C.J.G. van; Berg, F. van den; Heul, J.W. van der; Keeken, O.A. van; Wessels, P. ; Winter, H.V. - \ 2011
    IJmuiden : IMARES (Report / IMARES Wageningen UR C092/11) - 138
    larven - vissen - geluidshinder - overleving - gezondheidsgevaren - diergezondheid - health impact assessment - noordzee - windmolenpark - larvae - fishes - noise pollution - survival - health hazards - animal health - health impact assessment - north sea - wind farms
    Fish can suffer lethal damage to their swim bladder or other organs due to loud impulse sounds such as pile driving noise. However, detailed dose-response studies are still scarce, especially for the early life stages. In view of the rapid extension of offshore wind farms in the North Sea, there is an urgent need to acquire more knowledge on the effects of noise caused by pile driving. This study focussed on the effect of piling noise on the survival of fish larvae.
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