Scholeksters en hun voedsel in de Westerschelde; een verkenning van de voedselsituatie voor de scholeksters in de Westerschelde over de periode 1992-2003 met het simulatiemodel WEBTICS

Dit rapport bevat een analyse van de voedselsituatie van overwinterende scholeksters in de Westerschelde tussen 1992 en 2003. Met behulp van het model WEBTICS (Wader Energy Balance and Tidal Cycle Simulator) worden berekeningen gedaan aan de draagkracht van het gebied voor scholeksters, uitgaande van de verspeiding van de kokkels en de nonnetjes, enkele droogvalduurkaarten, weergegevens en waterstanden. Voor de verschillende deelgebieden stemt de berekende draagkracht en de verandering ervan tijdens de bestudeerde periode ongeveer overeen met de waargenomen aantallen scholekster

Synchronisation of egg hatching of brown hairstreak (Thecla betulae) and budburst of blackthorn (Prunus spinosa) in a warmer future

Synchronisation of the phenology of insect herbivores and their larval food plant is essential for the herbivores’ fitness. The monophagous brown hairstreak (Thecla betulae) lays its eggs during summer, hibernates as an egg, and hatches in April or May in the Netherlands. Its main larval food plant blackthorn (Prunus spinosa) flowers in early spring, just before the leaves appear. As soon as the Blackthorn opens its buds, and this varies with spring temperatures, food becomes available for the brown hairstreak. However, the suitability of the leaves as food for the young caterpillars is expected to decrease rapidly. Therefore, the timing of egg hatch is an important factor for larval growth. This study evaluates food availability for brown hairstreak at different temperatures. Egg hatch and budburst were monitored from 2004 to 2008 at different sites in the Netherlands. Results showed ample food availability at all monitored temperatures and sites but the degree of synchrony varied strongly with spring temperatures. To further study the effect of temperature on synchronisation, an experiment using normal temperatures of a reference year (T) and temperatures of T + 5°C was carried out in climate chambers. At T + 5°C, both budburst and egg hatch took place about 20 days earlier and thus, on average, elevated temperature did not affect synchrony. However, the total period of budburst was 11 days longer, whereas the period of egg hatching was 3 days shorter. The implications for larval growth by the brown hairstreak under a warmer climate are considered.

Global Production of Marine Bivalves. Trends and Challenges

The global production of marine bivalves for human consumption is more than 15 million tonnes per year (average period 2010–2015), which is about 14% of the total marine production in the world. Most of the marine bivalve production (89%) comes from aquaculture and only 11% comes from the wild fishery. Asia, especially China, is by far the largest producer of marine bivalves, accounting for 85% of the world production and responsible for the production growth. In other continents, the production is stabilizing or decreasing (Europe) the last decades. In order to stimulate growth, sustainability (Planet, Profit, People) of the aquaculture activities is a key issue. Environmental (Planet) aspects for sustainable aquaculture include the fishery on seed resources, carrying capacity, invasive species and organic loading. Food safety issues due to environmental contaminants and biotoxines should be minimized to increase the reliability of marine bivalves as a healthy food source and to stimulate market demands. Properly designed monitoring programs are important tools to accomplish sustainable growth of marine bivalve production

Reciprocal responses in the interaction between Arabidopsis and the cell-content feeding chelicerate herbivore spider mite

Most molecular-genetic studies of plant defense responses to arthropod herbivores have focused on insects. However, plant-feeding mites are also pests of diverse plants, and mites induce different patterns of damage to plant tissues than do well-studied insects (e.g. lepidopteran larvae or aphids). The two-spotted spidermite (Tetranychus urticae) is among the most significant mite pests in agriculture, feeding on a staggering number of plant hosts. To understand the interactions between spider mite and a plant at the molecular level, we examined reciprocal genome-wide responses of mites and its host Arabidopsis (Arabidopsis thaliana). Despite differences in feeding guilds, we found that transcriptional responses of Arabidopsis to mite herbivory resembled those observed for lepidopteran herbivores. Mutant analysis of induced plant defense pathways showed functionally that only a subset of induced programs, including jasmonic acid signaling and biosynthesis of indole glucosinolates, are central to Arabidopsis's defense to mite herbivory. On the herbivore side, indole glucosinolates dramatically increased mite mortality and development times. We identified an indole glucosinolate dose-dependent increase in the number of differentially expressedmite genes belonging to pathways associated with detoxification of xenobiotics. This demonstrates that spider mite is sensitive to Arabidopsis defenses that have also been associated with the deterrence of insect herbivores that are very distantly related to chelicerates. Our findings provide molecular insights into the nature of, and response to, herbivory for a representative of a major class of arthropod herbivores

Effecten van het rapen van oesters in de Waddenzee op de benthosgemeenschap en vogelpopulatie

Eind 2009 en begin 2010 zijn er door de Provincie Fryslân een 18-tal vergunningen verleend voor het experimenteel commercieel handmatig rapen van oesters voor een periode van 4 jaar. Omdat oesterrapen een nieuwe activiteit is in de Waddenzee is nog niet bekend of deze activiteit negatieve effecten heeft op Natura 2000 instandhoudingsdoelstellingen. Het gaat dan met name om habitattype H1140-A (Slik- en zandplaten, getijdengebieden) en verschillende vogelsoorten die foerageren op mossel- en oesterbanken

Population size of Oystercatchers Haematopus ostralegus wintering in Iceland

The first ever survey of Oystercatchers wintering in Iceland found around 11 000 individuals. This is an estimated 30% of the Icelandic population, including juveniles, suggesting that approximately 26 000 Icelandic Oystercatchers migrate to western Europe in the autumn. More Oystercatchers winter in Iceland than at similar latitudes elsewhere in Europe, which may reflect the remoteness and milder winter temperatures on this oceanic island

Rethinking classic starling displacement experiments : evidence for innate or for learned migratory directions?

Funding for the present work came from the Spinoza Premium 2014 awarded to TP by the Netherlands Organization for Scientific Research (NWO), with supplementary funding from an anonymous donor, the Gieskes-Strijbis Fonds and the Ubbo Emmius Fonds of the University of Groningen. TO was supported by Rubicon a grant from NWO (ref. 019.172EN.011)In an attempt to encourage the discourse on sources of individual variation in seasonal migration patterns and the microevolution of bird migration, we here critically examine the published interpretations of a now classic displacement study with starlings Sturnus vulgaris. Based on the ring recoveries after experimental displacement towards the south and southeast of Dutch capture sites of over 18 000 hatch‐year and older starlings, in a series of analyses published in Ardea from 1958 to 1983, A. C. Perdeck established that displaced starlings showed appropriately changed orientations only when they were experienced. During both southward and northward migration, released adults navigated to an apparently previously learned goal (i.e. the wintering or the breeding area) by showing appropriately changed orientations. Juveniles showed appropriate directions when returning to the breeding grounds. In contrast, during their first southward migration displaced juveniles carried on in the direction (and possibly the distance) expected for their release at the Dutch capture site. From the mid‐1970s this work has become cited as evidence for starlings demonstrating ‘innate’ migratory directions. If the definition of innateness is ‘not learned by the individual itself’, then there is a range of non‐innate influences on development that are not ruled out by Perdeck's experimental outcomes. For example, young starlings might have carried on in the direction that they learned to migrate before being caught, e.g. by observing the migratory directions of experienced conspecifics. We argue that, despite over 60 citations to Perdeck as demonstrating innate migratory directions, the jury is out.Publisher PDFPeer reviewe

Naar een reproductiemeetnet voor broedvogels in de Waddenzee

Als onderdeel van het door het ministerie van LNV gefinancierde onderzoek “Voedselaanbod voor Vogels” (bestek 5a) is er door SOVON in samenwerking met Alterra een pilotstudy uitgevoerd naar de mogelijkheden om een reproductiemeetnet in het Waddengebied op te zetten. Die studie had betrekking op zes soorten die algemeen voorkomen in het Nederlandse Waddengebied (Eider, Scholekster, Kluut, Kokmeeuw, Zilvermeeuw en Visdief). Deze soorten zijn aangewezen op verschillende belangrijke voedselbronnen in de Waddenzee: vis, schelpdieren, garnalen of bodemdieren als Wadpier en Zeeduizendpoot). Voor de zes soorten is beschreven welke informatie over de reproductie kan worden verzameld en welke methoden hiervoor gebruikt kunnen worden

Bearded Reedlings Adjust Their Pair-Bond Behaviour in Relation to the Sex and Attractiveness of Unpaired Conspecifics

An individual's investment in mating or keeping a pair bond intact may be influenced not only by the attractiveness of its current mate, but also by that of other potential mates. In this study, we investigated the effect of relative attractiveness on pair-bond behaviour in bearded reedlings, Panurus biarmicus. We showed that mate attractiveness, in terms of beard length in males and tail length in females, influenced courtship behaviour when the pair was kept isolated. In the presence of a conspecific, contact initiations within a pair increased. This increment was mainly related to the sex of the unpaired conspecific, however, and less to differences in attractiveness between the current partner and the unpaired conspecific. Female contact initiations towards potential extra mates were independent of male attractiveness, whereas male contact behaviour was significantly influenced by female attractiveness. However, females displayed more contact initiations to their current mate when they were less attractive than the unpaired females. Males decreased their overtures towards other females with increasing attractiveness of their current mates. Overall, our results suggested that, when there was a risk of losing their mate, bearded reedlings adjust their pair-bond investment mainly in response to the presence or absence of a competitor, and fine-tune investment to a lesser extent in response to the attractiveness of that potential competitor