Acoustic phenomena related to an enriched benthic zone in the North Sea

In late summer and autumn 1985 and 1986, acoustic recordingswere made with a 38 kHz echo-sounder in a series of transectsoverlying the hydrographical front area south of the OysterGrounds (North Sea). The echograms revealed a narrow band ofincreased backscattering, which seemed related to an enrichedbenthic zone, located underneath this band at depths of 30–40m below the sea surface. This phenomenon is a permanent featureat this time of year, caused by locally high concentrationsof larger zooplanktonic and nektonic organisms. The peak inbackscattering showed a 6 h periodical shift in a north-southdirection as a result of tidal movements. ³Present address: University of Amsterdam, Institute of TaxonomicZoology, Department of Marine Invertebrates, P.O. Box 4766,1009 AT Amsterdam, The Netherlands     

Cover‐weighted averaging of indicator values in vegetation analyses

Question: How should species cover be weighted when calculating average indicator values of vegetation relevés? Location: The Netherlands. Method: Various weighting methods were statistically investigated with 188 relevés from The Netherlands for which accurate groundwater levels were available. For each method the correlation between average Ellenberg indicator value for moisture and mean spring groundwater level was calculated. A permutation test on correlation coefficients revealed whether differences between methods were significant or not. Results: Optimization of a general weighting function did not produce a significantly higher correlation than disregarding cover and calculating the average as the arithmetical mean of indicator values. Giving a higher weight to species at both ends of the indicator scale and using indifferent species as indicators of mediocre conditions did improve the correlation significantly. Weighting species proportionate to their cover yielded a significantly lower correlation than the correlation obtained with the method that disregards cover. A significantly lower correlation was also established when taking into account the fact that cover is related to the growth strategy of species.     

The diagnostic significance of nuclear deoxyribonucleic acid measurement in automated cytology.

Flow cytometric analysis of cytologic samples from four different organs shows that nuclear DNA content of malignant cell populations depends to a large extent on organ of origin of the tumor. This fact must be considered in planning screening systems.     

Technique for the quantification of transient quadratic phase couplings between heart rate components.

A technique for the time-variant analysis of quadratic phase coupling (QPC) in heart rate data is introduced and tested in 6 human neonates during quiet sleep. The set up of the approach is based up on the assumption that QPCs in the heart rate variability (HRV) are related to amplitude modulation effects. The application of the biamplitude deals with the detection of the coupling pattern and the bicoherence is used for the statistical quantification of coupling. By means of the results of bispectral analysis the time-variant processing has been adapted. The frequency-selective complex demodulation of the HRV leads to the envelope of the respiratory sinus arrhythmia (RSA), this has been used as one input for a time-variant coherence analysis. The other input is the low-pass filtered 10-second-rhythm of the HRV. A time-continuous quantification of the QPC, caused by amplitude modulation (10-second-rhythm modulates the RSA), is possible using this approach. According to our observed results in neonatal HRV both a phase co-ordination between the 10-second-rhythm and RSA as well as a non-linear coupling (amplitude modulation) between these HRV components can be seen.     

A model to predict and assess the impacts of hydrologic changes on terrestrial ecosystems in The Netherlands,and its use in a climate scenario

Current water management policy in The Netherlands aims to serve a multitude of land use functions, such as agriculture, industry, shipping, and drinking water supply. To attune this policy to the diversity of functions, computer models are used to predict the consequences of various policy options as a part of PAWN: the government's Policy Analysis of Water management for The Netherlands.Nature conservation and development is a relatively new aspect of water management policy. This article describes the PAWN model DEMNAT, which is designed to predict the impact of hydrologic changes on terrestrial ecosystems in The Netherlands. The main components of the model are explained and the predicted effects of an assumed climatic change are discussed.     

Balance of glutamate and dopamine in the nucleus accumbens modulates self-stimulation behavior after injection of cholecystokinin and neurotensin in the rat brain.

Subpopulations of dopamine (DA) neurons in the ventral mesencephalon have been reported to contain cholecystokinin (CCK) and neurotensin (NT), giving rise to DA, DA/NT, NT/CCK and DA/CCK/NT projections. More precisely, colocalized DA/CCK neurons project mainly to the caudal part of the medial nucleus accumbens, whereas its rostral portion receives CCK and DA nerve terminal networks that are structurally independent. We investigated the respective effects of both CCK and NT on the intracranial self-stimulation behavior (ICSS) from the posterolateral hypothalamus after their direct administration into the lateral ventricle (ICV), into both portions of the nucleus accumbens, into the ventral tegmental area (VTA), and into the subiculum of the hippocampal formation (SUB). The ICV injection of 150 pmol CCK8 induced a decrease in the rate of ICSS. By contrast, the direct administration of 150 pmol CCK8 into the mediocaudal part of the nucleus accumbens induced an enhanced rate of ICSS while a similar injection into its rostral portion gave rise to a slight transient decrease of ICSS. When injected into the SUB, both CCK8 and glutamate produced decreased rates of ICSS at femtomolar doses one thousand-fold under the picomolar concentrations used for ICV injections. Neurotensin induced similar behavioral profiles to that observed after the ICV injection of CCK8 or into both portions of the nucleus accumbens. Neurotensin and CCK8 displayed opposite effects on ICSS when administered into the SUB or into the VTA, suggesting they may regulate ICSS most probably through different synaptic mechanisms and through different anatomical pathways.     

Parasitoid vibrations as potential releasing stimulus of evasive behaviour in a leafminer

Abstract. The aim of this study was to characterize the vibratory signals produced by the parasitoid Sympiesis sericeicornis Nees (Hymenoptera: Eulophidae) while foraging on apple leaves infested by one of its hosts, the spotted tentiform leafminer Phyllonorycter malella (Ger.) (Lepidoptera: Gracillariidae).This leafminer changes its behaviour as a function of the parasitoid's behaviour to escape parasitization.We propose that the leafminer uses vibrations triggered by the parasitoid to detect the presence of its enemy.We measured vibrations produced by a foraging parasitoid on a mine with a laser vibrometer.By recording concurrently the behaviour of the parasitoid on video, vibrations could be assigned to particular behaviours.Subsequently, vibrations were characterized by their dominant frequencies and intensities.The behaviours Landing and Take-off both produced strong impact-like vibrations characterized by an initial irregular phase during which frequencies up to 25 kHz occurred followed by a slow decaying regular phase.Vibrations elicited by Moving, Standing and Probing showed no clear temporal pattern.During Probing , dominant frequencies of up to 5.6 kHz were observed frequently at intensities well above the background noise (>10 dB).During Moving and Standing , vibrations were more scarce and of lower frequencies and intensities.Due to their impact-like nature, vibrations produced by Landing and Take-off are probably not specific to the parasitoid.Vibrations produced by Moving and Standing are difficult to detect and not reliable because of their non-specificity.Therefore, only Probing provides a reliable and detectable source of information for the host.The vibrations elicited during Probing could account for the evasive behaviour that is observed in this and other leafminers.     

Review Canalized pathways of change and constraints in the evolution of reproductive modes of microarthropods

This study investigates how the course of evolutionary change of an organismal pattern is canalized by organismal properties. As an example we use the mechanisms of indirect sperm transfer of some microarthropod groups. Miniaturized droplet spermatophores, characterized by a rather similar pattern of structural and functional components, are shown to have evolved independently in the Acari–Actinotrichida and the Pseudoscorpiones within the Arachnida and in the Entognatha (Collembola and Diplura–Campodeoidea), Symphyla, Pauropoda and Pselaphognatha within the Antennata. At least in the phylogenetic lineages leading to the various antennatan groups, evolution of miniaturized spermatophores took place in a similar sequence of transformation steps. It is likely that – originally – large sac spermatophores with a rigid sheath were deposited on the ground. The subsequent sequence of evolution involved carrying structures, a viscous sheath of the spermatophore-droplets, a stable water balance of the spermatophore under habitat conditions and miniaturized spermatophore droplets with immobilized sperm cells. Finally, mate dissociation became a common mode of behaviour in all groups mentioned. Each of the transformation steps was not only an adaptation to a particular selective condition, but additionally a precondition for further adaptive innovation. In this way the sequence of evolutionary change was rigidly determined. Moreover, integration of subsequently evolved components of the spermatophores into a complex network of interacting components obviously caused constraints of interaction, which in turn have caused a remarkable evolutionary stability of the character patterns. Using water mites as an example, it is shown how in a changed environment few behavioural changes have initiated an evolutionary sequence which has finally led convergently in several lineages to semi-direct or direct sperm transfer and to a massive repatterning of the original reproduction pattern. © Rapid Science Ltd. 1998