Quantitative composition of the defensive secretion ofBledius species (Coleoptera: Staphylinidae: Oxytelinae) is adapted to naturally occurring predators

Summary The adaptation of defensive secretions to their target organisms was examined for the abdominal gland secretions ofBledius furcatus, B. spectabilis andB. arenarius. Therefore the target organisms of the secretion of theseBledius species (i.e. their predators) had to be identified. At the collection sites examined these were the earwigLabidura riparia, the antCataglyphis bicolor, the flyLispe candicans, different carabids of the generaPogonus, Dichirotrichus, Dyschirius, Bembidion andCalathus and the wading birdsHaematopus ostralegus andCalidris alba. The secretion of the abdominal glands contains the toxin ptoluquinone dissolved in either-dodecalactone and 1-undecene (B. furcatus andB. spectabilis) or in octanoic acid and octyloctanoate (B. arenarius). The ratio of these solvents is species-specific. Application experiments using some of the natural insect predators (L. riparia, C. bicolor, Pogonus, Di. gustavii, Dyschirius) revealed that these solvent ratios provided a more effective deterrent than other possible ratios. Thus by combining the solvents in certain ratios, the capability of cuticular penetration and therefore the effectiveness of the defensive secretions are adapted to their natural targets.     

Seasonal and interannual variability in krill (Nyctiphanes australis) stocks and their relationship to the fishery for jack mackerel (Trachurus declivis) off eastern Tasmania,Australia

Nyctiphanes australis was collected from the east coast of Tasmania between January 1989 and April 1991. Density and biomass were significantly higher in autumn than in any other season. The population was dominated by juveniles, except in autumn and spring 1990 when there was a significant increase in the proportion of adults. Our data indicated that N. australis does not regularly migrate vertically and that it forms aggregations of particular size classes which vary both temporally and spatially. Stomach fullness in Trachurus declivis, a major predator of N. australis, rose to a peak in autumn when N. australis stocks and the monthly catches by the fishery for T. declivis were at their highest. The stomachs of T. declivis were also dominated by adult size classes during this period. The virtual absence of N. australis in 1989 and the subsequent failure of the T. declivis fishery in that year underline the interrelationship between these two species. We suggest that this was the result of an influx of subtropical northern waters low in nutrients onto the shelf, which corresponded with a major La Niña cold event at that time.     

Verteilungskoeffizienten chlorierter Kohlenwasserstoffe zwischen Muskulatur und Leber bei Fischen

Zusammenfassung  Lipidbezogene Verteilungskoeffizienten (KL_M/L) zwischen Muskelkonzentrationen-(C_ML) und Leberkonzentrationen (C_LL) zweier Friedfischarten Brassen (Abramis brama) und Aalmutter (Zoarces viviparus) ergeben theoriekonform (KL_M/L=C_ML/C_LL=1) nominale Werte um 1 für persistente (hochchlorierte PCB) und Werte über 1 für metabolisierbare lipophile Umweltchemikalien wie chlorierte Cyclohexane oder DDT.      

Early loss and multiple return of the lower temporal arcade in diapsid reptiles

The temporal arches of diapsid reptiles have received attention for several decades. In particular, it has been observed that the lower temporal bar at the ventral margin of the cheek is frequently reduced due to the absence of a contact between jugal and quadratojugal. The loss of the arcade was formerly considered to be of high systematic value, but is now often interpreted as being autapomorphic for the respective taxon, and the presence of both arcades is generally regarded as a plesiomorphic feature. Here I show, based on a cladistic analysis as well as on further anatomical evidence, that the lower temporal arcade was lost only once in diapsid evolution, and that the presence of the arch in "higher" diapsids is secondary, which is indicated by the different ratio between jugal and quadratojugal as well as by ontogeny. This result also sheds new light on the understanding of the cheek configuration of enigmatic taxa such as ichthyosaurs and turtles.Electronic Supplementary Material  Supplementary material is available for this article if you access the article at . A link in the frame on the left on that page takes you directly to the supplementary material.     

A new look at Op art: towards a simple explanation of illusory motion

Vivid motion illusions created by some Op art paintings are at the centre of a lively scientific debate about possible mechanisms that might underlie these phenomena. Here we review emerging evidence from a new approach that combines perceptual judgements of the illusion and observations of eye movements with simulations of the induced optic flow. This work suggests that the small involuntary saccades which participants make when viewing such Op art patterns would generate an incoherent distribution of motion signals that resemble the perceptual effects experienced by the observers. The combined experimental and computational evidence supports the view that the illusion is indeed caused by involuntary image displacements picked up by low-level motion detectors, and further suggests that coherent motion signals are crucial to perceive a stable world.     

Baseline Standardisation with Optimising Energy-System Models

Determining adequate baselinesis a major methodological problem whenquantifying emissions reductions achievedwith the project-based flexibilitymechanisms. Possible methodologies forbaseline setting may be classified intomulti-project and project-specificapproaches. While multi-project approachesprovide baselines for a series of typicalprojects within a certain geographicregion, a sector, or a load range,project-specific (orproject-by-project/single-project)approaches only cover one specific project.Project-by-project baseline approaches havebeen tested extensively within theActivities Implemented Jointly (AIJ) pilotphase; multi-project methodologies, on theother hand, have only rarely been applieddue to the (perceived) political andeconomic complexity of the issue, whichmakes the process of introducingstandardised baselines a very sensitivetask. In particular, there is a lack ofmulti-project baseline approaches takingadvantage of optimising computer modelswithin the electricity sector, even thoughother fields of research have made use ofsuch models quite successfully in the past.Experiences made in the PROBASE projectwith the calculation of standardised,aggregated multi-project baselines forJI/CDM projects using optimising energysystem models are illustrated in this paperfor South Africa, Russia, and Indonesia.Increased transparency and credibility ofstandardised approaches along withpotentially lower transaction costs areidentified as the main arguments for theiruse and further development. In addition,the text gives recommendations wheremodel-based baseline standardisation canpreferentially be applied.     

Habitat related growth and reproductive investment in estuarine waters,illustrated for the tellinid bivalve <Emphasis Type="Italic">Macoma balthica</Emphasis> (L.) in the western Dutch Wadden Sea

In estuarine areas, bivalve species can be found in a variety of environments, where they experience large differences in environmental conditions. In the present paper, the importance of different habitats (intertidal, subtidal and adjacent coastal waters) for the persistence of the population was evaluated for the bivalve Macoma balthica (L.) in the western Dutch Wadden Sea estuary. Intra-specific variation in growth and reproductive output were followed during the year and related to local abiotic conditions. Significant differences in growth and reproductive investment were found between locations. Young individuals were mostly found in the intertidal area, where growth in terms of somatic mass was good. These areas were not favourable for adult individuals, since growth in shell length was low and many individuals did not reproduce. In the subtidal, where the highest densities were found, somatic and gonadal mass indices were low. Coastal areas had the lowest densities and showed high growth in terms of shell length and body mass. The habitat with the highest reproductive effort per individual was not the most important habitat in terms of reproductive output due to differences in density and in size of the habitat type. For M. balthica, the subtidal habitat contributed the most to the reproductive output of the western Dutch Wadden Sea population although the highest reproductive output per individual was in the coastal area.