Low Dose Isoflurane Exerts Opposing Effects on Neuronal Network Excitability in Neocortex and Hippocampus

The anesthetic excitement phase occurring during induction of anesthesia with volatile anesthetics is a well-known phenomenon in clinical practice. However, the physiological mechanisms underlying anesthetic-induced excitation are still unclear. Here we provide evidence from in vitro experiments performed on rat brain slices that the general anesthetic isoflurane at a concentration of about 0.1 mM can enhance neuronal network excitability in the hippocampus, while simultaneously reducing it in the neocortex. In contrast, isoflurane tissue concentrations above 0.3 mM expectedly caused a pronounced reduction in both brain regions. Neuronal network excitability was assessed by combining simultaneous multisite stimulation via a multielectrode array with recording intrinsic optical signals as a measure of neuronal population activity

Male pygmy hippopotamus influence offspring sex ratio

Pre-determining fetal sex is against the random and equal opportunity that both conceptus sexes have by nature. Yet, under a wide variety of circumstances, populations shift their birth sex ratio from the expected unity. Here we show, using fluorescence in situ hybridization, that in a population of pygmy hippopotamus (Choeropsis liberiensis) with 42.5% male offspring, males bias the ratio of X- and Y-chromosome-bearing spermatozoa in their ejaculates, resulting in a 0.4337±0.0094 (mean±s.d.) proportion of Y-chromosome-bearing spermatozoa. Three alternative hypotheses for the shifted population sex ratio were compared: female counteract male, female indifferent, or male and female in agreement. We conclude that there appears little or no antagonistic sexual conflict, unexpected by prevailing theories. Our results indicate that males possess a mechanism to adjust the ratio of X- and Y-chromosome-bearing spermatozoa in the ejaculate, thereby substantially expanding currently known male options in sexual conflict

Effects of experimental small-scale grassland fragmentation on the extent of grazing damage in Trifolium repens seedlings

We examined the extent of grazing damage to seedlings of white clover (Trifolium repens) in experimentally fragmented calcareous grasslands. The experimental set-up consisted of 12 blocks distributed over three sites. Each block contained one large (4.5x4.5 m), one medium (1.5x1.5 m) and two small (0.5x0.5 m) fragments and corresponding control plots (Zschokke et al 2000). Fragmentation was maintained by frequently mowing the area between the fragments. A fence around the study sites excluded large herbivores. Seedlings of T. repens planted in petri dishes were exposed to invertebrate herbivores in fragments and control plots for 2-3 days both in summer and autumn. In summer - unlike autumn - grazing intensity expressed as leaf biomass loss per petri dish and day was 43% lower in fragments than in control plots. Grazing intensity in summer was positively correlated with relative gastropod density (number of individuals from 12 species), but not with relative grasshopper density (number of individuals from 15 species). In autumn, grazing intensity was correlated neither with gastropod nor with grasshopper density. It is suggested that a combination of factors can explain the seasonal difference in fragmentation effect on grazing intensity. Different herbivore species are active at different seasons and/or under different environmental conditions. Furthermore, different herbivore species react differently to the type of grassland fragmentation chosen in the present study. We conclude that fragmentation effects on grazing depend on which of the potential herbivore species react to fragmentation and which of them are active during the investigation period

Habitat characteristics of the endangered flightless beetle 'Dorcadion fuliginator' (Coleoptera, Cerambycidae) : implications for conservation

Betr. den Erdbockkäfer in Basel Habitat destruction and degradation are the major causes for the decline of the endangered grass-feeding flightless beetle Dorcadion fuliginator in Central Europe. We examined habitat characteristics at 19 localities which still support abundant D. fuliginator populations in the southern part of the Upper Rhine valley (border region of Switzerland, Germany and France) to obtain basic information for the management of deteriorating habitats with declining beetle populations. Populations of D. fuliginator were found in different types of grassland on south, south-west and south-east facing slopes and flat ground. Correspondence analysis showed that plant communities of D. fuliginator localities overlap widely with fertilized, dry hay meadows (phyto-sociologically defined as dry type of the Arrhenatheretum community) and to a minor extent with traditionally extensively cultivated dry grasslands (Xerobrometum and Teucrio-Mesobrometum communities). Average indicator scores of the plant communities characterize the habitat of D. fuliginator as fairly light-exposed and warm, but with relatively large ranges in humidity and nutrient content. The results of a 16-year study on the timing of emergence of the first beetles in a population provided further evidence for the high temperature requirements of D. fuliginator. Proposed conservation measures include traditional cultivation of the present secondary, man-made D. fuliginator habitats, introduction of beetles to suitable motorway embankments as well as large-scale measures allowing natural dynamics in the flood plain along the river Rhine, the presumably primordial habitat of this highly endangered beetle

Grain-dependent relationships between plant productivity and invertebrate species richness and biomass in calcareous grasslands

The relationships among productivity, species richness and consumer biomass are of fundamental importance for understanding determinants of biodiversity. These relationships may depend on grain size. We examined the relationships between productivity (above-ground phytomass) and plant species richness and between productivity and species richness and biomass of gastropods and grasshoppers using sampling units of different sizes (0.5, 2.75 and 23 m(2)) in nutrient-poor, calcareous grasslands in north-western Switzerland in two successive years. Species richness of forbs had a unimodal relationship with productivity in sampling units of 0.5 m(2) and was negatively correlated with productivity at the other two plot sizes in one year. In the other year, forb species richness tended to decrease with productivity in sampling units of 23 m(2). No similar relationship was found for grasses. Gastropod biomass had a unimodal relationship with productivity at 0.5 m(2) in the first year. Grasshopper species richness was correlated with forb species richness at plot sizes of 2.75 and 23 m(2). This study demonstrates that patterns detected between productivity and diversity and between productivity and biomass of consumers depend on the grain size used in the investigation and vary among years. Betr. Untersuchungsgebiete im Nordwestschweizer Jura in Nenzlingen, Movelier und Vicque

A new Davaineid Cestode-Raillietina (Pa-roniella) macropa sp. n., from a wallaby

Volume: 9Start Page: 602End Page: 61

Short-term responses of plants and invertebrates to experimental small-scale grassland fragmentation

Untersuchungsgebiete: Nenzlingen, Movelier, Vicques The fragmentation of natural habitats is generally considered as a major threat to biodiversity. We investigated short-term responses of vascular plants (grasses and forbs) and four groups of invertebrates (ants, butterflies, grasshoppers and gastropods) to experimental fragmentation of calcareous grassland in the north-western Jura mountains, Switzerland. Three years after the initiation of the fragmentation -- which was created and maintained by mowing the area between the fragments -- we compared species richness, diversity and composition of the different groups and the abundance of single species in fragments of different size (area: 20.25 m², 2.25 m² and 0.25 m²) with those in corresponding control plots. The abundances of 19 (29%) of the 65 common species examined were affected by the fragmentation. However, the experimental fragmentation affected different taxonomic groups and single species to a different extent. Butterflies, the most mobile animals among the invertebrates studied, reacted most sensitively: species richness and foraging abundances of single butterfly species were lower in fragments than in control plots. Of the few other taxonomic groups or single species that were affected by the experimental fragmentation, most had a higher species richness or abundance in fragments than in control plots. This is probably so because the type of fragmentation used is beneficial to some plants through a decreased competition intensity along the edge of the fragments, and because some animals may use the fragments as retreats between their foraging bouts into the mown isolation area