Life cycle, growth, mortality and production of Ephemerella major Klapalek (Ephemeroptera) in a trout stream in Belgium

SUMMARY. 1. The life cycle of Ephemerella major Klapalek in a chalk trout stream in Belgium took 1 year. Emergence was highly synchronized with a flight period from mid-May to mid-June. Tiny nymphs occurred from June to late August.
2. The mean instantaneous growth rate was high in autumn (3.6% wet wt day⁻¹), very low from November to February (0.8% wet wt day⁻¹) and high until emergence (2.3% wet wt day⁻¹); short day length seemed to be the major factor reducing growth rate during winter.
3. Mortality was close to zero during winter and 1.4—1.7% day⁻¹during other seasons. Total mortality from egg to adult was 99.6%.
4. The annual production was about 9g wet wt m⁻² year⁻¹ and the annual P/ ratio was 7.5. There was good agreement between the production values estimated by four methods. Production rate was highest in May (13 mg wet wt m⁻² day⁻¹) and zero in February.     

Soil organic carbon changes in landscape units of Belgium between 1960 and 2000 with reference to 1990

The present study quantifies changes in soil organic carbon (SOC) stocks in Belgium between 1960, 1990 and 2000 for 289 spatially explicit land units with unique soil association and land‐use type, termed landscape units (LSU). The SOC stocks are derived from multiple nonstandardized sets of field measurements up to a depth of 30 cm. Approximately half of the LSU show an increase in SOC between 1960 and 2000. The significant increases occur mainly in soils of grassland LSU in northern Belgium. Significant decreases are observed on loamy cropland soils. Although the largest SOC gains are observed for LSU under forest (22 t C ha^?1 for coniferous and 29 t C ha^?1 for broadleaf and mixed forest in the upper 30 cm of soil), significant changes are rare because of large variability. Because the number of available measurements is very high for agricultural land, most significant changes occur under cropland and grassland, but the corresponding average SOC change is smaller than for forests (9 t C ha^?1 increase for grassland and 1 t C ha^?1 decrease for cropland). The 1990 data for agricultural LSU show that the SOC changes between 1960 and 2000 are not linear. Most agricultural LSU show a higher SOC stock in 1990 than in 2000, especially in northern Belgium. The observed temporal and spatial patterns can be explained by a change in manure application intensity. SOC stock changes caused by land‐use change are estimated. The SOC change over time is derived from observed differences between SOC stocks in space. Because SOC stocks are continuously influenced by a number of external factors, mainly land‐use history and current land management and climate, this approach gives only an approximate estimate whose validity is limited to these conditions.     

ISOPOD TRACKWAYS FROM THE CRAYSSAC LAGERSTÄTTE, UPPER JURASSIC, FRANCE

Abstract:  Well-preserved arthropod trackways are described from the laminated limestones of the Crayssac Lagerstätte (south-west France, Lower Tithonian). They occur in sediments deposited in the temporary coastal mudflats of intertidal to supratidal zones. The trackways are referred to Pterichnus isopodicus isp. nov., and are interpreted as the locomotion traces of isopods. Different trackway morphotypes are recognized and clearly resulted from variations in the original consistency of the sediment. Sinuous trackways may correspond to vagrant activity on wet mud whereas numerous straight ones indicate a more rapid crawling on a soft-to-firm substratum (e.g. tidal flat during emersion). The preferred orientation of trackways indicates that isopods were crawling in a direction perpendicular to shoreline as a result of possible taxis induced by sediment wetness and/or by a migratory behaviour controlled by tidal rhythm. Unusually long emergence of the sediments may have favoured the preservation of dense networks of trackways. An isopod identity is supported by the general morphology of the tracks and the association of trackways with isopod body fossils. Archaeoniscus , which occurs abundantly in Late Jurassic deposits of England and France, was probably the trace-maker.     

Multi-scale analysis of responses of stream macrobenthos to forestry activities and environmental context

1. Forestry activities can greatly modify the structure and function of invertebrate communities in streams, but the ability to detect effects of forestry may depend on the spatial scale considered, the choice of response metric and the environmental context. In this study, a multi‐scale, multi‐metric approach was used to compare the usefulness of proximate and larger‐scale measurements of forestry activity for understanding the impacts of forestry on stream macrobenthos. 2. Site‐specific responses of macrobenthic communities to forestry activities measured at four spatial scales (sub‐basin and 8‐, 2‐ and 0.5‐km radii upstream of study sites) were examined for 90 riffle sites distributed among 22 tributary streams (Strahler order 1–5) of the Cascapedia River basin, Quebec, Canada. 3. Multiple regression models and canonical correspondence analysis were used to relate six biological metrics (taxonomic richness, numerical density, biomass density, normalised biomass spectrum, individual body mass and community structure) to variables quantifying logging 1–19 years prior to the study and road density. Environmental predictors (variables quantifying local habitat or landscape features) were included in all analyses to statistically account for environmental context and increase the likelihood of detecting potentially subtle forestry impacts. 4. Forestry activities measured at the larger (sub‐basin and 8 km) scales were linked to decline in taxonomic richness, increase in numerical and biomass densities and shift in size structure of benthic macroinvertebrates, indicating that analyses encompassing larger areas, up to the full basin, may allow for more sensitive detection of effects than those of more limited span. 5. These responses primarily reflected marked increases in the abundance of chironomids and decline in the number of trichopteran taxa with increasing areal coverage of recent (≤2–4 years) cuts, suggesting that larger, longer‐lived and possibly more specialised taxa were more vulnerable to forestry impacts than smaller, multivoltine, generalist invertebrates. After partialling out the influence of other variables, rapid decline in richness occurred even when <1% of the basin had been clear cut in the year prior to the study. 6. Effects of forestry were detected after statistically accounting for natural environmental variability, which may have otherwise concealed those effects. The combined use of multiple biological metrics, partialling out of environmental effects and measurement of impacts at multiple spatial scales may be a broadly applicable approach for enhancing sensitivity and facilitating interpretation in studies of anthropogenic effects on macroinvertebrate communities.     

The Use of Protamine-Coated Slides for Immobilizing Protozoa*

Fresh-water, marine or parasitic protozoa can be immobilized for microscopic observation on protaminecoated slides. They appear not to be harmed by this procedure. The type of protamine derivative and its concentration are important, best results being obtained with 0.015–0.05% (w/v) of protamine sulfate.     

Postzygotic isolation between the two European subspecies of the house mouse: estimates from fertility patterns in wild and laboratory-bred hybrids

We assessed the fertility (reproductive success, litter size, testis weight, spermatocyte-to-spermatid ratio) of F₁s and backcrosses between different wild-derived outbred and inbred strains of two mouse subspecies, Mus musculus domesticus and M. m. musculus . A significant proportion of the F₁ females between the outbred crosses did not reproduce, suggesting that female infertility was present. As the spermatocyte-to-spermatid ratio was correlated with testis weight, the latter was used to attribute a sterile vs. fertile phenotype to all males. Segregation proportions in the backcrosses of F₁ females yielded 11 (inbred) to 17% (outbred) sterile males, suggesting the contribution of two to three major genetic factors to hybrid male sterility. Only one direction of cross between the inbred strains produced sterile F₁ males, indicating that one factor was borne by the musculus X-chromosome. No such differences were observed between reciprocal crosses in the outbred strains. The involvement of the X chromosome in male sterility thus could not be assessed, but its contribution appears likely given the limited introgression of X-linked markers through the hybrid zone between the subspecies. However, we observed no sterile phenotypes in wild males from the hybrid zone, although testis weight tended to decrease in the centre of the transect.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 84 , 379–393.