Cryopreservation of rainbow trout sperm by deep-freezing

International audienc

Enzymatic variation in African clariid catfishes

Enzymatic polymorphism was examined at 13 protein loci in four African clariid catfish species : #Claria anguillaris (Linnaeus, 1758), #C. gariepinus (Burchell, 1822) and #Heterobranchus longifilis Valencienne, 1840. The latter appears to be closer to #C. anguillaris and #C. gariepinus than #C. ebriensis. These results correspond with recently published karyological and morphometrical data. Reproductive compatibility, under laboratory conditions at least, is demonstrated between #C. gariepinus and #H. longifilis. The hybrids were shown to be completely intermediate between the parental strains. (Résumé d'auteur

Transitional random matrix theory nearest-neighbor spacing distributions

This paper presents a study of the properties of a matrix model that was introduced to describe transitions between all Wigner surmises of Random Matrix theory. New results include closed-form exact analytical expressions for the transitional probability density functions, as well as suitable analytical approximations for cases not amenable to explicit representation

Currents under land-fast ice in the Canadian Arctic Archipelago Part 2: Vertical mixing

During an acoustic Doppler current profiler (ADCP) study of the velocity field under land-fast ice, coincident CTD casts showed three instances of pronounced instability in the water column, immediately above and below the pycnocline. In this paper we demonstrate that the density inversions are associated with the passage of high frequency linear internal waves and finite amplitude waves. Contours of ADCP acoustic return intensity display pronounced vertical eddy-like features which may indicate overturning. A Richardson number calculation showed that even the most highly stratified portion of the pycnocline had sufficient vertical velocity shear to promote dynamic instability. Finally, we calculate that the vertical nutrient flux, resulting from the high frequency internal wave field, could supply a significant portion of the ice-algae nutrient budget

The global spread of crop pests and pathogens

AimTo describe the patterns and trends in the spread of crop pests and pathogens around the world, and determine the socioeconomic, environmental and biological factors underlying the rate and degree of redistribution of crop-destroying organisms. LocationGlobal. MethodsCurrent country- and state-level distributions of 1901 pests and pathogens and historical observation dates for 424 species were compared with potential distributions based upon distributions of host crops. The degree of saturation', i.e. the fraction of the potential distribution occupied, was related to pest type, host range, crop production, climate and socioeconomic variables using linear models. ResultsMore than one-tenth of all pests have reached more than half the countries that grow their hosts. If current trends continue, many important crop-producing countries will be fully saturated with pests by the middle of the century. While dispersal increases with host range overall, fungi have the narrowest host range but are the most widely dispersed group. The global dispersal of some pests has been rapid, but pest assemblages remain strongly regionalized and follow the distributions of their hosts. Pest assemblages are significantly correlated with socioeconomics, climate and latitude. Tropical staple crops, with restricted latitudinal ranges, tend to be more saturated with pests and pathogens than temperate staples with broad latitudinal ranges. We list the pests likely to be the most invasive in coming years. Main conclusionsDespite ongoing dispersal of crop pests and pathogens, the degree of biotic homogenization of the globe remains moderate and regionally constrained, but is growing. Fungal pathogens lead the global invasion of agriculture, despite their more restricted host range. Climate change is likely to influence future distributions. Improved surveillance would reveal greater levels of invasion, particularly in developing countries

Study of the Effect of Certain Supplements and Additives in Steer Fattening Rations

Animal Nutritio