Changes in the expression of genetic characteristics across cohorts in skeletal deformations of farmed salmonids

Genetic analysis of disorder incidence in farmed animals is challenged by two factors. Disorders in different cohorts and environments could be caused by different factors, leading to changes in heritability and to less than unity genetic correlations across cohorts. Moreover, due to computational limitations, liability scale heritabilities at very low incidence may differ from those estimated at higher incidence. We tested whether these two dilemmas occur in skeletal deformations of farmed salmonids using multigeneration data from the Finnish rainbow trout breeding programme and previous salmonid studies. The results showed that heritability was close to zero in cohorts in which management practices maintained incidence at a low level. When there was a management failure and incidence was unusually high, heritability was elevated. This may be due to computational limitations at very low incidence and/or because deformations are induced by different factors in different cohorts. Most genetic correlations between deformations recorded in different generations were weakly to strongly positive. However, also negative correlations between generations were present, showing that high liability at one time can be genetically connected to low liability at another time. The results emphasise that genetic architecture of binary traits can be influenced by trait expression.     

Plant colonization of a bare peat surface: population changes and spatial patterns

Abstract. Changes in size and spatial arrangement of plant populations established on an initially bare peat surface were described over a period of 5 yr by following plant individuals on a 1-cm grid in an area of 10 m x 25 m. The spatial pattern of populations and association between species was analyzed statistically. The study site was very slowly colonized by 14 perennial plant species. The early successional stage was dominated by Carex rostrata, with a clumped spatial distribution, and the homogeneously distributed Eriophorum vaginatum and Pinus sylvestris. Both the growth in size of populations and changes in their spatial distribution were interpreted as a result of species dispersal ability, tolerance to severity of the substrate and pattern of reproduction.     

Evidence for p15 cleavage site in myc-specific proteins of avian MC29 and OK10 viruses

Myc-related proteins were precipitated from MC29 virus-transformed cells (PR-2) and from OK10 virus-transformed cells (9C) by anti-gag and anti-myc sera. Immunoprecipitates were cleaved with the avian retroviral protease p15 and the cleavage products analyzed in SDS-PAGE. Cleavage fragments of p110gag-myc (product of MC29 virus) and p58myc (product of OK10 virus) showed the presence of a p15 cleavage site within the myc-specific region. The site is missing in deletion mutants of MC29 virus.     

The flagellar structure of the flame cell in fish tapeworm (Diphyllobothrium latum)

Summary The flame cell of the fish tapeworm (Diphyllobothrium latum) is investigated. In cross-section the flagella originating from the flame cell are hexagonal, except the incomplete ones facing the tubular wall. The function, as regards this unusual structure, is discussed. The axial filament complexes in one flame cell are arranged in opposite directions to each other. Thus the flame cell flagella seem to show many deviating characteristics as compared with those hitherto described. This investigation is supported by Oskar Öflunds Stifteise.It is a pleasure to acknowledge the skilful technical assistance of Miss Tellervo Huima.     

A simplified technique to measure respiration rates of aerobic heterotrophic populations

A simplified technique to trap respired carbon dioxide in a closed bottle system was developed from the technique introduced by Hobbie & Crawford in 1969. In this technique carbon dioxide was trapped in ethanolamine in a glass cup without the use of chromatographic paper. The results show that there is no need to enlarge the absorption surface with filter paper as practically complete recovery was achieved with ethanolamine alone in the cup.