First videotaped infanticide in the common pochard Aythya ferina

A growing body of literature suggests that infanticide is common in a variety of animals. However, most reports are concerned with infanticide by males and these evidences are often indirect or questionable. Here we describe the first videotaped non-parental infanticide by a female common pochard (Aythya ferina) which killed one conspecific duckling. Our observation does not suggest that this attack was caused by a high density of breeding pairs as was found for other ducks (resource competition hypothesis). We speculate that infanticide in this particular case might be adaptive because a reduced number of ducklings in the pond decreased the vulnerability to predation by raptors.     

A Comparative Study on the Role of Cytokinins in Caryopsis Development in the Maize miniature1 Seed Mutant and Its Wild Type

We report here on a comparative developmental profile of plant hormone cytokinins in relation to cell size, cell number and endoreduplicaUon in developing maize caryopsis of a cell wall invertase-deficient miniature1 （mn1） seed mutant and its wild type, Mn1, genotype. Both genotypes showed extremely high levels of total cytokinins during the very early stages of development, followed by a marked and genotype specific reduction. While the decrease of cytokinins in Mn1 was associated with their deactivation by 9-glucosylation, the absolute and the relative part of active cytokinin forms was higher in the mutant. During the exponential growth phase of endosperm between 6 d after pollination and 9 d after pollination, the mean cell doubling time, the absolute growth rate and the level of endoreduplication were similar in the two genotypes. However, the entire duration of growth was longer in Mnl compared with mnl, resulting in a significantly higher cell number in the Mnl endosperm. These data correlate with the previously reported peak levels of the Mn1-encoded cell wall invertase-2 （INCW2） at 12 d after pollination in the Mn1 endosperm. A model showing possible crosstalk among cytokinins, cell cycle and cell wall invertase as causal to increased cell number and sink strength of the Mn1 developing endosperm is discussed.