The uropygial gland is an organ exclusive of birds that secretes an oily substance, the uropygial secretion, the functions of which are still debated. One of the proposed hypothesis is its possible action against chewing lice (order Phthiraptera), a group of avian ectoparasites that feed on feathers, causing different types of harm. However, this hypothesis lacks support. The present study anal...

[1] Regression-type, hybrid empirical/process-based models (e.g., SPARROW, PolFlow) have assumed a prominent role in efforts to estimate the sources and transport of nutrient pollution at river basin scales. However, almost no attempts have been made to explicitly accommodate interannual nutrient loading variability in their structure, despite empirical and theoretical evidence indicating that ...

SUMMARY A 'switchover' from synthesis of predominantly embryonic hemoglobin to synthesis of predominantly adult hemoglobin occurs during differentiation of the house sparrow. This 'switchover' is demonstrated by a change in electrophoretic pattern generally comparable with that of the chicken, slightly different from those of the duck and man, and, perhaps, dissimilar to that of the red-wing bl...

normal cell fate decisions are reiterated in subsequent larval stages. Examples include mutations in lin-4 and lin-29. Worms with such mutations do not express certain adult cell fates, despite being sexually mature (Figure 1). Is there conservation in heterochronic gene pathways? An important regulator of the larval-to-adult transition in worms, let-7, is conserved across diverse phyla, having...