Adaptations in the common cuckoo (Cuculus canorus) to host eggs in a multiple-hosts system of brood parasitism

The common cuckoo Cuculus canorus parasitism greatly reduces the reproductive success of its hosts and imposes strong selection pressure for hosts to evolve defences against parasitism, such as the ability to recognize and reject dissimilar parasitic eggs, which, in turn, selects for better egg mimicry by the cuckoo. In the co-evolutionary interaction, however, it remains unknown how the cuckoo successfully expanded its range of host usage and how they developed egg mimicry. Most previous studies were conducted in areas where a very few number of host species (i.e. one or two at most) are sympatric with the cuckoo. Several host species, however, breed sympatric with the cuckoo and have been parasitized in the study site in Nagano, central Japan. Such a multiple-hosts system will provide valuable insights for understanding the cuckoo–hosts interactions in the past. In the present study, we report quantitative profiles of eggs based on spectrometer reflectance for four major host species and the corresponding cuckoo gentes. The hosts include the oriental reed warbler ( Acrocephalus orientalis ), bull-headed shrike ( Lanius bucephalus ), azure-winged magpie ( Cyanopica cyana ), and black-faced bunting ( Emberiza spodocephala ). We show that (1) egg morphs of each host and corresponding cuckoo gens can be categorized by two chromatic components of reflectance spectra and (2) there is a significant difference in a particular chroma component between hosts and the cuckoo. We suggest that the cuckoo parasitism in central Japan originated from parasitism on the black-faced bunting.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 291–300.     

CHRONOLOGICAL CHANGES IN THE INDUCTIVE ABILITY OF THE MESENCHYME OF THE DIGESTIVE ORGANS IN AVIAN EMBRYOS

Dissociation and reassociation experiments were carried out to study the inductive ability of mesenchyme of the oesophagus, gizzard and intestine of the chicken embryo, using 3-day-old quail embryonic allantoic endoderm as an effector tissue. The mesenchyme of the oesophagus and gizzard possesses inductive ability until the Ilth day of incubation. Thereafter, it no longer has inductive influence upon the allantoic endoderm. The intestinal mesenchyme was favourable to differentiation of allantoic endoderm into intestinal epithelium even on the I5th day of incubation. In all types of recombination tested, goblet cells differentiated among allantoic endodermal cells.     

EFFECT OF AIR IONS ON IAA CONTENT OF BARLEY SEEDLINGS

Exposure of barley seedlings (Hordeum vulgaris) growing in sandand liquid cultures to either negatively- or positively-ionizedair results in increased growth in terms of integral elongation,and fresh and dry weight increase. Using large quantities oftissue and a modified method it was found that free and boundIAA contents were not significantly modified by exposure ofseedlings to ionized air. It might be supposed that an equilibriumbetween free and bound IAA was not modified by exposure to airions. (Received August 3, 1965; )