RESUMO
The common cuckoo Cuculus canorus is divided into host-specific races (gentes). Females of each race lay a distinctive egg type that tends to match the host's eggs, for instance, brown and spotted for meadow pipit hosts or plain blue for redstart hosts. The puzzle is how these gentes remain distinct. Here, we provide genetic evidence that gentes are restricted to female lineages, with cross mating by males maintaining the common cuckoo genetically as one species. We show that there is differentiation between gentes in maternally inherited mitochondrial DNA, but not in microsatellite loci of nuclear DNA. This supports recent behavioural evidence that female, but not male, common cuckoos specialize on a particular host, and is consistent with the possibility that genes affecting cuckoo egg type are located on the female-specific W sex chromosome. Our results also support the ideas that common cuckoos often switched hosts during evolution, and that some gentes may have multiple, independent origins, due to colonization by separate ancestral lineages.
Assuntos
Aves/genética , Animais , Comportamento Animal , Evolução Biológica , Aves/fisiologia , DNA Mitocondrial , Feminino , Frequência do Gene , Haplótipos , Interações Hospedeiro-Parasita , Masculino , ReproduçãoRESUMO
Retinal ganglion cell distribution in nine species of procellariiform seabirds was studied by Nissl staining of retinal whole-mounts and the construction of density contour maps. Most species showed a horizontal linear area of high cell density, but concentric distributions with dorsal and central cell concentrations were found in two species. These results are discussed in relation to the birds' foraging behaviour.
Assuntos
Aves/anatomia & histologia , Células Ganglionares da Retina/citologia , Animais , Biometria , Contagem de Células , Células Ganglionares da Retina/fisiologiaRESUMO
During studies on the etiology of puffinosis, a disease of the Manx shearwater, 1 to 4% of full-grown birds were found to have dry, non-pigmented lesions on the webs of the feet. Poxvirus infection was detected in six of seven full-grown birds with such lesions. The lesions contained large encapsulated inclusions which were packed with mature and immature poxvirus particles. Poxvirus infection was not apparent in shearwater fledglings during puffinosis epizootics, and its spatial distribution was not related to that of puffinosis. The results indicate that poxvirus infection produces a mild, self-limiting disease in shearwaters and is not the cause of puffinosis.