A neuroendocrine model for prolactin as the key mediator of seasonal breeding in birds under long- and short-day photoperiods.
Seasonal breeding is associated with sequential increases in plasma luteinizing hormone (LH) and prolactin in the short-day breeding emu, and in long-day breeding birds that terminate breeding by the development of reproductive photorefractoriness. A model of the avian neuroendocrine photoperiodic reproductive response is proposed, incorporating a role for prolactin, to account for neuroendocrine mechanisms controlling…
Read MoreEmbryonic heart rate measurements during artificial incubation of emu eggs.
Daily changes in embryonic heart rate (HR) of emu were determined non-invasively at 36 degrees C by acoustocardiography (ACG) during the last 30% of artificial incubation (predicted incubation time is 50 d). The pattern of daily changes in mean HR of hatched embryos decreased from about 175 bpm to about 140 bpm towards the end…
Read MoreEfferent axons in the avian auditory nerve.
The sensory hair cells of the inner ear receive both afferent and efferent innervation. The efferent supply to the auditory organ has evolved in birds and mammals into a separate complex system, with several types of neurons of largely unknown function. In this study, the efferent axons in four different species of birds (chicken, starling,…
Read MoreDMRT1 in a ratite bird: evidence for a role in sex determination and discovery of a putative regulatory element.
Unlike mammals, birds have a ZZ male/ZW female sex-determining system. In most birds, the Z is large and gene rich, whereas the W is small and heterochromatic, but the ancient group of ratite birds are characterized by sex chromosomes that are virtually homomorphic. Any gene differentially present on the ratite Z and W is therefore…
Read MoreDistribution of spermatozoa in the outer perivitelline layer from above the germinal disc of emu and ostrich eggs
To whom correspondence should be addressed. email: imalecki@agric.uwa.edu.au Abstract In the present study, we determined the distribution of spermatozoa in the perivitelline layer above the germinal disc (GD) of emu and ostrich eggs that had been laid at random intervals after mating. Eggs were opened, the perivitelline layer overlying the GD region was collected and…
Read MoreDistribution and characterization of microsatellites in the emu (Dromaius novaehollandiae) genome.
This study generates data concerning the genome of a flightless species of bird, the emu. We examined and ultimately rejected the following hypotheses: Microsatellites are randomly distributed throughout the emu genome. The relative order of abundance of dinucleotides will be constant across genomes. Interspersion distances for a given dinucleotide will be equal across vertebrate genomes.…
Read MoreComplete mitochondrial genome sequences of two extinct moas clarify ratite evolution.
The origin of the ratites, large flightless birds from the Southern Hemisphere, along with their flighted sister taxa, the South American tinamous, is central to understanding the role of plate tectonics in the distributions of modern birds and mammals. Defining the dates of ratite divergences is also critical for determining the age of modern avian…
Read MoreComplete mitochondrial DNA genome sequences of extinct birds: ratite phylogenetics and the vicariance biogeography hypothesis.
The ratites have stimulated much debate as to how such large flightless birds came to be distributed across the southern continents, and whether they are a monophyletic group or are composed of unrelated lineages that independently lost the power of flight. Hypotheses regarding the relationships among taxa differ for morphological and molecular data sets, thus…
Read MoreComparative painting reveals strong chromosome homology over 80 million years of bird evolution.
Chickens and the great flightless emu belong to two distantly related orders of birds in the carinate and ratite subclasses that diverged at least 80 million years ago. In the first ZOO-FISH study between bird species, we hybridized single chromosome paints from the chicken (Gallus domesticus) onto the emu chromosomes. We found that the nine…
Read MoreA new animal model of femoral head osteonecrosis: one that progresses to human-like mechanical failure.
Existing animal models of femoral head osteonecrosis, while displaying varying levels of concordance with early histopathologic features of the human disorder, generally fail to progress to end-stage mechanical collapse. A new animal model of osteonecrosis is here introduced, utilizing the emu (Dromaius novaehollandie). These animals’ bipedality and their high activity level represent a much more…
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