Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Mother birds increase progesterone to hatch females

18.05.2005


In mammals, sperm from the male determines the sex of the offspring. In birds, however, it is the female’s sex chromosome that determines offspring sex. Now, Cornell University researchers think they understand the mechanism that several bird species use to bias the sex ratios of their offspring toward female.



By experimenting with domestic chickens, they have determined that the presence of higher-than-normal levels of the hormone progesterone during the first meiosis -- the cell division that divides the sex chromosomes and genetically determines the sex of an offspring -- produces significantly more females.

"For years, behavioral biologists have been trying to figure out how the females of a few species, such as the Seychelles warbler, the zebra finch and tree swallow, adaptively manipulate the sex of their offspring before an egg is laid," says Stephanie Correa, a doctoral student in neurobiology and behavior at Cornell and the lead author of the study that was posted online recently in The Royal Society’s Biology Letters (Vol. 1, 2005). "Most investigators have looked primarily at testosterone, but we decided to look at progesterone, the major hormone produced by the female bird’s preovulatory follicle."


To test the influence of progesterone on the sex ratio of offspring, Correa, along with Elizabeth Adkins-Regan, professor of neurobiology and behavior and of psychology, and Patricia Johnson, professor of animal science, both at Cornell, experimentally manipulated levels of progesterone in female chickens during the first meiosis. They injected either a low dose or a high dose of progesterone (dissolved in sesame oil) or a control dose of pure sesame oil.

The low dose of progesterone produced 61 percent males, which was very close to the control group rate of 63 percent males. The high dose of progesterone, however, produced only 25 percent males. "Thus, we think that how much progesterone the female follicle produces during the first meiosis is the mechanism in birds that manipulates the sex ratio of offspring," says Adkins-Regan.

"Researchers think that birds such as the Seychelles warbler may bias the sex of their offspring when, for example, their territory has plenty of food and the mother bird needs help in feeding the next generation," says Correa. Since males disperse, the mother bird may adaptively bias her offspring to female so that plenty of females from one generation will be available to help raise the next generation.

Although the finding is not of practical use in the near future for the poultry industry, Correa and Adkins-Regan say that understanding the basic mechanism of biasing sex ratios in birds could provide the foundation for learning how to manipulate the sex ratio of avian offspring in the future. Research in this area is just beginning, they note, because the molecular methods used to determine the sex of the eggs has only recently been made available.

Susan S. Lang | EurekAlert!
Further information:
http://www.cornell.edu

More articles from Life Sciences:

nachricht eTRANSAFE – collaborative research project aimed at improving safety in drug development process
26.09.2017 | Fraunhofer-Gesellschaft

nachricht Beer can lift your spirits
26.09.2017 | Friedrich-Alexander-Universität Erlangen-Nürnberg

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: The fastest light-driven current source

Controlling electronic current is essential to modern electronics, as data and signals are transferred by streams of electrons which are controlled at high speed. Demands on transmission speeds are also increasing as technology develops. Scientists from the Chair of Laser Physics and the Chair of Applied Physics at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) have succeeded in switching on a current with a desired direction in graphene using a single laser pulse within a femtosecond ¬¬ – a femtosecond corresponds to the millionth part of a billionth of a second. This is more than a thousand times faster compared to the most efficient transistors today.

Graphene is up to the job

Im Focus: LaserTAB: More efficient and precise contacts thanks to human-robot collaboration

At the productronica trade fair in Munich this November, the Fraunhofer Institute for Laser Technology ILT will be presenting Laser-Based Tape-Automated Bonding, LaserTAB for short. The experts from Aachen will be demonstrating how new battery cells and power electronics can be micro-welded more efficiently and precisely than ever before thanks to new optics and robot support.

Fraunhofer ILT from Aachen relies on a clever combination of robotics and a laser scanner with new optics as well as process monitoring, which it has developed...

Im Focus: The pyrenoid is a carbon-fixing liquid droplet

Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.

A warming planet

Im Focus: Highly precise wiring in the Cerebral Cortex

Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.

The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Bacterial Nanosized Speargun Works Like a Power Drill

26.09.2017 | Life Sciences

The fastest light-driven current source

26.09.2017 | Physics and Astronomy

Beer can lift your spirits

26.09.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>