Navigation Links
Mother birds increase progesterone to hatch females

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 dur ing 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.


'"/>

Source:Cornell University News Service


Related biology news :

1. Antiretroviral Therapy May Prevent HIV Transmission From Breastfeeding Mothers To Infants
2. Mother birds give a nutritional leg up to chicks with unattractive fathers
3. Mother knows best: Plant knowledge key to childhood health in remote Amazon
4. Migratory songbirds have a specialized night-vision brain area
5. The lopsided brain: Attention bias is shared by humans and birds
6. Bobbing birds do it for a reason
7. Overbearing colored light may reveal a second mechanism by which birds interpret magnetic signals
8. Industrial contaminants spread by seabirds in High Arctic, new Canadian study shows
9. Displaced songbirds navigate in the high Arctic
10. Oil spills and climate change double the mortality rate of British seabirds
11. Wild birds help to create human flu vaccine
Post Your Comments:
*Name:
*Comment:
*Email:


(Date:5/16/2017)... , May 16, 2017   Bridge Patient ... organizations, and MD EMR Systems , an ... partner for GE, have established a partnership to ... product and the GE Centricity™ products, including Centricity ... These new integrations will allow ...
(Date:4/19/2017)... April 19, 2017 The global ... landscape is marked by the presence of several large ... held by five major players - 3M Cogent, NEC ... accounted for nearly 61% of the global military biometric ... in the global military biometrics market boast global presence, ...
(Date:4/13/2017)... 13, 2017 UBM,s Advanced Design and Manufacturing ... feature emerging and evolving technology through its 3D Printing ... run alongside the expo portion of the event and ... demonstrations focused on trending topics within 3D printing and ... manufacturing event will take place June 13-15, 2017 at the ...
Breaking Biology News(10 mins):
(Date:5/23/2017)... Canada (PRWEB) , ... May 23, 2017 , ... ... Firmex FileSend, a cloud-based file transfer solution that makes it easy for organizations ... without having to worry about cumbersome FTP software or email file size limitations. ...
(Date:5/23/2017)... ... May 22, 2017 , ... NetDimensions has been ranked ... Research Globe™ for Corporate Learning, 2017. , Aragon Research defines Leaders as organizations ... effectively perform against those strategies. NetDimensions’ ranking as a Leader due to its ...
(Date:5/23/2017)... ... May 23, 2017 , ... Kathy Goin is ... Clinical Operations. She brings years of expertise in establishing and leading clinical operations ... as a licensed occupational therapist, through a variety of leadership roles in Clinical ...
(Date:5/22/2017)... ... May 22, 2017 , ... Stratevi, a boutique firm that partners ... Coast. It has opened an office in downtown Boston at 745 Atlantic Ave. ... more important to generate evidence on the value they provide, not just to patients, ...
Breaking Biology Technology: