Senin, 11 April 2011

Ayam Bisa Berganti Kelamin



KOMPAS.com - Siapa bilang pergantian kelamin hanya bisa terjadi pada manusia? Ayam milik pasangan suami istri Jim dan Jeanette Howard yang berasal dari Huntington, Inggris mengalami pergantian kelamin dari betina ke jantan.
Ayam piaraan bernama Gertie itu mulai mondar-mandir di halaman rumah dan berkokok layaknya pejantan. Beberapa minggu kemudian, karakter pejantan mulai tumbuh, seperti pial di dagu, jengger di kepala, serta bulu coklat gelap khas pejantan.
Jim Howard mengatakan pada Cambridge News, "Saya tahu ini kedengarannya aneh, tapi saya bisa memastikan ini semua benar. Orang pikir ini hal yang konyol, tapi ternyata ini adalah benar adanya."
Publikasi Institut Ilmu Pangan dan Pertanian Universitas Florida tahun 2000 menyatakan, "Perubahan kelamin nyatanya terjadi, meski tak begitu sering. Namun hingga sekarang, belum dijumpai perubahan dari jantan ke betina."
Perubahan kelamin ini bisa dijelaskan dari perkembangan biologis ayam. Pada masa embrionik, terdapat bakal kelamin jantan dan betina. Sekali gen betina dominan, maka ovarium akan berkembang.
Tapi tak seperti manusia, ovarium ayam hanya berkembang di pinggang kiri saja. Sementara, bakal kelamin di pinggang kanan akan mengalami dormansi, tak berkembang menjadi jantan maupun betina. Bagian yang mengalami dormansi disebut ovotestis.
Dalam kondisi tertentu seperti adanya kista, tumor ataupun penyakit kelenjar anak ginjal, ovarium ayam bisa mengalami degenerasi. Saat itulah, ovotestis  mungkin tumbuh menjadi organ kelamin jantan.
"Jika bakal kelamin di sebelah kanan berkembang jadi testis, maka akan mensekresikan androgen," kata Mike Hulet, profesor ilmu peternakan di Pennsylvania State University. Androgen adalah hormon yang bertanggung jawab terhadap karakteristik jantan.
"Produksi androgen inilah yang akan menyebabkan perubahan perilaku pada betina dan membuatnya bertingkah layaknya pejantan," ucap Hulet seperti dikutip Life's Little Mysteries kemarin (31/3/2011).
Namun, ayam tak akan sepenuhnya menjadi jantan. Meski tampak jantan, secara genetik ayam seperti Gertier tetap betina. Jadi, meski tak akan mampu bertelur lagi, ayam yang berganti kelamin juga takkan mampu membuahi betina lain. Akibat pergantian kelamin, Gerte kini berganti nama menjadi Bertie.

Changing Sex Can Chicken
KOMPAS.com - Who says sex change can only occur in humans? Chickens belonging couple Jim and Jeanette Howard who came from Huntington, England had gender reassignment from female to male.
Pet chicken named Gertie began pacing in the yard and crowed like a stud. A few weeks later, the male characters begin to grow, like wattle on the chin, cockscomb on his head, and dark brown fur typical male.
Jim Howard said at the Cambridge News, "I know it sounds weird, but I can confirm this is all true. People think this is a silly thing, but this turned out to be true."
Publication of the Institute of Food and Agricultural Sciences University of Florida in 2000 stated, "Changes in sex in fact happened, though not so often. But until now, have not found the change from male to female."
These sex changes can be explained from the biological development of the chicken. In the embryonic period, there will be male and female sex. Once a female dominant gene, then the ovaries will develop.
But unlike humans, chicken ovaries developed only in the left hip only. Meanwhile, would have sex in the right hip will experience dormancy, do not develop into males and females. Part of dormancy called ovotestis.
Under certain conditions such as cysts, tumors or disease adrenal glands, ovaries can degenerate chicken. When it is, ovotestis may grow into a male sex organ.
"If going to the right genital develop into testes, it will secrete androgens," said Mike Hulet, a professor of poultry science at Pennsylvania State University. Androgens are hormones responsible for male characteristics.
"The production of androgens is what will cause changes in female behavior and make it behave like a stud," Hulet said as quoted by Life's Little Mysteries yesterday (03/31/2011).  However, the chicken will not fully be male. Although looking male, genetically female chickens as Gertier fixed. So, though no longer will be able to lay eggs, chicken sex change also would not be able to fertilize another female. As a result of gender reassignment, Gerte now renamed Bertie.

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