Sexual differentiation of the zebra finch song system: Positive evidence, negative evidence, null hypotheses, and a paradigm shift
✍ Scribed by Arnold, Arthur P.
- Book ID
- 101258306
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 85 KB
- Volume
- 33
- Category
- Article
- ISSN
- 0022-3034
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✦ Synopsis
Permanent sex differences in the amounts of functional testicular tissue but with virtubrain are found in many vertebrates, and are thought ally no ovarian tissue nevertheless have a feminine to be induced by sex differences in secretion of gonadal song circuit. The latter studies fail to support the idea steroid hormones during critical periods of early deof steroid induction of sexual differentiation. An altervelopment. This theory has received support primarnative to the steroidal control hypothesis is that nonily from many experiments conducted on mammals, hormonal gene products expressed in the brain early but also from studies on other vertebrate classes, inin development trigger sexually dimorphic patterns cluding birds. The only avian neural dimorphism that of development. Although current evidence in several has allowed extensive tests of this hypothesis is the neural and nonneural systems indicates that sexual neural circuit for song in passerine birds, which is differentiation of some somatic phenotypes cannot be much larger in males than in females. Experiments explained by the actions of gonadal steroids, the idea in zebra finches have yielded contradictory results. of direct genetic (nonhormonal) induction of sexual Although it is relatively easy to induce masculine patdifferentiation has yet to be proved. ᭧ 1997 John terns of development in genetic females with estrogen,