Plasma thyroid hormones and growth hormone in embryonic and growing emus (Dromaius novaehollandiae)
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Published:2001
Issue:3
Volume:13
Page:125
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ISSN:1031-3613
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Container-title:Reproduction, Fertility and Development
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language:en
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Short-container-title:Reprod. Fertil. Dev.
Author:
Blache D.,Blackberry M. A.,van Cleeff J.,Martin G. B.
Abstract
Growth hormone (GH), thyroxine (T4) and
tri-iodothyronine (T3) are known to be involved in the
regulation of growth and development in a variety of avian species. It has
been suggested that an absence of GH and thyroid hormones in ostriches is the
cause of their neoteny, a phenomenon in which juvenile characteristics are
retained into adulthood. Neoteny is typical of all ratites, the single group
of flightless birds that includes the ostrich, but similar endocrine studies
have not been performed for other members of the group, such as the emu. To
test the neoteny hypothesis further, in the present study we measured the
plasma concentrations of T4, T3
and GH in emus during embryonic development and from hatching to 1 year of
age. Concentrations of T4 and GH increased during the
last weeks of incubation, whereas concentrations of T3
were highly variable. After hatching, the concentrations of both thyroid
hormones were high during the first 3 days of life and then fell to a constant
low level. Plasma concentrations of GH were high at the time of hatching and
decreased gradually over the first 22 weeks of age; thereafter, the
concentrations of GH were highly variable. No correlation was observed between
hormone concentrations and live weight at any time. These results support the
hypothesis that thyroid function is abnormally low in ratites, whereas
patterns of GH secretion are similar to those observed in other birds.
Dysfunction of the thyroid axis could explain, in part, the neotenous physical
aspect of adult emus.
Publisher
CSIRO Publishing
Subject
Developmental Biology,Endocrinology,Genetics,Molecular Biology,Animal Science and Zoology,Reproductive Medicine,Biotechnology
Cited by
2 articles.
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