Download e-book for iPad: Development of the Avian Embryo: A Behavioural and by B. M. Freeman, Margaret A. Vince (auth.)

By B. M. Freeman, Margaret A. Vince (auth.)

ISBN-10: 9400957106

ISBN-13: 9789400957107

ISBN-10: 9400957122

ISBN-13: 9789400957121

In this publication we've defined the key occasions of embryonic improvement and thought of the underlying mechanisms which bring about the creation of a workable hatchling. now we have, because the subtitle of the publication shows, con­ centrated on behavioural and physiological themes: it's not our goal to contemplate the early embryology of the chook - that is properly coated through different texts - yet we now have integrated morphogenetic info the place acceptable. the shape of the e-book was once dictated by way of a trust that curiosity during this element of improvement isn't really restrained to embryologists, biochemists and physiolo­ gists. as a result after describing the stipulations within which the egg mostly develops we've got thought of first the complete embryo: what it really is like at varied phases, what it does, the way it will get from one place to a different in the shell and the way, later, it involves have interaction with the broader environ­ ment of the nest. in basic terms after this have we thought of the advance of the worried and sensory mechanisms on which this modification relies and at the challenge of the extent of behavioural adulthood with which the chick emerges from the egg. With the most strains of improvement defined now we have, within the moment a part of the booklet, became to a close attention of the body structure of improvement: starting from what could be very easily defined because the 'life-support' structures - gaseous trade, provision of power, and so forth. - to the of hormones in avian development.

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Extra info for Development of the Avian Embryo: A Behavioural and Physiological Study

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In the fowl the yolk tends to be fully withdrawn about 20 h before hatching * 23 DEVELOPMENT OF THE AVIAN EMBRYO (Vince & Tolhurst, unpublished). Once withdrawn the umbilical ring develops and closes round the blood vessels of the allantoic circulation before they are finally sealed off. During this last period there are changes in the extra-embryonic structures; from 17 days there is a sudden sharp fall in the mechanical resistance of the amnion, although its weight remains approximately the same (Romanoff, 1960) - presumably it stretches with the increased rate of embryonic growth.

On the other hand the absence of normally functioning legs resulted in the absence of stemming movements against the shell and failure to hatch, as the embryos could not turn in the shell (Oppenheim & Narayanan, 1968; Helfenstein & Narayanan, 1969). In the fowl the onset of hatching movements follows a period of relative quiescence and its onset is noticeably sudden. Once they have begun, hatching movements continue at intervals of about 10 s until the chick has freed itself from the shell. The onset of hatching, is, however, not only sudden, it is relatively unpredictable.

Exceptions include the palm swift which builds on the undersides of palm leaves, glues its eggs to the nest and broods them vertically (Lack, 1956), and also megapodes (Frith, 1952; Baltin, 1969), where the eggs are buried upright in the incubation mound, and remain in this position until hatching. In the swift it would seem that the egg contents could be shifted by 18 INCUBATION REQUIREMENTS leaf movements. In megapodes Baltin (1969) has observed that the air space is movable. Possibly this, or other structural peculiarities, obviates the necessity for turning in these species.

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Development of the Avian Embryo: A Behavioural and Physiological Study by B. M. Freeman, Margaret A. Vince (auth.)

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