Structure and function of the external gill filaments of embryonic skates (Raja erinacea).
Respir Physiol
; 89(1): 1-13, 1992 Jul.
Article
em En
| MEDLINE
| ID: mdl-1518982
ABSTRACT
We have investigated structure and function of the external gill filaments, which occur transiently in the embryonic little skate, Raja erinacea. Approximately 25-30 days after spawning (body mass 0.03-0.05 g) external gill filaments appear as an outgrowth from the caudal side of the gill arches. These filaments are thread-like, each containing one afferent and one efferent blood vessel, and by day 70-75 (body mass 0.4-0.5 g) they reach their maximum size at a length of about 1 cm and a blood vessel diameter of 70-80 microns. Subsequent resorption of the filaments is characterized by a decrease in both length and diameter of the blood vessel. By day 90-95 (body mass 0.9-1.0 g) the external gill filaments are completely resorbed and replaced by internal gills. Blood velocity, measured in these external filaments, increased with development from 0.1 mm.sec-1 to about 0.7 min.sec-1, and decreased again during resorption. Blood flow, calculated therefrom with blood vessel diameter, showed a similar maximum curve. A model analysis supports the hypothesis that in a full grown filament respiratory gas exchange is mainly perfusion-limited and can contribute significantly to the total oxygen uptake of the embryo. Analysis of the results indicates, however, that the gill filaments are not adequate as a gas exchange organ for later developmental stages.
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Base de dados:
MEDLINE
Assunto principal:
Rajidae
/
Brânquias
Limite:
Animals
Idioma:
En
Revista:
Respir Physiol
Ano de publicação:
1992
Tipo de documento:
Article