Gill morphogenesis in the oyster Ostrea chilensis |
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Authors: | O R Chaparro J A Videla R J Thompson |
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Institution: | (1) Instituto de Biología Marina, Universidad Austral de Chile, Casilla 567, Valdivia, Chile Fax: +56-63-221455 e-mail: ochaparr@valdivia.uca.uach.cl, CL;(2) Ocean Sciences Centre, Memorial University of Newfoundland, St. John's, NFL A1C 5S7, Canada, CA |
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Abstract: | Despite the importance of the gills in the acquisition of food by suspension-feeding bivalve mollusks, there is almost no
information on gill organogenesis. By means of a series of stereoscan electron micrographs, this paper describes gill development
in the Chilean oyster, Ostrea chilensis, from the brooded larval stages to 1-month-old spat. A single gill rudiment was observed on each side of the mantle at a
shell length of 320 μm, and the rudiments increased in number and size until the end of the brooding period. During metamorphosis
the gill filaments increased in number from 5 or 6 to between 7 and 9. The loss of the velum and the absence of functional
gill filaments during metamorphosis are consistent with previous observations of weight loss during this critical period of
the life history, because the newly settled juvenile lacks the ability to remove particles from suspension. The end of metamorphosis
(100% of spat with dissoconch edge) was reached 36 h after larval settlement, when the gill filaments began to grow cilia,
which increased in density and differentiated as the spat developed and acquired the capability of suspension-feeding, accounting
for the increase in body weight previously recorded during this stage. The larval rudiments gave rise to the inner demibranchs.
The outer demibranchs were observed 10 days after settlement, located between the inner demibranch and the mantle. In 1-month-old
spat, the gill did not show differentiation between primary and secondary filaments, indicating that the heterorhabdic condition
characteristic of adult oysters had yet to be attained.
Received: 11 December 1998 / Accepted: 21 August 2000 |
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