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Molluscan engrailed expression, serial organization, and shell evolutionWhether the serial features found in some molluscs are ancestral or derived is considered controversial. Here, in situ hybridization and antibody studies show iterated engrailed-gene expression in transverse rows of ectodermal cells bounding plate field development and spicule formation in the chiton, Lepidochitona cavema, as well as in cells surrounding the valves and in the early development of the shell hinge in the clam, Transennella tantilla. Ectodermal expression of engrailed is associated with skeletogenesis across a range of bilaterian phyla, suggesting a single evolutionary origin of invertebrate skeletons. The shared ancestry of bilaterian-invertebrate skeletons may help explain the sudden appearance of shelly fossils in the Cambrian. Our interpretation departs from the consideration of canonical metameres or segments as units of evolutionary analysis. In this interpretation, the shared ancestry of engrailed-gene function in the terminal/posterior addition of serially repeated elements during development explains the iterative expression of engrailed genes in a range of metazoan body plans.
Document ID
20040112515
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Jacobs, D. K.
(University of California Los Angeles 90095-1606, United States)
Wray, C. G.
Wedeen, C. J.
Kostriken, R.
DeSalle, R.
Staton, J. L.
Gates, R. D.
Lindberg, D. R.
Date Acquired
August 21, 2013
Publication Date
November 1, 2000
Publication Information
Publication: Evolution & development
Volume: 2
Issue: 6
ISSN: 1520-541X
Subject Category
Life Sciences (General)
Distribution Limits
Public
Copyright
Other
Keywords
Non-NASA Center
NASA Discipline Exobiology

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