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Larval Ontogenetic Stages of Chaetopterus: Developmental Heterochrony in the Evolution of Chaetopterid Polychaetes
Steven Q. Irvine, Oleg Chaga and Mark Q. Martindale
Vol. 197, No. 3 (Dec., 1999), pp. 319-331
Published by: The University of Chicago Press
Stable URL: http://www.jstor.org/stable/1542786
Page Count: 13
You can always find the topics here!Topics: Larvae, Larval development, Exoskeletons, Ocelli, Ontogeny, Midgut, Evolution, Cilia, In situ hybridization, Juvenile stages
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Seven post-gastrulation larval stages are described for the sedentary polychaete Chaetopterus. Analysis of larval anatomy and morphology through ontogeny reveals significant differences in the temporal sequence of segmentation, and in the character of segments formed, from the typical embryological pattern described for other polychaete families, such as nereidids or spionids. When compared in alternative phylogenetic schemes, these differences represent significant developmental heterochrony, among other evolutionary transitions, which has arisen in the chaetopterid lineage. The heterochrony is correlated with the extreme morphological regionalization along the anterior-posterior body axis, a feature that is also characteristic of chaetopterids.
Biological Bulletin © 1999 Marine Biological Laboratory