Biol. Bull. Sign up for etocs!
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

This Article
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Amemiya, S.
Right arrow Articles by Emlet, R. B.
Right arrow Search for Related Content
PubMed
Right arrow Articles by Amemiya, S.
Right arrow Articles by Emlet, R. B.

The Biological Bulletin, Vol 182, Issue 1 15-30, Copyright © 1992 by Marine Biological Laboratory

DEVELOPMENT AND REPRODUCTION

The Development and Larval Form of an Echinothurioid Echinoid, Asthenosoma ijimai, Revisited

S. Amemiya and R. B. Emlet
Misaki Marine Biological Station, Miura-shi, Kanagawa 238-02, Japan

The modified development from cleavage to late larval form of the echinothurioid echinoid, Asthenosoma ijimai, was re-examined using light microscopy and scanning electron microscopy of whole and sectioned stages. Although an original study (Amemiya and Tsuchiya, 1979) reported direct development without evidence of a pluteus larva, we found that the unusual development can be interpreted as a topologically reflected, reduced pluteus, with vestigial larval arms and a greatly reduced larval skeleton. This developmental pattern produces the third and most reduced pluteus form known among the six echinoid lineages with modified development that have been studied thus far. Features such as an equal fourth cleavage, extrusion of yolk into the blastocoel, and the presence of large numbers of cells within the blastocoel are convergent with traits reported for other species with modified development. Coelom formation is clearly modified from that of species with feeding larval development, but notably the hydrocoel begins to develop podial buds prior to separation from the archenteron. Echinothurioid sea urchins are considered to be the most primitive living euechinoids, and in A. ijimai the timing of mesenchyme cell ingression and the formation of epineural folds were similar to these features in other euechinoids. Indentation of the juvenile oral surface relatively late in larval development raises the possibility that the amniotic invagination (vestibule), common in all other euechinoids, may be a trait incorporated into the development of echinoids at the time of origin of the echinothurioids. The structural comparisons reported here show a need for further detailed morphological studies of developmental modifications in other echinoid species.


This article has been cited by other articles:


Home page
 Integr. Comp. Biol.Home page
G. A. Wray
The evolution of embryonic gene expression in sea urchins
Integr. Comp. Biol., June 1, 2006; 46(3): 233 - 242.
[Abstract] [Full Text] [PDF]

Home page
 Integr. Comp. Biol.Home page
M. S. Vickery and J. B. McClintock
Comparative Morphology of Tube Feet Among the Asteroidea: Phylogenetic Implications
Integr. Comp. Biol., June 1, 2000; 40(3): 355 - 364.
[Abstract] [Full Text] [PDF]


HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Copyright © 1992 by the Marine Biological Laboratory.