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Abstract

Next article FreeAbout the CoverPDFPDF PLUSFull Text Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinked InRedditEmailQR Code SectionsMoreA defining feature of echinoderms is their five-fold symmetry, which arises during the metamorphosis of a bilaterally symmetrical larva. During echinoderm metamorphosis, the coelomic cavities undergo an elaborate transformation from early mesodermal pouches to a complex system of tubes and rings that make up the numerous internal components of the animal. In this issue (pp. 283–298), H. C. Sweet and several undergraduate research students (G. Azriel, N. Jaff, J. Moser, T. A. Riola, C. Ideman, M. Barton, J. Nelson, and M. M. Lenhart) demonstrate the origin of the coelomic structures and their morphogenesis in the vitellaria larva of the brittle star Ophioplocus esmarki. Many of the structures first form when the archenteron becomes subdivided into an unpaired axocoel, hydrocoel, somatocoel, and stomach rudiment. The right somatocoel and part of the left somatocoel originate as bilateral invaginations of the larval ectoderm. This supports the findings of others that ectodermal invagination of the somatocoels is an unusual feature of brittle star development. Confocal microscopy and 3D modeling were used to document the later morphogenesis of the coelomic cavities as they form juvenile structures with five-fold symmetry.The cover image demonstrates the complex structure of the vitellaria larva. The image shows the color-coded coelomic cavities superimposed with an image of the skeleton and an outline of body of the vitellaria larva. At this stage, the outer ectoderm has ciliary bands on raised ridges that are used for swimming (grayscale outline), but most of the internal structures are patterned in five-fold symmetry with the axial complex near the anterior end (top). Coelomic structures include the water vascular system derived from the hydrocoel (yellow), hypogastric coelom derived from the left somatocoel (purple), genital coelom (peach) derived from the left somatocoel, epigastric coelom derived from the right somatocoel (magenta), pericardial coelom (green), axial coelom (orange), and pore canal (red). The juvenile skeletal plates form adjacent to the coelomic structures and the overlying ectoderm. The image was generated with confocal microscopy, polarized light imaging, and image colorizing and processing in GIMP and Fiji.Credits: Photo, Hyla C. Sweet; cover design, Olivia Kinker. Next article DetailsFiguresReferencesCited by The Biological Bulletin Volume 243, Number 3December 2022 Published in association with the Marine Biological Laboratory Article DOIhttps://doi.org/10.1086/724434 © 2022 The University of Chicago. All rights reserved.PDF download Crossref reports no articles citing this article.