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Abstract

Next article FreeAbout the CoverPDFPDF PLUSFull Text Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinked InRedditEmailQR Code SectionsMoreCoverThe reef-dwelling octocoral Sarcophyton auritum Verseveldt & Benayahu, 1978, shown on the cover, is a common sight on the shallow reefs of the Red Sea. S. auritum generally appears as patches of mushroom-shaped colonies. The larger examples typically feature folded margins, which are lacking in the smaller ones. The polyps, when expanded, give a velvety look to the colony surface; but when they are retracted, the octocoral appears smooth and leathery.Observations of S. auritum have uncovered the presence of numerous, silk-like fibers when the colonies are torn apart. These fibers can be stretched to a remarkable degree, reaching tenths of a centimeter in length without tearing. An examination of their chemical nature using specific histological staining and peptide profiling reveals fibers that are comprised of collagen, and that collagen closely resembles the collagen of mammals. Comprehensive light and electron microscopy studies have further disclosed that six of the eight mesenterial filaments of S. auritum polyps possess a spring-like collagen fiber, surrounded by a ciliated gastrodermis. For the first time in cnidarian-collagen, high-resolution electron microscopy has made visible the interwoven, three-dimensional arrangement of the fibrils that contract the fibers. The resemblance of these fibers to vertebrate collagen is seen in these fibrils, some of which feature free ends and bifurcation. With the aid of peptide profiling, the coiled nature of the fibers and the 3-D configuration of the fibrils are shown to closely resemble those elements found in vertebrate collagen. Findings at both the microscopic and biochemical levels demonstrate the conserved nature of the collagen fibers among both diploblastic cnidarians, such as octocorals, and the higher vertebrates.On pages 68–77 of this issue, Yael Mandelberg, Dafna Benayahu, and Yehuda Benayahu theorize that the location, arrangement, and small-diameter size of the fibers and fibrils serve an important protective function in S. auritum. Their strength and flexibility help the coral to withstand injury and possible rupture during bending of the octocoral's extended polyps under strong current conditions. The authors conclude that these unique collagen fibers are well adapted to counteract the strong drag forces characterizing this octocoral's reefal habitat. The features of these fibers, as well as their suggested function, argue for an attempt at artificial replication in the laboratory—for future use in biomedical applications.Credits: Photo, Yehuda Benayahu, Tel Aviv University, Israel; layout, Beth Liles. Next article DetailsFiguresReferencesCited by The Biological Bulletin Volume 230, Number 1February 2016 Published in association with the Marine Biological Laboratory Article DOIhttps://doi.org/10.1086/BBLv230n1cover Views: 247Total views on this site © 2016 by Marine Biological Laboratory. All rights reserved.PDF download Crossref reports no articles citing this article.