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Abstract

Next article FreeAbout the CoverPDFPDF PLUSFull Text Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinked InRedditEmailQR Code SectionsMoreCoverThe cover shows an image, taken with confocal microscopy, of part of the light organ of the Hawaiian bobtail squid. In this view of the epithelial surface of the organ, cilia are green and nuclei of the epithelial cells are purple.This light organ, found inside of the squid's body cavity, houses luminescent marine bacteria whose light production helps the squid camouflage itself to avoid predators. In return, the squid provides the bacteria with a hospitable environment.The symbiosis between squid (Euprymna scolopes) and bacteria (Vibrio fischeri) has a number of remarkable features. These include the way that the light organ “harvests” the bacteria from the surrounding seawater and the role the bacteria play in development of the light organ. The latter function is examined in detail here by Koropatnick et al. (pp. 56–68) as an example of the influence of beneficial bacteria on developmental processes in animals.Soon after hatching, the squid host harvests the symbiotic bacteria from the marine environment using two specialized ciliated epithelial fields on the surface of its light organ. Each of those fields is composed of a base with three pores leading to epithelium-lined crypts, and two prominent ciliated epithelial appendages. In the nascent light organ, the tips of these appendages oppose to form a ring-like structure, and the ciliary motion generated by these fields serves to capture particles from the seawater in mucus secreted from the epithelial fields and suspended above the pores. Cells of V. fischeri then migrate through the pores, down ducts, and into epithelium-lined crypts deep within the light organ. Once the light organ is colonized in this manner, the symbiont population within the crypts triggers the loss of the epithelial harvesting apparatus by releasing tracheal cytotoxin (TCT), a monomer of the bacterial cell wall component peptido glycan. The epithelial morphogenesis begins with the induction of widespread death of cells and culminates in the complete regression of the ciliated appendages.Although previous studies have characterized key biochemical, molecular, and morphological aspects of this light organ morphogenesis, Koropatnick et al. provide the first in-depth description of the cellular mechanisms that precipitate the loss of the ciliated epithelial fields. The results of the study demonstrate that the bacterial symbionts change the form, function, and biochemistry of the host cells as part of the light organ's morphogenic program.Credits: Photo taken by Bethany Rader, University of Oregon; cover design, Beth Liles, Marine Biological Laboratory. Next article DetailsFiguresReferencesCited by The Biological Bulletin Volume 226, Number 1February 2014 Published in association with the Marine Biological Laboratory Article DOIhttps://doi.org/10.1086/BBLv226n1cover © 2014 by Marine Biological Laboratory. All rights reserved.PDF download Crossref reports no articles citing this article.