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Abstract

Next article FreeAbout the CoverPDFPDF PLUSFull Text Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinked InRedditEmailQR Code SectionsMoreThis issue’s cover shows clonal sea anemones Diadumene (Haliplanella) lineata. Sea anemones are sessile marine cnidarians. Cnidarians use organelles called nematocysts made and deployed by cnidocytes to capture and kill prey rapidly following sensory stimulation. When triggered, nematocysts deploy an eversible barbed tubule through which a venom is injected into prey. Backward-facing barbs and an anchoring mechanism on the tentacle combine to retain captured prey, while tentacles bearing prey bend toward the mouth for ingestion.Nematocyst discharge is under hierarchal control of two classes of chemoreceptors: vibration-sensitive mechanoreceptors (VSMs) and contact-sensitive mechanoreceptors (CSMs). Chemoreceptors and VSMs on two or more supporting cells adjacent to cnidocytes form cnidocyte-supporting cell complexes (CSCCs), the functional units of nematocyst discharge. Three types of CSCCs regulate nematocyst discharge in D. lineata: (i) Type As have associated NANA chemoreceptors that tune vibration-sensitive mechanoreceptors (VSMs) to the movements of swimming prey that, in turn, predispose CSMs to trigger; (ii) Type Bs are sensitized by N-acetylneuraminic acid (NANA) that predisposes triggering CSMs to physical contact; and (iii) Type C CSCCs are activated by physical stimulation of contact-sensitive mechanoreceptors. The CSMs and VSMs require extracellular calcium, and the delay from triggering to discharge is measured in milliseconds. Such features suggest mechanogated ion channels, features shared by several types of transient receptor potential (TRP) channels.On pages 48–61 of this issue, A. Nam, S. Quarshie, M. Kimble, and D. A. Hessinger test general and selective TRP channel blockers, using a quantitative prey killing assay to implicate a variety of TRP channels involved in nematocyst-mediated prey killing. They found that non-selective TRP blockers, such as gadolinium (Gd+3) and lanthanum (La+3), potently and broadly inhibit both nematocyst discharge and prey killing from Type Bs and Cs, which is consistent with TRP channel involvement. They then demonstrated that three selective TRPV4 blockers inhibited prey killing from vibration-sensitive Type A CSCCs. Their data implicate TRPV4-like channels in nematocyst discharge from vibration-sensitive Type As and pharmacologically distinct TRP channels in Type Bs and Cs.Credits: Photo of Diadumene lineata by David Reed, with permission. Available under Creative Commons License CC BY-NC-SA 2.0. Cover design: Olivia Kinker, University of Chicago Press. Next article DetailsFiguresReferencesCited by The Biological Bulletin Volume 242, Number 1February 2022 Published in association with the Marine Biological Laboratory Article DOIhttps://doi.org/10.1086/719750 Views: 936Total views on this site © 2022 The University of Chicago. All rights reserved.PDF download Crossref reports no articles citing this article.