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Sea anemones (Exaiptasia pallida) use a secreted adhesive and complex pedal disc morphology for surface attachment

Lookup NU author(s): Jessica Clarke, Dr Peter Davey, Dr Nick Aldred

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).

Abstract

© 2020 The Author(s).Background: The mechanism by which sea anemones attach to surfaces underwater remains elusive, which is surprising given their ubiquitous distribution in the world's oceans and tractability for experimental biology. Their adhesion is mechanically interesting, bridging the interface between very hard and soft materials. The Cnidaria are thought to have evolved adhesion to surfaces at least 505 Ma ago implying that, among the Metazoa, only Porifera developed this capability earlier. The purpose of this study was primarily to address an existing hypothesis, that spirocysts (a sticky class of cnidocyst) facilitate adhesion to surfaces, as observed during prey capture. Results: We demonstrated conclusively that spirocysts were not involved in the pedal disc adhesion of Exaiptasia pallida. Second, we applied a variety of imaging methods to develop an understanding of the true adhesion mechanism. Morphological studies using scanning electron microscopy identified a meshwork of adhesive material, unique to the pedal disc. Serial block-face SEM highlighted four classes of cells that could secrete the adhesive from the pedal disc ectoderm. A variety of histochemical techniques identified proteins, glycans and quinones in the cell contents and secreted adhesive, with variation in contents of specific cell-types in different areas of the body. Conclusions: Spirocysts are not used by Exaiptasia pallida for adhesion to surfaces. Instead, a structurally and compositionally complex secreted glue was observed, firmly attaching the animals underwater. The results of this study provide a basis for further investigations of adhesion in Cnidaria, and establish E. pallida as a new model organism for bioadhesion research.

Publication metadata

Author(s): Clarke JL, Davey PA, Aldred N, Aldred N

Publication type: Article

Publication status: Published

Journal: BMC Zoology

Year: 2020

Volume: 5

Issue: 1

Online publication date: 05/06/2020

Acceptance date: 21/05/2020

Date deposited: 06/07/2020

ISSN (electronic): 2056-3132

Publisher: BioMed Central Ltd.

URL: https://doi.org/10.1186/s40850-020-00054-6

DOI: 10.1186/s40850-020-00054-6

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