Abstract
The deep-sea hydrothermal vent solenogaster Helicoradomenia is covered with calcium carbonate sclerites. Light and electron microscopy reveal varying morphologies of these sclerites. Many sclerites have hollow tips and/or are pitted and etched. Bacteria are found on and in sclerites. Initial sclerite formation occurs in an extracellular crystalline chamber formed by the invagination of a cuboidal basal cell of the columnar microvillus mantle epithelium. As the sclerite grows, it fills the crystalline chamber resulting in direct contact with the microvilli of both the basal cell and neighboring secondary sclerite-forming cells. These cells shape a collar around the base of the growing sclerite. As growth continues, the sclerite-forming cells stretch around the sclerite forming a sheath in which the base of the sclerite resides. Mature sclerites grow through the cuticle into the external environment. The erosion pattern of sclerites reveals a less stable inner medullary region and a harder outer cortical region. This points to a secondary character state, where foremost hollow acicular sclerites develop into solid sclerites. This is in agreement with the systematic position of the genus Helicoradomenia within Simrothiellidae, a taxon typically with hollow sclerites.
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Acknowledgments
We thank the anonymous reviewers for their detailed and helpful comments. Thank you to undergraduate students Rachel Ruberto and Eric Wong for their contributions to the ultrastructural imaging. Special thanks to Cindy Lee Van Dover for providing us with specimens. This research was funded by University of Richmond Faculty and Undergraduate Research funds.
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Communicated by T. Bartolomaeus.
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Kingsley, R.J., Froelich, J., Marks, C.B. et al. Formation and morphology of epidermal sclerites from a deep-sea hydrothermal vent solenogaster (Helicoradomenia sp., Solenogastres, Mollusca). Zoomorphology 132, 1–9 (2013). https://doi.org/10.1007/s00435-012-0168-x
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DOI: https://doi.org/10.1007/s00435-012-0168-x