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Updated: Aug 17, 2026

Inducing Complete Polyp Regeneration from the Aboral Physa of the Starlet Sea Anemone Nematostella vectensis
Published on: January 14, 2017
Novel surface specialization on a sea anemone egg: "Spires" of actin-filled microvilli
1Friday Harbor Laboratories, University of Washington, Friday Harbor, Washington 98250.
Abstract:
The ultrastructure of the "spiny" surface of Tealia crassicornis eggs is examined in detail by scanning and transmission electron microscopy in order to understand its function. Long microvilli are clustered together in spiral aggregates of 50-75 microvilli called "spires." There are about 15,000 spires per egg. Dense bundles of microfilaments making up the cores of these microvilli are shown to be composed of actin by staining with the fluorescent dye nitrobenzoxadiazole (NBD)-phallacidin. It is postulated that the bundles of actin and the spires of microvilli are stiff and provide reinforcement to the egg surface. Such postulated properties would provide physical protection for these large eggs which, unlike the eggs of most invertebrates, appear to lack all extracellular investing coats.
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