Spirula spirula?

[Emma]

Hello again!

I found these tiny, curious, ram-horn-shaped white attachments to seaweed collected on Amager Strand beach, Copenhagen, Denmark in December 2012. I initially thought that they were Spirula spirula, but I would like a second opinion.

Thanks a lot!

Emma.

[paul monfils]

No, these are not Spirula, though they do superficially resemble it.  Actually these are not even mollusks.  These tubes are made by actual worms, of the phylum Annelida - same phylum as the earthworms in your garden.  These are commonly called "tubeworms", though that is a pretty general term that can refer to quite a variety of marine organisms, some of which are not even closely related.  There are somewhat similar attached coiled tubes that actually are made by mollusks, such as gastropods in the family Vermetidae, but these appear to be annelids.  The coiled "shell" of Spirula is actually an internal flotation structure from a squid-like animal.  When the animal dies and decomposes, the buoyant coiled "shell" is released and floats to the surface where it can be carried a long distance by waves and currents before being washed ashore on a beach.

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[Emma]

Thanks very much!

Best wishes,

Emma.