Just a Common Whelk Shell (4)

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This empty Common Whelk shell, picked up on the beach, is mostly covered with the calcareous tubes of a marine polychaete worm called Pomatoceros triqueter, also known as “German writing”. The tubes are a frequent sight on rocks at the beach and also on objects such as pebbles and driftwood. The tubes attached to the outer surface of the shell may have been made while the whelk was still alive and moving about. Those within the mouth of the empty shell were definitely attached after the gastropod mollusc had died and its flesh had been removed from the shell.

Organisms that live on the outside of other creatures in this way are known as epibionts. Usually epibionts are neither parasites that occupy a rather one-sided relationship with the host where they rely on it for nutrients and frequently damage it; nor symbionts where both organisms depend on each other in a mutually beneficial relationship; but maybe they could be called commensals in that the host is not damaged by the attached organism but merely provides a surface of attachment, and both organisms share the same environment.

The images below show the distinct patterns where calcareous tubes of Pomatoceros triqueter have been attached (but now removed) on a pebble at Chesil Cove in Dorset; also some in situ shots of Pomatoceros tubes attached to low shore rocks, along with the sand-grain tubes of the Honeycomb Worm (Sabellaria alveolata), at Mewslade Bay in Gower.

COPYRIGHT JESSICA WINDER 2014

All Rights Reserved

5 Replies to “Just a Common Whelk Shell (4)”

  1. Why on Earth are they known as “German writing”??? I’m sure there is an obvious answer to this, but as I’m not very proficient at German I don’t know what it is…?

    Like

  2. In a way – but the term epiphyte is used just to describe plants living on plants (without eating them) whereas the word commensal can refer to plants or animals living on other organisms where they ‘share the same table’ and do not affect the other in any way.

    Liked by 1 person

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