Just a Common Whelk Shell (4)

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.

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Just a Common Whelk Shell (3)

Lots of barnacles on a whelk shell

Whelk shell with an encrustation of mostly acorn barnacles – some complete with all plates and in other areas only the basal plate remains

Acorn Barnacles (Cirripedia) settle on almost anything in the sea or on the seashore. These images show the empty shell of a Common Whelk (Buccinum undatum) that I picked up on the beach at Rhossili on the Gower Peninsula in South Wales – it has proved to be an ideal substrate for them.

The outer surface of the shell is almost entirely covered with barnacles. The majority are intact with the lateral and also the terminal plates. Many specimens are mature but there are juveniles too. In one area, the barnacles have been knocked off but you can still see the basal plates by which they were attached. Some barnacles may have been living on this common British seashell while it was still alive. However, it is equally possible that the shell became colonised by barnacles once it was empty. The few calcareous tubes of marine worms which are stuck on the inner surface of the aperture or mouth of the shell would have settled there once the whelk flesh had disappeared.

The close-up shots reveal the details of the structure of the barnacles, made up generally from six fixed lateral plates overlapping each other to form the shell for the animal, with four articulating terminal plates forming the lid to the chamber. The whole barnacle shell is in this instance securely attached to the whelk shell by a basal plate that often remains in place even when the barnacle becomes detached. Not all species of barnacle have a basal plate.

The macro-photographs also show the intricate pattern and texture of the whelk shell surface with a regular criss-crossing of ridges. This gives an almost lattice-like effect where the growth lines intersect with the natural ornamentation or sculpturing of the shell. In close-up, it is also possible to see small areas of the colonial microscopic animals called Bryozoa or Sea Mats (resembling fragments of lace) which are clinging to the bases of some of the barnacle shells.

Macro-photograph of growth lines and natural sculpturing on a whelk shell

Close-up image of pattern and texture in a barnacle-encrusted whelk shell

Barnacle encrustation on a whelk shell

Whelk shell with mature and juvenile barnacles attached

Macro-photograph of growth lines and natural sculpturing on a whelk shell

Close-up image of growth lines and natural sculpturing in a barnacle-encrusted whelk shell

Apertural view of epibiont encrustation hard parts on a Common Whelk shell

Whelk shell with barnacles attached to the outside and calcareous tubes inside

COPYRIGHT JESSICA WINDER 2014

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Mother of Pearl 2

Mother of pearl decorative inlay on a 16th century Japanese coffer

Mother of Pearl from tropical seashells decorates this fabulous Kyoto Japanese coffer made for the European market around the end of the 16th century and beginning of the 17th century. The pieces of rainbow-hued iridescent shell are held in place by gilded copper rivets on a black and gold lacquered wood base (On display in the Victoria and Albert Museum, London; FE.33-1983).

Mother of pearl decorative inlay on a 16th century Japanese coffer

Mother of pearl decorative inlay on a 16th century Japanese coffer

Mother of pearl decorative inlay on a 16th century Japanese coffer

Mother of pearl decorative inlay on a 16th century Japanese coffer

Mother of pearl decorative inlay on a 16th century Japanese coffer

Mother of pearl decorative inlay on a 16th century Japanese coffer

COPYRIGHT JESSICA WINDER 2014

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Mother of Pearl 1

Ornamental iridescent veneer of mother-of pearl on an 18th century  bureau-bookcase

Mother of pearl is a wonderful iridescent material that is frequently used for artistic purposes. It comes from the inner surface of certain shells, sometimes gastropods like the Button Top Shell, and other times from bivalves such as the Freshwater Pearl Mussel. The inner or nacreous layer of certain shells is composed of crystals which are arranged in layers that reflect light in an attractive way. The colours reflected, and the intensity of the sheen, depend on the type of shell from which it has been obtained and also on the quality of light to which it is exposed. The same piece of mother of pearl can look different in different lights.

The photographs here show the details of the decorative veneer on a bureau-bookcase probably made in Mexico between 1780 and 1820. This is one of many fine items of antique furniture displayed in the Victoria and Albert Museum in London. The veneer is composed of about 7,000 individual pieces of shell, each piece from a separate individual shell (most likely freshwater mussel), and each one having taken about 40 minutes to prepare and shape. The shape of every shimmering piece is highlighted to great effect by a very narrow border of contrasting dark wood.

Ornamental iridescent veneer of mother-of pearl on an 18th century  bureau-bookcase

Ornamental iridescent veneer of mother-of pearl on an 18th century  bureau-bookcase

COPYRIGHT JESSICA WINDER 2014

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Just a Common Whelk Shell (2)

Study of a Common Whelk shell

Close-up, even the most common seashell picked up on the beach has a wealth of detail in its colour, pattern, and texture that tell the story of what it is and the life it has led, stage by stage: the shape and form, the size, the inherent sculpturing, the fine growth lines, breaks, scarring, and staining. Unusually, this Common Whelk shell (Buccinum undatum) has no attached epibiont organisms like barnacles or sea mats, or evidence of boring organisms like marine worms and sponges. Its black and orange staining show that it has spent some time buried in the sand near the top of the boundary from 5 – 15 cm deep that is a gradation between the anoxic black sediment where mostly only anaerobic bacteria thrive – and the yellow sand above which has enough free oxygen to support the life of immense populations of micro-organisms and to decompose their waste products.

Detail of growth lines and pattern in a Common Whelk shell

Study of a Common Whelk shell

Close-up image of seashell texture

Study of a Common Whelk shell

COPYRIGHT JESSICA WINDER 2014

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Sea Creatures in St Fin Barre’s Cathedral

Mosaic of a lobster

In front of the altar of St Fin Barre’s Cathedral in Cork City, Ireland, is a wonderful mosaic floor made by craftsmen from Udine in the north-east of Italy, using marble from the Pyrenees. The mosaic represents a vision of heaven as described by St Matthew, likening it to a net that has been cast into the sea gathering every kind of creature. Here are a few photographs of the sea creatures depicted.

Mosaic fish

Mosaic fish

Mosaic seashell

Mosaic fish

The mosaic floor before the altar in St Fin Barre's Cathedral

COPYRIGHT JESSICA WINDER 2014

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At Dogs Bay

Dogs Bay in Connemara has a wonderful white sandy beach composed of the tiny shells of microscopic one-celled creatures that live mostly on the mud of the ocean bed. These animals are called Foraminifera. When they die, millions upon millions of their calcium skeletons, bearing many chambers and holes, and not visible to the naked eye, wash ashore to form this unusual sand. This is such a rare occurrence that Dogs Bay beach is the only one composed of foraminifera in the northern hemisphere.

The bedrock of the land around this wonderful white sandy shore is made up of volcanic rocks including granite that has many different colour forms and patterns due to the different mineral crystals that it contains – if you get up really close to see it. The granite outcrops on the shores often have a rounded surface where ice sheets or glaciers passing over them have ground them smooth. The waterside rocks form attachments for a variety of seaweeds, along with many seashore creatures, particularly gastropod molluscs like periwinkles and limpets, whose brightly-coloured empty shells accumulate at the base of boulders low down in the intertidal zone.

COPYRIGHT JESSICA WINDER 2014

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