Marine Debris from the
Mediterranean Sea

by Brian Darnton, UK

Those who have been hunting for the foraminifera during the summer break will also have found many other treasures from Davy Jones' locker: These largely shelly mortalities have been cleaned by natural means in the sea and sunlight. Very little preparation is required before they can be dry mounted in a cell for observation and storage.

The Tube Worms

Many worm like creatures build little houses of chalk and then live in the tubes that they have created. In times of danger they can withdraw into the protection of the tube.

Some are quite simple and linear or slightly curved, but others as they grow larger, so the diameter of the tube increases and a beautiful spiral formation is created, rather like the fossil Ammonite.

The method of construction is commonly by secretion by the organism but sometimes a tube is constructed by the selection and cementing of small plates of sand or even the shells of other small creatures. One group of these is called the mason worms.

The Sea Mats

These are even more diverse. These are colonial animals that tend to live within a protective matrix .

Some appear to be almost woven as an encrustation over rocks and seaweeds alike. Tentacles are thrust out through apertures into the surrounding water to feed and breath but at a hint of danger they are rapidly withdrawn by a strong muscle.

The flat mushroom shaped Lichenopora radiata mimics the madrepore coral but of course its much smaller. Hundreds of tube like apertures allow the circular colony to feed and be protected.

The Sponge Spicules

Living sponges are not particularly attractive in themselves but the spiky reinforcements that support the body of the sponge in a skeletal like manner can be very ornamental in crossed polarised light. They too can be found washed up in the tide mark. Even in British waters they are not at all uncommon.

The Sea Urchins.

Spines from the urchin family are very common in most parts of the world. Some are exquisitely fluted like Roman pillars. Others seem to be cellular. The Victorians used to section the tubular structure of the spines to reveal a diversity of radial patterns. Occasionally whole shells can be found of a very small species. The egg shaped test seems to be able to withstand the enormous forces of the sea.

Mounting in Cells.

After gluing a thick 19 mm aluminium ring to a slide, a matt black background can be laid onto the base of the cell using NBS paint. The shelly remains may be tarnished, in which case two days immersion in hydrogen peroxide usually cleans them up . Washing in water through a fine sieve is always a useful precaution to remove salts.

The dry shells can be glued in the cell using a weakened solution of gum tragacanth. A small oooo brush may be used for transfer, to avoid scraping the background. After drying out under a lamp the coverslip can be applied on a ring of gold size, to be followed when dry, with an ornamental and protective external ring of shellac varnish. Do not forget to label the finished slide.

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Observation

A low power binocular microscope is ideal for this work . Reflected illumination from above at 45 degrees should give glare free clarity of vision.

Comments to the author Brian Darnton welcomed.

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Editor's notes

Brian's other recent articles on marine subjects for the microscope can be found by typing his surname in the Library Search index.

Brian prepares and sells a selected range of strewn and type microscope slides of foraminifera. Visit Brian's Home Pages for details.

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Published in September 1998 Micscape Magazine.

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