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Homebush Bay.
A Microscopical Investigation.  
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Visitors at Homebush Bay.
Visitors to Homebush Bay exploring the mudflats via the boardwalks

Two Microscopic Inhabitants of Homebush Bay, Sydney.

Map: Homebush Bay Area. The two specimens pictured on this page, a loricate ciliate protozoan and a small isopod crustacean, were collected at Homebush Bay, Sydney, at locations accessible from the boardwalks which give members of the public access to the mudflats and mangrove swamps which characterize the area.

The ciliate turns out to be Folliculina spp., and was identified in a recent (22/01/2003) email from Wim van Egmond, a Netherlands-based microscopist who responded constructively to Micrographia's request for help in naming these creatures. Thanks Wim.

Folliculina inhabits a vase-like lorica, which in this species has an inclined neck with a pronounced spiral groove running from its slightly flanged opening. In appearance, its nearest freshwater relatives are Cothurnia, Vaginicola, Thuricola and similar peritrichs living in transparent tubular loricas, but these are a good deal (about x10) smaller. The body ciliature follows lengthwise parallel kineties having a blue-green pigmentation as seen by transmitted light, similar to some species of the freshwater ciliate Stentor, a creature of similar size, but without a lorica. An unusual feature of this pigmentation is that it is a pronounced red under darkfield illumination.

When fully extended, it displays two ribbon-like "tentacles", with thickened edges bearing cirri along their entire length. The exterior surface of the ribbon has the body ciliature described above. The cytoplasm was densely filled with food vacuoles. No contractile vacuole was seen in any individual, but this is the case with marine ciliates in general.
Some species of Folliculina are found in fresh water -- presumably these have a contractile vacuole.

After a day or two in a shallow dish, these specimens abandoned their loricas, assumed a cylindrical shape resembling a very dark (almost black) turbellarian worm, and swam smoothly in the surrounding water.

Ciliate. In this picture, a single Folliculina extends itself from its lorica. Only one of the "tentacles" is in focus, showing the thickened edges and flattened structure.
Brightfield, x200.
Ciliate: B/F  x400. Here it is seen cautiously extending itself from its lorica after a disturbance had caused a sudden contraction. The cirri can be faintly seen on the inner surfaces of the "tentacles".
Brightfield, x400.
Ciliate: D/f x120. The same specimen as the top picture. The pronounced red of the creature under darkfield conditions was completely unexpected.
Darkfield, x150.
Ciliate clusters, x35 Throughout the filamentous algae of the sample were numerous Folliculina. Most conspicuous were the dark clumps consisting of several individuals with their loricas cemented together. Here are two such clumps, the individual organisms fully extended.
Incident light, x35.
Ciliate amongst algae. A single extended individual amongst typical filamentous algae found between the aerial roots of the mangroves.
Incident light, x35.
Ciliate amongst algae. A single Folliculina, fully extended.
Transmitted light, x60.
Ciliate amongst algae. Two extended individuals, their loricas cemented together on an algal filament. The flattened, ribbonlike form of the "tentacles" can be clearly seen.
Transmitted light, x90.

Here is a link to Wim van Egmond's External Website article on Folliculina, with photomicrographs showing other interesting structural features, in Micscape online magazine.

An Isopod Crustacean.

This small crustacean was found amongst the algae fringing the shallow open waters of Homebush Bay, close to the marshy shores. It is an isopod crustacean, probably of the genus Cymodoce -- commonly called marine pill bugs from their habit of rolling into a ball when disturbed. They were quite numerous, scuttling rapidly about the surface of the predominant alga of the area, which resembled chopped lettuce. The specimen in the photograph was one of the smaller individuals, about a millimetre long.

Here is a link to External Website a site which identifies isopod crustaceans in the southern coastal waters of Australia.

Crustacean Looking very much like the familiar wood louse (slater) but much smaller, this young crustacean (probably Cymodoce spp.) was found amongst the algae along the shore.
Brightfield, x20.