Thursday, Jan. 15, 2004
* Japanese name: Oomari-kokemush
* Scientific name:Pectinatella magnifica
* Description:The common name says it all. This organism looks like nothing so much as a quivering lump of jelly. It is often mistaken for the egg mass of some animal, but in fact the blob is itself a colony of tiny animals. They are bryozoans, which literally means "moss animals." Bryozoans form slimy gelatinous colonies, 99 percent water in composition. Colonies may be around 60 cm in diameter, but can form large balls over 1 meter in diameter.
* Where to find them: Most bryozoans are marine, but some are found in fresh water. Jelly blobs can be found in warm, fertile ponds and lakes, and slow-moving rivers from Honshu to Kyushu.
* Food: Bryozoans feed by beating a crown of tiny ciliated tentacles, called the lophophore. This creates currents that draw in microscopic plankton such as algae; the jelly blob filters out the plankton. The water flow around bryozoan colonies is attractive to other types of freshwater invertebrates. Flatworms, snails, mites and insect larvae such as caddis flies and midges may live near the jelly blob, and feed on the larvae it produces.
* Special features: Bryozoa are fortunate in that they can enjoy both sexual and asexual reproduction. Sexually produced larvae look like tiny balloons (you'll need a microscope to see them). They float in the water for anywhere between a few minutes and 24 hours, until they bump into a stone or a plant, to which they attach themselves. Then they start "budding": dividing asexually and creating a new individual that is a clone of the original animal. Asexual budding also forms multicellular structures called "statoblasts." These are also clones of the parent animal, but are dormant in winter and resist drying and cold temperatures. Statoblasts bob around in the water until they encounter a suitable structure, which they hook onto with the aid of tiny claws. When the amount of sunlight reaches suitable levels and the temperature rises to around 25 degrees, the statoblast germinates and buds one to five new animals, so forming a new colony.