Bryozoan

Plant-like animal in the phylum Bryozoa which form colonies arising from the continual budding of the cells. There are 4,300 known species. The majority are marine, but many occur in fresh water. Colonies exhibit a wide variation in form and habit, occurring as crusts on rocks, masses, broad fronds, or branched growths.

The texture and consistency of colonies may be gelatinous, horny, flexible, or stony. A typical form is Flustra foliacea, the broad-leaved hornwrack or sea-mat, which is common in heaps of seaweed cast up on sandy temperate coasts. Its brown horny fronds branching from a narrow flat stem are reticulated with little oblong boxes or cells (zooecia), each with a lid through which a coronet of tentacles emerges to set up currents that convey food to the mouth.

Reproduction is by means of eggs which hatch into ciliated embryos, each of which, after a few hours' swimming, settles down and, by budding, gives rise to a new colony. An example of a freshwater species is Plumatella repens.

In 1993 a unique form of mobile bryozoan was identified. The colonies formed 3-cm/1-in floating balls off the Brunt Ice Shelf, Antarctica.