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 Major Groups | Bryozoa (moss animalcules)

Bryozoa (moss animalcules)

Descriptive Features:

  • body colour brownish, opaque
  • cuticular horny or gelatinous covering on body wall (zooecium), zooecium thick or thin, delicate or tough, often covered in detritus
  • lophophore bearing numerous ciliated tentacles (tentacular crown), with mouth opening
  • Size: individuals are microscopic, colonies may spread several square metres or form balls the size of an orange

    colony as found in samples

    Distribution: Qld, NSW, Vic, Tas, SA, WA

    Sensitivity Rating: SIGNAL grade 4

    Functional Feeding Group: filtering collector


    colony as found in the river

    Ecology: Bryozoa occur in shaded littoral areas of clear lakes, swamps, large rivers and stream backwaters. They are found on twigs, underside of logs, stones, boulders and submerged plants. Some species favour willow roots. Bryozoa are sessile and colonial. Encrusting and branching colonies may look like moss, thus earning the common name ‘pipe moss’ or ‘moss animalcules’. An individual bryozoan is called a zooid. They feed on detritus, bacteria, protozoans and minute metazoans that are caught in the tentacular crown. When disturbed each zooid withdraws the tentacular crown into the zooecium. Asexual reproduction is more common than sexual reproduction. Asexual reproduction takes place by budding, forming a new zooid to expand the colony, or fission, where one colony becomes two, or production of highly resistant resting bodies (statoblasts). Statoblasts are formed internally. They germinate into a single zooid that buds into a new colony. This enables the colony to survive unfavourable conditions. Sexual reproduction involves self fertilization within hermaphroditic individuals. An ovary and testis are formed as required. The egg develops internally into a small ciliated larva that leaves by a pore near base of lophophore or is freed when the parent dies. The larva is free swimming for a brief period then attaches to a submerged object and forms a new colony by budding.


    Information Sources: Williams 1980




    colony still attached to statoblast


    colonies and statoblasts