you learn only 3 things about them ...
They are animals and NOT plants.
is a colony of many tiny animals.
sponges, bryozoans are complex animals with internal organs.
lacy creatures, bryozoans encrust hard surfaces and even living seagrasses
and seaweeds. Larger ones are sometimes seen on our Northern shores,
but tiny ones are probably quite common but simply overlooked.
What is a bryozoan? Bryozoans
belong to Phylum Bryozoa. 'Bryozoa' means 'moss animals' in Greek.
Indeed, they often look like moss, mats of algae or lacy, branching
seaweed. Bryozoans are often mistaken for plants. There are about
5,000 species of bryozoans.
Features: Bryozoans are colonies
of minute individual animals called zooids. Each zooid is about the
size of a pinhead but has distinct organs and ring of tentacles (called
the lophophore) forming a funnel around a mouth. Each zooid builds
a hard casing around itself (called a house), usually made of calcium
carbonate. The tentacles emerge through an opening to filter feed.
The tentacles can be quickly withdrawn into the house and the opening
secured with a tiny lid.
The colony forms as the zooids reproduce by budding. Each new casing
remaining attached to the colonial members around it. A colony may
have millions of individual zooids. Some colonies take the shape of
encrusting layers, others develop into delicate ruffles or branching
forms. So bryozoans are sometimes called sea mats, moss animals or
lace corals. They grow over hard surfaces in the sea, including seaweed
and the surface of sand grains.
Colonies that we have seen are lacy and white, to about 5-7cm wide.
Some are much smaller and encrust hard surfaces or living seaweeds
and seagrasses. They may also encrust living horseshoe crabs.
Bryozoan Food: Bryozoans are believed
to feed on bacteria and plankton. Their tentacles are covered with
cilia (tiny beating hairs) that generate a current through the lophophore
and thus filter out edible titbits.
A bryozoan has a U-shaped digestive tract that brings its anus back
to the opening in the house, next to the lophophore, for waste disposal.
Bryozoan Rebirth: Each individual
zooid may completely degenerate within its house and is later regenerated
again by the house. Remains of the old zooid might be consumed by
the new zooid. Each zooid might do this 4 or more times. In a single
colony, various zooids might be at one of these stages of death and
Bryozoan Babies: A bryozoan colony
grows by budding, but bryozoans also reproduce sexually. Most bryozoan
colonies are hermaphrodites, but each zooid is usually either male
or female. Most bryozoans shed their sperm into the water but brood
their eggs. The parent zooid usually degenerates as the embryo develops.
It may later be regenerated after the free-swimming larva literally
leaves the house. These eventually settle down and start a new bryozoan
colony. Some produce a particular kind of larva called cyphonautes
that is enclosed by a pair of shells and can remain drifting for many
months. Here is a photo
of bryozoa cyphonautes on Image
Quest 3-D Marine Library.
Human uses: Being immobile, bryozoans
may help protect themselves with chemicals which deter potential predators.
Some of these chemicals are being studied for human medical applications.
A bryozoan compound is part of the drug bryostatin which is being
tested as an anti-cancer drug.
Encrusting a living seagrasses
Changi, Aug 08
Bryozoans are complex animals
with tiny tentacles and live inside
a hard case that they can retract into.
Encrusting a living seaweed!
Changi, Aug 05
Pulau Sekudu, Oct 11
Pulau Ubin, Dec 09
Chek Jawa, Oct 03
Beting Bronok, Jun 04
Pulau Ubin, Dec 09
Chek Jawa, Aug 13
Growing on a living horseshoe crab.
on Singapore shores
Punggol, Dec 10
Photo shared by Loh Kok Sheng on flickr.
- K. J. Tilbrook & D. P. Gordon. 29 June 2016. Checklist of Singapore Bryozoa and Entoprocta. The Raffles Bulletin of Zoology 2016 Supplement No. 34 (Part I of II) Pp. 593-603.
- K. J. Tilbrook & D. P. Gordon. Bryozoa from the Straits of Johor, Singapore, with the description of new species. 10 July 2015. The Comprehensive Marine Biodiversity Survey: Johor Straits International Workshop (2012) The Raffles Bulletin of Zoology 2015 Supplement No. 31, Pp. 255-263.
- Edward E.
Ruppert, Richard S. Fox, Robert D. Barnes. 2004. Invertebrate
Zoology : A Functional Evolutionary Approach
Brooks/Cole of Thomson Learning Inc., 7th Edition. pp. 963
Jan A., 2005. Biology
of the Invertebrates.
5th edition. McGraw-Hill Book Co., Singapore. 578 pp.