"Moss Animals" Bryozoans (found in Mercer Lake)
Size: Colonies may be 2 feet in diameter, but more commonly 1
foot in diameter or less. Individual zooids are microscopic, can be as
small as a couple millimeters.
Description: Bryozoans, or "Moss Animals", are a very unique
group of animals. So unique in fact, that they are often not recognized
as animals to the untrained eye. Bryozoans are sessile, colonial
invertebrates. This means they live in large groups that permanently
attach to hard underwater surfaces. In that regard, they are kind of
like coral but are much more complex organisms. Each individual organism
in the colony is called a zooid. The many species of bryozoa lead to the
many different shapes and styles of the underwater colonies. One of the
most commonly observed species in New Jersey is Pectinatella magnifica.
This species can often be found growing on underwater brush or other
woody structure in what appears to be a large, gelatinous mass.
Habitat: Most common in warm, fertile lakes and ponds or very
slow moving rivers.
Food: Bryozoa use a crown of tiny ciliated tentacles, called the
lophophore, to create currents and then filter out microscopic plankton
such as algae.
Life Cycle: Most bryozoa are hermaphroditic, meaning each zooid
has both male and female organs. Sexual reproduction, where a sperm cell
fertilizes an egg, occurs only in a single brief period each year. After
fertilization, a free-swimming larva is formed composed of two zooids.
The larva may be free-swimming for only a few minutes up to about 24
hours. When it contacts suitable substrate, it settles and becomes
permanently attached, the zooids begin feeding and will eventually form
a new colony by asexual reproduction called budding . This is simply a
process whereby an entirely new organism buds or grows from another. The
new organism is a genetic clone of the parent. The bryozoan colony
disintegrates as the water starts to cool in the fall. The statoblasts
are released and become new colonies in the spring.
Status: Common; abundant in certain areas
Ecological Role: The constant flow of water around bryozoan
colonies created by the millions of tiny beating tentacles provides
favorable habitat for many other types of freshwater invertebrates.
Flatworms, oligochaete worms, snails, mites and insect larvae such as
caddisflies and midges often feed on the zooids of the bryozoan colony.
Fun Facts: Freshwater bryozoans can reproduce sexually and also
asexually by budding or forming tiny structures called statoblasts .
Statoblasts are dormant multi-cellular clones of the adult. They are
very resistant to drying and extreme temperatures and are equipped with
tiny hooks that aid in dispersal. When the statoblast encounters
suitable habitat it germinates into a new zooid, which then buds 1-5 new
zooids and so on forming, forming a new colony. The different
distinctive structure of statoblasts produced by various species are
very important for identification purposes. There are about 50 described
species of freshwater bryozoans in the world.
Taxonomy: Kingdom Animalia, Phylum Ectoprocta, Class
Phylactolaemata, Order Plumatellida, Family Pectinatellidae, Genus
Pectinatella, Species magnifica