Procotyla fluviatilis
Copyright, Mark Cooper, Mt. San Antonio College
Flatworms, also called
"planarians," are found just about everywhere there is
water. There are many different species of flatworms, but
this page will focus on Procotyla fluviatilis, one of
our more common ones. It is difficult to find
pictures of Procotyla fluviatilis, so the images on
this page are not necessarily that species. Most flatworms
look very similar, though, so Procotyla fluviatilis
looks a lot like these pictures. One of the reasons
Procotyla fluviatilis is so common is because it is
able to live in most bodies of water, including streams,
ponds, and lakes. Like most flatworms, they prefer shallow
water. Electronic Field Guide to
Aquatic Invertebrates of Small Streams in Eastern
Massachusetts Procotyla
fluviatilis grows up to 20 millimeters long. They are
usually brown or greenish. All flatworms have a soft
body and a triangle-shaped head. They also have eye-spots on
top of their heads which can see light. Flatworms are not
closely related to most other "worms," such as earthworms.
Bodies are flat instead of round, and they do not have
segments. Flatworms spend most of
their time on the bottom, especially since they can't swim.
They release sticky mucus (a lot like slugs and snails)
which they glide on top of. They can crawl up plants, and
they can glide upside down on the surface of the
water. Flatworms do not like
light. They stay in the shade or under rocks or other items
during the day. There are no male or
female flatworms. They are hermaphrodites, which means when
they mate, both flatworms can lay eggs. Several eggs are
laid in one cocoon two to four millimeters wide. Eggs hatch
in about two weeks, unless it's near Winter. Then the eggs
wait until Spring. Young Procotyla
fluviatilis are 1 to 3 millimeters long when they
hatch. Most flatworms, including
Procotyla fluviatilis, are predators. They eat
protists (including Amoeba, Paramecium, and Euglena),
rotifers, nematodes, small crustaceans, aquatic worms, and
other soft-bodied animals. They also feed on dead animal
matter and larger animals that are injured. Sometimes they
even eat other flatworms, including their own kind! A
flatworm is able to stretch part of its mouth and use it to
suck the juices of its prey. Procotyla
fluviatilis can also release some mucus as a trap to
catch small crustaceans. Cabot School Dr. Rick Gillis,
http://www.uwlax.edu/biology/faculty/Gillis/gillis.htm Flatworms have many
predators, including aquatic insects, such as dragonfly
naiads and diving beetles. Tadpoles, small fish, and
crustaceans also eat them. Sometimes flatwoms, such
as Procotyla fluviatilis, are transported by larger
animals to new places. When a bird, raccoon, or other animal
gets mud on its feet, flatworms inside the mud get a free
ride. Of course, if the larger animal doesn't go somewhere
there is water, and the flatworm dries out, it
dies. Procotyla
fluviatilis can also migrate by streams to other bodies
of water. Flatworms are less active
when the water is very warm or when they are fully
fed.
