Hyalella azteca
The Saskatchewan Aquatic Insects Page
Scuds are tiny
crustaceans, close relatives of crayfish, water fleas, and
shrimp. They probably look the most like shrimp. There are many different
species of scud, but this page will focus on Hyalella
azteca, one of our more common species. Scuds live in water, such
as streams, ponds, and lakes. They are rarely found in
rivers. They like shallow water and do best in water where
there are no fish. Hyalella azteca
grows up to 1/4 inch long. It spends most of its time in mud
or sand on the bottom. This scud's color can vary. They can
be white, green, bluish, brown, or reddish. Scuds have two pairs of
antennae (like all crustaceans) and seven pairs of legs
(like isopods). Wirbellose Scott Bauer,
USDA Scuds are most active at
night. They don't like light, so they hide under plants,
stones, and other objects during the day. Scuds walk on the
bottom or swim just above it. They often swim on their
sides, which has earned them the nickname, "side-swimmers."
They stay close to the bottom so they can wriggle into it
when a predator comes close. Hyalella azteca,
and other scuds, eat plant and animal matter. They rarely
attack living animals their size, but they move quickly to a
dead animal in the water. Their main food is microscopic
plants, animals, and debris found on plant leaves and stems,
or rocks, sticks, etc. Scuds help keep water healthy for
other animals by eating up dead leaves, sticks, and other
matter that ends up on the bottom. They are considered
scavengers. Hyalella azteca
breeds from February to October, depending on the
temperature. A male scud carries a female on his back
anywhere from a day to a week. After mating, the female scud
carries her eggs under her body. After hatching, young scuds
stay with their mother (she keeps carrying them) for several
days. Females can have about 15 young at a time. Scuds molt (shed their
exoskeleton) at least nine times in their lifetime. A scud
molts every 3 to 40 days, depending on food, temperature,
and other conditions. The scud gets bigger with each
molt. Predators of scuds
include small fish (especially fry), tadpoles, newts,
aquatic insects, and other water predators. They do not do
well in water with fish, since they are a favorite
food. Laboratorium ECCA
NV Copyright 2002, Chris
Westhauser Many species of algae and
protists grow on scud exoskeletons. Scuds can be hosts for
parasites, such as tapeworms and nematodes. Usually, these
parasites use scuds to grow, and eventually move on to a
bird or larger animal.
