Scud

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.

Relationships in Nature:

PREY/FOOD
PREDATORS
SHELTER
OTHER

Amoeba

Creek Chub

Lizard's Tail

Euglena

Eastern Mosquitofish

Tussock Sedge

Paramecium

Bluegill

Green Algae

Green Algae

Channel Catfish

Pickerelweed

Largemouth Bass

Yellow Pond Lily

Yellow Bullhead

Greater Bladderwort

Yellow Perch

Long-leaf Pondweed

Bullfrog

Common Reed

Spring Peeper

Common Cattail

Southern Leopard Frog

Buttonbush

American Toad

Arrow Arum

Eastern Newt

Spotted Salamander

Three-lined Salamander

Large Diving Beetle

Green Darner

Ebony Jewelwing

Eastern Dobsonfly

Greater Bladderwort

Predatory Nematode

Relationship to Humans:

Even though scuds are small, they're sometimes used as fishing bait. More importantly, scuds, such as Hyalella azteca, help keep our waters clean. They are also a good indicator. This means scientists look for them when they are trying to find out how healthy water is.

SCIENTIFIC CLASSIFICATION

KINGDOM
Animal
PHYLUM
Arthropod
CLASS
Crustacean
ORDER
Amphipoda
FAMILY
Hyalellidae
GENUS
Hyalella
SPECIES
Hyalella azteca

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