Predatory Nematode

Mononchus genus

Dr. Charles Opperman and Aimee Salstead

Nematodes, also called "roundworms," are a group of tiny animals found just about everywhere. Some live in the soil, some in the water, and some even live as parasites inside other animals.

Mononchus is the name of a group of nematodes. Some Mononchus species live in the water, and some on land. This kind of nematode is not a parasite.

Mononchus nematodes are predatory, meaning they feed on other animals, including other nematodes.

You can find Mononchus in damp soil, sand or gravel on the shore of a water source, or on the bottom of a lake, pond, stream, river, or marsh.

Copyright 2000, Peter Mullin

Nematodes are transparent, meaning you can see through them. If they have color, you're just seeing what they ate.

Mononchus nematodes are only about a millimeter long, so you need a microscope to see one well. Females are a little bigger than males.

As they move through soil, Mononchus looks for food. Young Mononchus eat microscopic creatures, such as protists (Amoeba, Paramecium, Euglena, etc.). Adult nematodes attack protists as well as Rotifers, Water Bears, Aquatic Worms, and other nematodes. Mononchus will even eat each other!

The mouth of a Mononchus has a "tooth" that it uses to grab prey. Then the nematode swallows it whole. The picture below shows a Mononchus attacking prey.

After mating, female nematodes lay eggs in the soil. Some species of Mononchus are hermaphrodites, meaning there are no males and females. With hermaphrodtic nematodes, both animals lay eggs after mating.

Eggs hatch in a few hours or up to several weeks, depending on the species and the temperature.

Nematode eggs are tough. They resist freezing and can survive without oxygen. Sometimes they are transported when the mud they're in sticks to a large animal's feet.

Aquatic Mononchus spend most of their time crawling through the soil, or on plants, looking for food. Nematodes are important, because they help mix up the soil, which keeps a healthy environment for plants and other animals.

Mononchus can release a sticky fluid from its tail to grab onto objects when it needs to hang on.

Copyright 2000, Peter Mullin

Predators of nematodes include small fish, insects, crustaceans (water fleas and copepods), and others.

Nematodes are not closely related to earthworms, flatworms, or other kinds of "worms." The word "worm" is used by people to describe any animals that is small, long, and skinny. There are lots of animals that fit this description, but they are very different.

Relationships in Nature:

PREY
PREDATORS
SHELTER
OTHER

Amoeba

Water Flea

Arrow Arum

Euglena

Copepod

Common Cattail

Paramecium

Eastern Mosquitofish

Marsh Bulrush

Rotifer

Creek Chub

Pickerelweed

Water Bear

Golden Shiner

Common Reed

Aquatic Worm

Large Diving Beetle

Yellow Pond Lily

Brainworm Nematode

Eastern Dobsonfly

Lizard's Tail

Flatworm

Southern Leopard Frog

Greater Bladderwort

Scud

Wood Frog

Green Algae

Asian Tiger Mosquito

American Toad

Hydrilla

Water Flea

Eastern Newt

Buttonbush

Green Hydra

Greater Bladderwort

Swamp Rose Mallow

Water Mite

Flatworm

Skunk Cabbage

American Sycamore

Yellow Poplar

Black Willow

Red Maple

Long-leaf Pondweed

Relationship to Humans:

Even though some nematodes are dangerous to people, Mononchus nematodes are not. They can be very helpful, since they eat other nematodes, including harmful ones. They also help the soil by moving it, which keeps everything growing.

SCIENTIFIC CLASSIFICATION

KINGDOM
Animal
PHYLUM
Nematoda
CLASS
Enoplea
ORDER
Mononchida
FAMILY
Mononchidae
GENUS
Mononchus
SPECIES
Mononchus (many species)

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