How Do Copepods Move?

Identification

Copepods are tiny crustaceans. They belong to the same family as crabs, lobsters and shrimp. According to the University of California Museum of Paleontology, there are about 9,000 species and they range in size from .5 to 15 mm in length. Copepods are an important link in the food chain. They supply many aquatic animals with protein. They are eaten by fish and whales. Many copepods are parasites. Several copepods feed on microscopic algae. Copepods are so abundant that their habitat is worldwide. They can live in fresh water or salt water. They are found in high mountain habitats and deep oceanic trenches. The can live in polar ice water and hot thermal vents. They can live inside other animals or they can swim freely in their aquatic environment. Their eggs can stay viable in shallow ponds for 300 years.

Physical Makeup

Copepods are usually transparent and colorless. There are species that have some pigments that give them a reddish or bluish color. They have tiny, elongated, pear-shaped bodies. This body is divided into two regions. The prosome is the front portion of the copepod body. This section contains their single eyes, long antennae, mandibles and swimming legs. The number of legs differs among species. It is common to find four to six legs on a copepod. The urosome is the back portion of the copepod. The urosome has no limbs and takes the form of a short tail. This tail may be split.

Movement

Copepods have a unique way of locomotion. They basically have two swimming speeds. One speed is slow and steady, which the copepod uses for feeding. This is accomplished with its antennae or mouthparts. As the copepod feeds it creates small eddies of motion that push the animal along. The other speed is faster and more deliberate. This is characterized as a jump, pause and then another jump. The term copepod means oar-footed and is taken from this jerky movement. The copepod uses all of its swimming legs at the same time. They act as one unit. It is like the oars on a Viking boat. Both sides are in sync and move at the same time to gain forward motion. The forward stroke of the copepod legs creates the jump forward, and the back stroke causes the pause between jumps.

References

• Introduction to Copepoda
• Smithsonian: Department of Invertebrate Zoology

Resources

• Kids Splash: Copepods