Scientists Say: Copepod

These tiny crustaceans can be found wherever there’s water


It may not look like it, but this tiny copepod is actually related to lobsters and shrimp.

Uwe Kils/Wikimedia Commons/ CC BY-SA 3.0

Copepods (noun, “KOAP-eh-pods”)  

A group of small crustaceans found in water. These animals are related to shrimp and lobsters, but are only a fraction their size. In length, they typically run only one to two millimeters (between 0.039 and 0.079 inch). Some are plankton — creatures that drift in the sea. Others live along the sea floor. Copepods can even be found in fresh water, from sidewalk puddles to drops of water cradled in plant leaves. These animals eat phytoplankton — microscopic plant-like organisms. Copepods are a source of food for many kinds of fish, birds and even whales.

In a sentence

After eating plankton in a harmful algal bloom, copepods swim faster and straighter — making them more likely to encounter predators.

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Power Words

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copepod  A group of small crustaceans found in salt and fresh water. Some species of copepods are plankton, while others spend time on the sea floor. They aren’t limited to oceans — copepods are also found in freshwater, from ponds to puddles. They eat phytoplankton.  

crustaceans    Hard-shelled water-dwelling animals including lobsters, crabs and shrimp.

phytoplankton     Sometimes referred to as microalgae, these are microscopic plants and plant-like organisms that live in the ocean. Most float and reside in regions where sunlight filters down. Much like land-based plants, these organisms contain chlorophyll. They also require sunlight to live and grow. Phytoplankton serve as a base of the oceanic food web.

plankton     A small organism that drifts or floats in the sea. Depending on the species, plankton range from microscopic sizes to organisms about the size of a flea. Some are tiny animals. Others are plantlike organisms. Although individual plankton are very small, they form massive colonies, numbering in the billions. The largest animal in the world, the blue whale, lives on plankton.

predator   (adjective: predatory) A creature that preys on other animals for most or all of its food.

Bethany Brookshire was a longtime staff writer at Science News Explores and is the author of the book Pests: How Humans Create Animal Villains. She has a Ph.D. in physiology and pharmacology and likes to write about neuroscience, biology, climate and more. She thinks Porgs are an invasive species.

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