Although almost no one talks about copepods because they are tiny creatures, they’re extremely important for the world’s ecological system! They clean the earth’s water bodies because they feed on dead or decaying matter. They help control the zooplankton population and are the main food source for many other aquatic species.
On the other hand, aquarium enthusiasts may know more about copepods, as they’re great at cleaning the water and clearing algae tanks! Moreover, what if we told you that a character from “SpongeBob SquarePants” is a copepod? Since we aren’t sure if the television series managed to depict a copepod’s feeding habits, we invite you to read this article that will tell you everything about their diet!
What Are Copepods?
Copepods are small crustaceans that live in freshwater and saltwater habitats. They are part of a subclass of aquatic creatures further divided into ten orders. These orders include planktonic, benthic, and parasitic species. There are more than 10,000 copepod species worldwide, but only a third live in freshwater. Some species live in swamps, wet forests, ephemeral ponds, freshwater caves, stream beds, and sinkholes.
Since there are more than 10,000 copepod species, it would be impossible to list a description that would fit them all. However, most are 0.03 – 0.09 inches long, while some polar copepods can get as large as 0.5 inches! They usually have large antennae and bodies shaped like teardrops. Most copepods have transparent bodies and exoskeletons. Some species have short, cylindrical bodies with rounded heads. Some copepods have a bright red compound eye, while others may be eyeless.
Copepods are extremely important to the worldwide ecosystem. They control the zooplankton population and represent the primary food source for many fish species, such as Alaskan pollock, killifish, and dragonet.
What Do Copepods Eat?
Unfortunately, we cannot predict a 100% accurate diet for all 10,000 copepod species. However, we can tell you that most copepods eat phytoplankton – one copepod can eat almost 400,000 phytoplankton daily! If they don’t eat the daily required amount, they won’t cover their nutritional needs.
A study shows that the copepod diet is more diverse, as it eats dinoflagellates, diatoms (most commonly called algae or microalgae), and microzooplankton. That’s because copepods often change from being herbivorous to carnivorous.
Small planktonic carnivorous and omnivorous copepods may eat the following:
- Anchovy larvae (small fish)
- Chaetognaths (it’s the main food for Candacia bradyi copepods)
- Artemia nauplii (aquatic crustaceans also called brine shrimp), although copepods only ate these in laboratory investigations;
- Copepod nauplii
- Mosquito larvae
Some species change their feeding habits once a few hours or once a few days.
Some copepod species are completely herbivorous and eat plankton blooms during spring and summer. They store food in the form of oil droplets and use them to generate energy when it’s cold.
Other copepod species have mouths adapted to eating detritus, a dead organic material, and the bacteria on it. Detritus refers to the bodies of dead organisms and feces. Certain larger copepods may eat smaller copepods.
A List of Foods Copepods Eat
Here’s a list of foods copepods eat:
- Anchovy larvae
- Mosquito larvae
- Copepod nauplii
- Plankton blooms
Do Copepods Eat Algae?
Yes, copepods can eat algae, as some species are herbivorous. A study shows that herbivores are most common in colder habitats, while carnivores are linked with oligotrophic and tropical conditions. Even more, herbivorous copepods are considered more abundant than carnivorous copepods, as per this study.
Do Copepods Eat Bacteria?
Yes, some copepod species may eat the bacteria they find on detritus, meaning dead organisms, parts of dead organisms, or feces.
How Do Copepods Catch and Eat Prey?
According to this study, copepods have two feeding methods: ambush feeding and feeding-current feeding.
The first method implies hanging motionless in the water and attacking prey that swims nearby. Ambush feeding is better for catching large and powerful zooplankton.
The feeding-current feeding technique is more efficient because it may be used with moving and non-moving creatures, while ambush feeding is suitable only for moving prey.
While most species adopt only one feeding technique, some species can periodically switch from one to another.
Copepod Predators and Threats
Since they’re extremely small, copepods have many predators in their habitats, including other copepods, jellyfish, chaetognaths, fish, and whales.
Are Copepods Good for Tanks?
Since they eat algae, copepods are great for tanks, especially reef tanks. Although they won’t be able to solve the algae issue entirely, they’ll be of much help. If they eat almost 400,000 phytoplankton daily, just imagine how much algae they eat!
Incredible Copepod Facts
- Copepods evolved from benthic ancestors in the Paleozoic era, approximately 200 – 400 million years ago!
- Scientists believe copepods are the ocean’s and, most likely, the world’s most abundant metazoans!
- Copepods are excellent swimmers! They can reach a swimming speed of 295 feet per hour.
- In Vietnam, copepods have been used to control mosquitoes that transmit diseases such as dengue fever.
- Did you know that Sheldon J. Plankton in “Spongebob SquarePants” is a copepod?
- Copepods can be found in public water supplies in many parts of the world. They are a problem in some U.S. cities, but chemical or mechanical treatment can generally solve the issue. In other countries, copepods in water supplies have been associated with cholera and Guinea worm disease. However, these countries can also solve the problem by properly filtering the water.
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- Wiley Online Library, Available here: https://onlinelibrary.wiley.com/doi/10.1111/jbi.13166
- Oxford Academic, Available here: https://academic.oup.com/plankt/article/33/5/677/1482868
- IMAS, Available here: https://www.imas.utas.edu.au/zooplankton/image-key/copepoda