The zooplankton is the common name given to many small species of animals found in freshwater and marine . The meaning of the word in Greek means ” wandering animals “. They float in the water and they do so specifically with the currents . Most of these animals are so tiny that they are only visible under a microscope, although some species can reach greater lengths. They are made up of microscopic adults and others in their larval stages.from other organisms. Many of these animals are very similar for example to shrimp and other crustaceans, as well as worms, fish and jellyfish.

What is zooplankton?

Zooplankton is a group composed of small animals that are located and live near the surface in aquatic environments . They are not good swimmers so they generally only move with the movement of the ocean currents .

  • Zooplankton characteristics
  • Types
  • Zooplankton feeding
  • Representative species
  • Use
  • Importance

Zooplankton characteristics

Some of its most relevant characteristics are the following:

  • They are capable of living in both fresh and salt water .
  • They are bad swimmers.
  • It reproduces asexually through a process called bipartition .
  • Juvenile fish are part of zooplankton.
  • They move up and down in the water.
  • They search the surface of the water at night to find food .
  • Stay in deeper water to get away from the sun during the day.
  • It is classified by size and by the stage of development in which it is.
  • They are made up of secondary and tertiary producers.
  • The zooplankton Fresh water is formed mainly by protozoa , unicellular animals and some crustaceans .
  • When they die, their shells fall off and are deposited on the bottom of the sea.
  • Most are located in the North Atlantic and the greatest diversity in the Pacific Ocean .
  • The zooplankton known as ” krill ” is the whale’s favorite food and lives in cold water.


The zooplankton can be divided into two different types of animals: holopancton , which are passing their life cycle within the plankton; and meroplankton , which includes eggs, larvae, and small fish in their early life stage. It is classified depending on its size, in this way, we have the following classification:

  • Protozooplankton is  also part of the microplankton and the organisms that compose it are classified according to the locomotion system they present, we can find the following organisms:
    • Zoomastigines : they are mobilized by means of flagella and are normally known as zoo flagellates.
    • Sarcodins : it moves through pseudopods and among them we find the phylum rhizopoda, phoraminiphera and actinipoda.
    • Ciliaphores : they move using cilia, such as suctoria, hotricos and spirotricos.
  • Metazooplankton : is part of mesoplankton, macroplakton and megaplankton. In this category there is also a sub-classification that includes holoplankton and meroplankton.
    • Holoplankton : they live in plankton and can be gelatinous like mollusks and chordates or they can be chitinous like annelids and arthropods .
    • Meroplankton : a part of their life is inhabited by plankton,

According to their size, they can be classified into:

  • Picoplankton : less than 2 micrometers
  • Nanoplankton : 2 to 20 microns
  • Microplankton : 20 to 200 microns
  • Mesoplankton : 200 microns to 20 millimeters
  • Macroplankton : 20 to 200 millimeters
  • Megaplankton : more than 200 millimeters

Zooplankton feeding

The phytoplankton gets its energy and food directly from the sun through the process known as photosynthesis , and they do just as plants do. Zooplankton feeds on phytoplankton and small organisms such as diatoms and other types of protozoa and is then consumed by larger zooplankton that includes animals such as fish, but larger. Plankton are at the base of a complex aquatic food web. It is important to mention that zooplankton is located in the last position of the food chain oceanic and outside the oceanic food web. That means that many creatures eat them.

Representative species

Some of the most representative species are mentioned below:

  • Jumping talitrus
  • Asellus aquaticus
  • Salmon louse
  • Exotic ligia
  • Armadillidium vulgare
  • Krill
  • Euphasia pacific
  • Arubolana imulates
  • Aequorea victoria


The use and the different studies with respect to zooplankton leaves us as a teaching that they have many good practical utilities for the human being. For example, Artemia salina , which is a type of a brachiopod crustacean belonging to zooplankton which is used in aquaculture and in aquariums to feed fingerlings and small fish with one of the best diets . The  Artemia franciscana is distributed in the form of cysts that have to be hatched for it to develop and can be used as live food directly.


On the other hand, one of the most important aspects of zooplankton is that it contains krill . This is a type of malacostraceous crustacean that, in addition to being the main food for whales , has been cultivated and consumed as human food in Japan . Today it can be found as krill oil which is very rich in omega-3 acids . It can also be used in various types of industrial applications since chitin or chitosan is extracted from them, which has multiple industrial, food and pharmaceutical applications.

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