All you need to know about Copepods

Copepods Zooplankton are one of our most popular live foods and before people purchase them for the first time, it is common to have questions about them. Although they have heard they are undoubtedly great for the health of their tank, many people are unsure about what copepods really do for their tank and what to expect when adding them into the mix. So we are here to answer the main questions people have about Copepods and explain all you need to know before purchasing these creatures.

What is a Copepod?

So let’s start with the basics. Copepods zooplankton are small aquatic crustaceans and are one of the most numerous metazoan groups in aquatic communities. Copepods inhabit a huge range of salinities, from fresh water to hypersaline conditions, and they can be found virtually everywhere there is water; from subterranean caves to pools collected in bromeliad leaves or in damp leaf litter on the ground, from streams, rivers, and lakes to the open ocean and the sediment layers beneath. Their habitats range from the highest mountain lakes to the deepest ocean trenches and from the cold polar ice-water interface to the hot active hydrothermal vents. Copepods zooplankton may be free-living, symbiotic, or internal or external parasites on almost every major metazoan phylum. Adults typically have a body length in the 1-2 mm range, but adults of free-living species may be as short as 0.2 mm

Copepod Zooplankton Species

There are currently 10 Orders of Copepod Zooplankton:

If you’re wondering about how many types of copepod zooplankton there are out there and which you may have, the below list is the current species of Copepoda:


The Copepoda currently comprises 10 Orders

  1. Platycopioida (Platycopiidae is a family of copepods. Until the description of Nanocopia in 1988, it contained the single genus Platycopia. It now contains four genera, three of which are monotypic the exception is Platycopia, with 8 species.)
  2. Calanoida (Calanoida is an order of copepods, a kind of zooplankton. They include around 46 families with about 1800 species of both marine and freshwater copepods. Calanoid copepods are dominant in the plankton in many parts of the world’s oceans, making up 55%–95% of plankton samples.)
  3. Misophrioida
  4. Canuelloida (Canuelloida family Longipediidae. Longipedia comprises 23 accepted species and is distributed worldwide. The Longipediidae generally are long and missile shaped, with segmented bodies covered by hard chitin. Longipedia utilize thoracopods to move, pulling themselves through the water.)
  5. Gelyelloida (Gelyella is a genus of freshwater copepods which are “surrounded by mystery. They live in groundwater in karstic areas of southern France and western Switzerland. The two species are the only members of the family Gelyellidae and, although previously placed in the order Harpacticoida, a new order, Gelyelloida, was erected for this family alone.)
  6. Harpacticoida
  7. Mormonilloida (Mormonillidae is a family of planktonic marine copepods, the only member of the order Mormonilloida. There are five known species in two genera.)
  8. Cyclopoida (The Cyclopoida are an order of small crustaceans from the subclass Copepoda. Like many other copepods, members of Cyclopoida are small, planktonic animals living both in the sea and in freshwater habitats. They are capable of rapid movement.)
  9. Siphonostomatoida (Siphonostomatoida is an order of copepods, containing around 75% of all the copepods that parasitise fishes. Their success has been linked to their possession of siphon-like mandibles and of a “frontal filament” to aid attachment to their hosts. Most are marine, but a few live in fresh water. There are 39 recognised families:)
  10. Monstrilloida (Monstrilloida is an order of copepods with a cosmopolitan distribution in the world’s oceans. The order contains a single family, Monstrillidae; the family Thaumatopsyllidae was formerly included in the order, but is now usually placed in the Cyclopoida.)

Copepod Behaviour

The second pair of cephalic appendages in free-living copepods is usually the main time-averaged source of propulsion, beating like oars to pull the animal through the water. However, different groups have different modes of feeding and locomotion, ranging from almost immotile for several minutes (e.g. some harpacticoid copepods) to intermittent motion (e.g., some cyclopoid copepods) and continuous displacements with some escape reactions (e.g. most calanoid copepods

What do Copepods eat?

Copepods exhibit varied and adaptive feeding behaviors, primarily feeding on phytoplankton while also engaging in predatory activities and detritus consumption. These feeding habits contribute to their ecological role and energy storage mechanisms.

Primary Diet: Phytoplankton

Free-living copepods predominantly consume phytoplankton, capturing individual cells to meet their nutritional needs. With their efficient feeding mechanisms, a single copepod can consume a staggering 373,000 phytoplankton cells daily, clearing a significant volume of water to obtain sufficient nutrients.

Predatory Behavior Among Copepods

Larger copepod species exhibit predatory tendencies, often preying on their smaller counterparts to satisfy their dietary requirements. This predatory behavior reflects the diversity and complexity within copepod communities and their dynamic interactions.

Detritus and Bacteria Consumption

Many benthic (bottom-dwelling) copepods rely on organic detritus and the associated bacteria as primary food sources. These copepods have mouthparts specifically adapted for scraping and biting, facilitating the consumption of detritus and contributing to the decomposition and recycling of organic matter in aquatic ecosystems.

Energy Storage through Oil Droplets

Herbivorous copepods, especially those residing in nutrient-rich, cold seas, efficiently store energy obtained from their food in the form of oil droplets. These droplets, accumulated during periods of abundant plankton blooms in spring and summer, can constitute a significant portion of their body volume, providing essential energy reserves for survival in challenging conditions. For polar species, these energy-rich oil droplets may occupy over half of their body volume, underlining the importance of this adaptive energy storage mechanism.

What is the Lifecycle of a Copepod?

Copepods exhibit a unique and fascinating lifecycle, predominantly existing in a planktonic state throughout their lives, with specific behaviors and adaptations for reproduction and survival.

Holoplanktonic Nature of Copepods

Most copepods are holoplanktonic, living as plankton throughout their entire lifecycles. However, harpacticoids, while still free-living, usually prefer a benthic (bottom-dwelling) lifestyle over being planktonic. This adaptability allows them to thrive in various aquatic environments, contributing to their widespread distribution and abundance.

Mating and Reproduction Process

During mating, male copepods use their first pair of antennae to grasp the female securely, often modifying these appendages specifically for this purpose. This interaction ensures successful mating and transfer of sperm, facilitating the reproductive process and the generation of the next copepod generation.

Egg-Laying and Hatching Mechanism

Copepod females lay eggs, which can either be released directly into the water or enclosed within a protective sac attached to the female’s body. This sac offers a secure environment for the eggs until they are ready to hatch, providing the new copepods with a safe start to their lifecycle.

Survival Adaptations of Eggs

For some species residing in ponds, copepod eggs feature a tough outer shell that allows them to withstand adverse conditions, including extended periods of dryness. This adaptation enables the eggs to remain dormant and viable until the environmental conditions are favorable again, ensuring the survival and continuity of the copepod population.

The Vital Role of Copepods Zooplankton in Ecology

Planktonic copepods play a significant role in global ecology and the carbon cycle due to their dominance in zooplankton communities and status as a primary food source for various aquatic species.

Crucial Food Source for Aquatic Life

Serving as the main diet for small fish like dragonets, banded killifish, Alaska pollock, and crustaceans such as krill, copepods are indispensable in both oceanic and freshwater environments. These small organisms support the livelihood of various aquatic species, enhancing the biodiversity and health of aquatic ecosystems.

Contribution to the World’s Biomass

Some experts argue that copepods constitute the largest animal biomass on the planet. Their relatively small size, rapid growth rates, and widespread distribution make them a significant contributor to the world’s secondary productivity and the global ocean carbon sink.

Impact on the Global Carbon Sink

Copepods are believed to contribute substantially more to the global ocean carbon sink than krill and possibly more than all other organism groups combined. The ocean surface layers, where copepods are prevalent, absorb approximately 2 billion tons of carbon annually, mitigating the impact of human carbon emissions significantly. This absorption capacity equates to roughly a third of human-generated carbon emissions, making copepods essential players in maintaining the Earth’s carbon balance.