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Why are Copepods Important in Ecosystems
[Kingdom: Animalia] [Copepod Phylum: Arthropoda] [Subphylum: Crustacea] [Class: Copepoda]
Copepods are a diverse group of microscopic aquatic crustaceans. Yet, almost all of the 12,000 different copepod species measure less than two (2) millimetres in size.
This guide highlights some of the key facts about copepod crustaceans and the pivotal role they have in healthy marine ecosystems.
The Essential Role of Copepod Crustaceans
The National Oceanic and Atmospheric Administration produces and maintains an online global database of current copepod populations and composition changes.
Why?
In fact, the NOAA recognises the critical role of copepods as ecological bio-indicators of oceanic pollution and cleanness.
Studies show that the behaviour and composition of the class known as copepoda may also serve as key indicators of larval fish food shortages and changes to global weather patterns.
One reason is that many copepod species drift in the seas and oceans as planktonic organisms, even though most of the species live a benthic zone existence on the ocean floor.
Copepods consume miniscule water-borne organic particles which often contain harmful toxins. Hence, the species helps to purify oceanic and freshwater systems because they take the toxins with them as they settle (and die) on the sea bed.
Facts about Free Floating and Parasitic Copepods
Copepods are members of the phylum Arthropods, and as such, they make up the ocean's single-most source of nutritional protein.
Despite being related to the spider crab and some shrimp species, copepod crustaceans only have the one single red eye with a large antenna centrally located on its head.
Here's the thing:
The typical crustacean hard exoskeleton shell is missing from their teardrop shaped transparent body. Around half of the species are external parasites that range from one (1) millimetre (e.g. even smaller than krill) to almost one (1) centimetre in total size.
Copepods consume tiny fish fry and algae, but rarely fully digest all the algal material. Photosynthesised algae produces oxygen inside the body which provides a rich food source for hungry aquatic animals, fish species, and even some marine mammals.
Common Copepod Groups
Copepods fall into four different groups which are determined and identified by their role in marine ecosystems and their behavioural characteristics.
Free floating copepod groups include:
- Calanoida
- Cyclopoida
- Harpacticoida
- Misophrioida (least common)
Calanoid
Calanoids Calanoida is the largest of all copepod species and their role in the ecosystem provides plentiful food sources for most marine animals.
Calanoids have developed water-resistant bristle structures all over their body segments which provide them with additional buoyancy for their free swimming movements.
They are also clearly characterized from other copepods by a large protruding antenna (rostrum) sprouting from the center of its upper body.
Cyclopoids
Cyclopoids thrive most in freshwater environments. They are planktonic surface swimmers and quite rare, when compared to other marine or brackish copepod crustacean species.
But, cyclopoids are easily identified from other species because they do not develop a rostrum. Rostrums are tiny pointed projections sprouting from the copepod's head.
Harpacticoids
Harpacticoids are free-living copepods which spend their short life cycle swimming along the ocean floor. A newly hatched harpacticoid has only a few days of existence before it dies.
Nonetheless, they provide an invaluable role as a food source for sea anemones, small reef fishes, and most coral species, although some harpacticoids parasitize coral. Harpacticoids are often the first bugs to adorn fish aquarium tanks as they colonise the glass walls.
Misophrioids
Misophrioida Misophrioids make up only a few species of the subclass Copepoda. They have the one anterior and one posterior subdivisions of their body which distinguishes them from other copepods.
Most Misophrioids, along with Calanoids, have a dorsal heart which is a very different feature than cyclopoids and harpacticoids.