Zooplankton- Copepod

Students Name: Ramya Nambiar, Shwetha Santhosh, Gopika Anil

College Name: CMR National PU College ITPL

Sample observed: Sample of water from an infected lake

Site of collection of sample: Lake in Indira Nagar

When we studied a sample of water from an infected lake, we were surprised to see a small microscopic organism moving in the water. When we studied the organism and researched about it, we learnt that it was a crustacean called Copepod.

Copepods are a group of small  crustaceans found in nearly every freshwater and saltwater habitats. They belong to subphylum Crustacea of Phylum Arthropoda of Kingdom Animalia. They show extremely fast responses when predators are sensed.

MORPHOLOGY:. Copepods vary considerably, but can typically be 1 to 2 mm long, with a teardrop-shaped body and large antennae. Like other crustaceans, they have an armoured exoskeleton, but they are so small that in most species, this thin armour and the entire body is almost totally transparent. Some polar copepods reach 1 cm . Most copepods have a single median compound eye, usually bright red and in the centre of the transparent head; subterranean species may be eyeless. Like other crustaceans, copepods possess two pairs of antennae; the first pair is often long and conspicuous.

OCCURRENCE: Some species are planktonic (drifting in sea waters), some are benthic (living on the ocean floor), and some continental species may live in other wet terrestrial places, such as swamps, bogs, springs, ephemeral ponds, and puddles. Many live underground in marine and freshwater caves, sinkholes or stream beds. Copepods are sometimes used as biodiversity indicators.

LIFE CYCLE:. As with other crustaceans, copepods have a larval form. For copepods, the egg hatches into a nauplius form, with a head and a tail but no true thorax or abdomen. The larva molts several times until it resembles the adult and then, after more molts, achieves adult development. The nauplius form is so different from the adult form that it was once thought to be a separate species.

USES: Planktonic copepods are important to global ecology and the Carbon cycle. They are usually the dominant members of the zooplankton, and are major food organisms for small fish such as the dragonet and other crustaceans such as krill in the ocean and in fresh water. Some scientists say they form the largest animal biomass  on earth.

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