Cyclops are the most familiar copepod of class-Crustacea. These crustaceans are found in fresh water ponds, lakes and in slight brakish water of the estuary. They are regarded as zoo-planktons. Cyclops acts as intermediate host of guinea-worm, Dracunculus medinensis.
The coiled larvae of Dracunculus are released in water by rupturing the blister of human beings. In case of guinea- worm man is the definitive host which harbours the adult parasite in the subcutaneous tissues. Each Cyclops can ingest as many as 15-20 guinea- worm larvae.
The infected Cyclopses usually die at the end of 42 days but with a heavy infection they do not live for more than 15 days. In Cyclops, the larvae moult twice and become infective in three weeks-time. When infective Cyclops is taken in by the man with water, the larvae escape and bore their way into subcutaneous tissue where they attain adulthood (Fig. 15.19).
Cyclops also acts as the intermediate host of Diphyllobothrium latum, an intestinal helminth parasite of human beings. The fertilised eggs of D. latum are liberated through the faeces of definitive host (man) in water. A spherical ciliated embryo or larva containing 3 pairs of hooklets, called coracidium, develops within each egg-shell in the course of 1 to 2 weeks.
The mature coracidium escapes into the water and is ingested by a Cyclops. Inside the intestine of Cyclops, the coracidium loses its cilia and the supporting cubical cells and penetrates the intestinal wall to reach the body cavity of the Cyclops.
Within the body cavity it is metamorphosed into an elongated solid body with a caudal spherical appendage containing six hooks. This larval stage is known as Precoracoid larva. Two larvae develop within the body cavity of Cyclops. The Cyclops, containing the developing larvae, is in its turn devoured by the second intermediate host, a fresh water fish.
Control:
Before drinking the water of the tank and lake the water should be boiled, cooled and bleached with chlorine. At about 100°C temperature of water the Cyclops can be destroyed.