FRESHWATER CRUSTACEANS AS BIOLOGICAL CONTROL AGENTS OF MOSQUITO LARVAE IN EGYPT

Abstract

This work is dealing with biological control of mosquito larvae. We first started with testing the efficiency of The Louisiana red swamp crayfish, Procambarus clarkii (Gerard, 1852) accidently introduced from USA to Egypt and the cyclopoid copepod, Mesocyclops sp. isolated from Beni Swaif and Kaliobia governorates, Egypt both as predators of Culex quinquefasciatus mosquito larvae. Data for Procambarus clarkii have shown that 4th instar mosquito larvae were the most consumed stage compared to other mosquito instars. Due to the need for animal proteins required in the growth and development of eggs, gravid crayfish females consumed more mosquito larvae than males. Mosquito population densities had positive significant effect on predation rate, with higher mosquito densities, the animal feed on more mosquito larvae. When a mixed diet of fresh vegetables (lettuce) and mosquito larvae were introduced to the crayfish, it depended more on mosquito predation as a source of animal proteins than vegetal food. Data for the cyclopoid copepod have shown that, when 5, 10 and 50 mosquito larvae were used as preys of one female copepod, predation rate was found to be 4.7, 9.1and 11.7 after one day post prey/predator exposure respectively. Predation rate of both egg carrying (ovigerous) and already post hatched females (non-ovigerous) of the copepod was compared for 3 days, with a predation rate of 23.4, 20, and 16.8% in the first, second, and third days respectively post exposure of the preys to the ovigerus copepod females with a total predation rate of 60.2% after the 3rd day of exposure. When copepod females were kept after egg hatching (non-ovigerous) and exposed to mosquito larvae, predation rate has reached 23.4, 18.2, and 17.2% in the first, second and third days respectively with a total of 58.8% at the end of the 3rd day. Four types of water was used to test preference of adult Culex quinquefasciatus gravid females to lay their eggs, i) copepod natural water brought from the fields where copepods are commonly existed and having 50 copepods, ii) tap water, iii) distilled water, and iv) mosquito culture water after pupal emergence. Data have shown that copepod