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Predatory activity of Rhantus sikkimensis and larvae of Toxorhynchites splendens on mosquito larvae in Darjeeling, India

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Author(s): Gautam Aditya, Anirban Ash & Goutam K. Saha

Journal: Journal of Vector Borne Diseases
ISSN 0972-9062

Volume: 43;
Issue: 2;
Start page: 66;
Date: 2006;
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Keywords: Beetles | Culex quinquefasciatus | Darjeeling | larvae | predation | Rhantus sikkimensis | Toxorhynchites splendens

ABSTRACT
Background & objectives: Predation potential of the dytiscid beetle, Rhantus sikkimensis Regimbart1899 and the larvae of Toxorhynchites splendens Wiedemann 1819 occurring along with the larvalstages of the mosquitoes in the annual lentic water bodies of Darjeeling was evaluated using thelarvae of Culex quinquefasciatus Say 1823 as preys, in the laboratory under simulated naturalconditions.Methods: Field collected R. sikkimensis and larvae of Tx. splendens were offered IV instar larvae ofCx. quinquefasciatus to observe the rate of predation, at varying prey and predator densities. Basedon the data obtained on the predation for a period of three consecutive days, two indices of predation,predatory impact (PI) and clearance rate (CR) values were estimated, and compared between thepredator species.Results: The rate of predation of IV instar Cx. quinquefasciatus larvae by R. sikkimensis rangedbetween 21.56 and 86.89 larvae per day, depending on the prey and predator densities. The PI valueremained between 18.67 and 35.33 larvae/day depending on prey densities, while the CR rangedbetween 2.21 and 2.23 larvae litres/day/predator. Compared to these, the Tx. splendens larvaeconsumed the prey larvae at the rate of 0.67 to 34.22 larvae per day, depending on the prey andpredator densities. The PI value ranged between 7.67 and 11.33 larvae/day, and the CR value rangedbetween 1.41 and 1.76 larvae litres/day/predator. The rate of predation, CR values and PI values ofR. sikkimensis and Tx. splendens varied significantly.Interpretation & conclusion: Both the predators R. sikkimensis and larvae of Tx. splendens canconsume a good number of mosquito larvae, though the rate of consumption between the twopredators vary owing to the difference in the life history traits and features. It can be assumed thatthese predators play an important role in larval population regulation of mosquitoes and therebyimpart an effect on species composition and interactions in the aquatic insect communities ofDarjeeling Hills, India.
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