Showing papers by "Gautam Aditya published in 2007"

A comparative study of predation of three aquatic heteropteran bugs on Culex quinquefasciatus larvae

Abstract: The aquatic bugs Anisops bouvieri Kirkaldy 1704 (Heteroptera: Notonectidae), Diplonychus (=Sphaerodema) rusticus Fabricius 1781, and Diplonychus annulatus Fabricius 1781 (Heteroptera: Belostomatidae) are common members of the freshwater insect communities of the East Calcutta Wetlands along the eastern fringe of Kolkata, India. These insects are established predators of dipteran larvae and other organisms. A comparative account of their predatory efficiency was made using larvae of Culex quinquefasciatus Say 1823 in the laboratory. It was revealed that a single adult of A. bouvieri could consume 28–34 fourth-instar mosquito larvae per day, D. rusticus 11–87 fourth-instar mosquito larvae per day, and D. annulatus 33–122 fourth-instar mosquito larvae per day, depending upon the prey and predator densities. The mean predation rate of A. bouvieri and D. annulatus remained stable over a 6-day feeding period but varied for D. rusticus. The predatory impact (PI) values were 14.77–17.31, 46.9–55.73, and 61.74–72.72 larvae/day for A. bouvieri, D. rusticus, and D. annulatus, respectively. Compared to these, the clearance rate (CR) value range was 9.06–13.25 for A. bouvieri, 13.64–15.99 for D. rusticus, and 13.50–16.52 larvae l/day/predator for D. annulatus. The values of mutual interference, “m,” remained 0.06–0.78 for A. bouvieri, 0.003–0.25 for D. rusticus, and 0.09–0.27 for D. annulatus, and did not vary between the days. The difference in predatory efficiency, CR, and PI values varied significantly among the three predators, indicating the possible difference in the function as predators occupying the same guild. It can be assumed that these predators play an important role in larval population regulation of mosquitoes and thereby impart an effect on species composition and interactions in the aquatic insect communities of the wetlands and other similar habitats where they occur.

Comparative Study of Functional Response of Common Hemipteran Bugs of East Calcutta Wetlands, India

Abstract: The common and abundant hemipteran water bugs Anisops bouvieri, Diplonychus rusticus, D. annulatus, of the wetlands of East Kolkata are known predators of a wide range of aquatic insects including the mosquito larvae. In the laboratory their predation were assessed in respect to short term and long term periods using the larvae of Culex quinquefasciatus to reveal their possible role in regulating the dipteran population in nature. The attack rate (a) and handling time (Th) of these predators varied with respect to the prey size. For the backswimmers A. bouvieri the values for a and Th for the small prey were 5.47 L and 18.72 min respectively, while in case of the belostomatid bugs, the values for the same were 5.37 L and 8.64 min (for D. rusticus), 5.81 L and 20.16 min (for D. annulatus). The predation rate varied with prey and predator densities for both the prey sizes. It was revealed that on an average A. bouvieri can kill and consume 10–82 and 6–44, D. rusticus 10–118 and 10–84 and D. annulatus 10–70 and 10–138 small and large sized prey per day, respectively. However the mutual interference (m) values of the three predators varied with the prey size and ranged between 0.053–0.326 for A. bouvieri, 0.0381–0.066 for D. rusticus and 0.0556–0.115 for D. annulatus, respectively. In the long term experiments A. bouvieri killed between 6–119 small preys and 3–31 large preys, D. rusticus killed 50–94 small preys and 50–96 large preys and D. annulatum were found to kill between 14–74 small prey and 50–131 large prey per day, respectively. The clearance rates were found to be proportional to the predator density as well to the prey size and density, and differed between the predator species significantly. These data are supportive of qualifying the water bugs, A. bouvieri, D. rusticus, and D. annulatus as potential biological resources in regulating the population of mosquito larvae in the wet-lands. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Seasonal prevalence of Aedes aegypti immatures in Kolkata, India.

Abstract: Dengue and dengue hemorrhagic fever (DHF) is recurring in India in recent years, affecting many cities including Kolkata (Calcutta) In view of this, a survey of three years was carried out on the prevalence of immatures of the vector mosquito Aedes aegypti in the city of Kolkata Mosquito immatures were found throughout the year with fluctuating densities in the habitats surveyed An index of density of immatures (I/S) m employed in the study revealed that in the months of August and September a peak in abundance occurs, irrespective of the habitats, with the values ranging between 112 and 114 The (I/S) m values were low during the months of April and May ranging between 04 and 38 As larval habitats, earthen containers and the sewage drains were positive throughout the year, while during the months of December to February, air-coolers and conditioners as habitats remained totally dry, without immature Ae aegypti The number of positive sites and monthly density between the habitat types were significantly different with an I/S- value (for a year) ranging between 264 (air-coolers) and 497 (earthen containers) The survey, while providing preliminary baseline data on immature abundance in Kolkata, calls for continuous entomological surveillance using standard protocols as carried out in Thailand for the vector management program against dengue

Predatory efficiency of the sewage drain inhabiting larvae of Toxorhynchites splendens Wiedemann on Culex quinquefasciatus Say and Armigeres subalbatus (Coquillett) larvae.

Abstract: The rate of predation by stage IV instar Toxorhynchites splendens larvae on the equivalent instar stage larvae of Culex quinquefasciatus and Armigeres subalbatus, co-occurring in sewage drains, were noted for a period of three consecutive days in the laboratory using different prey densities and combinations. The rate of predation varied by age of the predator, density of prey, and prey type. The number of Ar. subalbatus larvae consumed by a single Tx. splendens larva ranged between 0.50 +/- 0.71 and 16.40 +/- 2.01; while for Cx. quinquefasciatus larvae, the number consumed ranged from 0.20 +/- 0.42 to 20.40 +/- 1.43 per day. The pupation rates of the prey species varied in respect to control, with a minimum of 0.20 +/- 0.42 pupa/day to a maximum of 12.20 +/- 2.30 pupa/day in the presence of Tx. splendens. The values for the controls were 1.00 +/- 0.87 and 14.44 +/- 2.83 pupa/day, respectively. Irrespective of prey densities and combinations, a single Tx. splendens fourth instar larvae was found to consume on average 10.07 larvae on the first day 16.57 larvae on the second day and 4.38 larvae on the third day, killing a total of 17.70 to 45.10 larvae, in three days. In the presence of Tx. splendens, the cumulative pupation, irrespective of prey, remained between 12.20 and 45.10, and differed significantly from control where the values were between 13.90 and 54.70. The results indicate that Tx. splendens can significantly reduce immature numbers and lower the rate of pupation of Cx. quinquefasciatus and Ar. subalbatus. Tx. splendens may be a potential biological resource in the control of mosquitoes inhabiting sewage drains.