Factors influencing predation of the Waterbugs Sphaerodema annulatum (Fab.) and S. rusticum (Fab.) on the Disease Transmitting Snail Lymnaea (Radix) luteola (Lamarck)

Abstract

Variations in the rate of predation of the waterbugs Sphaerodema annulatum and S. rusticum on the snails Lymnaea (Radix) luteola have been noted in respect to the morphs of the waterbugs, size of the prey individuals, densities of prey and predators, temperature and surface area of the waterbody concerned and the seasons. Consumption rate was highest (7.2 and 2.2 individuals per day per individual of S. annulatum and S. rusticum, respectively) in prereproductive ages of the waterbugs. This was followed by a gradual decline with the increase in age of the predators. The consumption rate was gradually higher with the increase of temperature from 20 degrees C to 35 degrees C. The bugs failed to survive beyond 35 days at 35 degrees C. Though the bugs prey upon the snails of all sizes preference for 6.5 x 4.5 mm to 8 x 5 mm individuals by S. annulatum and for 5 x 3 mm to 6.5 x 4.5 mm individuals by S. rusticum is established. The waterbugs, irrespective of species, consumed the snail individuals belonged to 3 x 2 - 4 x 3 mm size group maximum when supplied separately. The rate of predation gradually declined with the rise of predator's density irrespective of waterbug species. Predation rate increased with increasing prey density. This was level off when the prey snails were 1100 and 700 in number for S. annulatum and S. rusticum respectively. An adult S. annulatum and S. rusticum consumed 5.04, 3.7, 1.43 and 3.36, 2.49, 1.04 snails per day respectively in summer, monsoon and winter.

Feeding of the leech Glossiphonia weberi on the introduced snail Pomacea bridgesii in India

“…Moreover, the phytophagous snail L. (R.) luteola occurring in the fresh water bodies of eastern India is the source of food of a number of predators (Sinha and Ramachandran 1985;Roy and Raut, 1994;Aditya and Raut 2002) as shown by the food-chain presented in Figure 2.…”

Opportunistic foraging by heteropteran mosquito predators

“…In India and other tropical areas (Mogi et al 1995(Mogi et al , 1999Victor et al 1991;Victor and Reuben 1999;Sunish and Reuben 2002;Das et al 2006), hemipteran bugs like Anisops bouvieri Kirkaldy 1704 (Heteroptera: Notonectidae), Diplonychus (=Sphaerodema) annulatus Fabricius 1781 (Heteroptera: Belostomatidae), and D. rusticus Fabricius 1781 (Heteroptera: Belostomatidae) are predators of dipteran immatures (Panickar and Rajagopalan 1977;Hati 1988;Saha and Raut 1992;Nishi and Venkatesan 1997;Aditya et al 2004Aditya et al , 2005 and a wide range of other aquatic organisms like snails of the genera Lymnaea, Gyraulus, Indoplanorbis, and Physa (Raut et al 1988;Roy and Raut 1994;Raut 2001, 2002a, b). These predators regulate dynamics of the communities in these aquatic habitats and thus can be considered as biological resources against pest and vector mosquitoes.…”