Predation Potential of the Water Bugs Sphaerodema rusticum on the Sewage Snails Physa acuta

Abstract

The sewage snail Physa acuta is a serious threat to certain economic plants and to the purification plant of sewage works by rendering the biofilters ineffective. Various attempts are being made to control it. The efficacy of the predacious water bugs Sphaerodema rusticum was judged experimentally, in the laboratory in the potential control of P. acuta. It is revealed that, when supplied separately, the first, second and third instar and the adult S. rusticum did not attack P. acuta belonging to 3. 1-8 mm, 5.1-8 mm, 7.1-8 The snail Physa acuta Draparnaud is thought to be from North America from which it was introduced to Europe (Ali 1993). In recent years it has spread a good deal further. It is now common in certain parts of Australia (Madsen & Frandsen 1989) and Africa including Madagascar (Brown 1980, Curtis 1991, Brackenbury & Appleton 1993. In Asia, P. acuta has been recorded from Iran, Iraq, Israel, Japan, Macao (Madsen & Frandsen 1989), Malaysia (Ali 1993) and India (Raut et al. 1995). In all these areas P. acuta is a common inhabitant of ponds, streams, river, rice fields and municipality drains (Macha 1971, Brown 1980, Godan 1983, Alexandrawicz 1986, Appleton & Bailey 1990, Ali 1993, Brackenbury & Appleton 1993, Raut et al. 1995. P. acuta is a prolific breeder and can survive in polluted waters. It is also able to spent a considerable length of time in the agrihorticultural gardens. Consequently, it can be a serious threat to certain economic plants (Godan 1983) and to the purification plant of sewage works by rendering the biofilters ineffective (Macha 1971). Thus, it is now a serious problem. Though application of molluscicides could give a temporary relief the idea is not being used in view of possible adverse effects on the flora and fauna -algae, bacteria, amoebae and worms which occur in the biofilters. Therefore, the only option left is the employment of biological control agents. Following our record of occurrence of P. acuta in Kolkata (Calcutta), India (Raut et al. 1995) and in continuation to our studies on the bioecology of this species, we noted predation of water bugs Sphaerodema rusticum on P. acuta in the municipality drains in Kolkata. This prompted us to determine the ability of S. rusticum to control P. acuta. Accordingly, we carried out some experiments in the laboratory and the results are communicated.

Invasion of ancient Lake Titicaca by the globally invasive Physa acuta (Gastropoda: Pulmonata: Hygrophila)

“…Physa acuta has been shown to be associated with polluted water (Brown 1994) and one common name of the species is ''sewage snail''. It cannot be excluded that the sewage treatment facilities of Puno will be invaded; potentially leading to economic loss as seen in, for example, Indian sewage treatment facilities (Aditya and Raut 2002).…”

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.…”

Experimental evaluation of Candonocypris novaezelandiae (Crustacea: Ostracoda) in the biocontrol of Schistosomiasis mansoni transmission

“…To study the effect of eggs density on the predatory activity of C. novaezelandiae, a number of Petri dishes containing 50 mL dechlorinated water were provided each with 100 C. novaezelandiae and different numbers of B. alexandrina eggs (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) egg masses containing 22-371 eggs). Three replicates were set up and all Petri dishes were maintained at (25依2) °C in the laboratory and examined after 24 h using a stereomicroscope.…”

“…Among them, 3 Petri dishes were provided with excess of blue green algae (Nostoc muscorum), another 3 with excess of boiled lettuce leaves and the third group (3 Petri dishes) was left as control. This means that 3 replicates were set up and the eggs were examined daily for 3 d using a stereomicroscope and the consumed eggs were counted in each case.…”

“…One of the main methods of snail control comprises the application of chemical molluscicides which could give only a temporary relief [3] . Another method is the biological control using specific organisms to eliminate or minimize the population of the Comments In general, this is a well designed and laboratory-based study on the effectiveness of C. novaezelandiae in reducing the populations of both the intermediate snail stage and the freeswimming larvae of S. mansoni.…”