Invasion potential of the aquarium pet snail Planorbella trivolvis in India: impact of certain abiotic and biotic factors

Planorbella trivolvis (ramshorn snail) is one of India's most extensively sold exotic aquarium pet snails. The unintentional or deliberate release of P. trivolvis may result in the colonisation and establishment as an invasive snail in freshwater ecosystems. However, the successful invasion of P. trivolvis will depend on several abiotic and biotic factors of the concerned freshwater ecosystem. We have assessed the possibility of overcoming the opposing factors in P. trivolvis invasion through laboratory-based experiments and examined the effects of household-derived pollutants on egg hatchability, adult survivability and fecundity, and temperature (15 to 35 °C) on growth, sexual maturity, and reproduction. Additionally, we have evaluated the potential of native predators as biotic resistance to invasion by prey-choice experiment. The results indicated that egg hatchability, adult survivability, and fecundity were reduced with increasing pollutant concentration. However, the same traits did not differ from a native freshwater snail, Indoplanorbis exustus. The fecundity of P. trivolvis increased with increasing body size, but no considerable differences at different temperature levels suggest a wide range of adaptation to temperature. Faster growth and the requirement of comparatively few days to attain sexual maturity were observed in the higher temperatures. The native predators, Glossiphonia weberi and Diplonychus rusticus, avoided P. trivolvis as prey over the alternative prey snails in most instances, suggesting the masking of biotic resistance against the colonisation. Our observations indicate that the chance dispersal of P. trivolvis from household or commercial aquaria may lead to a possible invasion of freshwater ecosystems under suitable conditions.

Phosphate ion removal from aqueous solution using snail shell dust: biosorption potential of waste shells of edible snails

The freshwater snails, Filopaludina bengalensis and Pila globosa are widely used for human consumption and as a feed in aquaculture in India and Bangladesh. The generation of shells as a waste product following meat extraction from the live snails incites their utilisation as a potential biomaterial. Shell dust was prepared from the dried shells of F. bengalensis (FSD) and P. globosa (PSD) and employed for phosphate adsorption from aqueous solutions. Batch adsorption experiments were performed to examine the effects of various experimental conditions, such as biosorbent dose, agitation speed, temperature, contact time, pH, initial concentration of phosphate ions, and presence of co-existing ions. SEM, EDS, ICP-OES, FTIR, and XRD results indicated that phosphate ions were adsorbed onto the surface of shell dust particles. The experimental data fitted with the Langmuir isotherm with a maximum adsorption capacity of 62.50 and 66.66 mg g^-1 for FSD and PSD. The pseudo-second order kinetic model was well fitted, indicating the chemical adsorption process, and the thermodynamic parameters indicated that the adsorption mechanism of phosphate was spontaneous, feasible, and endothermic. Therefore, the results have established the potentiality of the waste shells of edible snails to be used as an eco-friendly and low-cost biosorbent for phosphate removal from wastewater.

Macroinvertebrates as engineers for bioturbation in freshwater ecosystem

Bioturbation is recognized as a deterministic process that sustains the physicochemical properties of the freshwater ecosystem. Irrigation, ventilation, and particle reworking activities made by biotic components on sediment beds influence the flow of nutrients and transport of particles in the sediment-water interface. Thus, the biogenic disturbances in sediment are acknowledged as pivotal mechanism nutrient cycling in the aquatic system. The macroinvertebrates of diverse taxonomic identity qualify as potent bioturbators due to their abundance and activities in the freshwater. Of particular relevance are the bioturbation activities by the sediment-dwelling biota, which introduce changes in both sediment and water profile. Multiple outcomes of the macroinvertebrate-mediated bioturbation are recognized in the form of modified sediment architecture, changed redox potential in the sediment-water interface, and elicited nutrient fluxes. The physical movement and physiological activities of benthic macroinvertebrates influence organic deposition in sediment and remobilize sediment-bound pollutants and heavy metals, as well as community composition of microbes. As ecosystem engineers, the benthic macroinvertebrates execute multiple functional roles through bioturbation that facilitate maintaining the freshwater as self-sustaining and self-stabilizing system. The likely consequences of bioturbation on the freshwater ecosystems facilitated by various macroinvertebrates - the ecosystem engineers. Among the macroinvertebrates, varied species of molluscs, insects, and annelids are the key facilitators for the movement of the nutrients and shaping of the sediment of the freshwater ecosystem.

Biodegradation of Paper Wastes by Freshwater Snails: Implications for Management

The different types of paper wastes constitute a major portion of municipal solid waste. The present study was aimed to justify the use of freshwater snails for the biological degradation of the paper waste and subsequent availability of cellulose from fecal matter. Three aquatic snails Racesina luteola, Indoplanorbis exustus, and Physella acuta were used to degrade newsprint, cardboard, and common writing paper as paper waste. The consumption of papers by the snail species was subjected to statistical analysis, and the results of Kruskal-Wallis test indicated a significant variation in the paper-specific consumption pattern (K = 181.762, df = 2, p <0.0001) and no variation in the species-specific pattern. Among the three types of paper used for the study, cardboard was consumed at the highest rate (4.655 ± 0.401 mg per day), and the per capita consumption remained highest for the snail I. exustus (2.253 ± 0.273 mg per day). The microscopic images and SEM micrographs of the consumed paper revealed prominent grazing and scraping marks by the snails. The disintegration and relaxation of the papers after consumption indicated that they were on the pathway to degradation. The traditional way of degrading paper waste includes physical, chemical, or microbial treatment of paper pulp. This study represents a novel approach considering the freshwater snails as model organisms for the biodegradation process. Considerable amount of cellulose was present in the fecal samples, which can be extracted and purified for utilization as potent raw material.

Association of Body Mass Index with Angiographic Severity of Coronary Artery disease in patients with Acute Coronary Syndrome

Coronary artery disease (CAD) is the leading cause of death in developed and developing countries. Associated co-morbidities like diabetes, hypertension and obesity are making the situation worse. WHO enlisted obesity as an epidemic which also affects a great number of young population. Some recent studies showed the presence of an apparent paradoxical relationship between obesity and cardiovascular prognosis in certain subsets of patents. As BMI is an established marker of obesity; an attempt has been made to assess relationship between BMI and angiographic severity of coronary artery disease in Acute Coronary Syndrome (ACS) patients of Bangladeshi origin. To assess the association between body mass index and angiographic severity of coronary artery disease in patients with acute coronary syndrome; this cross sectional analytical study was conducted in the Department of Cardiology, Mymensingh Medical College Hospital (MMCH) and Bangabandhu Sheikh Mujib Medical University (BSMMU) from December 2016 to February 2018 among purposively selected 65 patients. Relevant ethical issues were taken into consideration. Coronary angiogram was done in the same index hospitalization period. After coronary angiogram performed patients were grouped into two groups according to their BMI. Patients with BMI <25kg/m² as Group I and those ≥25kg/m² as Group II. Angiographic severity of coronary artery disease was assessed by vessel score and Syntax score. Mean age of Group I was 54.45±10.42 years, while in Group II it was 50.76±8.89 years reflecting the early presentation of higher BMI patients. Male to female ratio was 12:1. Mean BMI of Group I and Group II was 22.56±1.59 and 28.67±2.64 respectively. In Group I, 10(25.0%) had single vessel lesion, 15(37.5%) had double vessel lesion and 14(35.0%) had triple vessel lesion, while in Group II, 6(24.0%) had single vessel lesion, 12(48.0%) had double vessel lesion and 5(20.0%) had triple vessel lesion. Mean Syntax score of Group I and Group II was 13.18±8.45 and 10.42±7.14 respectively. Patients in the increasing BMI class had a higher prevalence of diabetes, hypertension and dyslipidaemia. A negative correlation was observed between BMI and angiographic severity (Vessel score, Syntax score and HRCA e.g. LM disease) of CAD indicating that patients with higher BMI had a lower coronary artery disease (CAD) severity than their normal BMI counterparts. Patients with high BMI have a lower CAD severity than usually expected. After adjustment for co-morbidities, BMI was not found as an independent predictor of severity of coronary artery disease.

Land snail assemblages and microhabitat preferences in the urban areas of Kolkata, India

Due to the minimal dispersal capabilities and dependency on particular microhabitat, the land snails are susceptible to anthropogenic and natural disturbances. Considering the increasing anthropogenic threats, especially in urban areas, information on species’ requirements for particular habitat is very essential for land snail conservation and sustenance. In the present commentary, diversity and distribution of small-sized land snails in relation to their microhabitat preference in urban habitats of Kolkata, West Bengal, had been carried out through the quadrat method. The information on the richness and abundance of snails and their habitat places in Kolkata, India, was used to construct a bipartite network. A total of 13 land snail species were linked with 16 microhabitats. The network indices were used to justify the specialist or generalist nature of the snail species in the context of microhabitat preference. The snail species Succinea daucina and Allopeas gracile were observed to be associated with the maximum number of habitats while species strength was highest for S. daucina. The low value of connectance (0.288, &lt;0.5) and niche overlap (0.34), the high value of specialization index H2′ (0.58) and d′ (0.44) indicate that the snail–microhabitat interactions were highly specialized. The network ecology of snail–microhabitats illustrated in the present instance will enable the identification of preferred microhabitats, which are required for the enhancement of the population of land snails in urban areas like Kolkata, India.

Does the micro land snail, Kaliella barrakporensis (Mollusca: Gastropoda), exhibit plant preference and aggregation? A spatial scale analysis

The spatial scale occurrence of the micro land snail Kaliella barrakporensis (L. Pfeiffer, 1852) in the host plants was assessed in selected sites of West Bengal, India. In course of a survey, the collection of K. barrakporensis from randomly selected plants was accomplished for the purpose of highlighting – (a) distribution in host plants, (b) variation in abundance in different height and (c) the dispersion pattern. Although the snails were observed in seven different plants, the presence was more prominent in the lemon plant (Citrus limon), with an average of about 24 individuals / 100 leaves. The logit based principal component regression indicated significant differences in the choice of the host plants with abundance in C. limon followed  by Hibiscus rosa sinensis  and  Nyctanthes arbor-tristis, which was further substantiated through ANOVA (F(1),6, 69 = 10.918; P < 0.001). The heterogeneity in the distribution of K. barrakporensis at different heights of the plant C. limon was also observed with maximum abundance at about 90cm height with least number of snails at the ground level (F(1)6,139 = 3.797;P < 0.0001). On the basis of the variance to mean ratio (s2/m = 1.847±0.161SE), negative binomial aggregation parameter k (1.034± 0.33 SE) and Lloyd mean crowding (ṁ) (1.083 ± 0.16SE) the dispersion of the snail appeared to comply with the clumped distribution in host plants. Apparently, the micro land snail K. barrakporensis exhibited clumped distribution in selected plant species that serve as the preferred resource and complies with the arboreal adaptation. However, further studies should be initiated on the resource preferences of the micro snail K. barrakporensis, to support conservation initiative and spread beyond native habitats.

Prevalence and Pattern of Dyslipidemia in Diabetes Mellitus Patients Admitted in the Department of Cardiology, Mymensingh Medical College Hospital, Mymensingh, Bangladesh

Patients with Diabetes Mellitus are at high risk of cardiovascular events because of abnormal lipid metabolism. Dyslipidemia is common in patients with Diabetes Mellitus (DM). However; in Bangladesh this issue is not yet properly addressed. The aim of this study is to determine the prevalence and patterns of dyslipidaemia in patients with DM in a divisional city Mymensingh. This cross-sectional study was conducted in randomly selected eligible patients from the indoor registry of the Department of Cardiology, Mymensingh Medical College Hospital (MMCH), Bangladesh from April 2012 to March 2013. A well structured questionnaire and blood investigation for lipid profile and blood sugar were the tools of data collection from 120 randomly selected DM patients registered in the department of cardiology, MMCH. Out of 120 enrolled participants the prevalence of dyslipidemia in DM patients was 86.0%, prevalence of dyslipidemia in males was 88.0% while in females was 85.0% but the difference was not significant (p=0.42). Regarding age group, BMI and duration of DM, there is no significant association exists with dyslipidemia. About half of the studied DM patients have high serum total cholesterol level (50.83%), while 22.5% had low serum HDL-C levels and 35.0% had high serum LDC-C level, most of patients had serum triglyceride levels above normal range (67.5%) and so the common patterns of dyslipidemia in this study were serum triglyceride level followed by total cholesterol. High prevalence of dyslipidemia among diabetes mellitus in Mymensingh city were observed and so the common patterns of dyslipidemia is triglyceride followed by total cholesterol. This study emphasizes the importance of screening of lipid profile as these abnormalities may lead to development of cardiovascular diseases.

Microstructure Analysis and Chemical and Mechanical Characterization of the Shells of Three Freshwater Snails

The shells of freshwater snails are discarded as waste, which qualify as biological materials with prospective multiple uses. To substantiate this proposition, an attempt was made to elucidate the physical and chemical properties of the shells of three freshwater snails, namely, Bellamya bengalensis, Pila globosa, and Brotia costula. The shells were prepared for electron microscopy and assessment of the calcium carbonate content, apart from the Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), and nanoindentation studies. The results indicated that the calcium carbonate content (y) of the shells ranged between 87 and 96% of the total weight (x) and complied with a power regression equation: y = 0.801x 1.016; R 2 = 0.994; r = +0.998; P < 0.001. Observations through SEM depicted different snail species-specific arrangement patterns of calcium carbonate crystals in the diverse layers of shells. The XRD, FTIR, and EDS observations revealed the dominance of the aragonite form of the calcium carbonate crystal in the microstructures of each snail shell with the occurrence of different shell surface functional groups. The Brunauer-Emmett-Teller analysis elucidated the surface textures of shell dust taken from each snail species; in addition, the nanohardness properties indicate the shells as a tough biocomposite exoskeleton. Species-specific variations in the shell morphology, microstructure, and calcium carbonate content were prominent for the three freshwater snails considered for the study. Nonetheless, the physical and chemical properties substantiate that the shells of B. bengalensis, P. globosa, and B. costula qualify as biological materials for sustainable use in various fields including bioremediation, biocatalyst, biomedical applications, and a source of lime. Since the shells of the freshwater snails are discarded as aquaculture waste, subsequent use as a biological material will support the "waste made useful" paradigm in sustainability, both from ecological and economic perspectives.

Choosing exotic over the familiar taste: habitat-specific preferences of a malacophagous leech for freshwater snails as prey gastropod establishment?

The spread of freshwater invasive species through aquarium trade poses a threat to the ecosystem, economy and human health. The availability of the exotic freshwater gastropod mollusc, Planorbarius corneus (Linnaeus, 1758) (Gastropoda: Planorbidae), in pet shops in Kolkata, West Bengal, India, raises concern for its potential establishment as an invasive species. Assuming the role of the native predators as a potential biotic barrier for invasion, observations on the predation pattern of the malacophagous leech, Glossiphonia weberi (Blanchard, 1897) (Clitellata: Glossiphoniidae) against P. corneus was made in single as well as in combination with the native snail Indoplanorbis exustus (Deshayes, 1834) (Gastropoda: Planorbidae). Using varying size classes and densities of P. corneus, the predation potential of G. weberi was estimated after a 24 hour period. In another set of experiments, the predation of G. weberi against the snail P. corneus was observed in the presence of I. exustus under four different habitat conditions. The purpose was to justify - (1) the effect of conspecific and heterospecific conditions of the prey availability and (2) the effect of habitat complexity on the predatory efficacy of G. weberi. The results indicated that G. weberi consumed varied numbers of P. corneus, depending on the size and the densities of the prey and predator. Although the prey heterogeneity and complex habitats caused significant reduction of predation on both of the prey species, G. weberi significantly preferred P. corneus over I. exustus in open (P < 0.0001), macrophyte (P = 0.002) and pebbles and macrophyte containing habitats (P < 0.0001). Apparently, G. weberi preferred the exotic snail P. corneus in presence of alternative prey snail I. exustus, under different habitat conditions. Therefore, G. weberi may act as a significant biotic resistance against the colonization and establishment of P. corneus in the Indian context. However, further studies including the multiple prey and predators are required to ascertain the food web level impact of the exotic snail P. corneus in invaded freshwater ecosystems.

An insight into the structure, composition and hardness of a biological material: the shell of freshwater mussels

The shell of the freshwater mussel (Mollusca: Bivalvia) is a composite biological material linked with multifunctional roles in sustaining ecosystem services. Apart from providing mechanical strength and support, the shell is an important site for adherence and growth of multiple types of algae and periphyton. Variations in the shell architecture are observed in the mussels both within a species and among different species. Considering the prospective utility of the shell of the freshwater mussels as a biological material, an assessment of the shell characteristics was accomplished using Corbicula bensoni and Lamellidens marginalis as model species. The calcium carbonate (CaCO₃) content of the shells, physical features and mechanical strength were assessed along with the morphometric analysis. The CaCO₃ content of the shell (upto 95% to 96% of the shell weight) of both the mussels was positively correlated with the shell length, suggesting increased deposition of CaCO₃ in shells with the growth of the species. The cross sectioned views of FE-SEM images of the shells exhibited distinct layered structure with external periostracum and inner nacreous layer varying distinctly. In the growing region, the growth line was prominent in the mussel shells revealed through the FESEM images. In addition XRD, FTIR and EDS studies on the mussel shells confirmed the existence of both aragonite and calcite forms of the calcium carbonate crystals with the incidence of various functional groups. The mechanical strength of the mussel shells was explored through nanoindentation experiments, revealed significant strength at the nanoparticle level of the shells. It was apparent from the results that the shell of the freshwater mussel L. marginalis and C. bensoni qualify as a biological material with prospective multiple applications for human well-being and sustaining environmental quality.

Freshwater mussel shells: prospects as multifunctional biological material.

Prediction of outcomes in chest trauma patients using chest trauma scoring system: A prospective observational study

Background and Aims:

Prognostication of chest trauma patients by scoring systems is of vital importance to predict morbidity and mortality. We aimed to predict outcomes in chest trauma patients using chest trauma scoring system (CTS) in Indian patients.

Methods:

This was a prospective observational study done in a trauma care centre at a tertiary care teaching public hospital. CTS was calculated by scores of age, severity of pulmonary contusion, number of rib fractures and presence of bilateral rib fractures. Final CTS ranges from 2 to 12. We evaluated CTS to predict outcome that is mortality as primary objective and development of complications like pneumonia and need for ventilator support as secondary objective in Indian population.

Results:

Data were collected from 30 patients and they were divided into two groups, CTS <5 (15) and CTS ≥5 (15). High CTS ≥5 was statistically significantly associated with high incidence of pneumonia (P = 0.046), increased requirement of mechanical ventilation (P = 0.025) and mortality (P = 0.035) in chest trauma. Area under the ROC for mortality shows that the test is acceptable (0.75) and at CTS score 5.5 maximum sensitivity is 87.5% and specificity is 68%.

Conclusion:

This study concludes that a CTS ≥5 is associated with poor outcomes. This scoring system may be used to identify patients at risk of complications and institute early intensive focussed care.

Community structure of Coleoptera in Bethuadahari Wildlife Sanctuary, West Bengal, India

We focused on the coleopteran species assemblage in a tropical deciduous forest in the Bethuadahari Wildlife Sanctuary, West Bengal, India. During a 2-year survey, we collected 56 species belonging to 13 families of Coleoptera, in varying relative abundance. Among the species, 15 belong to the family Chrysomelidae, nine to the Staphyllinidae, and four to the Coccinellidae. Our results substantiate the importance of the Bethuadahari Wildlife Sanctuary for the conservation of coleopteran insects.

Life table estimates of the invasive snail Physa acuta Draparnaud, 1805, occurring in India

The life table characteristics of the invasive snail Physa acuta were assessed in the laboratory using the individuals occurring in a newly colonised area in Burdwan, West Bengal, India. Using the changes in the shell length and the body weight of the snails as surrogate, the population growth of the snails was estimated along with longevity and the fecundity schedule. The cohort of P. acuta lived for a maximum of 22 weeks with a life expectancy (ex) of 7.27 weeks and the age-specific survivorship being 0.825. Increment of the shell length of the snails complied with the von Bertalanffy growth equation, lt = 11.75(1 − exp−0.17(t−0.06)), and the observed and the expected data of the length at time t (lt) did not vary significantly (z score = 0.230; P = 0.818; n=20 pairs). Following attainment of sexual maturity between 28 and 42 days, oviposition continued till 20 weeks time, with 0.1-10 eggs laid by each individual. The eggs present per capsule remained between 01 and 11, whilst the net reproductive rate (R0), intrinsic rate of increase (rm) and the finite rate of increase (λ) were 116.07, 0.1 and 1.11, respectively. The observations are similar to those made earlier on the same species but from African and South American continents. The results of the present observation are pioneer in providing the initial studies about the life history of the invasive snail P. acuta in Indian context. Using the present information as a basis, further studies including long-term population monitoring should be initiated to understand the effects of the invasive snail P. acuta in the freshwater ecosystem of West Bengal, India.

Pupal productivity & nutrient reserves of Aedes mosquitoes breeding in sewage drains & other habitats of Kolkata, India: Implications for habitat expansion & vector management

Background & objectives:

The quality of breeding sites is reflected through the pupal productivity and the life history traits of Aedes mosquitoes. Using nutrient reserves and pupal productivity of Aedes as indicators, the larval habitats including sewage drains were characterized to highlight the habitat expansion and vector management.

Methods:

The pupae and adults collected from the containers and sewage drains were characterized in terms of biomass and nutrient reserves and the data were subjected to three way factorial ANOVA. Discriminant function analyses were performed to highlight the differences among the habitats for sustenance of Aedes mosquitoes.

Results:

Survey of larval habitats from the study area revealed significant differences (P<0.05) in the pupal productivity of Aedes among the habitats and months. Despite sewage drains being comparatively less utilized for breeding, the pupae were of higher biomass with corresponding adults having longer wings in contrast to other habitats. The nutrient reserve of the adults emerging from pupae of sewage drains was significantly higher (P<0.05), compared to other habitats, as reflected through the discriminant function analysis.

Interpretation & conclusions:

The present results showed that for both Ae. aegypti and Ae. albopictus, sewage drains were equally congenial habitat as were plastic, porcelain and earthen habitats. Availability of Aedes immature in sewage drains poses increased risk of dengue, and thus vector control programme should consider inclusion of sewage drains as breeding habitat of dengue vector mosquitoes.

Household Wastes as Larval Habitats of Dengue Vectors: Comparison between Urban and Rural Areas of Kolkata, India

Porcelain and plastic materials constitute bulk of household wastes. Owing to resistibility and slow degradability that accounts for higher residence time, these materials qualify as potential hazardous wastes. Retention of water permits these wastes to form a congenial biotope for the breeding of different vector mosquitoes. Thus porcelain and plastic wastes pose a risk from public health viewpoint. This proposition was validated through the study on the porcelain and plastic household wastes as larval habitats of Dengue vectors (Aedes spp.) in rural and urban areas around Kolkata, India. The wastes were characterized in terms of larval productivity, seasonal variation and a comparison between urban and rural areas was made using data of two subsequent years. The number of wastes positive as larval habitats and their productivity of Aedes spp. varied among the types of household wastes with reference to months and location. Multivariate analysis revealed significant differences in the larval productivity of the household wastes based on the materials, season, and urban-rural context. Results of Discriminant Analysis indicated differences in abundance of Ae. aegypti and Ae. albopictus for the urban and rural areas. The porcelain and plastic wastes were more productive in urban areas compared to the rural areas, indicating a possible difference in the household waste generation. A link between household wastes with Aedes productivity is expected to increase the risk of dengue epidemics if waste generation is continued without appropriate measures to limit addition to the environment. Perhaps, alternative strategies and replacement of materials with low persistence time can reduce this problem of waste and mosquito production.

Intraguild Predation in Heteroptera: Effects of Density and Predator Identity on Dipteran Prey

In tropical freshwaters, different species of water bugs (Heteroptera) constitute a guild sharing similar prey resources including chironomid and mosquito larvae. Assuming possibilities of intraguild predation (IGP) among the constituent members, an attempt was made to evaluate the effects of prey and predator density on the mortality of mosquito and chironomid larvae (shared prey), using Laccotrephes griseus Guérin-Méneville (Hemiptera: Nepidae) and Ranatra filiformis Fabricius (Hemiptera: Nepidae) as IG predators and Anisops bouvieri Kirkaldy (Hemiptera: Notonectidae) as IG prey. The predation on mosquito and chironomid larvae varied with the density and combinations of the predators. When present as conspecific IG predators, L. griseus exhibited greater effect on the prey mortality than R. filiformis. The effects on shared prey suggest that the two predators are not substitutable in terms of the effect on the shared prey mortality. The mortality of A. bouvieri (IG prey) at low shared prey density was significantly different (p < 0.05) from high shared prey density. In view of predatory effect of the heteropteran predators on the dipteran larvae, the results suggest possible interference by the presence of A. bouvieri as an intermediate predator. It seems that the presence of heteropteran predators including A. bouvieri as IG prey may benefit the dipteran prey under situations when the density is low in tropical waters. The intensity of the predatory effect may differ based on the species composition at IG predator level. For mosquito biological control, the interactions between the predators may not be substitutable and are independent in their effects.

Acute inferior myocardial infarction with right ventricular infarction is more prone to develop cardiogenic shock

Cardiogenic shock is rare in isolated acute inferior myocardial infarction but there is relationship of cardiogenic shock with inferior myocardial infarction if associated with right ventricular infarction. A prospective study was carried out to see the association of cardiogenic shock with inferior myocardial infarction if associated with right ventricular infarction. This study was conducted from January 2011 to November 2011. A total of 100 cases were selected as study population which was taken from the Department of Cardiology, Mymensingh Medical College Hospital, Mymensingh, Bangladesh. Among them 50 were in Group A and 50 were in Group B. Group A was the patients of acute myocardial infarction with right ventricular infarction. Group B was the patients of acute myocardial infarction without right ventricular infarction. It revealed that 9(18%) in Group A and 3(6%) in Group B developed cardiogenic shock which is statistically significant (p<0.05). The study concluded that AMI (Inf) with RVI is significantly associated with cardiogenic shock.

ASSESSMENT OF PUPAL PRODUCTIVITY OF AEDES AND CO-OCCURRING MOSQUITOES IN KOLKATA, INDIA

Monitoring of dengue vectors provide baseline information about the abundance and subsequent management strategy. An appraisal of mosquito abundance using dengue vectors as focal species was made in respect to Kolkata, India as geographical area. The data on immature abundance in the container larval habitats viz, earthen, porcelain and plastic materials were subjected to three-way factorial ANOVA, using months, habitats and species as variables. Similar tests were done on pupal weight and wing length. It was observed that Anopheles subpictus, Culex quinquefasciatus coexist with Ae. aegypti and Ae. albopictus in different container habitats, that varied with months and habitats. Ae. aegypti and Ae. albopictus were found in higher proportions in porcelain and plastic containers. In earthen containers a stable ratio of three mosquitoes was observed. Sex specific variations in pupal weight and wing length were noted in both species of Ae. aegypti and Ae. albopictus. The wing length of adult Aedes mosquitoes showed correspondence with pupal weight suggesting the use of pupal weight can be used as indicator of prospective adult body size. Although less known as container breeding, presence of An. subpictus and Cx. quinquefascistus along with Aedes indicates that availability of waste containers in environment increases risks of dengue and other mosquito borne diseases. The present habitat-based study calls for a strict vector management strategy to reduce the sources of ovipostion in various container habitats to minimize the mosquito vectors and thus potential risk of dengue and other mosquito borne diseases.

Chironomid midges as allergens: evidence from two species from West Bengal, Kolkata, India

BACKGROUND & OBJECTIVES

Arthropods of different taxonomic identity including chironomid midges are known to induce allergic response in humans. The present study was done to access two common chironomid species Chironomus circumdatus and Polypedilum nubifer for their sensitizing potential as an allergen in atopic patients and controls.

METHODS

Following preparation of allergenic extracts of the two chironomid species separately, 198 atopic patients attending an allergy clinic and 50 age matched controls were tested along with a routine panel of allergens to assess sensitization.

RESULTS

The skin prick test (SPT) results revealed that 189 of the 198 patients (95.4%) demonstrated sensitization to both the chironomid species. Higher levels of total IgE was observed in atopic subjects than in the control group.

INTERPRETATION & CONCLUSIONS

The results suggest that the chironomid midges Chironomus circumdatus and Polypedilum nubifer can elicit sensitization in humans. A potential risk for allergic reactions by susceptible individuals exists due to these chironomid species, owing to their abundance and chances of contact with human beings. Further studies may be initiated to characterize the nature of the allergens and to assess their clinical relevance.

Prey preferences of aquatic insects: potential implications for the regulation of wetland mosquitoes

Wetlands are potential sites for mosquito breeding and are thus important in the context of public health. The use of chemical and microbial controls is constrained in wetlands in view of their potential impact on the diverse biota. Biological control using generalist aquatic insects can be effective, provided a preference for mosquito larvae is exhibited. The mosquito prey preferences of water bugs and larvae of odonate species were evaluated using chironomid larvae, fish fingerlings and tadpoles as alternative prey. Manly's selectivity (αi ) values with 95% confidence intervals (CIs) were estimated to judge prey preference patterns. Multivariate analysis of variance (manova) and standardized canonical coefficients were used to test the effects of density on prey selectivity. The αi values indicated a significant preference (P < 0.05) in all of the insect predators tested for mosquito larvae over the alternative prey as a density-dependent function. On a comparative scale, chironomid larvae had the highest impact as alternative prey. In a multiple-prey experiment, predators showed a similar pattern of preference for mosquito larvae over alternative prey, reflecting a significant (P < 0.05) niche overlap. The results suggest that, in a laboratory setting, these insect predators can effectively reduce mosquito density in the presence of multiple alternative prey.

Pupal productivity of dengue vectors in Kolkata, India: implications for vector management

BACKGROUND & OBJECTIVES

Entomological surveillance of the dengue vectors using pupal productivity as indicators can be helpful in effective management. On this basis, an assessment was made on the relative importance of the larval habitats of Aedes mosquitoes in Kolkata, an endemic zone for dengue in West Bengal, India.

METHODS

Monthly collection of larvae and pupae of Aedes from larval habitats categorized as earthen, plastic and porcelain containers and tyres, was carried out from selected sites. Pupal weight was recorded and degree of sexual dimorphism was calculated. The data on pupal weight, sexual dimorphism and immature density were used for regression analysis.

RESULTS

The number of positive sites for each type of larval habitats varied with months and mosquito species. Based on mean density per month, the plastic containers were the most productive habitats and the tyres were least productive for both Aedes species. The pupal weight of both Ae. aegypti and Ae. albopictus varied with the relative density and type of larval habitats. Significant differences in pupal productivity, positive sites and the proportion of pupae were observed in the habitats. Species-specific differences in the degree of dimorphism were noted with the females being larger in size than males, irrespective of the habitats.

INTERPRETATION & CONCLUSIONS

Pupal productivity of Aedes mosquitoes in Kolkata differed in terms of the type of the larval habitats with the immature density affecting the body size of the adults. This habitat-based study is a pioneer effort considering Kolkata and calls for a management plan for source reduction of these habitats to minimize Aedes mosquitoes and thus potential risk of dengue.

Household disposables as breeding habitats of dengue vectors: linking wastes and public health

An assessment of the household wastes as larval habitats of the dengue vectors was made considering Kolkata, India, as geographical area. Wastes of four major categories, namely, earthen, porcelain, plastic and coconut shells were monitored for positive with immature of either Aedes aegypti or Aedes albopictus. Twenty six types of wastes with varying size and shape, resembling containers, were identified that hosted mosquito immature. The number of waste containers positive for Aedes immature varied significantly (P<0.05) with respect to location, type and month. The relative density of Aedes immature in the waste containers varied significantly (P<0.05) with the types and months. The significant interaction between the month, waste container types and density of Aedes immature suggest that the household wastes are important contributors to the maintenance of the population of Aedes mosquito in the city. Based on the relative density of mosquito immature in the wastes, cluster analysis allowed segregation and classification of the wastes and their importance as mosquito larval habitats. Apparently, the containers that are most frequently disposed off contributed largely to the sustenance of Aedes mosquito population in the city. This calls for a strict legislation towards disposal as well as enhanced management of the household wastes. A link between the wastes disposed and subsequent conversion to the mosquito larval habitats cautions for continuance of Aedes population and possibility of dengue epidemics if the existing management practices are not improved.

Efficacy of indigenous larvivorous fishes against Culex quinquefasciatus in the presence of alternative prey: implications for biological control

BACKGROUND & OBJECTIVES

Indigenous larvivorous fishes bear potential for regulating vector mosquitoes through trophic interactions. The mosquito prey preference of five indigenous larvivorous fishes in the presence of alternative food items was assessed to highlight their use in mosquito vector management.

METHODS

Laboratory experiments were carried out using the larvivorous fishes Ambassis (=Chanda) nama, Parambassis (=Chanda) ranga, Colisa fasciatus, Esomus danricus and Aplocheilus panchax, as predators and IV instar Culex quinquefasciatus larvae as target prey. Mosquito prey preference of these fishes in the presence of chironomid larvae, tubificid worms and artificial fish foods, in varied proportions, were assessed using preference index.

RESULTS

The fishes consumed considerable amount of mosquito larvae both in absence and presence of alternative food items. However, the positive selectivity for mosquito larvae at all densities were significantly (p <0.05) affected by the alternative foods. The chironomid larvae and tubificid worms were consumed proportionately higher than expected (p <0.05), while the artificial fish food was consumed at lower than expected proportions (p <0.05). The niche overlap was significantly similar among the fish species suggesting likeliness in predation pattern and prey preference.

INTERPRETATION & CONCLUSION

The results reflect that the alternative food items influence the mosquito prey selectivity and thus the efficacy of indigenous larvivorous fishes. While use of these fishes in the wetlands and allied mosquito larval habitats in different parts of the country is suggested, impact of the alternative prey may affect the successful regulation of mosquitoes. Assessment of appropriate predator-prey ratio under natural habitat conditions is recommended to enhance successful mosquito control by these fishes.

Habitat heterogeneity and prey selection of Aplocheilus panchax: an indigenous larvivorous fish

OBJECTIVE

The ability of the native larvivorous fish Aplocheilus panchax (Hamilton, 1822) (Cyprinodontiformes: Aplocheilidae) as predator of mosquito larvae was assessed under laboratory conditions using multiple prey and habitat conditions.

METHODS

The consumption of larvae of the mosquito Culex quinquefasciatus Say 1823 (Diptera: Culicidae) by A. panchax was evaluated in the presence of tubificid worms and chironomid larvae under complex and simple habitat conditions. The number of mosquito larvae consumed in comparison to other prey types was noted and an index of prey selectivity was used to evaluate the preference for mosquito larvae.

RESULTS

Aphlocheilus panchax consumed 53 to 65 mosquito larvae in a three hour feeding bout contrast to 29- 38 tubificid worms and 43-62 chironomid larvae depending on the habitat conditions. The prey consumption differed significantly between the habitats and the prey type. The index of prey selectivity was positive for Cx. quinquefasciatus larvae over other alternative prey in all the habitat conditions.

CONCLUSION

It is apparent from the study that the larvivorous fish A. panchax can be employed for biological regulation of mosquitoes in rice -fields and similar wetlands where the multiple prey choices are available under complex habitat conditions. However, field studies including other prey species will be required to substantiate this finding.

An assessment of macroinvertebrate assemblages in mosquito larval habitats--space and diversity relationship

The aquatic bodies designated as mosquito larval habitats are diverse in size and species composition. The macroinvertebrate predators in these habitats are elements that influence the abundance of mosquito species, providing a basis for biological control. Assessment of species assemblage in these habitats will indicate the possible variations in the resource exploitation and trophic interactions and, therefore, can help to frame biological control strategies more appropriately. In the present study, the species composition is being investigated in five different mosquito larval habitats at a spatial scale. A random sample of 80 each of the habitats, grouped as either small or large, was analyzed in respect to the macroinvertebrate species assemblage. The species composition in the habitats was noted to be an increasing function of habitat size (species number = 1.653 + 0.819 habitat size) and, thus, the diversity. The relative abundance of the mosquito immatures varied with the habitat, and the number of useful predator taxa was higher in the larger habitats. In the smaller habitats-plastic and earthen structures and sewage drains, the relative and absolute number of mosquito immatures per sampling unit were significantly higher than the pond and rice field habitats. This was evident in the cluster analysis where the smaller habitats were more related than the larger habitats. The principal component analysis on the species diversity yielded four and six components, respectively, for the smaller and larger habitats for explaining the observed variance of species abundance. The species composition in the habitats was consistent with the earlier findings and support that the abundance of coexisting macroinvertebrate species regulates the relative load of mosquito immatures in the habitats. The findings of this study may be further tested to deduce the relative importance of the habitats in terms of the productivity of mosquito immatures at a temporal scale.

Determining the optimal fluoride concentration in drinking water for fluoride endemic regions in South India

Fluoride ion in drinking water is known for both beneficial and detrimental effects on health. The prevalence of fluorosis is mainly due to the intake of large quantities of fluoride through drinking water owing to more than 90% bioavailability. The objective of this study is to predict optimal fluoride level in drinking water for fluoride endemic regions by comprising the levels of fluoride and other water quality parameters in drinking water, prevalence of fluorosis, fluoride intake through water, food and beverages such as tea and coffee and also considering the progressive accumulation of fluoride in animal bones, by comparing with non fluoride endemic areas comprise of the same geological features with the aid of regression analysis. Result of this study shows that increase of fluoride level above 1.33 mg/l in drinking water increases the community fluorosis index (CFI) value more than 0.6, an optimum index value above which fluorosis is considered to be a public health problem. Regression plot between water fluoride and bone fluoride levels indicates that, every increase of 0.5mg/l unit of water fluoride level increases the bone fluoride level of 52 mg/kg unit within 2 to 3 years. Furthermore, the consumption of drinking water containing more than 0.65 mg/l of fluoride can raise the total fluoride intake per day more than 4 mg, which is the optimum fluoride dose level recommended for adults by the Agency for Toxic Substances and Disease Registry. From the result, the people in fluoride endemic areas in South India are advised to consume drinking water with fluoride level within the limit of 0.5 to 0.65 mg/l to avoid further fluorosis risk.

Vulnerability of the mosquito larvae to the guppies (Poecilia reticulata) in the presence of alternative preys

BACKGROUND & OBJECTIVES

The predatory potential of the larvivorous fishes can be affected by the presence of alternative preys. In the present study the predation pattern of the sewage dwelling Poecilia reticulata (Peters 1872) on the larvae of Culex quinquefasciatus Say 1823 (Diptera: Culicidae) was evaluated in the presence of alternative preys.

METHODS

The predation of Cx. quinquefasciatus larvae by different size groups of R. reticulata fishes was evaluated. In addition to this, the niche breadth (N) and diet breadth (B) were measured following Manly's selectivity index (Si) as an indicator of variation of such predation pattern in the presence of alternative prey types, like chironomid larvae and tubificid worms.

RESULTS

The consumption of IV instar Cx. quinquefasciatus larvae by individual P. reticulata ranged between 65 and 84 in a 3 h feeding period and varied with the size of fish (F2,33 = 34.91; p < 0.001). The selectivity coefficient revealed a significantly low preference for the Cx. quinquefasciatus larvae (0.16, CL: 0.05-0.27; p < 0.05) compared to the chironomid larvae and tubificid worms, when all the three prey types were present. The niche breadth (N) and diet breadth (B) ranged from 0.77 to 0.92 and 0.69 to 0.93, respectively. The total consumption of all the prey types varied with the predator density, but the selectivity index for the mosquito larvae was significantly low in all the instances.

INTERPRETATION & CONCLUSION

P. reticulata can consume a good number of mosquito larvae, with the consumption rate varying with the body size. P. reticulata fishes exhibit low preference for mosquito larvae as prey in the presence of alternative controphic preys like chironomid larvae and tubificid worms. Though establishment and sustenance of P. reticulata in new habitats will be favoured by the presence of alternative preys, but vulnerability of mosquito larvae may be reduced with availability of multiple preys in natural conditions.

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

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.

Seasonal prevalence of Aedes aegypti immatures in Kolkata, India

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 1.12 and 11.4. The (I/S)m values were low during the months of April and May ranging between 0.4 and 3.8. 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 2.64 (air-coolers) and 4.97 (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 activity of Rhantus sikkimensis and larvae of Toxorhynchites splendens on mosquito larvae in Darjeeling, India

BACKGROUND AND OBJECTIVES

Predation potential of the dytiscid beetle, Rhantus sikkimensis Regimbart 1899 and the larvae of Toxorhynchites splendens Wiedemann 1819 occurring along with the larval stages of the mosquitoes in the annual lentic water bodies of Darjeeling was evaluated using the larvae of Culex quinquefasciatus Say 1823 as preys, in the laboratory under simulated natural conditions.

METHODS

Field collected R. sikkimensis and larvae of Tx. splendens were offered IV instar larvae of Cx. quinquefasciatus to observe the rate of predation, at varying prey and predator densities. Based on 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 the predator species.

RESULTS

The rate of predation of IV instar Cx. quinquefasciatus larvae by R. sikkimensis ranged between 21.56 and 86.89 larvae per day, depending on the prey and predator densities. The PI value remained between 18.67 and 35.33 larvae/day depending on prey densities, while the CR ranged between 2.21 and 2.23 larvae litres/day/predator. Compared to these, the Tx. splendens larvae consumed the prey larvae at the rate of 0.67 to 34.22 larvae per day, depending on the prey and predator densities. The PI value ranged between 7.67 and 11.33 larvae/day, and the CR value ranged between 1.41 and 1.76 larvae litres/day/predator. The rate of predation, CR values and PI values of R. sikkimensis and Tx. splendens varied significantly.

INTERPRETATION AND CONCLUSION

Both the predators R. sikkimensis and larvae of Tx. splendens can consume a good number of mosquito larvae, though the rate of consumption between the two predators vary owing to the difference in the life history traits and features. 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 Darjeeling Hills, India.

Larval habitats and species composition of mosquitoes in Darjeeling Himalayas, India

BACKGROUND & OBJECTIVES

A preliminary survey of larval mosquito habitats and temporal variation in mosquito diversity in the hill town of Darjeeling, India was made during 2003, for a qualitative and quantitative assessment of mosquito distribution.

METHODS

The possible larval habitats of mosquitoes were surveyed and the species diversity in the sites positive for mosquito larvae was noted. Bi-weekly sampling from a particular habitat was carried out to reveal the temporal variation in mosquito species.

RESULTS

A good number of lentic aquatic habitats were found to be hosting mosquito immatures, though difference in the physical and biological features of these habitats was prominent. Altogether, immatures of six mosquito species, belonging to four genera--Aedes, Armigeres, Culex and Toxorhynchites were noted with significant difference in temporal variation in their relative and absolute numbers. A positive correlation (r = + 0.707) was found between population of the prey mosquito immatures and the population of immatures of Tx. splendens. The species diversity index (H') for the mosquitoes remained between 0.87 and 1.53. The evenness components ranged between 54.03 and 95.03% and differed significantly.

INTERPRETATION & CONCLUSION

In the present study, the aquatic bodies could be categorised into six types depending on the size and structural complexity that may account for the observed variation in the species composition of the larval habitats. In addition to this, other factors like temperature, rainfall and other related climatic attributes may be responsible for the observed species variation, which needs to be confirmed through further studies.

Frequency-dependent prey-selection of predacious water bugs on Armigeres subalbatus immatures

BACKGROUND & OBJECTIVES

The predatory behaviour with reference to the frequency-dependent prey-selection of the water bugs Sphaerodema annulatum Fabricius and S. rusticum Fabricius was studied in the laboratory using the IV instar larvae and pupae of Armigeres subalbatus as prey to ascertain their efficacy as predator of mosquito immatures.

METHODS

Field collected adult morphs of the water bugs were allowed to predate on larvae and pupae provided in different ratios and densities as per the model of Greenwood and Elton' for a fixed time period. The data obtained on their predation rate were analysed with respect to the model parameters, lnV--the frequency independent component and b--the frequency dependent component of selection.

RESULTS

It was found that the prey-selection was dependent on the relative numbers of prey available, favouring apostatic selection. The b values and lnV values for S. annulatum were 0.54 +/- 0.01 and 0.92 +/- 1.04 respectively whereas the corresponding values for S. rusticum were 0.71 +/- 0.03 and 0.17 +/- 1.57 respectively.

INTERPRETATION & CONCLUSION

The selection of preys by the water bugs was dependent on the relative number of the prey forms and thus they are expected to predate on the form more abundant in a heterogeneous prey population and adversely affect the adult emergence.

Predatory efficiency of the water bug Sphaerodema annulatum on mosquito larvae (Culex quinquefasciatus) and its effect on the adult emergence

The daily number of IV instar larva of Culex quinquefasciatus killed, rate of pupation and adult emergence was noted in presence of the predatory water bug Sphaerodema annulatum for a period of seven consecutive days, experimentally, in the laboratory. The rate of IV instar larva killed by the water bugs on an average was 65.17 per day. The rate of pupation ranged between 7.6 and 48 in control while in presence of water bugs it ranged between 6 and 35. The rate of adult emergence in control experiments varied between 1.4 and 4.8 per day, which was reduced to only 0.4-28.8 per day in case of the water bugs. The results clearly indicate that the water bugs on its way of predation reduces the rate of pupation and adult emergence of Cx. quinquefasciatus significantly which calls for an extensive field trials.

Predation potential of the water bugs Sphaerodema rusticum on the sewage snails Physa acuta

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 mm and </= 3 mm size classes respectively. In the remaining trials predation rate varied from zero to eight (average 2.3) individuals per predator per day. In experiments with P. acuta belonging to all the size classes supplied together, none, except the first instar S. rusticum, attacked the prey individuals belonging to the lowest (</= 3 mm) size class. The first and second instar S. rusticum, in both trials did not attack P. acuta larger than 4 mm and 5 mm in shell length respectively. The water bugs belonging to the third, fourth, fifth instar and adult stages though preyed upon P. acuta with 3.1-8 mm shell length. The average rate of predation by a single S. rusticum varied from 0.14-3.08 individuals per day depending upon the size of P. acuta and the stage of S. rusticum. A single S. rusticum, irrespective of instar and adult stages, destroyed on average 4.16 P. acuta daily irrespective of sizes. It is estimated that one S. rusticum could destroy 1,360 P. acuta in its life time. The results clearly indicate that the water bug S. rusticum may be used to control the snails P. acuta.