Survey of aquatic insects and molluscs of Pune
Rupesh N. Raut1, Shruti Desai2 and Rohini Bapat3.
136, Budhwar Peth, Pune, 411 002. Email: email@example.com
2- 10, Hill View Apartments, Lane 9, Dahanukar Colony, Kothrud, Pune, 411 029.
3- A/6, Suryodaya Complex, Kalbhornagar, Chinchwad, Pune, 411 029.
Microinvertebrates such as insect larvae and snails play critical role in maintaining aquatic ecosystem by breaking down the organic matter and thereby recycling both nutrients and energy. Further, they also constitute the bottom stratum of the energy pyramid by serving as nutrition for fish. Especially aquatic insects have dual roles in foodweb and multiple ecosystem functions, besides double contribution to biodiversity as aquatic larvae and arboreal adults (Hammond ). Unfortunately Tonapi (1980), who carried out survey of aquatic molluscs and aquatic insects around Pune.
The survey was conducted in the area nearby Pune city at various locations. The sampling sites within 25 Km radius from city core (city post) were selected. They include rivers Mula, Mutha, and Pavana as well as Pashan lake, Bhugaon lake, and Taljai.
The location of various sites is given in Figure 1.
Various localities were visited during the period December 1999 to October 2000. Collection of aquatic insects and molluscs was done by picking and by using simple fish-net. The aquatic insects were preserved on field using 4% buffered formalin in the vials and mollusc shells were dry preserved in Polythene bags in the laboratory. They were identified with the help of “The field guide to fresh water molluscs of Western Ghats” by Madhyastha (1998), “field guide to aquatic macro-invertebrates” by Sivaramkrishnan, Madhyastha and Subramanian and labeled. The various details like habitat, microhabitats, pollution and human interference were noted down in the field itself. Identification of aquatic insects was one up to family level.
Records of the observations of the species, habitat, and distribution is given in Table 1 and Table 2.
In the study, dominant group of aquatic insects was formed by chironomidae, orthroptera and naucoridae, as they are dominant in polluted water, marshy area and water-body with vegetation cover respectively. Among the nondominating groups, calopterygidae, ditiscidae, notonectidae, carydalidae, were recorded at some places. Among the others, economidae, aeschnidae, libullidae, gerridae and perlidae were quite common in relatively unpolluted water-bodies and parts of rivers.
In the molluscs, viviparidae, lymnaedae and thiaroidae were found dominant. Among thiaroidae, Thiara scabra and Paludonus inflatus, and Gyralus labiatus from planorbidae were very rare (Table 1 and Table 2).
Result and discussion
During the study, molluscs of 15 species belonging to 10 genera and aquatic insects belonging to 13 families from 9 orders were recorded from various localities. (Table 1 and Table2)
Aquatic insects and molluscs are highly sensitive to water quality. Certain groups of aquatic insects and molluscs prefer unpolluted water while the other prefer the polluted water. Heavily polluted water-bodies include Mutha river near Warje, Mula-Mutha river near Kawadi, Pavana river near Chinchwad, Pashan lake and Taljai. Less polluted water-bodies include Pavana river near Punavale, Bhugaon lake, Khadakwasla dam.
At warje, in the part of Mutha river forms like libellulidae, aeschnidae, culicidae and molluscs like Bellamya bengalensis, B. dissimilis, Thiara tuberculata, Lymnea luteola, Pila globosa and Lamelliden species were common. In this part of the river, various industial effluents are released in the water. The river also receives waste material, sewage from the drainage system. The river in this part has bottom substrate of rocks and detritus matter. The river bed on both the sides is bounded by grassy patches, farmland and few brick industries.
Taljai is situated on Pachgaon Parvati hills. There is small pond behind the temple. Here, chironomidae and were very common. Molluscs included Bellamya bengalensis, Lymnea acuninata, L. luteola, Indoplanorbis exustus. Among them, Lymea species were very common. The lake is muddy and almost dead due to continuous dumping of nirmalya, plastic along with other waste material. In water reservoirs on the hill, aesichnidae, gerridae were recorded.
Kawadi is located on the bank of Mula-Mutha river. Here mos of the river bed is covered by thick Eicchornia mass due to which proper sampling was not possible. On the banks and ditches along the river, chironomidae was very common in the mud and naucoridae was observed beneath the vegetation cover. Here Bellamya bengalensis was a common mollusc species. In this part, a bund is constructed across the river which blocks the solid waste deposited in the Pune city area.
Pashan lake is facing the problem of pollution. Ramnadi, which is the main source of water to the lake carries drainage water, liquor, along with industrial effluents. The lake in some part is mudy while in some part is covered by Azolla. Beneath the Azolla bed, naucoridae was dominant. Here Lymnea acuninata, L. luteola were also common. In the muddy areas, orthoptera and chironomidae, were observed. On West side of the lake where there is heavy organic pollution, culicidae and notonectidae were common. In the ditch along the lake a single form of diticidae was observed. Khadakwasla dam has been constructed on Mutha river. The front part of the dam is with large boulders where forms of chironomidae, orthoptera, gerridae and perlidae were observed. Molluscs included Thiara tuberculata, T. scabra and Indoplanorbis exustus. Here major part was formed by geridae and Thiara tuberculata while perlidae and Thiara scabra were recorded only here and were very rare. In the backwaters, along the bank of the dam, Lamellidens marginalis, Corbicula striatella were very common in the pebbles. Single specimen of unidentified Lamellidens sps. and Perrysia corrugata was recorded here. Though the dam is less polluted, now a days, it is exhibiting organic pollution.
Bhugaon lake exhibits bottom substrate of stones in some part and mud in most of the area. In the areas with stones, forms like calypterygidae was dominant. In some parts of the lake, where water is covered with algae, diticidae and naucoridae were very common. Family calipterigidae was only recorded here.
Punavale is located near Pavana river. Here pumping station and bund has been constructed. The bottom substrate mainly rocky. Here forms of orthoptera, naucoridae, gerridae were recorded. The dominant group was libellulidae, corydalidae and notonectidae. The river near the village and in the down-streams is facing pollution due to fecal matter, oil split and detergents. The above study indicates that certain groups of aquatic macro-invertebrates are highly specific for their microhabitats, as substrate type influences the distribution of most of the forms of aquatic insects and molluscs (Arunachalam et al, 1991). The distribution of various forms of aquatic macro-invertebrates is highly diverse at various localities. The reason for this may be increasing pollution, human interference and habitat loss. The presence of chironomid larvae in most of the localities indicates that the rivers and water-bodies are polluted as these members are often present in polluted waters (Krishnamurthy and Reddy, 1995). Habitat loss is also affecting presence of many forms. Few years ago, in kothrud region, where in the ditches, some forms of aquatic macro-invertebrates were prevailing, due to urbanization, their habitats are lost (personal communication with A. D. Padhye). Though above mentioned causes are threatening the existence of aquatic macro-invertebrates, on Pachgaon parvati hills, the tanks constructed by forest department are inhabited by few forms of aquatic insects.
Many roles performed by macro-invertebrates in aquatic ecosystem underscores the importance of their conservation. Macro-invertebrates have served as valuable indicators of degradation of aquatic ecosystem, and as increasing demands are placed on our water resources, their value in assessments of these impacts is necessary (Wallace and Webster, 1996).
Authors are thankful to RANWA for providing financial assistance. They are thankful to Smt. S. P. Modak, Head, Department of Zoology, Abasaheb Garware College, Pune - 4, for providing laboratory facilities. They are also thankful to A. D. Padhye, Utkarsh Ghate, And S. S. Kharat for their valuable suggestions. They are also thankful to Milind Watve for valuable guidance. They are also thankful to their friends Neelesh Dahanukar and Mukul Mahabaleshwarkar for their kind co-operation.
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Sivaramkrishnan K. G., Madhyastha N. A. and Subramanian K. A. Field guide to aquatic macro-invertebrates, CES, IISc, Banglore, 1998.
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