International Research Journal of Environmental Sciences ___________________________ _____ ISSN 2319–1414 Vol. 6(4), 6-12, April (2017) Int. Res. J. Environmental Sci. Impact of lead on survival and biophysiological parameters of Horn snail, Indoplanorbis exustus Deshayes, 1834 Prabhakaran P. * and Rajan M.K. Department of Zoology, Ayya Nadar Janaki Ammal College, Virudhunagar District, Sivakasi-626124 , India [email protected] Available online at: www.isca.in, www.isca.me Received 27 th January 2017, revised 4th April 2017, accepted 20 th April 2017 Abstract The toxicity of lead on the biophysiological parameters of fresh water horn snail, Indoplanorbis exustus was evaluated under laboratory condition. Mortality rate was assessed and lethal concentration LD 50 was calculated as 9.886 ppm at 96 h. To determine the toxic properties of lead on metabolism the oxygen consumption rate, biochemical content and bioaccumu lation rate were observed in adult snail on exposing them to acute and chronic exposure of lead. The oxygen consumption rate and biochemical content showed decrease in increasing exposure time and concentration. The biomagnifications after chronic exposure to lead showed an accumulation rate of 32 ppm in the snail body at higher concentration. The results showed that the snail I. exustus was sensitive to lead on comparing with other tolerant gastropods. Keywords: Horn snail, Lead, Mortality, Oxygen consumption rate, Bioaccumulation. Introduction (PbS) contribute lead to natural waters 7. It causes a wide range of biological effects that depends on the level and duration of Humans are facing one of the most horrible ecological crises in exposure. Its principal biochemical effect in humans and the form of pollution. Among the various kinds of pollutants, animals is defective haemoglobin formation and also suppresses heavy metals form one of the toxic pollutants released into the the activity of enzymes like, Na -K ATPase of red cell environment by anthropogenic activities, which can be bio - membranes, alkaline phosphatase, aldolase and monoamine magnified in the food chain. Among 104 elements existing in oxidase 2. the nature, there are only 80 metals, among which 18 of them 1 are toxic . Heavy metals are those groups of metals and non - Snails are one of the important components of the aquatic metals which have density above 6gm/cm3. Several toxic ecosystem. These are tiny creatures sprout in the polluted water elements, such as arsenic, cadmium, lead, mercury, uranium, like weeds. They can sense accurately the very low levels of 2 chromium and bismuth are often included in this group . Water metals 8. Aquatic snails are able to use chemical cues to sense sediments and biota are generally metal reservoirs in aquati c the pollution. Since, toxicants in polluted environments are 3 environment . often patchily distributed, they have developed the ability to defeat and avoid toxicants 9. Heavy metals directly or indirectly The extent of this wide spread but diffused contamination has affect the distributions and abundance of snails in freshwater by raised concern about their hazards on plants, animals and affecting their growth and reproduction. humans. Lead is one of the naturally occurring metals in small amount in the earth’s crust. Metallic lead is usually i nsoluble in The present study deals with aquatic fresh water horn snail, water, but it combines with other chemicals in water to form Indoplanorbis exustus . It is one of the freshwater aquatic snail lead compounds, that depends on the acidity and temperature of and an important vector, involved in the spread of 4 the water . schistosomiasis, fasciolasis and amphistomiasis in domestic animals and sometimes in humans in various South -East Asian Lead has been used in various processes like manufacturing of countries 10 . The planorbid group of snails is ext remely storage batteries, piping, cable sheeting, so lders for electronics, adaptable to any type of polluted water and in water with too in ammunition and as a shielding material for X -rays and other little oxygen. They avoid simply flowing water, since they 5 radiations . As chemical form, lead is used as gasoline additives, cannot get a foothold on the moving substrate, because they in PVC stabilizers (0.7-2% Pb), pigments (lead chromate) in have a high sinistral shell. On the basis of respiratory plastics, paint and ceramics, as rust-inhib itive primers (red equipment, they are well adapted to unfavorable conditions 11 . lead), lubricants (lead naphthenate), in glasses (lead silicate), Fewer data is available on the toxicity of lead on horn snail I. fluorescent tubes, for glazing in table ware (PbSiO3) and in exustus. Hence the present study has been undertaken and 6 small electric motors as permanent magnets (lead -ferrite) . In focused to bring out the impact of lead on the biophysiological addition to pollutant sources, lead bearing lim estone and galena parameters of I. exustus . International Science Community Association 6 International Research Journal of Environmental Sciences _________________________________________ ___ISSN 2319–1414 Vol. 6(4), 6-12, April (2017) Int. Res. J. Environmental Sci. Materials and methods calculated every time before replacement of water. The mg of oxygen consumed per snail was calculated for different Collection of animal: The freshwater aquatic horn snails, concentration from the data recorded. During the chronic Indoplanorbis exustus Deshayes, 1834 (Fam: Planorbidae, exposure period the snails were fed with detritus. Class: Gastropoda) were collected from the college pond in Sivakasi (9.45°N 77.8167°E 101 MSL, Tamil Nadu, India). Biochemical analysis: The biochemical analysis such as, total Identified based on Panha and Burch. They have well- carbohydrate content (Anthrone method) 16 , proteins 17 and vascularized erectile skin flap in the respiratory cavity, which lipids 18,19 were determined in acute and chronic exposed snails. serves as a “gill”. The animal has planispiral shell, which wound The foot tissues were dissected out using dissection knife and in a flat plane, with small aperture. They have filiform tentacles, weighed every 24 h upto 96 h for acute exposure. In chronic tubular pneumostome and separate gonopores at left side, with exposed snails the biochemical changes were analysed once in 12 pseudobranch . Prior to analysis the snails were acclimatized 10 days upto 30 days. The biochemical contents were then for three days under lab condition with ambient temperature compared with control. 0 (25- 32 C) and 16:8 light: dark cycle in 5 L capacity plastic tub using dechlorinated water and fed with leaf detritus ad libitum Bioaccumulation: After 30 days of exposure to toxicant lead, at Snails of 0.6 - 0.8 mm in diameter and with a weight varying sub-lethal doses from 1 to 5 ppm, the animal was taken out. The between 0.199 – 0.225g were selected for the study. whole body was removed carefully from the shell and placed in a watch glass of 10 mm dia. It was then dried in an oven at 80°C Preparation of toxicant: The stock solution of lead 10 g/l was for 2 days. The dried powder of snails was then kept in an prepared from lead acetate A.R. grade purchased from Fischer airtight specimen bottle. The dried sample was digested in 10ml Scientific chemicals using deionized water in a volumetric flask. mixture of nitric acid and perchloric acid of 9:1 ratio at 100 0C till dryness and cooled down to room temperature. Then it was Determination of LC 50 value: From the stock solution, one to diluted to 25ml using distilled water. The solution was filtered ten ppm concentrations of lead were prepared in dechlorinated and lead content was estimated using Atomic Absorption tap water taken in 500 ml bottles. A group of 10 snails were Spectrophotometer 20 , AA-6300 Shimadzu. introduced into each bottles (specific concentration) and three replicates were maintained and an appropriate control was Results and discussion maintained using water alone. The test solutions were replaced daily and the number of snails survived under different Molluscans serve as a pertinent species for monitoring the effect concentrations was recorded at 24 h interval. The experiment of pollution. Therefore, in the present work the effect of heavy was carried out under static conditions. The no. of adults died in metal lead on mortality rate, physiology, biochemical each treatment was corrected with the control using Abbott’s characteristics and on rate of bioaccumulation in the horn snail, formula 13 . The percentage kill was converted to probit kill by I. exustus has been carried out to establish the relationship 14 using the conversion table given by Finney and the LD 50 value between them. The results of this investigation are presented was determined by XLSTAT software package for probit and discussed below. analysis. Mortality rate : The rate of mortality in horn snails was Effect on physiology: To evaluate the effect of lead on the significantly increased with increase in concentration of lead physiology of snail, the test animals were divided into two and period of exposure. 50% mortality of snail occurred at a groups. The first group was exposed to acute dose of lead (LC 50 concentration of 10ppm after 96 h of exposure and at 120 h of = 4.8 mg/l). The second group was exposed to sub-lethal doses exposure 50% of mortality occured at 9ppm when compared to of lead such as 1, 2, 3, 4 and 5 ppm respectively. 20 control. The probit analysis showed LD 50 as 9.886 ppm at 96 h. acclimatized animals were introduced into each concentration whereas, after 120 h of exposure LD 50 was 8.628 ppm ± 0.05, for determining its oxygen consumption rate. The experiment 144 h of exposure 50% mortality was observed at 8 ppm was carried out in 1 L bottles under static conditions. Triplicates concentration.