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Journal of Chemical, Biological and Physical Sciences Survey Of JCBPS; Section B; August 2015–October 2015, Vol. 5, No. 4; 4065-4070 E- ISSN: 2249 –1929 Journal of Chemical, Biological and Physical Sciences An International Peer Review E-3 Journal of Sciences Available online atwww.jcbsc.org Section B: Biological Sciences CODEN (USA): JCBPAT Research Article Survey of Freshwater Snails in Malabar, Kerala and an Account on the Prevalence of Infection by Digenean (Platyhelminth) Parasites Ramitha U.C.* & Vasandakumar M.V. Postgraduate & Research Department of Zoology, Sree Narayana College, PO. Thottada, Kannur -670007, India. Received: 3 September 2015; Revised: 14 September 2015; Accepted: 20 September 2015 Abstract: Snails from different freshwater habitats of Malabar region in Kerala were collected for 51 months and a study on the digenetic trematodes infecting the snails were carried out. A total of twelve species of freshwater snails was recorded and Bulinus indicus SubhaRao et al. 1994 forms a new geographic record in the Malabar region of this state. Snails acts as intermediate host of digenetic trematodes and in the present study prevalence of infection was 10.6%. The biodiversity of digenea in snail populations was high. Among the five different digenean larval forms recovered, furcocercous cercaria or the forked tailed cercaria were dominant during the study indicating diversity in bird population around the habitats under study Comparative study of habitats with respect to number of snails collected and infection showed that ponds harboured the maximum number of snails while snails collected from swamps and ditches were the most infected. Keywords: Bulinus indicus, ponds, biodiversity, furcocercous, bird, swamps. 4065 J. Chem. Bio. Phy. Sci. Sec. B, August 2015 – October 2015; Vol.5, No.4; 4065-4070 Survey of freshwater… Ramitha & Vasandakumar INTRODUCTION Snails usually play a dominant role in the ecology of freshwaters by providing food for many other animals and by grazing on vast amounts of algae and detritus (debris). Freshwater snails occur across a variety of habitats, ranging from small temporary ponds and streams to large lakes and rivers, reflecting the wide-ranging biology of many different species. Many species spend their entire lives in a few square meters of habitat, making them extremely vulnerable to localized environmental habitat degradation. Although most species prefer clean, stable, and firm river bottoms, some prefer the soft substrates more common to ponds and lakes. Ponds are amongst the most diverse freshwater habitats and have been recently found to support more species, as well as more uncommon, rare, and threatened species compared to lakes, rivers, and streams. A few wide-ranging snail species can easily survive in polluted habitats. For example the snail Indoplanorbis exustus is highly invasive with high fecundity and is common across Southeast Asia and Indian Sub-continent1. Within one year of introduction the snail is able to colonize habitats with well- established populations of other pulmonate and prosobranch snails2. The present study was initiated to survey freshwater snails in the Malabar region of Kerala State and to analyse its habitat preferences. Parasites play a decisive role in sustaining the structure and biodiversity in ecosystems, both through their hosts and via other free living species that rely on these hosts3,4. Freshwater snails have been of interest to researchers as they serve as intermediate hosts for many digenetic trematode parasites that infect a range of final hosts including invertebrates, amphibians, fish, birds, and mammals. There is a need to identify the larval stages of all the digenetic trematodes, even of those which are non-human pathogens, because of the possibility of competition for the same intermediate host and that they provide safe models for an array of basic investigations. MATERIALS AND METHODS Freshwater snails found adhering to the aquatic vegetation, floating objects or stones in ponds, swamps, ditches, paddy fields were collected using hand or a scoop net. Collected snails were rinsed in chlorine- free tap water to remove mud and plants and were brought alive to the laboratory in specific containers with water. The snails were maintained in groups of 5-7 according to the size and left in beakers containing dechlorinated tap water. The mouths of the beaker were covered with fine meshed nets to prevent the escape of snails and to provide good aeration. Snails were examined for cercaria by using emerging or crushing methods. Live unstained specimens and stained cercariae were identified to the family level based on the morphological characteristics and swimming behavior. The snails were identified using keys5-7. The list of snails collected along with their classification and numbers is represented in Table 1. 4066 J. Chem. Bio. Phy. Sci. Sec. B, August 2015 – October 2015; Vol.5, No.4; 4065-4070. Survey of freshwater… Ramitha & Vasandakumar Table 1: List of freshwater snails collected from Malabar, Kerala Sl.No. Classification and Name of Snail No. collected Phylum : Mollusca Class : Gastropoda Subclass : Prosobranchia Order : Mesogastropoda Family: Viviparidae Subfamily: Bellamyinae 1. Bellamya bengalensis (Lamarck 1822) 995 2. Bellamya dissimilis (Mueller 1774) 114 Family: Ampullariidae 3. Pila virens (Lamarck 1822) 278 Family: Bithynidae 4. Bithynia (Digoniostoma) pulchella (Benson 1836) 56 Family: Thiaridae Subfamily: Thiarinae 5. Thiara (Thiara) scabra (Mueller 1774) 215 6. Melanoides tuberculata (Mueller 1774) 790 Family: Pleuroceridae Subfamily: Melanatriinae 7. Semisulcospira huegeli (Philippi 1841) 16 Subfamily: Paludominae 8. Paludomus (Paludomus) transchauricus (Gmelin 1771) 320 Subclass: Pulmonata Order : Basommatophora Family: Lymnaeidae 9. Lymnaea (Pseudosuccinea) luteola (Lamarck 1882) 1608 Family: Planorbidae Subfamily: Planorbinae 10. Gyraulus convexiusculus (Hutton 1849) 280 Family: Bulinidae Subfamily: Bulininae 11. Indoplanorbis exustus (Deshayes 1834) 3764 12. Bulinus indicus SubbaRao et al. 1994 320 RESULTS AND DISCUSSION A total of 8730 freshwater snails, comprising twelve species, was collected from Malabar during March 2008 and June 2012. Lentic and lotic habitats were explored and ponds were found to harbour the maximum number of snails (Figure 1). The planorbid snail, Indoplanorbis exustus (3764) dominated the collections and Bulinus indicus reported from a swamp at Thazhe Choova, Kannur forms a new geographic record from Kerala. Ponds and other stagnant waters were rich in algae stimulated by excess 4067 J. Chem. Bio. Phy. Sci. Sec. B, August 2015 – October 2015; Vol.5, No.4; 4065-4070. Survey of freshwater… Ramitha & Vasandakumar nutrients (pollution) and I. exustus were found to thrive well in them as they can survive in water with low oxygen pressure, because of the presence of haemoglobin in their haemolymph8. Nine hundred and twenty eight snails were found to be infected with trematode parasites and prevalence of infection was 10.6 %. Of the twelve species of snails, Bellamya bengalensis, Melanoides tuberculata, Lymnaea (Pseudosuccinea) luteola, Thiara (Thiara) scabra, Gyraulus convexiusculus, Paludomus (Paludomus) transchauricus, Bithynia (Digoniostoma) pulchella and Indoplanorbis exustus were found to be infected with cercaria while the rest of the snails Bellamya dissimilis, Pila virens, Semisulcospira huegeli and Bulinus indicus were free from infection. Swamps around Kannur region were found to cater large number of infected snails when compared to lotic habitats. The fact that the lowest prevalence rate occurred in rivers and other running water habitat may be due to the fast water currents that displace snails or at least keep them from congregating in large numbers and make snail-miracidia contact a rare occurrence. According to Pratt9 small enclosed bodies of water may contain more parasites than those of larger size because the fishes cannot escape by migration, while Faltýnková10 suggests that that parasite eggs emerging from vertebrate hosts of adult trematodes occur at a greater density in small still waters and the probability of snail and miracidium meeting is very high and this probably might be the reason for a high infection in snails of stagnant swamps in this region. Fig. 1: Graph showing snail density and trematode infection status in different habitats Morphologically five distinct cercarial forms were recovered namely, the fork tailed furcocercous, amphistome, echinostome, xiphidiocercous and the pleurolophocercous cercariae. I. exustus proved to be the most preferred host as maximum infection (prevalence 4.4%) was found and trematode species diversity was observed in this snail. The larval forms namely amphistome, echinostome, xiphidiocercous and furcocercous cercaria were recovered from this snail. M. tubercualta with a prevalence of 4.1% harboured furcocercous, xiphidiocercous and pleruolophocerous forms. B. bengalensis followed M. tuberculata in prevalence of infection (3.7%) and hosted only one furcocercous cercarial form. L. luteola (prevalence 3.2%) hosted furcocercous, echinostomes and xiphidiocercous forms. The snail S. huegeli collected from lotic habitats were always free of cercaria or other parthenitae forms. 4068 J. Chem. Bio. Phy. Sci. Sec. B, August 2015 – October 2015; Vol.5, No.4; 4065-4070. Survey of freshwater… Ramitha & Vasandakumar 18% 3% 31% 21% 27% Furcocercous Echinostome Xiphidiocercous Pleurolophocerous Amphistome Fig. 2: Percentage representation of larval trematodes in snails Parasites in first intermediate
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