Imposex in Thais spp. (Gastropod) Along Southern and Eastern Coast of as a Potential Monitoring Organism for TBT Contamination

Ahmad Ismail a, Syaizwan Zahmir Zulkifli ac, Ferdaus Mohamat Yusuff bc & Shahrizad Yusof a

a Department of Biology, Faculty of Science, Universiti Putra 43400 UPM Serdang, Selangor, Malaysia b Department of Environmental Science, Faculty of Environmental Studies Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia c International Coastal Research Center, Ocean Research Institute, The University of Tokyo, 2-106-1, Akahama, Otsuchi, Iwate 028-1102 Otsuchi, Japan

Introduction

Imposex cases in Thais sp. related to organotin pollution have been documented in many previous publications (Horiguchi et al. 1994. Horiguchi & Shiraishi, 1997, Tan 1997, Tan, 1999, Shim et al. 2000). Organotin is known to cause toxic to marine life at all stages (Schweinfurth 1985). Toxicological effects of organotin can caused decrease in aquatic products, imbalance in population of marine life and in turn will affect the ecological systems. Tributyltin was also reported to be harmful to mariculture and disrupt the endocrine system in some molluscs (Alzieu et al. 1986, Bryan et al. 1988). Organotin have been used as an effective antifouling agent since 1960s in shipping industries and agriculture (Ueno et al. 2004). Tributyltin (TBT) as an effective antifouling agent has been added to many ship-paint formulations to keep ship hulls free from algae, barnacles and other fouling organisms (Belfroid et al. 2000). Even though the use of TBT-based ship paints was recently banned but TBT still be encountered in the environment, because of its slow degradation and high sorption to suspended matter and sediment (Fent 1996). Many studies carried out in the Straits of Malacca, Singapore waters and South China Seas have shown that these waters received some levels of organotin contamination (Tong et al. 1996, Yamada et al. 1997, Hashimoto et al. 1998, Sudaryanto et al. 2002, Wagiman et al. 2002, Harino et al. 2008a). There are several ways to assess organotin contamination in the coastal ecosystem. Beside the determination of butyltin levels in sediment or animal tissues, an analysis of imposex cases in Thais spp. is one of the

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methods. Imposex as an indicator for tributyl tin pollution has been described in detail by Bryan et al. (1987) and Bryan et al. (1993). Imposex is a phenomenon that occurs in molluscs due to TBT contamination. Imposex female snail become sterile as the genital pore was mechanically blocked and the eggs cannot be released. The eggs aborted inside the females and cause mortality. Based on the above discussion, Thais sp. is a good indicator and it is a good and important tool to assess TBT contamination in the coastal areas. Toxicological effects of TBT on snails and others show this chemical is important to study and may affect the coastal ecosystem. Therefore this study was carried out to assess the distribution of Thais sp. and imposex incidence in Thais sp. along the Johor coastal areas. The distribution of Thais sp. and their habitat preferences along Johor coastline can be used in future study to assess TBT contamination.

Materials and Methods

Sampling of Thais sp. was carried out along the Johor coastline from the Straits of Johor to Kuala Rompin in the north of Johor in September 2008 (Figure 1 and Table 1). The survey and sampling activities were done during the low tide. Most of the snails were found on the rocks or jetty poles, but in some places the snails were hiding under the rocks and in the crevices. Thais sp. was collected after their population was confirmed at the specific site. The sampling activities were carried out using time searched formula as used by Bryan et al. (1986) and McClanahan and Muthiga (1992). This method is suitable for sampling singular species and at habitats with low population densities and covers various types of habitats (McClanahan & Muthiga 1992). Snail samples were searched and collected by hand at low tide and the time spent of collecting specimens per labor was recorded. The snails were collected by three persons walking at the same direction parallel to the beach with two meters distance from each other for 30 minutes intervals. The population density was assessed using timed search method (McClanahan & Muthiga 1992). The formula is as follows:

D= N Hour/person

Where, D = population density N = number of samples

All snails samples collected were brought back to the laboratory for imposex analyses and kept in the freezer for further use. Detail imposex examination in Thais was conducted according to description by Gibbs et al. (1987) and Horiguchi et al. (1994).

Results and Discussion

Table 1 shows the locations that were visited to search for Thais sp. Out of 17 locations, Thais sp. were observed and collected at only five locations (Table 2). The absent of

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TABLE 1: List of Locations Visited for Snail’s Survey and Collection with Sites Position and Description

bPhysical cSite aNo. Location Coordinate appearance Descriptions

1 Laut 01o 28.173’ N; 103o 46.967’ E Fs; Mx; Rb DA; P; I; TC 2 Kampung Pasir Putih 01o 26.036’ N; 103o 55.805’ E Fs; Mx DA; P;AQ; J; V; tc 3 Telok Kabung 01o 25.685’ N; 103o 57.296’ E Fs; Mx da; J; AQ; V 4 Kampung Nelayan 01o 25.581’ N; 103o 57.541’ E Fs; Mg Pr; v 5 01o 26.784’ N; 104o 0.252’ E Mg; E; Mf DA; P; I; J 6 Sungai Tiga 01o 28.669’ N; 104o 0.167’ E E; Mg pr; j; ag; aq; v 7 Kong kong 01o 31.113’ N; 103o 59.874’ E Fs; Mx da; J; V 8 Sungai 01o 20.964’ N; 104o 13.188’ E Fs; Mx; Sr DA; j; tc 9 01o 22.003’ N; 104o 15.146’ E Fs; Mx; Rb DA; OR; P; V 10 Batu Layar 01o 26.965’ N; 104o 17.588’ E Fs; S; Sr pr; r; v 11 Kecil 01o 49.468’ N; 104o 09.569’ E Fs; S; Sr pr; r; v 12 Teluk Mahkota 01o 53.856’ N; 104o 06.244’ E Fs; S; Br da; r; j; v 13 Tanjung Sedili 01o 55.801’ N; 104o 06.618’ E Fs; S; Sr pr; r; v 14 Sedili Besar 01o 55.987’ N; 104o 07.586’ E Fs; S; Sr pr; r; v 15 Mersing Beach 02° 26.863’ N; 103° 51.019’ E Fs; Mx; Sr; Rb DA; J; tc; r 16 Mersing Jetty 02° 26.863’ N; 103° 50.293’ E E; Mf DA; p; J; V; tc 17 Kuala Rompin 02° 48.530’ N; 103° 28.767’ E E; Mf da; j

Remarksa: - Number in map Remarksb: B - Bay Mf - Mud flat Rb - Rocky barrier E - Estuary Mg - Mangrove S - Sand Fs - Facing sea Mx - Mix substratum Sr - Sedimentary rock Remarksc: Symbols with capital letter/s indicate a particular area has more / active with this type of activity, where as small letter/s indicate a particular area has less / lower active with this type of activity AQ / aq - Aquaculture P / p - Port AG / ag - Agriculture PR / pr - Pristine area DA / da - Developed area R / r - Recreation I / i - Industrial area TC / tc - Town/City J / j - Jetty V / v - Village

Thais sp. may be not because of they are not available or the habitat is not suitable for them but may be they cannot be seen in abundance, they are available in smaller sizes or probably not available during sampling. There are many factors such as weather, current and may be exposed to high concentration of pollutants that disturbing their population. The sampling will be repeated to confirm their availability and potential as biomonitoring agent. Habitat descriptions in all locations that Thais sp. were collected and those Thais sp. were absent are almost simila