Phuket Marine Biological Center Special Publication 25 0): 31 39 (2001) JI

Population characteristics and feeding of the snail capucinus at Ang-Sila, Chonburi Province, Thailand

Fred E. Wells, Kashane Chalermwat, Nopadon Kakhai & pattama Rangubpit

Wells, F.E., K.Chalermwat, N.Kakhai & P.Rangubpit. 2001. population characteristics and feeding of the snail chicoreus cnpucinis at Ang-sila, chonburi Province, Thailand. - Phuket Marine Biological Center speciai publication 25(1): 3r-39.

The muricid snail is one of the few mollusc , which characteristically occurs only in mangroves. Howeve4, it has been found living on sandflats adjacent to mangroves at Kungkraeban Bay and Ang-Sila, Thaiiand. The present paper examines characteristics of the species at Ang-Sila. Chicoreus capucinus occupies a variety of habitats at Ang-Sila, but is most abundant and has a high density (7.7 m-21on an abandoned concrete.l,r'all. Howevel, very few (aboutl"h of ir-rdividuals) on the wall were feeding. Density (0.6 m-2; ls lower in the mangroves (Aaicennia alba),but the total number of individuals in mangroves is high because of the large area occupied by the tree zone. About 9"/o of the animals in the mangroves were feeding, primarily on the potamidid cerithidea sp. and bivalves. Density of C. caltucinus on the sandflat was low, about 0.01 m-r, but 45% of the animals were feeding, entirely on cerithidea sp. snail predation selectively targets rarge Cerithidea sp., but there is no relationship between predator size and prey size. The snails adhere to the concrete wall, anh to a lesser extent isolated small rocks, and move onto the sandflat or into the mangroves to feed. Data presented here suggest C. capucinus play a substantial role in structuring the molluscan assemblage on the sandflats and in the mangroves of the area.

Fred E. Wells. Western Australian Museum, Perth 6000 Australia E-mail : w [email protected]) a, go7:). au Kaslmne Chalermwat, Nopadon Kakhai & Pattama Rangubpit Department of Aquntic Science, Burapha l)niaersity, Bangsaen, Chonburi, Thailand

INTRODUCTION is widespread in the western West Pacific Molluscs living in mangroves can be classified Ocean. It occurs from Fiji to the Philippines, into two broad groups: species characteristic Thailand and Singapore (Houart 1992) and in mangroves; of and a larger group of species Australia from North West Cape, Western which occur on adjacent rocky, sandy or Australia to Queensland (Wells & Bryce 2000). muddy shores and also incidentally in Despite its widespread distribution, there is mangroves. Only a relatively small number of Iittle published information on C. cnpucinus molluscs are restricted to mangroves as their apart from its systematics and distributional primary habitat. Included in this group is the records. Nielsen (1976) reported that C. muricid Chicoreus capucinus, a species which capucinus fed on the rock oyster Sqccostrea JZ Tropicnl Marine Mollusc Programme (TMMP)

cuccullata and the barnacle Balanus amphitrite. basic information on the biology of C' Gribsholt (1997) also reported the species capucinus, particularly in relation to its use of feeding on S. cuccullota, and in addition the the sandflat. Ang-Sila was chosen for the gastropod Cerithides cingulata, the bivalve detailed examination because of its proximity Cultellus sp. and possibly also shipworms to Burapha University. (Teredo sp.). Middelfart (1'996) reported C. cnpucinus feeding on Saccostrea and other oysters, and briefly reported on egg capsules MATERIALS AND METHODS and development in the species. Aungtonya The detailed survey was undertaken during & Vongpani ch (1,997) provided a more detailed the first two weeks of November 1999. The analysis of reproduction in C, cnpucinus. Tan habitat was mapped and measured using a 30 (1999 b) recorded C. capucinus as one of the m long measuring tape marked off in two commonest gastropods predating on centimetres. All C. cnpucirt us encountered were barnacles and bivalves in Singapore carefully removed from the substrate to mangroves. Recently he (Tan 2000) presented determine if they were feeding. Snails were the results of a study of feeding of C. capucinus considered to be feeding if the proboscis was in mangroves at Sungei Buloh in Singapore. inserted into the sediment and/ or the foot was Tan recorded bivalves as the dominant prey holding a prey. The prey was identified and, and noted that the species switched from if it was a Cerithides sp., shell length was consuming small gastropods and mussels to measured to the nearest 1 mm with dial larger barnacles and other bivalves as they callipers. Shell length ol C. cnpucinus was also grew measured to the nearest 1 mm. The shell was Chicoreus capucinus has been reported as cleaned with a toothbrush and an individually living in several habitats. Wells and Slack- numbered plastic tag attached to the outer Smith (1981) examined distributions of shell with cryanoacetate glue ("Super Glue"). molluscs in five zones of a mangrove in the Tagging was done in the field during the first Kimberley, Western Australia. C. capucimt s was day, butbecause of concern over tags adhering most abund ant onRhizophora prop roots in the in the rain, tagging was done in the laboratory centre of the mangroves/ where it reached a on subsequent days. All specimens were maximum density of 3 m-2. Houart (7992) returned to the field the morning after they reported it living on muddy sand. Tan (1999a) were removed, and were placed aperture recently reported C. capucinus to be affected down on damp mud surface. Before the by imposex caused by tributyltin pollution. animals were replaced a search was made to During a field course on molluscs conducted locate individuals which had not been found at Burapha University, Bangsaery Chonburi the previous day. Estimates of the total number Province, Thailand in ]une-July L999, of snails in each habitat are thus the results of populations of C. capucil'Lus were located in at least two searches by four people. The only mangroves at Ang-Sila just north of Bangsaen, exception is the crevices in the wall on the and at Kungkraeban Day, approximately 100 eastern side of the holding pen, where no km to the south-east. As expected, C. capucittus attempt was made to remove C. capucinus was most abundant in RhizoPhorq at embedded in the holes. KungkraebanBay, but was also found on the mudflat seaward of the mangroves. Rhizophorn RESULTS does not occur in the study area at Ang-Sila, Habitats present but C. capuciT'tlls occurs in Articenniq and on the The area surveyed is near the shorer'vard adjacent sandflat, where it was observed to be margin of a large intertidal sandflat. The an active predator on the gastropod Cerithiden portion where Chicoreus capucinus occurs is at sp. The present study was initiated to provide a shore level of about 2.8-3.0 m in an area Phuket Marine Biological Center Special Publication 25 (1): 31-39 (2001) JJ

where high water spring reaches up to 3.6 m. The dominant habitat both inside the pen The sandflat occupied by C. capucinus is fully and on the adjacent sandflat is sand. Tidal drained at low tide and may remain dry for gates in the concrete near the middle of the several hours during daytime spring tides seaward section and the southern end of the during summer. landward wall provide access for seawater. On While the entire bay has not been surveyed the seaward end a small tidal creek enters the in detail, the only known population of C. pen and bifurcates soon after entering the capucinus at Ang-Sila is located in a relatively concrete structure. The bottoms of the small area (13'19'03"5; 755'47'05"8) where a channels have muddier sand. Isolated pieces mixture of habitats occurs. A disused concrete of wood occur in the pery primarily bamboo structure defines the margins of the study area. up to 4 m long. There are also small, isolated It was once used by fishermen as a holding rocks up to 30 cm in diameter on which C. area for crabs (Scylln sp. and Portunus sp.), but capucinus occurs. has been abandoned for at least 10 years. The Isolated small mangroves (Aaicennia alba) pen is nearly rectangular, and has a length occur within the pen, but most are 1.5 m or along the shoreline of 94 m and depth from less in height. A single 3 m tree is in the north- the shoreward to seaward of 110 mi one corner eastern corner of the pen. Mangroves are has a small rectangle missing. The pen has a common along the landward margin of the total area of approximately 10,130 m2, or just pen, including between the two walls, in the over t ha. area where the wall is doubled. These trees The pen consists of a low, vertical concrete are up to 2 m high. The largest assemblage of wall with a width of approximately 10 cm and mangroves fringes the southern end of the a height of up to 0.5 m. In most areas the wall wall. These trees occupy a total areaof 920m2. is the only concrete present above the sand; in They are dense and up to 3 m high. A low- some areas the wall has been dunlicated at a lying shrub ( S esuoium portulncastrum) lives on width of approximately 1 m, and the the sediment surface outside the pen on the intervening area is largely filled with sand. A landward and southern side. flat base 1.2 m wide occurs on the seaward side of the pen. This base may in fact occur in Hobitat preferences other areas of the sides of the pen, but is Chicoreus capucinus was distributed unevenly covered by sand. Bamboo poles, which extend among the habitats (Table 1). It was most vertically from the concrete wall at intervals abundant on the concrete wall, where almost of approximately 5 m were used to hold mesh half (49 %) of the animals were found; the wall to retain the crabs. The mesh has largely comprised only about 4'/" of the total habitat. disappeared, but portions adhere to the wall Densitv of C. caaucinus on the wall was in many areas. estimaied at L.7 m-2. The second largest Chicoreus capucinus was found along the number (555, or 40 %) occurred in the margins of the flat portion or on the base of mangroves. Only 53 of individuals occurred the vertical wall. Much of the population of on the sand, at a mean density of only 0.06 C, capucinus was within the rectangle, but a m-2. Thirty-one individuals were found on large number of animals also occurred outside, wood in the pen and 50 on rocks both inside primarily in the mangroves adjacent to the the pen and in the mangroves, despite the south of the pen. Isolated mangroves on the small area of these habitats. Only one sandflat further from the holding pen also individual was found in association with have C. capucinus, but these areas were not mangroves inside the pery but outside the pen included in the study. Similarly, mangroves the 555 animals had a mean density of 0.6 approximately 100 m south-east of the study m-2 in mangroves. area were not examined. Not only are the snails distributed unevenly J1+ Tropical Marine Mollusc Programme (TMMP)

Table 1. Habitats in which Chicoreus capucinus occurs on a sandflat at Ang-Sila, Thailand. Concrete Manp.rove Vangrove Sanct t(ocK ueao wooo . i- . Y total watl Insroe Pen outsroe Pen Number in habitat 62 679 50 JI 7 555 \378 Area of habitat (m':) 10,100 400 <10 <10 20 920 11,060 Density (no. m'Z) 0.01 1.7 5.0 6.2 0.05 0.6 0.72 among the five habitats, but distribution were most abundant on open sand inside the within each habitat is also patchy. This is most northernboundary of the rectangle. They were readily demonstrated by the fact that two also found along the upper margins of the aggregations of animals occurred on the wood; channels, but not in the bottom of the channels both had extensive deposits of egg capsules or in the muddy areas of the southern side of attached to the wood, but they did not appear the pen. to be fresh. One aggregation, on bamboo Feeding consisted of 7 individuals crowded together Numerous individuals of C. capucinus wete into the end of the bamboo, just below the last observed feeding, but prey consumed and septum. The larger aggregation, of 17 feeding rates differed considerably between individuals occurred along a break in a stick habitats (Table 2). Only one muricid was approximately 30 cm long. Together the two observed drilling a hole in the shell of aggregationshad 24 of the 31 animals found Cerithideo. Entry was through the aperture for on wood. Smaller aggregations occurred on gastropods, and the shell gape inLaternuls. the concrete. Many of the C. capucinus on the The largest number (50) of individuals wall were clumped into small holes and observed feeding during the major survey was depressions, frequently with egg masses in the mangroves, followed by the sandflat deposited in the depressions. Groups of up to (28). However, because of the marked 14 individuals were recorded. differences in density of C. capucinus, the In contrast, most of the C. capucinus on the proportion of animals feeding on the sandflat sand occurred as single individuals. Howeveq, (45 %) w as much higher than in the mangroves even here the animals were not evenly (9 %). OnIy 7 individuals, or 7 o/o, on the wall distributed. The centre of the study area is were feeding, and no animals found on the higher than the margins of the concrete wood or on rocks were feeding. Despite the rectangle. The sand is coarser and dries out small numbers of animals feeding on the wall, for a longer period than the margins. Few C. the prey was most diverse, with four food capucinus occurred in this area. The animals items being consumed (Table 3). The dominant

Table 2. Feeding habits of Chicoreus capucinus on a sandflat at Ang-Sila, Thailand during the first week of November 1999. Numbers in parentheses are for a supplemental survey on the sandflat and in the mangroves on 9 November 1999.

Concrete Dead Mangrove Mangrove )ano l(ocK Tnr:l watl,, wood inside pen outside pen Numberof feeding 62 (s0) 31 1 555 (136) 7378 (786) observations 679 50 Number feeding 28 (36) 7 0 0 0 s0 (s3) 8s (8e) Percent feeding 45(72) 1 0 0 0 e (3e) 6 (48) Phuket Marine Biological Center Special Publication 25 (1): 3L-39 (2001,) 35

prey was the gastropod Cerithidea sp., which Laternulo sp., which burrows 2-3 cm into the comprised all of the prey on the sandflat and mud. The snails were on the mud surface and 64 "/o of the prey in the mangroves. In total, extended their proboscis down the hole to the Cerithidea sp. was 77"/o of allprey items. Atotal bivalve. Bivalves dug up ranged from being of 7 species of prey items was recorded, 5 of completely intact, to partially eaten, and fully which are molluscs (four gastropods and one consumed. bivalve). There appears to be a strong selection of prey Feeding strategies in both mangroves and species on the sandflat (Table 4). Cerithidea sp. on the sandflat were thus similar, with C. was the dominant potential prey species, capucinus attacking animals on the mud accounting for 73.0 % of the potential prey surface. In addition, 76 of the snails in the items, but comprising all of the prey mangroves were found feeding on the bivalve consumed. Neritinn sp. (in mangroves) and Clypeomorus sp. (on the wall) are in fact consumed, but in small numbers. There is also Table 3. Prey of Chicoreus capucinus on a selection of larger Cerithidea sp. as prey (Fig. sandflat at Ang-Sila, Thailand. 1). The mean size of animals on the sandflat Con- . tvlan- _ , was 19.0 mm, but the mean size of Cerithideo Prey Sano crete rotal groves mm; the difference was watl,, sp. consumedwas2T.0 statistically significant (t-test, p<0.05). In MOLLUSCA contrast, the Clypeomorus were in the range of Cerithidea sp. 64 0 75 739 10-12 mm, and most of the Neritine sp. were Clypeomorus sp. 0 2 24 smaller than 5 mm, suggesting these species Planaxis niger 0 2 02 were ignored because of their small size. While C. capucinus on the sandflat chose Neritina sp. 0 0 11 large Cerithidea sp. as prey, there is no selection Bivalves 0 0 25 25 of larger Cerithideo sp. by large C. capucinus. A CRUSTACEA total of 61 predator-prey combinations were Balanus 2 0 2 sp. 0 recorded. Predated Cerithideo ranged in size POLYCHAETA O 1 0 1 from 13 to 28 mm (mean : 27.0 mm), and Totals 64 103 774 predators ranged fuom 27 to 60 mm. The smallest predatory C. cnpucinus was in fact feeding on the smallest predated Cerithideq, a Table 4. Density of molluscs on an intertidal specimen of 13 mm. However, the second sandflat at Ang-Sila, Thailand. smallest C. capucinus was feeding on a specimen of 22 mn while the largest C. Density cnpucinus was consuming a 20 mm long Mean l(angf',, Cer ithidea. A regression analysis demonstrated Species """D',. + t S.E. Percent ' (no. m.) no statistical relationship between predator ino. m_)) length and prey length (a : 18.605, b : A.078, 376.0 Cerithidea sp. 236-404 73.0 12:0.0367). !29.2 A second survey of feeding was conducted 10.0 on the sandflat and in the mangroves on 9 Clypeomorus sp. 4-24 z-c + 3.3 November 7999 (Table 2). Feeding rates were highea 72o/" on the sandflat and 39 % in the 706.7 Neritina sp. 24-768 z+. / mangroves. All 36 C. capucinus found feeding ! 30.7 in the mangroves were predating Cerithidea Total 364-544 100.0 sp., as were 43 of the 53 individuals feeding in t 39.8 the mangroves. 36 Tropical Marine Mollusc Programme (TMMP)

Figure 1. Size frequency oI Cerithidea sp. on a sandflat at Ang-Sila, f Population size frequency Thailand. Filled square: roo Prey size frequency Cerithidea sp. consumed f] by Chicoreus capucinus. Open square: Cerithidea sp. present on the sand- flat.

789 10 1l 12 13 14 SlZE CLASSEs

Table 5. Movement oI Chicoreus capucinus from of the wall the following morning (3 the base of a concrete wall in 24 hours at Ans- November). These animals were allowed to blla. Inallano. remain undisturbed for 24 hours then the Number of distance between the shells and the wall was Distance moved (cm) animals measured, providing an estimate of the minimum distance travelled during a24hour 0 1.21 period. Nearly half (48 %) had moved during a1 1-10 JI the 24 hours (Table 5). Most had moved only 11-20 14 a small distance; 55 had moved 30 cm or less. Howeve{, 13 animals had moved over 1 m, 21-30 10 with the greatest distance travelled being 2.3 31-40 5 m. The mean movement was 46.9 + 4.7 crn. 47-50 9 51-60 9 Size 61.-70 5 A total of 954 C. capucinus were measured in 71,-80 b November 7999 (Table 6). These animals ranged insize from 18 to7Lrrrm, with a mean 81-90 6 of 421 mm.Howeve(, small animals were only 91-100 3 a small proportion of the population. Only 130 101-150 6 (13.6 %) were smaller than 35 mm. The great /l 151-200 majority (751., or 829 %) of the animals were 20r-250 3 in the middle size ranges of 35 to 54 mm. Only Total animals moving 111 33 animals (3.5 %) were larger than 54 mm. Distance travelled (Mean + 15.E.) 46.9 + 4.7 cm DISCUSSION Mortement Habitat preferences Two hundred thirty-two animals collected This study demonstrates a verv wide range of from the southern wall of the holding pen on habitats are occupied by Chicoreus capucinus 2 November were tagged in the laboratory atAng -Sila. In a small area, with a maximum during the afternoon and replaced at the base linear dimension of just over 100 m, the Phuket Marine Biological Center Special Publication 25 (1): 31-39 (2001) 37

Table 6. Size frequency ol Chicoreus capucinus on feed on a wide variety of prey items, Chicoreus a sandflat at Ang-Sila, Thailand. capucinus having been reported by several authors (Nielsen 1976; Grlbsholt 1.997; Tan Shell length (mm) Number 1999 b) to feed on oysters, barnacles, and 0-4 0 several other taxa. Almost all individuals 5-9 0 recorded feeding in mangroves at Phuket were 70-74 0 consuming the oyster Saccostrea (Gribsholt 1997).The 15-79 Z most detailed study was of feeding by C. capucinLts was undertaken Tan (2000) 20-24 aa by in mangroves in Singapore. A total of 15 25-29 52 bivalve species, 7 gastropods and 2 barnacles 30-34 54 was consumed by C. capucinus in a total of 341 35-39 727 feeding observations. In contrast, prey items 40-44 268 at Ang-Sila were more limited: 4 gastropod 45-49 Laaatl species, l bivalve, l barnacle and 1 polychaete. observations 50-54 752 Combined, the various demonstrate that a wide variety of prey items, 55-59 26 particularly molluscs, is consumed by C. 60-64 6 capucinus. Essentially the same groups of 65-69 0 animals were consumed in Singapore. In order 70-74 I of abundance the dominant prey in Singapore were: Laternula spp., Modiolus cf. metcolfei, Total 954 B aI snus smahitr it e, and Musculist a senhousi a. muricid lives on open sand, attached to hard Small numbers of Cerithidea and Neritq were substrates including rocks/ concrete walls, also attacked. While the same groups of wood, and also on the sediment surface in molluscs were predated in Ang-Sila and mangroves. While other studies have not Singapore, the relative abundances in the two demonstrated such a wide habitat diversity in areas were very different, reflecting differences a small area, C. csaucinus is known to occur in prey availability. However, the studies at on the prop roots of Rhizophora (Wells & Slack- Ang-Sila demonstrated that C. capucinus does Smith 1981; MiddelfartTggT; Gribsholt 1997) not respond entirely to prey availability, but and on muddy sand (Houart 1992).Tan (2000) selects larger potential prey. Tan (2000) recorded C. capucinus on the mangrove floor believed the diet changes from small at a mean density of 3.6 m-2, a density similar gastropods and bivalves to larger gastropods, to that found at Ang-Sila. Gribsholt (1.997) barnacles and other bivalves as the snails recorded a mean density of 0.3 m-2 at Phuket. grow. While this may be true, there was no The Phuket study area was divided into four relationship demonstrated at Ang-Sila substrata, with the maximum density of 2.5 between shell lengths of C. capucinus and the m-2. The animals in Phuket had variable dominant prey, Cerithidea sp. habitats, being found on prop roots of Feeding rates at Ang-Sila were extremely Rhizophora, on the mud surface between roots, variable, ranging from zero on rocks, wood and on the open mud surface away from the and among the mangroves inside the crab pen mangroves. Most were found on the prop to 45 "/" on sand; the average was 6 "/". roots (Gribsholt 7997\. Gribsholt (7997) also recorded variable feeding rates, ranging from 5 to 70 % in the four Feeding substratum types examined. Tan (2000) found Muricids, including Chicoreus, are well known L6 % of C. capucinus in association with prey. to be active predators. As a family, muricids The majority (78.8 %) of prey consumed in 38 Tropical Marine Mollusc Programme (TMMP)

Singapore were drilled. The remainder were Congress and Workshop of the Tropical attacked through the aperture or the shell gape Marine Mollusc Programme, which allowed of bivalves (Tan 2000). Tan was not able to the research to be conducted. determine how entry was achieved through Dr. Tan Koh Siang of the National University the operculum in specimens not drilled. of Singapore very kindly provided advice and Secretions of the accessory salivary glands and information on C. capucinus, a draft of his the hypobranchial glands of many gastropods manuscript and some of the literature we have choline esthers, which are used to examined. paralyse prey (Andrewset a\.1991). However, Tan (2000) reported that the accessory salivary REFERENCES gland is absent inC. capucinus. He speculated Andrews,E.B., M.R.Elphick & M.C.Thorn- that there is a secretion of the hypobranchial dyke, 7991.. Pharmacologically active gland, which immobilises prey. In contrast to constituents of the accessory salivary and Singapore, where drilling is the dominant hypobranchial glands of I'lucells lapillus. - form of prey attack, only one prey individual Journal of Molluscan Studies 57:136-738. at Ang-Sila was drilled. Aungtonya,C. & V.Vongpanich, 1'997. Chicoreus capucinus is the major predatory Reproductive biology of Chicoreus capucinus gastropod at Ang-Sila. The data presented (Lamarck, 7822) from Phuket Island, above suggests the muricid plays a substantial Thailand. - PhuketMarine Biological Center role in structuring the molluscan assemblage Special Publication 17: 83-88. on the sandflats and in the mangroves of the Grib sholt,B. 1997 . D istribution and abundance area. of Chicoreus capucinus (Lamarck, 1822) (Prosobranchia: ) in the mangrove Moaement at Ao Nam Bor, Phuket, Thailand. - Phuket No other data appear to have been published Marine Biological Center Special Publication on movement rates rnC. cnpucirus. Movement 17:47-60. rates recorded in this paper were incidental, Houart,R. 1992. The Chicoreus and and a result of tagging and replacement of the related genera (Castropoda: Muricidae) in animals in the habitat. The rates could have the Indo-West Pacific. - M6moires du been artificially high because the animals had Mus6um National d'Histoire Naturelle been disturbed for tagging. Nearly half (48%) S6ries A Zoologie 154:1-188. of the animals moved in the 24 hours after they Middelfart,P. 1,996. Egg capsules and early had been tagged and replaced in the habitat. development of ten muricid gastropods The mean movement rate was 46.9 crr.. These from Thai waters. - Phuket Marine Biological movements were recorded on an open sand Center Special Publication 16:103-130. flat. It is likely that movement rates of Middelfart,P. 7997. An illustrated checklist of individuals on prop roots of Rhizophora or Muricidae (:Prosobranchia) among the pneumatophores of Auicennia from the Andaman Sea, Thailand. - Phuket would have moved significantly less. Marine Biological Center Special Publication 77:349-388. ACKNOWLEDGEMENTS Nielsen,C. 1976. Notes onLittorina andMurex F. Wells would like to acknowledge Prof' from the mangrove at Ao Nam-BoI, Phuket, Suchart Upatham, Dean of Science at Burapha Thailand. - Research Bulletin of the Phuket University, for the invitation to present the Marine Biological Center 17:7-4' workshop in marine molluscs and for Tan,K.S. 1999a. Imposex inThsis gradata and arranging the subsequent research visit. Prof. Chicoreus capucinus (, Neogastro- of Jorgen Hylleberg provided an invitation and poda, Muricidae) from the Straits ]ohor: partial airfare for participation in the Tenth a case study using penis lengt[ area and Phuket Marine Biological Center Special Publication 25 (1): 31-39 (2001) 39

weight as measures of imposex severity. - Cyprus, June 2000. In press. Marine Pollution Bulletin 39: 295-303. Wells,F.E. & C.W.Bryce, 2000. Seashells of TaruK.S. 1999b. Molluscs. Pages 101-128 in: Ng, Western Australia. Western Australian P.K.L. & Sivasothi, N. Aguide to themangroaes Museum, Perth. 208 pages. of Singapore. Il diaersity. Singapore Wells,F.E. & S.M.Slack-Smith, 7987. Zonation Science Centre, Singapore. of molluscs in a mangrove swamp in Tan,K.S. 2000. Feeding habits of Chicoreus northwestern Australia. Pages 265-274 in: capucinus (: Muricidae) in a Biological Surztey of Mitchell Plqteau and Singapore mangrove. Paper presented to the Admiralty Gulf Kimberley, Western Australia. international neogastropod symposium, Western Australian Museum. Perth.