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Phuket Marine Biological Center Special Publicntion 25 (1): 41-50 (2001) 41,

Observations on the feeding habits of nntator (: : ) in Singapore

G.W.K. Neo, L.M. Chou & K.S. Tan

Neo, G.W.K., L.M. Chou & K.S. Tan.2001. Observations on the feedinghabits of (Gastropoda: Tonnoidea: Ranellidae) in Singapore. - Phuket Marine Biological Center Special Publication 25(1): 41-50.

The diets of ranellid gastropods are little studied. Of several whose diets have been investigated, most are carnivorous, feeding on a wide variety of invertebrates, but Gyrineum natator is an exception in being omnivorous. In this study, field observations, gut content analysis and aquarium studies were done to determine the diet of G. natator. Field observations were made during daytime low tides over a period of three months between July 7999 and October 1999, and again during July 2000. Of a total of 360 individuals observed in the field, none were seen to be feeding, suggesting that these gastropods do not feed during low tide. Howevel, analyses of stomach and rectal contents revealed a high proportion of algae (47 %), sponges (43.5 %) and hydroids (31.2 "/"), with occasional occurrences of broken setae and barnacle cirri (both <20%) in a total of 21.0 samples examined. Aquarium observations also showed that G. natntor feeds on macroalgae, sponges and possibly bivalves, but not on serpulids, gastropods, echinoids and holothurians. These results confirm the observations of a previous study that G. natator is an atypical ranellid that consumes mainly algae and sponges, unlike other members of the same family whose diets consist of gastropods, echinoderms, ascidians, cirripeds and sedentary . Nonetheless, G. natator shares with other ranellids in possessing,Iarge, highly developed, acid-secreting salivary glands, whose purpose and function remain enigmatic in the light of the above mentioned observations.

G.W.K. Neo and K.S. Tnn. Tropical Mnrine Science lnstitute, National Uniaersity of Singapore, L0 Kent Ridge Crescent, Singapore 119260. E-mail K. S. Tan: [email protected] L.M. Chou. Department of Biological Sciences, Nstional Uniaersity of Singapore, Blk 52,14 Science Driae 4, Singapore L17543.

INTRODUCTION tively. The diets of ranellids, on the other hand, The neotaenioglossan gastropod superfamily differ from the other families in that they Toruroidea comprises four families, namely the consist of living and dead , , and Ranellidae representing a wide range of taxa (Riedel according to a recent taxonomic treatment by 1995). Of a total of 15 genera (80 species) in Beu (L998). Bursids prey on polychaetes and the family Ranellidae (Beu 1,998), the diets of sipunculans (Houbrick & Fretter 7969; Taylor only five genera (10 species) were investigated. 1978), while cassids and personids are These ranellids studied so far have generalist specialist echinoderm- (Hughes & Hughes diets, encompassing a wide variety of prey 1971,, 1981,; Hughes 1986; Morton 1991) and such as bivalves (Houbrick & Fretter 7969; polychaete-feeders (Taylor et al. 7980) respec- Laxton 797I; Littlewood 7989; Morton 1990), 42 Tropical Marine Mollusc Programme (TMMp)

gastropods (Houbrick & Fretter 7969; Taylor between july and October 1999, and again 1984), asteroids and ophiuroids (Laxton 7971), during July to August 2000. Each observation ascidians (Laxton 1971; Morton 7990), period lasted between 2 to 3 hours. The cirripeds (Morton 1990) and polychaetes (Duy gastropods were emerged during low spring 7969; Houbrick & Fretter 1969). tides (tidal height 0.3 m and below; Singapore Gyrineum natator (Roding) is an intertidal Tide Tables and Port Information 1999,2000). Indo-Pacific ranellid (Beu 7998) which has a Gyrineum natator was common at the base of diet quite unlike those of its carnivorous seawalls located along the beach at East Coast counterparts. In addition to other prey items Park, whereas at Changi Beach Park they were such as sponges, polychaetes, bryozoans, mostly on seawater supply pipes and under bivalves and crustaceans (Taylor 1,980; Taylor small rocks on muddy sand. A thorough & Morton 1996), substantial amounts of algae search was conducted at each site for G. nntntor. were found in gut samples (Thylor 1980). From For each individual found, the substrate on what little we know about the feeding ecology which it was attached to and feeding activity, of cassoideans, algae are absent in the diets of if any, were noted. The animals were tonnoideans other than G. natator.It is peculiar considered to be feeding when its proboscis is that G. natator ingests algae because its foregut everted and actively probing a particular anatomy does not differ from other tonnoide- substrate. ans. They all possess large, highly developed acid-secreting salivary glands, which allow Gut content annlysis cassids and ranellids to dissolve or anaesthe- Gyrineum nqtqtor were collected in the field tise prey (Duy 7969; Houbrick & Fretter 1969; and were broughtback to the laboratory. These Hughes & Hughe s 7981; Hughes 7986; West were boiled immediately and preserved in et nl. 7998). Whilst G. natator is capable of 80% ethanol. Subsequently, the animals were dissolving holes through young oyster shells cracked and their stomach and rectal contents in aquaria (Taylor 7998), attempts to observe were removed. The gut contents were G. natator feeding in the field were generally mounted on glass slides in Aquamount@ for unsuccessful (Taylor & Morton 1996; Neo examination under the compound micro- 7999), and there is little else to suggest that G. scope. nqtator has feeding habits that complement its foregut anatomy. Aquarium studies Available information on the diet of G. Several prey items were introduced to natator is currently based solely on the analysis Gyrineum natator in aquaria, including those of their gut and faecal remains of Hong Kong that were found together in the same habitat. specimens (Taylor 7980; Taylor & Morton The snails were starved for two weeks prior 7996). Detailed field and aquarium to transferring them into perforated vials each observations are needed to verify these results. containing a prey item. The following prey In this study, the feeding habits of Gyrineum items were presented to G. natqtor: a sponge natator were determined by a combination of C ally sp on gia sp . (Callyspongiidae ); two species field observations, gut content analyses and of green algae Enteromorpha sp. (Ulvaceae) and aquarium studies. This will allow us to Ulaa sp. (Ulvaceae); gastropo ds Nerita compare the feeding ecology of G. natator with chamaeleon (Neritidae) and l/odilittorinn other tonnoideans. trochoides (Littorinidae); bivalves P ernn airidis (Mytilidae), Xenostrobus sp. (Mytilidae) and MATERIALS AND METHODS Saccostres cucullata (Ostreidae); polychaetes Field obseraations P eriner eis sp. (Nereidae ) and Hy dr oides ele g ans Feeding observations of Gyrineumnntstor were (Serpulidae); echinoderms Salmacis sp. (E made in Singapore during daytime low tides chinoidea : Temnopleuridae ) and P ent act a sp . Phuket Marine Biological Center Special Publicstion 25 (L): 4L-50 (2001) 43

(Holothuroidea: Cucumariidae). Except for the observation (low spring tides), all individuals high littoral gastropo d Nodilittorina trochoides were inactive, and none were feeding although and two mussels P. airidis andXenostrobus sp., many were found adhering to various the other organisms occur in the same habitat organisms. These organisms include serpulid as that of G. natator.Prey items were identified polychaetes (22.7 "h of 362 G. nntqtor indivi- with the aid of Imajima (7976), Teo & Wee duals), sponges (5.2 %), cirripeds (2.5 %) and (1983), Cannon & Silver (1986), Tan & Ng ascidians (0.6 %). Howeve4, the bulk of the (1995) and Hooper (2000). In nearly all gastropods (68.7 %) were attached to "bare" experiments, the set-up comprised 20 substrate not occupied by any obvious sessile treatment replicates (snail + prey), 10 control organism (Figure 1). replicates (prey only) and another 10 control replicates (snail only). The control snails were to ensure that all the gastropods for the aquarium experiments had no stomach or rectal contents at the time of introduction. In the cases of P. airidls and Xenostrobrs sp. as (}c' prefi two individuals were introduced into g ()(J each vial (total 20 replicates) containing one () G. nntator. es In order to quantify the amounts of sponge and algae consumed, their wet weights were measured before and at the end of three and five days respectively. Faecal pellets produced by the gastropods were collected every day and examined for presence of sponge spicules Figure,;;^'-"::""r'::,:::::,.:T:}]:", and algal remains. Mean loss in wet weight intertidal substrata during daytime low tides along was calculated for control and predator vials the east coast of Singapore. A total of 362 in both experiments, and were compared individuals was examined in the field during the using t-test for each food item. periods July-October 1.999 and July-August 2000. found algae. Serpulans were introduced intact, i.e., with None were on calcareous tubes encasing the live polychaetes, Gut content analyses and these were checked for signs of predation Stomach and rectal contents of G. natator every day for five days. Other prey items were mostly contained algae (47 % of 270 indivi- similarly checked every day during the duals dissected), sponges (43.5 %) and experimental period. Feeding observations, if hydroids (31,.2 %). Seven species of algae were any, were noted. recorded in a total of 21,0 individuals examined. Red algae occurred most RESULTS frequently, with Stylonemn alsidii (Bangio- Field obseraqtions phycidae) and Erythrotrichiq sp. (Bangio- In the field, Gyrineum natator were usually phycidae) being the two predominant species found under rocks and between cracks and seen (Table 1). Green algae found in the gut crevices of large boulders. Many of these samples comprised of Cladophora sp. and gastropods were seen in groups of three or Enteromorpha sp., with Schizothrir sp. being the four individuals along the base of vertical sea onlyblue-green alga (Table 1). Sponge spicules walls, and were typically present in densities occurring in the gut contents were composed between two and four individuals per m2. of both megascleres and microscleres. There Shell heights of G, natqtor ranged between 14 : were chiefly two main types of megasclere and 37 mm (n 362). During the periods of spicules: oxeas and tylostyles. They consti- 44 Tropical Marine Mollusc Programme (TMMP)

Table 1. Breakdown of items found in the belonged to two families, Plumulariidae and stomach and rectum of Gyrineum nntator (n:210) Sertulariidae, with the latter occurring more from Singapore. often (40 sertulariid occurrences as compared to29 plumulariids; n:65).Other items found Prey items found in the Number of stomach and rectum of occunences were polychaete setae, barnacle cirri, Gyrineum natator (n:210) crustacean fragments, gastropods, bry ozo ans and ascidians (Figure 2A). Individuals without Total Algae recognisable contents in their gut comprised BACILLARIOPHYTA 11,.4 % of the total number of G. nntator Diatoms 18 examined. Other unidentified items occurring CYANOPHYTA in the stomach contents comprised of Schizothrix sp. 20 muscular and sponge-like tissue. All individuals examined contained more than CHLOROPHYTA one prey item (Figure 2B). More than 50 % of Cladophora sp. 43 all G. natator examined had two main items in Enteromorpha sp. 25 their gut, mainly a combination of algae and RHODOPHYTA sponges, or algae with hydroids. Bangia sp. 22 Erythrotrichia sp. 27 AQUARIUM STUDIES Polysiphonia sp. 16 Algne (1) Enteromorpha sp. Stylonema alsidii 29 Gyrineum nntator was observed feeding Foraminifera 46 directly onEnteromorpha sp. Gyrineum would crawl over the algal mass its proboscis Sponge spicules 91. with everted slightly. The algal thalli were then Oxea type 80 spicules consumed by 'sucking' action made by Tylote type spicules 7 peristaltic action of the proboscis wall. Sigma type spicules 6 Caulerpa sp. was consumed in a similar Hydroids 65 manner in one qualitative observation (pers. obs.). By d,ay, Plumulariidae 29 the secbnd 5 of 20 vials 1iS "t 7 Sertulariidae 40 containing Enteromorpha sp. and G. nntator were devoid of algae, with only faecal pellets Polychaetes 15 remaining in the vials. These faecal pellets Nereidae 10 contained large pieces of decolourised aIgal Serpulidae 8 filaments. At the end of five days, algae in 15 Gastropoda 2 of 20 vials (75%)were all consumed. The mean loss in wet weight of algae vials containing Triphoridae the predator was significantly greater than Barnacle cirri 74 algae in vials without the predator (t: -5.15, Other crustacean 11 df : 28, P < 0.01, one-tailed test). Snails in FRACMENTS control vials produced faecal pellets devoid Bryozoa 18 of algal filaments. Ascidians 7 Algae (2) IJlva sp. Unidentified items 27 We were unable to observe G. natator feeding on Ulaa directly. However, faecal pellets tuted 38 % and 3.3 "/" of 270 gut samples produced by G. natntor in the predator vials dissected, respectively. Sigma-type micro- contained algal remains. Also, the mean wet scleres were also found but were not abundant weight difference of the alga in the predator (2.9 %). Hydroid bodies in the gut of G. natator vials before and after five days was Phuket Marine Biological Center Special Publication 25 (1): 47-50 (2001) 45

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Figure 2. Analysis of stomach and rectal contents of Gyrineum natator. (A). Relative proportions of various items found in the stomach and rectum of a total of 270 individuals dissected. The rectum and stomach were empty (as indicated by "empty contents") in about 10% of the total number of G. natator examined. (B). Number of different kinds of items found in G. natator significantly different (t : -2.92, df :28, P < control and treatment vials before and after 0.01, one-tailed test)compared to the controls, the experimental period did not differ suggesting that Ulaa was indeed consumed. significantly (t: - 1.22, df :28, P : 0. 12, one- Snails in control vials either did not defecate, tailed test). In vials containing only G. natator, or produced faecal pellets with no algae in faecal pellets were found, but no sponge them. spicules were present in the pellets. Although the consumption of Callyspongia sp. was not Sponge as prey observed directly, the introduction of the The sponge Callyspongia sp., was eaten by G. sponge caused at least three G. natator natator. Sponge pieces in all20 vials containing individuals to immediately approach with the predator were consumed by G. nntator their proboscis everted and wrap their foot within one day after the commencement of the around the sponge within five minutes. The experiment. This was revealedby the presence experiment was terminated after three days of sponge spicules in the faecal pellets when it was observed that more than 50% of collected on the second day. Radular and jaw the sponges were decolourised. fragments were also present. This clearly showed that the gastropod actively fed on the Bianlaes (1) Perna viridis sponge. However, the mean percentage There was no predation by G. nntqtor (mean difference in wet weights of sponges in the shell height + std. dev. :29.8 + 3.1 mm, n: 46 Tropical Marine MoIIusc Programme (TMMP)

20) on juvenile P. airidis (mean shell length : during daytime spring low tide conditions, as 1,6.9 t 4.6 mm, n : 40) during the first four also observed by Taylor & Morton (1996) in days. Control vials containing only the mussel Hong Kong. All of the 362 G. natator all remained alive after four days. One mussel individuals were not seen moving or feeding died on the fourth day. On the fifth day of the during the several observation periods in the experiment, howevel, one mussel in a predator field. As G. nqtator is an intertidal organism, it vial was eaten and there were no shells or is susceptible to dehydration during low tides. tissue remaining. A possible strategy to avoid dehydration would be to remain stationary. Biaalues (2) Xenostrobus sp, Their occurrence on or near other organisms In the Xenostrobus experiment (predator mean might be an indication that they were feeding shell height + std. dev : 28.4 + 4.4mrn, n:20; on them when G. natator were covered by the prey mean shell length + std. dev. : 1,4.9 + 7.6 tides. It was noticed that a substantial mm, n:40), all individuals in the control vials proportion (22.7 %) of these gastropods was were alive except on the last day of the seen on serpulid tubes, but was not feeding experiment when two mussels died. On the on them. In aquarium observations, G. natqtor second day of the experiment, one of 40 generally did not feed on the serpulid mussels (2.5 %) in the treatment vials was elegans, although one of twenty preyed upon. Thereafteq, six (I5 % of total serpulids (5%) was eatenwhole. The quantity mussels), two (5 %) and four (I0 %) mussels of setae found in the stomach and rectum of were eaten on the third, fourth and fifth day G. natator collected in the field was too small respectively. Altogether, 10 G. nqtator to suggest deliberate consumption of poly- individuals consumed 13 mussels (32.5 %) in chaetes. Even though there were 25 occurren- the treatment vials after five days. TWo snails ces of serpulid setae registered in the stomach consumed two Xenostrobzs individuals each and rectal contents of G. natator (Table 2) there in the course of the experiment. were only 1-4 setae per gut dissected. Serpulid opercula were never present in the gut of G. Other prey nntator in the field. It is more likely that Most of the G. natqtorindividuals in aquarium serpulids and other polychaetes were ingested studies did not prey on the serpulid in the course of feeding on other organisms. polychaete, . All serpulids in Nevertheless, the high incidence of G. natator treatment and control vials remained alive occurring on serpulid tubes in the field might during the five-day experimental period suggest that it is perhaps feeding on organisms except for one serpulid, which was eaten on living on the surfaces of these tubes. Caulerpa the fifth day of the experiment. Careful sp., for example, was one of the few small dissection of the gut of G. nntator revealed the organisms that were found interspersed on intact serpulid in its oesophagus. rocks with serpulid tubes, together with other Other prey that were introduced to G. natntor errant polychaetes and foraminiferans (pers. in aquarium studies but were not eaten after obs.). When the green alga Caulerpa sp. was five days were the polychaete Perineris sp., the introduced to C. natqtor in aquarium gastrop o ds N er it n ch qm ael e o n and Ir'i o dilit t o r in a experiments, the gastropod fed on it. Gut trochoides, the rock oyster Saccostrea cucullnta, content analyses also showed that the barnacle Balanus amphitrite, the echinoid foraminiferans were ingested, although it Salmacis sp. and the holothurian Pentacta sp. remains to be seen if these were consumed purposefully. It is possible that G. natator were DISCUSSION grazing on the organisms attached to the Field observations on Gyrineum nqtator clearly surfaces of serpulid tubes. Similarly, the showed that this gastropod does not feed occurrence of G. natatol on barnacles and Phuket Marine Biologicnl Center Special Publicstion 25 (7): 41-50 (2001) 47

ascidians does not indicate predatory activity their habitat. but rather, suggest that G. natator may be The only other neotaenioglossan gastropod feeding on other small organisms attached to group whose members have a similar diet of them (such as hydroids; see below) that were consuming algae as well as sponges are the overlooked the time of observationbecause of Cypraeidae (Wilson, 7998). Unlike their small size. tonnoideans howeveq, the salivary glands of About 5 % of G. natator in the field were cowries are not hypertrophied. Although found on sponges but were not seen feeding Gy r ineum nat at or have a similar taenio g1o ssate on them. However, more than 40 % of radula as that of the cypraeids, the cusps of individuals examined for their gut contents the rachidian and laterals are comparatively contained sponge spicules. Megascleres, pointed compared to the smooth-edged teeth especially the oxeas type, formed the bulk of found in the cypraeid radula. Despite these spicules found (38.1 "/" of 186 samples), differences, G, natator and many cypraeids although tylotes were seen as well (3.3 %). have evolved similar feeding habits. It may Sigma-like microscleres were rare (2.9 %). be interesting to compare their anatomical and Gyrineum natator consumed the sponge secretory adaptations further. Callyspongiasp. in aquaria, as evident from the Hydroid bodies found in the gut contents oxea-type spicules found in faecal pellets of G. nntator were from two families, namely producedby the gastropods during the course the Plumulariidae and Sertulariidae. The of the experiment. Nonetheless it is probable frequent occurrence of these small hydroids that they feed on other sponges which have in the gut of G. natntor (31.2% of 270 samples) tylotes and sigmas as their structural elements. suggests that it preys on hydroids although it About 47 % of G. natator individuals is equally possible that algae consumedby G. obtained from the field contained algae in their natator have hydroids attached to them and gut, although none were actually seen feeding are ingested together. Aquarium studies will on them at low tide. At least seven types of determine if the occurrence of hydroids in the blue-green, green and red algae were found gut is merely the result of incidental ingestion in G. natator, but brown algae were or are actually part of the diet of G. natator. conspicuously absent. The green alga Although ranellids are known to consume Enteromorpha sp. was found in gut samples bivalves (e.9., Houbrick & Fretter 7969;Laxton and consumed in aquarium experiments. 1,977; Littlewood 1989; Morton 1990), the Caulerpa sp. was not found in the gut of G. behaviour of Gyrineum natator towards natator from the field, but can feed on it in bivalves remains equivocal. Of the three aquarium conditions (Neo, 1999). Similarly, bivalve species introduced to the predator in Ulaq sp. was not recorded via gut content aquaria, only one, the high-shore mangrove analysis but was consumed in aquaria. Red mussel Xenostrobus sp, was consumed in small algae occurred most frequently amongst the quantities. However, this mussel is never different types of algae in the stomach and found in the same habitat as G. natator. The rectal contents of G. natator, with Stylonema common green mussel Perna uiridis was qlsidii recorded most frequently. It is not generally not consumed, although one known why G. natator had more red algae in juvenile was swallowed whole by G.natator, the gut as compared to green algae and blue- indicating that the predator can feed on it. In green algae. Preference experiments will contrast to the observations of Taylor (1998) determine if G. natator preferentially consumes who reported that G. natntor dissolved a large red algae over green algae. However, the hole in the shell of juvenile Snccostrea cucullata, absence of brown algae in the gut contents none of the oysters provided to G. natator in suggests that G. natqtor prefers red algae over aquaria were preyed upon in this study. The brown algae since the latter are abundant in bivalves remained uneroded and alive after 48 Tropicnl Mnrine Mollusc Progrnmme (TMMP)

Table 2. Summary and comparison of food items consumed by members of the Ranellidae (sensu Beu 1,998) as reported in published sources and from this study. A: aquarium studies; F : field observations; 6 : gut content analysis.

Prey items g*,qE.g Subfamily speues $$Hggg$H$g$s€$ Cymatiinae Charania capax Laxton (1971) AF

Cabestana splengen Laxton {1971)AF

Cymatium genmatum Houbrick & Fretter (1969) A

Cynatium nicobaicum Houbrick & Fretter (1 963) A

Cymatiun pileare Littlewood (198S)Af

Linatella caudafa Morton {1990}A

Monoplex ausfralasla Laxton {1971) AF

Argobuccrnum argrs Day (1969) A

Gyrineum natator **** * Taylor {1980} G, Taylor & Morton (1996)AC

n***'*lr *** This study AG

one week. An interesting observation is that mainly on algae and sponges. This is evident for all the bivalves introduced to G. natator, from gut content analyses and is further the predator positioned its foot over the confirmed via aquarium studies. Cyrineum valves. The proboscis would then be everted natqtor is truly an atypical ranellid, in contrast to probe the gap between the valves. Neo to other members this family which prey on a (1999) observed G. natatol attempting to variety of gastropods, polychaetes and wedge open Xenostrobus sp. by using its echinoderms (Table 2). Nonetheless, G. natator , much like how another possesses features characteristic of ranellids, ranellid, Cymatiumpilenre, gained access to its such as hypertrophied salivary glands (Taylor bivalve prey Crassostren rhizophorae & Morton 1998). It is capable of dissolving (Littlewood 1989). Howeve4, this reaction to holes through bivalve shells (Taylor, I99B) as introduced prey might not be its preferred well as seeking out and consuming polychaete method of gaining access to its prey as there prey (Taylor 1980,1982). At the same time, it were no signs of chipping of the valves. In has adopted a " grazing" lifestyle, feeding on other ranellids, secretions of the salivary sessile organisms such as sponges and algae. glands were typically used to dissolve Crude extracts (pH:3, personal observation) calcareous tubes of polychaetes (Duy 7969) and taken from the accessory salivary glands of G. anaesthetise prey (Day 1969; Houbrick & natator were tested on a variety of potential Fretter 1969; West et al.1998). The absence of prey items such as algae, sponges, gastropods etch marks on the surfaces of the shells of P. and bivalves, but no obvious reaction was airidis and Xenostrobus sp. suggests that G. noted (pers. obs.). In the case of ranellids natator gained access to its shelled prey by as whose foregut anatomy are well known, all yet unknown means. correlate well with their observed diet. This is In conclusiory G. natntor appears to be an observed in Cymntium (Andrews et al. 1999) omnivorous browser of sessile organisms on and (Duy 7969). Howeveq, the the intertidal shores of Singapore, feeding salivary glands of G. nqtator have not been Phuket Marine Biological Center Special Publicntion 25 (1): 41-50 (2001) 49

investigated in any detail. The secretory Hughes,R.N. & H.P.I.Hughes, 197L A study constituents of the salivary glands should be of the gastropo d tuberosq (L.) preying examined to better understand the relation- upon sea urchins. - Journal of Experimental ship, if any, between its foregut anatomy and Marine Biology and Ecology 7:305-314. its observed diet. Hughes,R.N. & H.P.I.Hughes, 1981. Morpho- logical and behavioural aspects of feeding ACKNOWLEDCEMENTS in the Cassidae (Tonnacea, Mesogastro- We would like to thank Associate Professor poda). - Malacol ogia 20 385-402. Lawrence M. Liao (University of San Carlos, Imajima,M. 7976. Serpulinae (Annelida, The Philippines) for help with the identi- Polychaeta) from Japan. - Bulletin of the fication of algae. Thanks are also due to Dr. National Science Museum Series A Serena Teo (Tropical Marine Science Institute, (Zoology) 2:229-248. National University of Singapore) for help in LaxtoryJ.H.1977. Feeding in some Australian identification of sponges, and to Mr. Oh Tze (Gastropoda:Prosobranchia) - Ming, for kind assistance in field. Zoological Journal of the Linnean Society 50:1-9. REFERENCES Littlewood,D.T.J. l9B9 . Predation on cultivated Andrews,E.B., A.M.Page & J.D.Taylor, 7999. Crassostrea rhizophorae (Guilding) by the The fine structure and function of the gastropod pileare (Linnaeus). - anterior foregut glands of Cymatium Journal of Molluscan Studies 55: 1,25-1,27. Morton,B.1990. Prey capture, preference and int erme dius (Cassoide a. Ranellid ae ). - |ournal of Molluscan Studies 65:1-19. consumption by caudntq (Castro- Beu,A.G. 7998. Indo-West Pacific Ranellidae, poda: Tonnoidea: Ranellidae) in Hong Kong. Bursidae and Personidae (: - |ournal of Molluscan Studies 56: 477-486. Gastropoda). A monograph of the New MortoruB . lggl.Aspects of predation by Caledonian fauna and revisions of related zonatum (Prosobranchia : Tonnoidea ) feeding taxa. R6sultats de Campagnes MUSOR- on holothurians in Hong Kong. - Journal of STOM volume 19. M6moires du Mus6um Molluscan Studies 57 :77-19. National D'Histoire Naturelle 77 8:1-255. Neo,C.W.K. 1999 . Feeding biology of Gyrineum Cannon,L.R.G. & H.Silver, 1986. Sea Cucum- nat ntor (Gastropoda: Cassoidea: Ranellidae). bers of Northern Australia. Queensland Unpublished F{onours Thesis. National Museum, Brisbane. 60 pp. University of Singapore. Day,j.A. 1969. Feeding of the cymatiid Riedel,F. 7995.An outline of cassoidean phylo- gastropod Argobuccinum argus, in relation to geny (Mollusca, Gastropoda). - Contribu- the structure of the proboscis glands. - tions to Tertiary & Geology 32: American ZooIo gtst 9 : 909 -91,6. 97-1.32. Hooper,J.N.A. 2000. Sponguide: Guide to Singapore Tide Tables and Port Information, sponge collection and identification. 1999. Hydrographic Department, Maritime Queensland Museum, Australia. 1a0 pp. and Port Authority of Singapore. a76 pp. Houbrick,I.R. & V.Fretter, 1969. Some aspects Singapore Tide Tables and Port Information of the functional anatomy and biology of 2000. Hydrographic Department, Maritime Cymatium and Burso. - Proceedings of the and Port Authority of Singapore. a00 pp. to Malacolo gical Society of Londo n 38: 415- 429 . Tan,L.W.H. & P.K.L.Ng, 1995. A Guide Hughes,R.N. 1986. Laboratory observations Seashore Life. Singapore Science Centre, on the feeding behavioul, reproduction and Singapore. 159 pp. morphology of echinophora TayloaJ.D.l97B. Habitats and diets of preda- (Gastropoda: Cassidae). - Zoological Journal tory gastropods at Addu Atoll, Maldives. - of the Linnean Society 86: 355-365. ]ournal of Experimental Marine Biology and 50 Tropical Marine Mollusc Programme (TMMP)

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