The surf clam Mactra violacea (Bivalvia: Mactridae) is a fairly large marine clam with high meat content. These clams are

found in the surf zone of exposed sandy beaches. The proximate composition of M. violacea was studied. Moisture, crude

protein, crude fat, acid insolubles and ash were estimated. The protein content of M. violacea was estimated as 11.9 %, fat

1 %, ash 3.2 % and moisture 80 %. The surf clam is a good source of protein and minerals and has low fat content. The

nutritive value is high and comparable to other shellfishes

Laxmilatha, P

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147Indian J. Fish., 56(2) : 147-150, 2009Proximate composition of the surf clam Mactra violacea (Gmelin 1791)P. LAXMILATHACalicut Research Centre of Central Marine Fisheries Research InstituteWest Hill P. O., Calicut-673 005, Kerala, Indiae-mail: laxmil@yahoo.comABSTRACTThe surf clam Mactra violacea (Bivalvia: Mactridae) is a fairly large marine clam with high meat content. These clams arefound in the surf zone of exposed sandy beaches. The proximate composition of M. violacea was studied. Moisture, crudeprotein, crude fat, acid insolubles and ash were estimated. The protein content of M. violacea was estimated as 11.9 %, fat1 %, ash 3.2 % and moisture 80 %. The surf clam is a good source of protein and minerals and has low fat content. Thenutritive value is high and comparable to other shellfishes.Keywords: Mactra violacea, Proximate composition, Surf clamClams are one of the important varieties of shellfishand perhaps the most versatile seafood in the world. Theseedible bivalves are filter feeders; thereby have highconversion efficiency and consequently high levels ofbiochemical constituents. Clams are high in protein andthe nutritive value of several species of clams has beenestimated (Lakshmanan and Nambisan, 1981; Wenne andStyczyska-Jurewicz, 1987; George and Gopakumar, 1995;Dincer, 2006).  Shellfish meat, particularly clam meat havebeen recommended in several dietary regimes for theirhigh protein content, low calorific values, low fat/cholesterol profile and lower proportions of saturated fat,the presence of good lipids, significant amounts of omega-3-fatty acids, dietary essential amino acids, vitamin B12and several important minerals such as iron, zinc andcopper (Krzynowek et al., 1989; Dong, 2001; Trung tamTin hoc- Bo Thuy San, 2007). Various factors affectingthe proximate composition in shellfishes such as spawningseason (Durve, 1964), fecundity (Durve, 1964; Litaay andDe Silva, 2003), depth of culture area (Ngo et al., 2006)have also been investigated (Qasim et al., 1977;Nagabhushanam and Mane, 1978; Rivonker andParulekar, 1995).The surf clam M. violacea (Bivalvia: Mactridae) isa fairly large marine clam (>100 mm) with high meatcontent. These clams are found in the surf zone of exposedsandy beaches and occur in densities that will supportsignificant fisheries. These unexploited species haveattracted scientific and commercial interest and are thefocus of several investigations (Cranfield et al., 1992).This study presents the biochemical composition and thusthe nutritive value of the surf clam.NoteThe surf clam, M. violacea,  were collected by divingand picking from the surf zone along the Thalassery beach(11.75° N, 75.49° E) in Kannur district, North Kerala,during 2005. Clams could not be collected in June andduring September to December due to rough sea conditions.The clams were brought to the laboratory in live condition.After thorough washing, the shell was opened and the meatextracted, male and females identified and weighed afterremoving the excess moisture. Total weight and wet fleshweight were recorded to the nearest 0.1 g. The extractedmeat was stored at 4 °C until further analyses. Moisture,crude protein, crude fat, acid insolubles and ash wereestimated separately for males and females, according tothe AOAC (1990) procedure.  The results are presented asmean ± SD. The percentage edibility of the meat wasestimated as percentage of wet flesh weight to total weightof the clam (Durve, 1964).SPSS 7.5 for Windows program was used to searchfor significant differences between mean values for sexesand monthly variations in moisture, crude protein, crudefat, acid insolubles and ash. Differences between meanswere analyzed by one-way analysis of variance (ANOVA).Differences were considered to be significant when p<0.05.Cross correlations between the biochemical constituentswas also examined by Pearson’s Correlation test.Moisture, crude protein, crude fat, ash and acidinsoluble contents of M. violacea are shown in Table 1.The mean moisture content in M. violacea was higher infemales (80.6 %) than in males (79.7 %). The mean crudeprotein in males and females was almost same at 11.8 %and 11.9 %. The mean crude fat was slightly higher in males148P. Laxmilathaat 1.1 % as against 0.9 % in females. The mean ash contentwas higher in females at 3.3 % when compared to 3.1 % inmales. The mean acid insolubles were also slightly higherin case of females at 0.8 % than in males 0.6 %. However,differences between means of each of the biochemicalconstituents were not statistically significant (p>0.05)between sexes. Monthly/seasonal variations were also notstatistically significant (p>0.05) for any of the biochemicalconstituents.A significant positive correlation was observed in theash and acid insoluble contents (r = 0.895, p<0.01). Positivecorrelation was observed between moisture and ash(r = 0.018, p<0.01) and moisture and acid insoluble contents(r = 0.270, p<0.01) while a negative correlation existsbetween moisture and crude protein (r = -0.176, p<0.01)and moisture and crude fat (r = -0.159, p<0.01). Negativecorrelation exists between crude protein and crude fat(r = -0.209, p<0.01) and crude protein and ash (r = -0.437,p<0.01) and crude protein and acid insoluble contents(r = -0.352, p<0.01). Negative correlation was alsoobserved between crude fat and ash (r =-0.114, p<0.01)while a positive correlation exists between crude fat andacid insolubles (r = 0.114, p<0.01).The monthly variation in the meat content is shown inFig. 1. The mean meat content was 23.2 % and rangedbetween 15.2 and 26.7 %.  The meat content was highduring January to March declined during April-May andagain increased during July-August. This also reflected thechanges in the meat content in relation to the gonadalcondition. The meat content was very low during April-May when the clams are in spent condition and elevatedduring January to March and again in August when theclams are maturing.Table 2. Proximate composition (%) of selected commercially important molluscsSpecies Moisture Crude protein Crude fat Ash ReferenceMeretrix casta 77.5 13.74 2.00 1.50 Lakshmanan and Nambisan, 1981Villorita cyprinoides 82.05 9.3 1.5 2.5 Chinnamma George, 1985Perna viridis 78.27 12.8 2.24 2.72 Chinnamma George, 1985Crassostrea madrasensis 80.05 12.26 — 2.9 Chinnamma George, 1985Anadara granosa 81.3 11.7 1.1 2.4 Trung tam Tin hoc-Bo Thuy San, 2007A. subcrenulata 83.8 8.8 0.4 4.0 Trung tam Tin hoc-Bo Thuy San , 2007Paphia undulata 8.3 10.3 0.5 2.4 Trung tam Tin hoc-Bo Thuy San, 2007Meretrix lusoria 83.1 11.2 1.1 2.6 Trung tam Tin hoc-Bo Thuy San, 2007Perna viridis 85.4 9.3 0.9 2.4 Trung tam Tin hoc-Bo Thuy San, 2007Ruditapes decussatus 83.98 9.56 0.98 3.3 Dincer, 2006R. philippinarum 85.91 8.71 0.78 3.1 Dincer, 2006Mactra violacea 80.0 11.85 1.0 3.20 Present studyTable 1. Proximate composition (%) of surf clam M. violaceaMonths     Moisture Crude protein   Crude fat       Ash           Acid  insolublesM F M F M F M F M FJan 05 80.8 — 10.2 — 1.4 — 4.4 — 1.3 —Feb 77.7 80.4 11.7 11.4 1.2 0.9 3.0 3.1 0.3 0.32Mar — 80.3 — 11.3 — 0.9 — 3.9 — 1.1Apr 76.8 78.5 13.6 12.4 1.9 1.4 2.9 3.3 0.4 0.6May — 80.2 — 12.5 — 0.9 — 3.4 — 1.2Jul 82.0 82.4 11.7 11.8 0.5 0.4 3.5 3.9 1.0 1.3Aug 81.2 82.0 11.9 11.8 0.7 0.7 1.5 2.0 0.0 0.02Mean 79.7 80.6 11.8 11.9 1.1 0.9 3.1 3.3 0.6 0.8±SD 2.3 1.4 1.2 0.5 0.6 0.3 1.1 0.7 0.5 0.5M = Male, F= FemaleFig. 1. Monthly variations in meat % in M. violaceaJ F M A M J A35302520151050The evaluation of the proximate composition ofM. violacea clearly indicates that the surf clam has higherbiochemical composition comparable to those reported forseveral other shellfish species in India (Table 2). The proteinMonthMeat %149Proximate composition of Mactra violaceacontent is fairly high, almost similar to other clam speciessuch as Anadara granosa, Villorita cyprinoides andMeretrix casta and the green mussel Perna viridis. Thefat content is low while ash is high indicating that it ishigh in several of the essential trace elements. Theproximate composition is also comparable to many otherbivalve species (Table 2). The protein and ash contentis higher than those reported for several clam species(Wenne and Styczyska-Jurewicz, 1987; Dincer, 2006;Trung tam Tin hoc-Bo Thuy San, 2007).  A directrelationship exists between ash and acid insolubles whichis probably due  to the marine niche occupied byM. violacea. An inverse relationship exists between allother constituents. However, a direct relationship isreported in the backwater species, M. casta andV. cyprinoides  (Lakshmanan and Nambisan, 1981).The mean meat content in M. violacea also was veryhigh at 23 %. The meat content varies with spawningseason. It was very low during April-May when the clamsare in spent condition and high during January to Marchand again in August when the gonads are maturing.Similar pattern has been reported in most other bivalves,mussels, oysters and in abalones (Wenne and Styczyska-Jurewicz, 1987; Krzynowek et al., 1989; George andGopakumar, 1995; Dincer, 2006). However, such drasticchanges in the proximate composition levels were notobserved in M. violacea although it has been reportedin the abalone (Litaay and De Silva, 2003), edible oyster(Ngo et al., 2006) and green mussel P. viridis (Qasim etal., 1977; Nagabhushanam and Mane, 1978; Rivonkerand Parulekar, 1995).M. violacea is thus a potential source of goodprotein, high quality fat and minerals. M. violacea meatcould well be a source of alternative to high fat /cholesterol meat such as chicken, beef or other red meat.M. violacea is at present not commercially exploited,although it is consumed by the local population. Duringmonsoon, these clams are upwelled and beached in largequantities along Malabar coast. The local people collectthese clams for domestic consumption. During othertimes, these clams are dredged in large numbers in thering seines operated along the shore. In view of theirhigh nutritive value, attempts may be made to encouragetargeted exploitation of these protein rich shellfish.AcknowledgementsAssistance in analysis of proximate composition byShri T. Gangadharan, CIFT is thankfully acknowledged.Technical assistance rendered by Shri M. P. Sivadasanand Shri. V. G. Surendranathan, CMFRI is appreciated.ReferencesAOAC 1990. Official methods of analysis of theAssociation of Official Analytical chemists.Association of the official Analytical Chemists,Arlington.Cranfield, H. J., Michael, K. P., Stotter, D. R. andDoonan, I. J. 1992. Surf clams off New Zealandbeaches, Unpublished report, MAF Fisheries, NewZealand Ministry of Agriculture and Fisheries,60 pp.Dincer, T. 2006. Differences of Turkish clam (Ruditapesdecussates) and Manila clam (R. philippinarum)according to their proximate composition and heavymetal contents. J. Shellfish Res., 25 (2): 455-459.Dong, M. Fayne. 2001. The nutritional value of shellfish.www.wsg.washington.edu., p. 1-8.Durve, V. S. 1964. Preliminary observation on theseasonal gonadal changes and spawning in the clamMeretrix casta (Chemnitz) from the marine fishfarm. J. Mar. Biol. Ass. India, 6(2): 241- 248.George, C. and Gopakumar, K. 1995. Biochemical andmicrobiological studies on Clam  Villoritacyprinoides.  J. Mar. Biol. Ass. India, 37(1&2):27-30.Krzynowek, J., Daniel L. D’entremont and Murphy,J. 1989. Proximate composition and fatty acid andcholesterol content of squid Loligo pealei and Illexillecebrosus. J. Food Sci., 54(1): 45-48.Lakshmanan, P. T and Nambisan, P. N. K. 1981.Biochemical composition of the bivalve molluscsVillorita cyprinoides var. cochinensis (Hanley) andMeretrix casta (Chemnitz).  Indian J.  Mar. Sci.,9(1): 63-67.Litaay, M. and Sena S. De Silva 2003. Spawning season,fecundity and proximate composition of the gonadsof wild-caught blacklip abalone (Haliotis rubra)from Port Fairy waters, south-eastern Australia.Aquat. Living,  Resour., 16: 53-361.Nagabhushanam, R. and Mane, U. H. 1978.  Seasonalvariations in the biochemical composition ofMytilus viridis at Ratnagiri, on west coast of ofIndia. Hydrobiologia, 57: 69-72.Ngo, T. T. T., Sang-Gyun Kang, Do-Hyung Kang, PatrickSorgeloos and Kwang-Sik Choi 2006. Effect ofculture depth on the proximate composition andreproduction of the Pacific oyster, Crassostreagigas from Gosung Bay, Korea. Aquaculture, 253:712-720.150Qasim S. Z., Parulekar, A. H., Harikantra, S. N., Ansari  Z.A. and Nair, A. 1977. Aquaculture of green musselMytilus viridis L. cultivation on ropes from floatingrafts. Indian J. Mar. Sci., 6: 18-25.Rivonker, C. U and Parulekar, A. H. 1995. Proximatebiochemical composition and calorific potential in theraft grown green mussel Perna viridis. J. Mar. Biol.Ass. India, 37(1&2): 231-236.Trung tam Tin hoc- Bo Thuy San 2007,http:// www.fishnet.gov.vn/DMSP/index-e. asp.Wenne, R. and Styczyska-Jurewicz, E. 1987. Grossbiochemical composition of the bivalve Macomabalthica from the Gulf of Gdarisk (Southern Baltic).Mar. Biol., 96(1): 73-78.Date of Receipt : 18/06/08Date of Acceptance : 28/02/09P. Laxmilatha

Proximate composition of the surf clam Mactra violacea (Gmelin 1791)

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Proximate composition of the surf clam Mactra violacea (Gmelin 1791)

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