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Total carotenoid differences in scallop tissues of Chlamys nobilis (Bivalve: Pectinidae) with regard to gender and shell colour
Food Chemistry 122 (2010) 1164–1167
Contents lists available at ScienceDirect
Food Chemistry journal homepage: www.elsevier.com/locate/foodchem
Total carotenoid differences in scallop tissues of Chlamys nobilis (Bivalve: Pectinidae) with regard to gender and shell colour Huaiping Zheng a,b,*, Helu Liu a,b, Tao Zhang a,b, Shuqi Wang a,b, Zewei Sun a,b, Wenhua Liu a,b, Yuanyou Li a,b a b
Key Laboratory of Marine Biotechnology of Guangdong Province, Shantou University, Shantou 515063, People’s Republic of China Mariculture Research Center for Subtropical Shellfish & Algae, Shantou University, Shantou 515063, People’s Republic of China
a r t i c l e
i n f o
Article history: Received 14 December 2009 Received in revised form 31 January 2010 Accepted 24 March 2010
Keywords: Carotenoids Chlamys nobilis Shell colour Gender Body tissue
a b s t r a c t The aim of this study was to investigate whether total carotenoid content (TCC) in noble scallop Chlamys nobilis is related to body tissue, shell colour, and gender. TCC was determined by a UV–vis recording spectrophotometer in tissue of gonad, adductor, mantle, and gill separately sampled from male and female individuals with orange and brown shell colours from the same cultured population. TCC was significantly different among body tissues, depending on shell colour and gender, ranging from 0.73 to 59.85 lg g1. In general, TCC was greater in the order of gonad > mantle > adductor > gill. In the same gender, orange shell colour individuals contained significantly higher TCC than brown ones in all four tissues (P < 0.05). In the same shell colour, female contained significantly higher TCC than male in gonad and adductor tissues (P < 0.05). Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction Carotenoids are a diverse group of yellow-orange pigments, which are broadly divided in two general classes: hydrocarbon carotenes and their oxidised derivatives known as xanthophylls. More than 650 different carotenoids naturally occur in bacteria, fungi, plants, and animals, and the number is still increasing (Matsuno, 2001). Several studies have linked diets rich in carotenoids with a reduced risk of several chronic and degenerative diseases including cancer (Nishino, 1998; Wu et al., 2004), cardiovascular disorder (Sesso, Buring, Norkus, & Gaziano, 2004), and age-related macular degeneration (Zeegers, Goldbohm, & van den Brandt, 2001). Mollusks are invertebrates and divided taxonomically into seven classes. Researches have shown that carotenoids are abundant in some mollusks including Polyplacophora, Gastropoda, Bivalvia, and Cephalopoda (Matsuno & Hirao, 1989). The total carotenoid content (TCC) in mollusks ranges from 10 to 140 lg/100 g and varies in different tissues (Kantha, 1989). The mollusks are not able to synthesise carotenoids themselves, but they can absorb carotenoids from algae and accumulate them in their body; some carotenoids may be modified to other form during the accumulating process (Kantha, 1989). Some mollusks are an important food * Corresponding author. Address: Key Laboratory of Marine Biotechnology of Guangdong Province, Shantou University, Shantou, 515063, People’s Republic of China. Tel.: +86 754 82903285; fax: +86 754 82903473. E-mail address: [email protected] (H. Zheng). 0308-8146/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodchem.2010.03.109
source for fish, sea birds, and humans; so carotenoids in mollusks can be utilised as the important intermediary (Czeczuga, 1980). The noble scallop, Chlamys nobilis (Bivalve: Pectinidae), is an important edible marine bivalve and contains higher TCC in some body tissues (Matsuno & Hirao, 1989), which has been cultured in South China since the 1980’s. The scallop displays polymorphism in shell colours including orange, purple, brown, orange-brown, orange-purple, etc. Carotenoids are found to play key roles in organism colouration (Vershinin, 1996), so it is possible that there exists a correlation between shell colours and TCC in the noble scallop. Moreover, we found that colours of adductor and mantle in the scallop C. nobilis varied a lot with their shell colours. In general, the individuals with orange shells have orange mantle, and some of them have orange adductor, while the individuals with brown shells have white mantle and adductor (Fig. 1). Although Matsuno and Hirao (1989) reported different carotenoid composition in different tissues in the scallop, the relationship between TCC and its gender and shell colour has not been reported. The aim of this study was to investigate whether TCC in the noble scallop C. nobilis is related to body tissue, shell colour, and gender. TCC was determined by a UV–vis recording spectrophotometer in tissue of gonad, adductor, mantle, and gill separately sampled from male and female individuals with orange and brown shell colours from the same cultured population in this species. The present study compared differences of TCC in scallop tissues of C. nobilis with regard to gender and shell colour.
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Fig. 1. Chlamys nobilis. Four kinds of tissues: gonad (a), mantle (b), gill (c), and adductor (d) sampled from male (white gonad) and female (orange gonad) individuals with orange and brown shell colours.
2. Materials and methods 2.1. Animal collection and tissue sample Mature scallops were collected from a cultured population in Nanao Island, Guangdong Province, China, in April 2008, and all individuals are 16-month old, with 20 orange shell individuals that have orange adductor and 20 brown shell individuals that have white adductor: each selected shell colour group included 10 males with white gonad and 10 females with orange gonad (Fig. 1), totalling four groups of 10 as orange-female (OF), orange-male (OM), brown-female (BF), and brown-male (BM). Gonad, mantle, gill and adductor of each group were individually sampled and stored at 80 °C for further analysis. 2.2. Total carotenoids extraction and TCC determination The samples were dried in a vacuum freeze-dryer and then grinded to a fine powder in mortars. The total carotenoids were extracted in the method of Yanar, Celik, and Yanar (2004). Triplicate homogenised samples of 0.2–0.45 g were added 2 4 ml acetone and shaken at 200 rpm/min for 1 h in the dark at room temperature of 25 °C. The extraction was centrifuged at 5000 rpm for 5 min and then supernatant was scanned in a UV–vis recording spectrophotometer (UV2501PC, Japan) from 400 to 700 nm. The absorption value at 480 nm was used to calculate the TCC with the extinction coefficient E(1%,1cm) of 1.900 (Yanar et al., 2004). 2.3. Statistical analysis Difference in TCC among different tissues or groups was analysed by LSD of multiple comparisons. A preliminary analysis was undertaken to evaluate the fixed effects using a General Linear Model and Type III Sums of Squares. The model included fixed effects of tissue, gender, shell colour, replicate, and all interactions. The results indicated that all fixed effects of replicate, first-order interactions between replicate and tissue, replicate and gender, replicate and shell colour, and second-order interactions were not significant (P > 0.05). Consequently, a reduced General Linear Model, testing for the effects of ‘‘Tissue, T”, ‘‘Gender, G”, and ‘‘Shell colour, S” was used to calculate
the generalised least-squares estimates of means for tested traits; the reduced model was:
Y ijkm ¼ l þ T i þ Gj þ Sk þ ðT GÞij þ ðT SÞik þ ðG SÞjk þ ðT G SÞijk þ eijkm where Yijkm = the TCC of the m replicate in the i tissue from the j gender with the k shell colour; l = overall constant; Ti = the fixed effect of tissue (i = 1, 2, 3, 4); Gi = the fixed effect of gender (j = 1, 2); Sk = the fixed effect of shell colour (k = 1, 2); (T G)ij = interaction effect between tissue and gender; (T S)ik = interaction effect between tissue and shell colour; (G S)jk = interaction effect between gender and shell colour; (T G S)ijk = interaction effect among tissue, gender, and shell colour; and eijkm = random observation error (m = 1, 2, 3). All statistical analyses were carried out by using a SAS System for windows (SAS, 8.0, SAS Institute Inc., Cary, NC, USA) and significance for all analyses was set as P < 0.05 unless noted otherwise.
3. Results TCC ranged from 0.73 to 59.85 lg/g (Table 1). ANOVA (Table 2) indicated that TCC was significantly different (P < 0.05) among individuals between different shell colours, genders, and tissues,
Table 1 Meana (standard error) of the total carotenoid content (TCC) in different tissues of Chlamys nobilis (lg g1), where OF, OM, BF, and BM represent combinations of shell colour and gender as orange-female, orange-male, brown-female, and brown-male, respectively. Combination
OF OM BF BM
Tissue Gonad
Mantle
Adductor
Gill
59.9Aa (1.32) 15.7Ab (0.15) 26.6Ac (0.46) 3.58Ad (0.15)
16.2Ba (0.85) 16.5Aa (0.46) 6.93Bb (0.16) 3.04Ac (0.02)
15.6Ba (0.23) 10.0Bb (0.49) 2.98Cc (0.19) 0.73Bd (0.07)
7.77Ca (0.07) 8.99Bb (0.45) 2.65Cc (0.04) 1.96ABd (0.27)
a Means with different superscripts are statistically different (P < 0.05) by LSD (least-significant difference) of multiple comparisons with uppercase indicating comparison among the same line and lowercase indicating comparison among the same column.
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Table 2 Analyses of variance for differences in the total carotenoid content (TCC) of Chlamys nobilis between different shell colours, genders, and tissues. Source
df
MS
F
P
Shell colour (S) Gender (G) Tissue (T) SG ST GT SGT Error
1 1 3 1 3 3 3 30
1840.234209 1076.227874 991.880697 59.319666 131.921440 692.289015 89.698334 0.232825
7903.92 4622.47 4260.19 254.78 566.61 2973.42 385.26
<0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001
Mean square (MS) and degree freedom (df).
but there were significant interactions (P < 0.05) among these three factors. In general, TCC was higher in the order of gonad > mantle > adductor > gill, with the exception of BM whose adductor’s TCC was lower than gill’s. In the same gender, individuals with orange shell colour individuals always contained higher TCC than the brown ones in all four tissues (P < 0.05). Among those with brown shell colour females contained significantly higher TCC than males in all four tissues (P < 0.05). However, among those with orange shell colour, only female’s gonad and adductor contained significantly higher TCC than the male’s (P < 0.05).
4. Discussion Different TCC was found in different tissues of the noble scallops in this study; this is consistent with results reported in other marine mollusks (Matsuno & Hirao, 1989). For example, TCC from gonad, muscle, and viscera is respectively 6.2, 0.2, and 11.0 mg/ 100 g tissue in Haliotis discus, 1.9, 0.1, and 6.7 mg/100 g tissue in Modiolus modiolus difficans, and 1.30, 0.02, and 0.01 mg/100 g tissue in Atrina pectinata (Matsuno & Hirao, 1989). These and our results show that the TCC in marine mollusks varies among body tissues, and muscle generally contains lower TCC than gonad. Our most important finding is that TCC was related not only to tissue, but also to their shell colour and gender. For the same tissue, TCC in orange shell colour individuals was always significantly higher than that in brown shell colour individuals, and that in the female individuals was always significantly higher than that in the male individuals. This is the first report on marine mollusks, where researches have shown that distinctive shell colours are able to be inherited to filial generations and controlled by genes segregating at only one or two loci in several marine shellfish species, such as the bay scallop Argopecten irradians (Adamkewicz & Castagna, 1988; Kraeuter, Adamkewicz, Castagna, Wall, & Karney, 1984; Zhang & Zheng, 2009), the Chilean scallop Argopecten purpuratus (Winkler, Estévez, Jollán, & Carrido, 2001), the pearl oyster Pinctada fucata martensii (Wada & Komaru, 1990), the Pacific oyster Crassostrea gigas (Evans, Camara, & Langdon, 2009), and the Japanese abalone Hydnum rufescens (Kobayashi, Kawahara, Hasekura, & Kijima, 2004). However, it is not clear whether the colour of inner tissues (such as adductor and mantle) is correlated with the shell colour and inherited like the shell colour. The result that TCC was affected by shell colour in the noble scallop indicated a correlation between the colour of inner tissues and shell colour. Moreover, orange adductor and mantle contained significantly higher TCC than white adductor and mantle in the present study. This also indicated that TCC in the noble scallop was significantly affected by colour of inner tissues. The correlation of TCC with shell colour and gender, suggest that TCC in the noble scallop is under partial genetic con-
trol, and therefore is amenable to artificial selection and can be improved through selective breeding. Visual perception of food products is known to affect consumer preference and product value as the result (Kahn & Wansink, 2004). For example, the level of red pigmentation in salmon flesh is positively correlated with consumers’ enjoyment of the product (Sylvia, Morrissey, & Garcia, 1995). Similarly, consumer preference for the noble scallop may also be influenced by visual cues including shell and meat colour. In the present study, the orange adductors and mantles were only found in scallops with orange shell colour, while adductors from the brown shell colour individuals were all white, implying that the colours of inner tissues might be correlated with shell colour. Presently, this guess has been confirmed by our results from crossing experiment on genetics in this species, which the colours of inner tissues including adductor and mantle are inheritable and correlated with shell colour (manuscript in preparing). Colours of inner tissues can be able to act as important elements of visual perception. Diets rich in carotenoids are important for human health, such as reducing risk of several chronic and degenerative diseases including cancer (Nishino, 1998; Wu et al., 2004), cardiovascular disorder (Sesso et al., 2004), and age-related macular degeneration (Mozaffarieh, Sacu, & Wedrich, 2003; Zeegers et al., 2001). By predominantly feeding on marine plant sources, mollusks accumulate carotenoids in their body tissues, and then serve as an intermediary in incorporating carotenoids into human body tissues as an important source of food in many regions of the world. Moreover, result of genetic experiment showed that pigments of inner tissues in the noble scallop can be genetic (manuscript in preparing). Therefore, improving TCC in the noble scallop through selective breeding is of significance and promising. Acknowledgements We thank Professor Wenhua Lu and James Lazell for helping to revise the manuscript. Funding for this research was provided by a Special Research Fund for Fisheries Scientific and Technologic Extension of Guangdong Oceanic and Fisheries Administrator (A200899E03) and the Planned Science and Technology Project of Guangdong Province (2009B020308010), Shantou City (D200900135), and in part by The Conservation Agency (Rhode Island, USA). References Adamkewicz, L., & Castagna, M. (1988). Genetics of shell colour and pattern in the bay scallop Argopecten irradians. Journal of Heredity, 79, 14–17. Czeczuga, B. (1980). Carotenoid contents in Diodora graeca (Gastropoda:Fissurellidae) from the Mediterranean (Monaco). Comparative Biochemistry and Physiology, 65B, 439–441. Evans, S., Camara, M. D., & Langdon, C. J. (2009). Heritability of shell pigmentation in the Pacific oyster, Crassostrea gigas. Aquaculture, 286, 211–216. Kahn, B. E., & Wansink, B. (2004). The influence of assortment structure on perceived variety and consumption quantities. Journal of Consumer Research, 30, 519–533. Kantha, S. S. (1989). Carotenoids of edible molluscs: A review. Journal of Food Biochemistry, 13, 429–442. Kobayashi, T., Kawahara, I., Hasekura, O., & Kijima, A. (2004). Genetic control of bluish shell colour variation in the Pacific abalone, Haliotis discus hannai. Journal of Shellfish Research, 23, 1153–1156. Kraeuter, J., Adamkewicz, L., Castagna, M., Wall, R., & Karney, R. (1984). Rib number and shell colour in hybridized subspecies of the Atlantic bay scallop, Argopecten irradians. Nautilus, 98(1), 17–20. Matsuno, T. (2001). Aquatic animal carotenoids. Fisheries Science, 67, 771–783. Matsuno, T., & Hirao, S. (1989). Marine carotenoids. In R. G. Ackman (Ed.). Marine biogenic lipids, fats, and oils (Vol. 1, pp. 251–388). Boca Raton, FL: CRC Press. Mozaffarieh, M., Sacu, S., & Wedrich, A. (2003). The role of the carotenoids, lutein and zeaxanthin, in protecting against age-related macular degeneration: A review based on controversial evidence. Nutrition Journal, 68, 2–20. Nishino, H. (1998). Cancer prevention by carotenoids. Mutation Research, 402, 159–163.
H. Zheng et al. / Food Chemistry 122 (2010) 1164–1167 Sesso, H. D., Buring, J. E., Norkus, E. P., & Gaziano, J. M. (2004). Plasma lycopene, other carotenoids, and retinol and the risk of cardiovascular disease in women. American Journal of Clinical Nutrition, 79, 47–53. Sylvia, G., Morrissey, M. T., & Garcia, S. (1995). Organoleptic qualities of farmed and wild salmon. Journal of Aquatic Food and Production Technology, 4, 51–64. Vershinin, A. (1996). Carotenoids in mollusca: Approaching the functions. Comparative Biochemistry and Physiology, 113B(1), 63–71. Wada, K. T., & Komaru, A. (1990). Inheritance of white colouration of the prismatic layer of shells in the Japanese pearl oyster Pincada fucata martensii and its importance in the pearl culture industry. Nippon Suisan Gakkaishi, 56(11), 1787–1790. Winkler, F. M., Estévez, B. F., Jollán, L. B., & Carrido, J. P. (2001). Inheritance of the general shell colour in the scallop Argopecten purpuratus (Bivalvia: Pectinidae). The Journal of Heredity, 92(6), 521–525.
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Wu, K., Erdman, J. W., Jr., Schwartz, S. J., Platz, E. A., Leitzmann, M., Clinton, S. K., et al. (2004). Plasma and dietary carotenoids, and the risk of prostate cancer: A nested case-control study. Cancer Epidemiology, Biomarkers and Prevention, 13(2), 260–269. Yanar, Y., Celik, M., & Yanar, M. (2004). Seasonal changes in total carotenoid contents of wild marine shrimps (Penaeus semisulcatus and Metapenaeus monoceros) inhabiting the eastern Mediterranean. Food Chemistry, 88, 267–269. Zeegers, M. P., Goldbohm, R. A., & van den Brandt, P. (2001). Are retinol, vitamin C, vitamin E, folate and carotenoids intake associated with bladder cancer risk? Results from the Netherlands cohort study. British Journal of Cancer, 85, 977–983. Zhang, G. F., & Zheng, H. P. (2009). Genetics of shell colour. In Aquaculture genetics in bay scallop (pp. 13–35). Beijing: Science Press.
Contents lists available at ScienceDirect
Food Chemistry journal homepage: www.elsevier.com/locate/foodchem
Total carotenoid differences in scallop tissues of Chlamys nobilis (Bivalve: Pectinidae) with regard to gender and shell colour Huaiping Zheng a,b,*, Helu Liu a,b, Tao Zhang a,b, Shuqi Wang a,b, Zewei Sun a,b, Wenhua Liu a,b, Yuanyou Li a,b a b
Key Laboratory of Marine Biotechnology of Guangdong Province, Shantou University, Shantou 515063, People’s Republic of China Mariculture Research Center for Subtropical Shellfish & Algae, Shantou University, Shantou 515063, People’s Republic of China
a r t i c l e
i n f o
Article history: Received 14 December 2009 Received in revised form 31 January 2010 Accepted 24 March 2010
Keywords: Carotenoids Chlamys nobilis Shell colour Gender Body tissue
a b s t r a c t The aim of this study was to investigate whether total carotenoid content (TCC) in noble scallop Chlamys nobilis is related to body tissue, shell colour, and gender. TCC was determined by a UV–vis recording spectrophotometer in tissue of gonad, adductor, mantle, and gill separately sampled from male and female individuals with orange and brown shell colours from the same cultured population. TCC was significantly different among body tissues, depending on shell colour and gender, ranging from 0.73 to 59.85 lg g1. In general, TCC was greater in the order of gonad > mantle > adductor > gill. In the same gender, orange shell colour individuals contained significantly higher TCC than brown ones in all four tissues (P < 0.05). In the same shell colour, female contained significantly higher TCC than male in gonad and adductor tissues (P < 0.05). Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction Carotenoids are a diverse group of yellow-orange pigments, which are broadly divided in two general classes: hydrocarbon carotenes and their oxidised derivatives known as xanthophylls. More than 650 different carotenoids naturally occur in bacteria, fungi, plants, and animals, and the number is still increasing (Matsuno, 2001). Several studies have linked diets rich in carotenoids with a reduced risk of several chronic and degenerative diseases including cancer (Nishino, 1998; Wu et al., 2004), cardiovascular disorder (Sesso, Buring, Norkus, & Gaziano, 2004), and age-related macular degeneration (Zeegers, Goldbohm, & van den Brandt, 2001). Mollusks are invertebrates and divided taxonomically into seven classes. Researches have shown that carotenoids are abundant in some mollusks including Polyplacophora, Gastropoda, Bivalvia, and Cephalopoda (Matsuno & Hirao, 1989). The total carotenoid content (TCC) in mollusks ranges from 10 to 140 lg/100 g and varies in different tissues (Kantha, 1989). The mollusks are not able to synthesise carotenoids themselves, but they can absorb carotenoids from algae and accumulate them in their body; some carotenoids may be modified to other form during the accumulating process (Kantha, 1989). Some mollusks are an important food * Corresponding author. Address: Key Laboratory of Marine Biotechnology of Guangdong Province, Shantou University, Shantou, 515063, People’s Republic of China. Tel.: +86 754 82903285; fax: +86 754 82903473. E-mail address: [email protected] (H. Zheng). 0308-8146/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodchem.2010.03.109
source for fish, sea birds, and humans; so carotenoids in mollusks can be utilised as the important intermediary (Czeczuga, 1980). The noble scallop, Chlamys nobilis (Bivalve: Pectinidae), is an important edible marine bivalve and contains higher TCC in some body tissues (Matsuno & Hirao, 1989), which has been cultured in South China since the 1980’s. The scallop displays polymorphism in shell colours including orange, purple, brown, orange-brown, orange-purple, etc. Carotenoids are found to play key roles in organism colouration (Vershinin, 1996), so it is possible that there exists a correlation between shell colours and TCC in the noble scallop. Moreover, we found that colours of adductor and mantle in the scallop C. nobilis varied a lot with their shell colours. In general, the individuals with orange shells have orange mantle, and some of them have orange adductor, while the individuals with brown shells have white mantle and adductor (Fig. 1). Although Matsuno and Hirao (1989) reported different carotenoid composition in different tissues in the scallop, the relationship between TCC and its gender and shell colour has not been reported. The aim of this study was to investigate whether TCC in the noble scallop C. nobilis is related to body tissue, shell colour, and gender. TCC was determined by a UV–vis recording spectrophotometer in tissue of gonad, adductor, mantle, and gill separately sampled from male and female individuals with orange and brown shell colours from the same cultured population in this species. The present study compared differences of TCC in scallop tissues of C. nobilis with regard to gender and shell colour.
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Fig. 1. Chlamys nobilis. Four kinds of tissues: gonad (a), mantle (b), gill (c), and adductor (d) sampled from male (white gonad) and female (orange gonad) individuals with orange and brown shell colours.
2. Materials and methods 2.1. Animal collection and tissue sample Mature scallops were collected from a cultured population in Nanao Island, Guangdong Province, China, in April 2008, and all individuals are 16-month old, with 20 orange shell individuals that have orange adductor and 20 brown shell individuals that have white adductor: each selected shell colour group included 10 males with white gonad and 10 females with orange gonad (Fig. 1), totalling four groups of 10 as orange-female (OF), orange-male (OM), brown-female (BF), and brown-male (BM). Gonad, mantle, gill and adductor of each group were individually sampled and stored at 80 °C for further analysis. 2.2. Total carotenoids extraction and TCC determination The samples were dried in a vacuum freeze-dryer and then grinded to a fine powder in mortars. The total carotenoids were extracted in the method of Yanar, Celik, and Yanar (2004). Triplicate homogenised samples of 0.2–0.45 g were added 2 4 ml acetone and shaken at 200 rpm/min for 1 h in the dark at room temperature of 25 °C. The extraction was centrifuged at 5000 rpm for 5 min and then supernatant was scanned in a UV–vis recording spectrophotometer (UV2501PC, Japan) from 400 to 700 nm. The absorption value at 480 nm was used to calculate the TCC with the extinction coefficient E(1%,1cm) of 1.900 (Yanar et al., 2004). 2.3. Statistical analysis Difference in TCC among different tissues or groups was analysed by LSD of multiple comparisons. A preliminary analysis was undertaken to evaluate the fixed effects using a General Linear Model and Type III Sums of Squares. The model included fixed effects of tissue, gender, shell colour, replicate, and all interactions. The results indicated that all fixed effects of replicate, first-order interactions between replicate and tissue, replicate and gender, replicate and shell colour, and second-order interactions were not significant (P > 0.05). Consequently, a reduced General Linear Model, testing for the effects of ‘‘Tissue, T”, ‘‘Gender, G”, and ‘‘Shell colour, S” was used to calculate
the generalised least-squares estimates of means for tested traits; the reduced model was:
Y ijkm ¼ l þ T i þ Gj þ Sk þ ðT GÞij þ ðT SÞik þ ðG SÞjk þ ðT G SÞijk þ eijkm where Yijkm = the TCC of the m replicate in the i tissue from the j gender with the k shell colour; l = overall constant; Ti = the fixed effect of tissue (i = 1, 2, 3, 4); Gi = the fixed effect of gender (j = 1, 2); Sk = the fixed effect of shell colour (k = 1, 2); (T G)ij = interaction effect between tissue and gender; (T S)ik = interaction effect between tissue and shell colour; (G S)jk = interaction effect between gender and shell colour; (T G S)ijk = interaction effect among tissue, gender, and shell colour; and eijkm = random observation error (m = 1, 2, 3). All statistical analyses were carried out by using a SAS System for windows (SAS, 8.0, SAS Institute Inc., Cary, NC, USA) and significance for all analyses was set as P < 0.05 unless noted otherwise.
3. Results TCC ranged from 0.73 to 59.85 lg/g (Table 1). ANOVA (Table 2) indicated that TCC was significantly different (P < 0.05) among individuals between different shell colours, genders, and tissues,
Table 1 Meana (standard error) of the total carotenoid content (TCC) in different tissues of Chlamys nobilis (lg g1), where OF, OM, BF, and BM represent combinations of shell colour and gender as orange-female, orange-male, brown-female, and brown-male, respectively. Combination
OF OM BF BM
Tissue Gonad
Mantle
Adductor
Gill
59.9Aa (1.32) 15.7Ab (0.15) 26.6Ac (0.46) 3.58Ad (0.15)
16.2Ba (0.85) 16.5Aa (0.46) 6.93Bb (0.16) 3.04Ac (0.02)
15.6Ba (0.23) 10.0Bb (0.49) 2.98Cc (0.19) 0.73Bd (0.07)
7.77Ca (0.07) 8.99Bb (0.45) 2.65Cc (0.04) 1.96ABd (0.27)
a Means with different superscripts are statistically different (P < 0.05) by LSD (least-significant difference) of multiple comparisons with uppercase indicating comparison among the same line and lowercase indicating comparison among the same column.
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Table 2 Analyses of variance for differences in the total carotenoid content (TCC) of Chlamys nobilis between different shell colours, genders, and tissues. Source
df
MS
F
P
Shell colour (S) Gender (G) Tissue (T) SG ST GT SGT Error
1 1 3 1 3 3 3 30
1840.234209 1076.227874 991.880697 59.319666 131.921440 692.289015 89.698334 0.232825
7903.92 4622.47 4260.19 254.78 566.61 2973.42 385.26
<0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001
Mean square (MS) and degree freedom (df).
but there were significant interactions (P < 0.05) among these three factors. In general, TCC was higher in the order of gonad > mantle > adductor > gill, with the exception of BM whose adductor’s TCC was lower than gill’s. In the same gender, individuals with orange shell colour individuals always contained higher TCC than the brown ones in all four tissues (P < 0.05). Among those with brown shell colour females contained significantly higher TCC than males in all four tissues (P < 0.05). However, among those with orange shell colour, only female’s gonad and adductor contained significantly higher TCC than the male’s (P < 0.05).
4. Discussion Different TCC was found in different tissues of the noble scallops in this study; this is consistent with results reported in other marine mollusks (Matsuno & Hirao, 1989). For example, TCC from gonad, muscle, and viscera is respectively 6.2, 0.2, and 11.0 mg/ 100 g tissue in Haliotis discus, 1.9, 0.1, and 6.7 mg/100 g tissue in Modiolus modiolus difficans, and 1.30, 0.02, and 0.01 mg/100 g tissue in Atrina pectinata (Matsuno & Hirao, 1989). These and our results show that the TCC in marine mollusks varies among body tissues, and muscle generally contains lower TCC than gonad. Our most important finding is that TCC was related not only to tissue, but also to their shell colour and gender. For the same tissue, TCC in orange shell colour individuals was always significantly higher than that in brown shell colour individuals, and that in the female individuals was always significantly higher than that in the male individuals. This is the first report on marine mollusks, where researches have shown that distinctive shell colours are able to be inherited to filial generations and controlled by genes segregating at only one or two loci in several marine shellfish species, such as the bay scallop Argopecten irradians (Adamkewicz & Castagna, 1988; Kraeuter, Adamkewicz, Castagna, Wall, & Karney, 1984; Zhang & Zheng, 2009), the Chilean scallop Argopecten purpuratus (Winkler, Estévez, Jollán, & Carrido, 2001), the pearl oyster Pinctada fucata martensii (Wada & Komaru, 1990), the Pacific oyster Crassostrea gigas (Evans, Camara, & Langdon, 2009), and the Japanese abalone Hydnum rufescens (Kobayashi, Kawahara, Hasekura, & Kijima, 2004). However, it is not clear whether the colour of inner tissues (such as adductor and mantle) is correlated with the shell colour and inherited like the shell colour. The result that TCC was affected by shell colour in the noble scallop indicated a correlation between the colour of inner tissues and shell colour. Moreover, orange adductor and mantle contained significantly higher TCC than white adductor and mantle in the present study. This also indicated that TCC in the noble scallop was significantly affected by colour of inner tissues. The correlation of TCC with shell colour and gender, suggest that TCC in the noble scallop is under partial genetic con-
trol, and therefore is amenable to artificial selection and can be improved through selective breeding. Visual perception of food products is known to affect consumer preference and product value as the result (Kahn & Wansink, 2004). For example, the level of red pigmentation in salmon flesh is positively correlated with consumers’ enjoyment of the product (Sylvia, Morrissey, & Garcia, 1995). Similarly, consumer preference for the noble scallop may also be influenced by visual cues including shell and meat colour. In the present study, the orange adductors and mantles were only found in scallops with orange shell colour, while adductors from the brown shell colour individuals were all white, implying that the colours of inner tissues might be correlated with shell colour. Presently, this guess has been confirmed by our results from crossing experiment on genetics in this species, which the colours of inner tissues including adductor and mantle are inheritable and correlated with shell colour (manuscript in preparing). Colours of inner tissues can be able to act as important elements of visual perception. Diets rich in carotenoids are important for human health, such as reducing risk of several chronic and degenerative diseases including cancer (Nishino, 1998; Wu et al., 2004), cardiovascular disorder (Sesso et al., 2004), and age-related macular degeneration (Mozaffarieh, Sacu, & Wedrich, 2003; Zeegers et al., 2001). By predominantly feeding on marine plant sources, mollusks accumulate carotenoids in their body tissues, and then serve as an intermediary in incorporating carotenoids into human body tissues as an important source of food in many regions of the world. Moreover, result of genetic experiment showed that pigments of inner tissues in the noble scallop can be genetic (manuscript in preparing). Therefore, improving TCC in the noble scallop through selective breeding is of significance and promising. Acknowledgements We thank Professor Wenhua Lu and James Lazell for helping to revise the manuscript. Funding for this research was provided by a Special Research Fund for Fisheries Scientific and Technologic Extension of Guangdong Oceanic and Fisheries Administrator (A200899E03) and the Planned Science and Technology Project of Guangdong Province (2009B020308010), Shantou City (D200900135), and in part by The Conservation Agency (Rhode Island, USA). References Adamkewicz, L., & Castagna, M. (1988). Genetics of shell colour and pattern in the bay scallop Argopecten irradians. Journal of Heredity, 79, 14–17. Czeczuga, B. (1980). Carotenoid contents in Diodora graeca (Gastropoda:Fissurellidae) from the Mediterranean (Monaco). Comparative Biochemistry and Physiology, 65B, 439–441. Evans, S., Camara, M. D., & Langdon, C. J. (2009). Heritability of shell pigmentation in the Pacific oyster, Crassostrea gigas. Aquaculture, 286, 211–216. Kahn, B. E., & Wansink, B. (2004). The influence of assortment structure on perceived variety and consumption quantities. Journal of Consumer Research, 30, 519–533. Kantha, S. S. (1989). Carotenoids of edible molluscs: A review. Journal of Food Biochemistry, 13, 429–442. Kobayashi, T., Kawahara, I., Hasekura, O., & Kijima, A. (2004). Genetic control of bluish shell colour variation in the Pacific abalone, Haliotis discus hannai. Journal of Shellfish Research, 23, 1153–1156. Kraeuter, J., Adamkewicz, L., Castagna, M., Wall, R., & Karney, R. (1984). Rib number and shell colour in hybridized subspecies of the Atlantic bay scallop, Argopecten irradians. Nautilus, 98(1), 17–20. Matsuno, T. (2001). Aquatic animal carotenoids. Fisheries Science, 67, 771–783. Matsuno, T., & Hirao, S. (1989). Marine carotenoids. In R. G. Ackman (Ed.). Marine biogenic lipids, fats, and oils (Vol. 1, pp. 251–388). Boca Raton, FL: CRC Press. Mozaffarieh, M., Sacu, S., & Wedrich, A. (2003). The role of the carotenoids, lutein and zeaxanthin, in protecting against age-related macular degeneration: A review based on controversial evidence. Nutrition Journal, 68, 2–20. Nishino, H. (1998). Cancer prevention by carotenoids. Mutation Research, 402, 159–163.
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