What Accounting For Orange Color Of Yesso Scallop Muscle (Patinopecten Yessoensis) And Its Application In Breeding

1 The selection and breeding of Yesso scallop with orange muscleThe Yesso scallop (Patinopecten yessoensis) is one of most important commercial aquacultural shellfish in the north of China and since it was introduced from Japan in 1982. During the course of a research project aimed at optimizing a breeding strategy for this scallop, we identified a rare color variant that occurred at about 0.2% in the natural population. This muscle tissue of this variant was orange as opposed to the common white. Orange variants have not been reported before in shellfish, including scallops. In this study, gender ratio and shell color of the orange variant were investigated and it showed no difference with the common. 500 male and female individuals of color variant were screened for conventional breeding separately and a control was set with same amount of white ones. The proportion of F1 generation with orange muscle was 100% when it was 7 months old, while there was no orange muscle appeared in the control group. It demonstrated that the color of muscle can be steadily inherited and it can be used for breeding. Statistic analysis of growth traits of the 22-month Yesso scallops showed that there was significant difference between the the group with orange muscle and the control group in total weight, soft weight, muscle weight and shell length, it indicated that the growth rate of the Yesso scallops with orange muscle was faster than the control group significantly. The new variety of the Yesso scallop was named"Hai da jin bei".2 Isolation and identification of the main pigment from the rare orange muscle of the Yesso scallopThe wavelength spectrum scanning by UV-visible of the extract showed that the peaks were determined upslope, apex and downlope, and there was an obvious peak value at 450nm, the pigments were therefore identified as carotenoids preliminary. Two main carotenoids were isolated and purified by silica gel chromatography(TLC) and high performance liquid chromatography(HPLC), and were characterized by mass spectrometry(MS) and ¹H- and ¹³C-nuclear magnetic resonance(NMR) methods. Its structure was identified as (3S,3'R)-3,3'-dihydroxy-7',8'-didehydro-β,β-Caroten-4-one and (3S,3'S)-7,7',8,8'-tetra-dhydro-β,β-Carotene-3,3'-diol, with common name pectenolone and pectenoxanthin. This is the first report of pectenolone and pectenoxanthin, two types of carotenoid, in the muscle of the Yesso scallop.3 Roles of the carotenoids composition and accumulation in Yesso scallopThe method for detecting carotenoids using reverse phase high performance liquid chromatography (RP-HPLC) was developed. The conditions of RP-HPLC analysis were an analytical scale (200×4.6 mm, inner diameter 5μm) Eclipse XDB-C18 column of Agilent corporation; 10μl injection volume; 25°C column temperature; acetonitrile, methanol and methylene dichloride mobile phase (40:56:4, V/VV) with 0.1% BHT; 1.0 ml per minute flow rate; 450 nm UV-VIS detector; 8 minutes elution.The carotenoids from orange muscle of Yesso scallop of 7, 10, 12, 15, 18, 22 months old was detected using the method refered above. It showed that the carotenoids content was increasing during juvenile stage when the scallop grow rapidly, and reached plateau in the breeding reason, and then decreased after reproduction. It can also be concluded that the muscle mainly accumulated pectenoxanthin in November to February, while mainly pectenolone in April to October. The carotenoids content of orange muscle had no relationship with the size of the scallop, but the growth stage.The composition and content of carotenoids of various tissues in Yesso scallop with orange/white muscles was detected by RP-HPLC. It was showed that pectenolone and pectenoxanthin were all found in Gonads, hepatopancreas, mantle and gill, among of them, ovary, hepatopancreas and gill possessed more carotenoid than other tissues, but no carotenoids were found in the white muscles of Yesso scallops. Hepatopancreas contains a variety other carotenoids some kind of other not identified beside pectenolone and pectenoxanthin. The result also showed that the Yesso scallop with orange muscle had more the carotenoids in a variety of tissues than the common, and the female more than the male.4 Impacts of carotenoid accumulation on morphological structure and chemical composition in orange muscle of Yesso scallopThere was no difference between the orange and white muscle obserced by conventional HE staining, while musclular fiber type and matrix density in the orange muscle was different from white ones by the TEM observation of ultra-thin slices, and there were three musclular fiber types, among of them, the loose muscular fiber was orange muscle specifically. The fat and fat acid of orange and white muscle were ectracted through Soxhlet extraction method, the varieties and content were detected by GC-MS. The result showed that the fat of orange muscle was a little higher than the white ones, and the linoleic acid, oleic acid content in the orange muscle was more than white ones, which may be related to the carotenoids metabolism. Amino acids content of orange muscle were higher than common white ones except glycine and proline, and taurine was rich in orange muscle.5 Genetic structure of breeding population with orange muscleWe surveyed the level of genetic variation and the pattern of genetic structure in the breeding population with orange muscle using SSR markers. Based on 6 primers, the result showed that the breeding population has high genetic diversity and was no significant change with respect to the wild population. And MSAP with 24 primer was used for analysis in Yesso scallops with orange/white muscle, it was showed that there were 46 loci which had differences in the degree of methylation between the population with orange muscle and the white, among of which 18 were methylated or semi-methlated loci, which may be related to the appearance of orange muscle.