Genetic study on the three color variations in sea cucumber, Stichopus japonicus

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There are three color variant types, namely red-type, green-type and black type. These types are including in one species, but their habitat and breeding seasons are not always same. However few studies regarding to their color variation, ecological characteristics, growth, etc., have been carried out because of their biological characteristics. Japanese sea cucumber is familiar species but strange species scientifically.The aims of the present study are to evaluate the color variation quantitatively and qualitatively, to estimate genetic variability and divergence using isozyme marker genes, and to elucidate the fact of reproductive isolation using microsatellite DNA marker genes, which are developed by the present study.Following results are obtained ;(1)Discontinuous distribution and clear difference in the color system"L^*a^*b^* was observed between the red-type and green-type, and between the red-type and black-type, but not between green-type and black type.(2)Different pigment w … More as also observed between the red-type and green-type, and between the red-type and black type, but not between green-type and black-type.(3)High genetic variability of isozyme genes was observed in the three types.(4)Significant differences in allele frequencies were observed between the red-type and green-type, and between the red-type and black-type, but not between green-type and black-type.(5)Twenty microsatellite markers were developed and their genetic control was elucidate by mating experiments.(6)Using the above microsatellite marker genes, significant differences were detected between the red-type and green-type, and between the red-type and black type, but not between green type and black-type.From the above results, the red-type should be distinguished from the other two types, and the red-type should be recognized as new subspecies. On the other side, in any of color measurements, pigmentation, isozyme genes and microsatellite marker genes, no difference was observed between green-type and black-type. It could be interpreted that the two types are included in the same species and the same population in the same area. Less