1R & D Division, Marua Suisan Co., Ltd., Kamijima, Ehime 794-2410, 2South Ehime Fisheries Research Center, Tarumi Branch, Ehime University, Matsuyama, Ehime 790-8566, Japan
Artificially raised Japanese flounder exhibiting short body length were morphologically characterized and genetic investigations were conducted using microsatellite DNA. Individuals exhibiting short and normal body lengths were collected 60 days after hatching. Flounder with short bodies were morphologically analyzed by soft X-ray and divided into three groups, A, B and C, based upon body shapes and the positions of fused vertebrae. All short bodied individuals exhibited highly fused vertebrae. Main vertebrae fusion points were determined as follows: type A: all positions upon the vertebrae, type B: vertebra numbers 1 to 4 and 17 to 30, and type C: vertebra numbers 1 to 4 and 19 to 36. The frequency of these short body individuals observed in this study was 1.7%. Four microsatellite markers (Pol-1*, -3*, -4*, -5*) were deployed for parentage analysis and 99.3% of specimens were successfully assigned. One each of dam and sire were significantly associated with type B short body individuals. Furthermore, we identified that the same sire was also significantly associated with type C short body individuals. These results suggest that genetic factors are probably one of the underlying factors of short body individuals identified in juvenile Japanese flounder.