Abstract
Intraspecific morphological variation of Undaria pinnatifida sporophytes was investigated using two local strains from Taro and Okirai in the central and southern coastal areas, respectively, of Iwate Prefecture, northeastern Japan. Sporophytes of the two test strains were cultured at a commercial aquaculture site in Okirai Bay from December, 2006, to April, 2007. Thallus size as expressed by six parameters (blade length, stipe length, blade wet weight, stipe wet weight, blade width, and undivided blade width) differed between the strains under the same cultivation conditions and thallus density. Blade thickness and three morphological correlations (those between blade length and thallus length, blade wet weight and thallus wet weight, and undivided blade width and blade width) also differed between the strains. Cultured sporophytes of the Taro strain produced a longer and thicker blade than those of the Okirai strain whereas the latter produced a wider and more deeply incised blade, and a longer and heavier stipe than the former. These results show that variation in the morphology of local U. pinnatifida strains from Iwate Prefecture has a genetic basis.
