Studies on the extractive components of ascidians in Korea. I. Seasonal variation of extractive nitrogenous constituents in ascidian Halocynthia roretzi tissues.

Abstract

In order to investigate the composition and seasonal variation of extractive nitrogenous components in the ascidian Halocynthia roretzi cultured at the south coast of Korea, the muscle, liver, gill and gonad were analyzed separately for extractive nitrogen, free and combined amino acids, nucleotides and related compounds, quaternary ammonium bases, and guanidino compounds using specimens collected bimonthly from April 1988 to April 1989. The muscle was rich in free amino acids, such as taurine, proline, glutamic acid, glycine and alanine, and glycinebetaine. Most of analyzed nitrogenous extractives showed a marked seasonal variation with a maximum in summer and autumn and a minimum in winter. The liver contained more extractive nitrogen and free amino acids than the muscle, and the contents varied seasonally but differently from those in the muscle, being low in summer and autumn. The gill and gonad did not differ much from the muscle and liver in qualitative composition of extractive components, but their contents were generally low. In the gonad the increase of a considerably large amount of glycine was observed in December, the spawning season of the ascidian. The seasonal changes of nitrogenous extractives in muscle are consistent with the reputation in Korea that the ascidian is palatable in summer and autumn but not in winter.