Ultrastructural Studies on Gyrodinium sp. , a Marine Catenate Dinoflagellate

Abstract

This paper deals with the ultrastructure of Gyrodinium sp., a marine catenate dinoflagellate by using electron microscopy. This organism contains a large nucleus and other inclusions. The nucleus has nuclear pores and two layers of membrane like that of eucaryote. Numerous chromosomal bodies which have regular and complicated chromonemata coiled among them are always observed clearly. This fact suggests that the chromosomes of dinoflagellate are different from those of eucaryote which do not appear except during dividing stages. Concerning the electron staining of the cell sections, urany1 acetate gives better contrast than lead acetate for nucleus, especially for chromosome but not for cytoplasm. The catenate cells of Gyrodinium sp. are connected together by a narrow lamella joint. In the cytoplasm, rough endoplasmic reticulum is not distinct but free ribosomes are scattered. The chloroplast possesses three thylakoids and ribosomes in the interlamella space. The pyrenoid is often observed in the chloroplast having DNA fibrils coiled in the center. DNA fibrils are also observed in the electron transparent area of mitochodrion. A stratified concentric mitochondrion having four layers of membrane which are twice the width of nuclear envelope is considered to be the origin of usual mitochondrion.葉綠體的lamella構造是由三層thylakoid所組成，DNA纖維存在於澱粉核內，核糖體存在於lamella構造之問。粒線體由二層膜組成，其內膜有tubular cristae，此為渦鞭毛藻類粒線體的特徵。DNA纖維與核糖體也都存在於粒線體內。這些情形顯示著葉綠體和粒線體都能自行分裂也能行蛋白質合成。另外在這細胞質內發現有－由四層膜組成且呈同心圓的粒線體，在這特殊粒線體旁，常觀察到有普遍粒線體存在，作者認為這同心圓粒線體可能是普通粒線體的起源。