Shinya Ishio

Ultrastructural Studies on Gyrodinium sp. , a Marine Catenate Dinoflagellate

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.

THE REACTIONS OF FISHES TO TOXIC SUBSTANCES-III

In previous paper (1), the present author was able to introduce only about the structure of a new gradient tank and the principle of formation of toxic gradient in it. This paper deals with the method of avoidance tests of fishes applying the new tank, in combination with the reactions of Gin-buns, Carassius auratus (L.) and bluegill sunfish, Lepomis macrochirus to acid gradients resulted from adding hydrochloric acid to soft water and hard water. Some data of those tests proved the fact that against pH gradient, Gin-buna were able to approarch fairly acid water with pH as low as 2.8 when the concentration of carbonic acid was lower than 18 p.p.m., whereas bluegill sunfish could approarch only pH 5.8 where the concentration of carbonic acid was 240 p.p.m. Although the pH 2.8 for Gin-buna and the 240 p.p.m. of carbonic acid for bluegill sunfish are presumed to be quickly fatal (4), (9), it is safely to say that those fishes can avoid of fatal concentrations of either hydrogen ion or carbonic acid with a high frequency more than 70 per cent of total avoidance.