KATABLEPHARIS OVALIS, A COLORLESS FLAGELLATE WITH INTERESTING CYTOLOGICAL CHARACTERISTICS1

Abstract

ABSTRACT Katablepharis ovalis Skuja, isolated from an impoundment in Colorado, has a cell covering composed of two layers over the cell body and flagella. The outer component of the cell covering contains 25‐nm‐diameter hexagonal scales arranged in rows. The inner component of the cell covering is composed of a layer of interwoven microfibrils. The inner component of the cell covering is joined to the plasma membrane by one or more attachment strips that always occur outside, and along, one of the microtubular groups of the outer array. The attachment strips resemble hemidesmosomes and are composed of rows of electron‐dense material, 12 nm apart, that protrude through the plasma membrane into the extracellular space, to attach to the inner wall. The two flagella are inserted subapically into a raised area of the cell. The flagella do not have any fibrillar or tubular hairs and are covered only by the two‐layered cell covering. The cell has an inner and outer array of microtubules, both of which are spindle‐shaped, arising at the anterior end of the cell and continuing into the posterior end of the cell. A single large Golgi apparatus occurs in the anterior cytoplasm. The nucleus is in the center of the cell. Two rows of large ejectisomes occur posterior to the area of flagellar attachment. Smaller ejectisomes occur under the plasma membrane in the posterior and medial areas of the cell. Each ejectisome is composed of a single body containing a spirally wound, tapered ribbon. On discharge, the ejectisome ribbon rolls inward, creating a tubular structure. The possible relationship between Katablepharis, the green algae, and the cryptophytes is discussed.