Fine structure of the tail in the spermatozoa of the Mexican axolotl Ambystoma mexicanum

Abstract

The structure of the spermatozoa represents an extreme degree of diversity among the various species of metazoa. This diversity is most probably a reflection of the adaptation to the variable conditions for fertilization. The Axolotl sperm consists of head and tail. The tail is the subject of the present communication. It consists of neck region, intermediary and principal pieces. I. The neck (∼10μm) is inserted in the nucleus and can be designated as a region between immediately above the mitochondria (a construction zone between nucleus and sustained filament) and the upper region of the anterior centriole. In longitudinal section (Fig.l) it consists of a pair of centrioles and a mass of granular fibrillar substance. The anterior centriole (0.26 x 0.5μm) appears free, while the posterior one is continuous with the flagellum. The appearance of two central filaments indicates the transition between posterior centriole and flagellum. In front of the centrioles,there is a mass of granulo-fibrillar substance (Fig.l) which in vertical section (Fig.4) appear to be semi-circular and relatively thick (0.3μm). The granulo-fibriliar substance protrude outward (Fig.l,3,4) and thus the term protuberance seems appropriate. II.