Ultrastructure of post-fertilization development in the red alga Callophyllis linearis (Kallymeniaceae, Cryptonemiales, Rhodophyta)

Abstract

The ultrastructure of post-fertilization development of the red alga Callophyllis linearis (Kyl.) Abb. & Norr. of the Kallymeniaceae showed that the Kallymeniaceae are more closely related to the Cryptomeniales than to the Gigartinales. The auxiliary cell produces multinucleate gonimoblast initials which divide to produce generative gonimoblast cells. These cells undergo repeated cleavages to form clusters of carpospore initials, which finally differentiate into carpospores. Carpospore differentiation is simple and occurs in three developmental stages. In the first stage, young carpospores are avacuolate, contain a large nucleus, have few undeveloped plastids and exhibit incipient dictyosome activity. During the intermediate stage, plastids develop their internal thylakoid system, starch granules are formed and dictyosomes continue to produce vesicles that contribute carpospore wall material. The formation of fibrous vacuoles originates from the fibrous vacuole associated organelles (FVAOs). In the final stage, mature carpospores form cored vesicles. They also contain well-developed plastids, fibrous vacuoles, numerous starch granules and are surrounded by a two-layered carpospore wall.