DEVELOPMENTAL MORPHOLOGY OF CHONDRUS-CRISPUS (GIGARTINACEAE, RHODOPHYTA)

The vegetative and reproductive development of the type species of Chondrus, C. crispus Stackhouse (Gigartinaceae, Rhodophyta), is described based on material from Britain and Ireland. Chondrus is distinguished from other members of the Gigartinaceae primarily by the absence of enveloping secondary filaments in the cystocarp. The procarp of C crispus is typical for members of the Gigartinaceae and functional auxiliary cells form numerous enucleate protrusions, each of which potentially cuts off a gonimoblast initial. Gonimoblast filaments are narrow, uninucleate and resemble the connecting filaments found in non-procarpic families of red algae. Only the apical gonimoblast cells are densely filled with cytoplasm, the rest being highly vacuolate. Medullary cells are transformed into nutritive and potential generative cells as the gonimoblasts ramify through the medulla. The nuclei in each medullary cell undergo mitosis simultaneously, followed by protein synthesis and breakup of the central vacuole. Intercalary gonimoblast cells link progressively with the swollen, transformed medullary cells by means of secondary pit connections, and transfer a diploid nucleus. Both gonimoblast cells and heterokaryotic medullary cells bear carposporangia in short chains. Other gonimoblast filaments penetrate the cortex, causing gaps in the surface layer through which the carpospores are released, or produce secondary carposporangial filaments or are involved in tissue repair. Tetrasporangia are formed entirely in secondary filaments derived from medullary cells that cross-link to medullary cells in other filaments, forming secondary pit connections. Tetraspores are released through multiple pores in the outer layer of the sorus, and the tissue is subsequently repaired. A revised description of Chondrus is provided and the relationship of North Atlantic C crispus to species of Chondrus from the western North Pacific is discussed.