Sexual reproduction, early development and branching in Notheia anomala (Phaeophyta) and its classification in the Fucales

Publisher Website
Google Scholar
Abstract
Notheia anomala has been found growing only on two hosts, Hormosira banksii and Xiphophora chondrophylla. Notheia is monoecious; male and female gametangia develop in the same conceptacle. The gametangia have a three-layered wall. Male gametangia contain 64 spermatozoids, and female gametangia, eight larger motile cells. The biflagellate female and male gametes fuse only after the female gametes have become attached to the surface of the host. Zygotes germinate, penetrate the host meristoderm, and ramify through the host cortex forming localized pockets of Notheia tissue. Subsequently, Notheia grows out as a cushion on the surface of the host, a depression develops in the center of the cushion, and the apical cells of the primary erect axis differentiate from the cells forming the wall of the depression. Thallus branches are initiated in both sterile and fertile conceptacles in the same manner as the primary erect frond, and not by germination of reproductive cells, as previously thought. The occurrence of intercalary longitudinal cell divisions indicates that the thallus of Notheia is parenchymatous, not filamentous. On the basis of this study it is concluded that Notheia anomala is most appropriately classified in the order Fucales in the family Notheiaceae. Differences between the growth of Notheia on its two host species are discussed.