A preliminary study on life history of marine red alga Stylonema alsidii (Zandardini) Drew f. ramosum Zheng et Li

Stylonema alsidii (Zandardini) Drew f. ramosum Zheng et Li is a common species in the genus Stylonema, but there are limited reports on morphological taxonomy and a lack of studies on life history and the regulation of early development. The early development, discoid formation, and erect thallus growth of Stylonema alsidii f. ramosum were observed under laboratory conditions. In addition, the influence of main environmental factors such as temperature and light intensity on its development was briefly studied, and various stages of its life history were observed. The result shows: (1) there are two reproductive modes: asexual reproduction and sexual reproduction; (2) the morphology of this species varies in different degrees under laboratory culture conditions; (3) sexual reproduction and asexual reproduction can coexist under suitable conditions. Five pathways of life history were inferred from experimental phenomena. Mature sporophytes form mature gametophytes by producing initially isolated or initially attached monospore, and mature gametophytes form mature sporophytes by fertilization of eggs and sperms. The sexual and asexual reproduction processes of Stylonema alsidii f. ramosum were reported for the first time, and this is also the first report on sexual reproduction in the genus Stylonema.