The main type of seaweed used
as a raw material in Japan is Neopyropia yezoensis, and its gametophyte(thallus) is edible. When the
gametophyte matures, it forms the antheridium and carpogonium, which are the male
and female reproductive organs, respectively. Fertilization occurs when
immobile sperm released from the antheridium adheres to the trichogyne formed
at the tip of the carpogonium.After
fertilization, repeated cell division results in the formation and release of
spores called carpospores. After adhering to the substrate, these germinate and
become sporophytes (filamentous bodies). Sporophytes are thought to sneak into
the shells of mollusks and grow. At maturity, they form conchosporangiums, from
which conchospores are released and germinate to form gametophytes. In addition
to this, the gametophytes release asexual spores called monospores, which
become gametophytes (clones) when germinated.
