All raphidophytes are
unicellular, with large cells (50 to 100
μm), but no
cell walls. Raphidophytes possess a pair of
flagella, organised such that both originate from the same
invagination (or gullet). One flagellum points forwards, and is covered in hair-like
mastigonemes, while the other points backwards across the cell surface, lying within a
ventral groove. Raphidophytes contain numerous
ellipsoid chloroplasts, which contain
chlorophylls a, c1 and c2. They also make use of
accessory pigments including
β-carotene and
diadinoxanthin. Unlike other heterokontophytes, raphidophytes do not possess the
photoreceptive organelle (or eyespot) typical of this group. In terms of
ecology, raphidophytes occur as
photosynthetic autotrophs across a range of
aquatic systems. Freshwater species are more common in
acidic waters, such as pools in
bogs. Marine species often produce large
blooms in summer, particularly in coastal waters. Off the Japanese coast, the resulting
red tides often cause disruption to
fish farms, although raphidophytes are not usually responsible for
toxic blooms. == Classification ==