Some members of both naked and armored groups can prey upon smaller organisms
such as diatoms, ciliated protozoa even copepod nauplii. Some forms are not
photosynthetic; they lack chloroplasts, and depend exclusively upon prey for
nutrition. In Protoperidinium and the Diplopsalis group, a membranous sac, called a
pallium, is produced by an elaborate apparatus (Fig. 2.13) internal to a “mouth”, or
pallial pore, located in the sulcus. In Protoperidinium spinulosum, prey become
attached first to a slender pseudopod strengthened with protein microtubules called a
tow filament. The pallial membranes are then extruded around it and digestion
proceeds externally in a pallial sac (Jacobson & Anderson 1992).
Fig. 2.13 A dinoflagellate, Protoperidinium spinulosum, externally digesting a
cylindrical diatom in a pallial sac extruded from a microtubular basket (MB) through
an aperture in the cell armor near the flagellar pore. Other abbreviations: N – nucleus,
pp – pore plate, Pc – collecting pusule, P – sac pusule.
(^) (After Jacobson & Anderson 1992, with permission from the Journal of Phycology.)