The naked, non-photosynthetic Gymnodinium fungiforme attacks prey by insertion
into their tissue of a tubular peduncle (Fig. 2.14; Spero 1982). From a cell about 15
μm in diameter, the peduncle can extend at 3 μm diameter for 12 μm, supported by
microtubules derived from an internal microtubular “basket” similar to that seen in
forms secreting pallial sacs. Cytoplasm from the prey is actively transported through
the peduncle into the dinoflagellate cell, and forms a mass of food vacuoles. Many (if
not all) photosynthetic dinoflagellates are also phagotrophs, so that mixotrophy is a
hallmark of the group.
(^) Some dinoflagellates from all groups are bioluminescent (hence an older division
name, Pyrrophyta, meaning “fire plants”), although most groups also have forms that
are not. Their light production accounts for a wide variety of dramatic marine
phenomena, including shining boat wakes, night-sparkling beach sands, and entire
bays glowing in the tropical night. One bay in Puerto Rico, Bahia Fosforente (also
called Bahia Mosquito), is named for this glow, which is believed to arise from a
complex scheme in which organic matter from mangrove trees along shore supports
bacteria, which produce extracellular vitamin B 12 , which then allows the vitamin-
requiring and luminescent Pyrodinium bahamense to proliferate. Light is produced in
some forms by a diffuse, soluble luciferin–luciferase system (a chemoluminescent
compound and the enzyme moderating energy transfer to it), and in other forms by a
similar but membrane-bound biochemistry. Dinoflagellates with membrane-bound
luminescent organelles, called scintillons, are capable of remarkably intense, brief
flashes, usually in response to mechanical stimulation of the cell. In many species,