Speciation and symbiotic dinoflagellates.

Morphometric analyses based on three-dimensional reconstruction of the nuclei of four different strains of the symbiotic dinoflagellate Symbiodinium microadriaticum, the algae that inhabit corals, giant clams, and other marine invertebrates, revealed marked differences in chromosome numbers and chromosome volumes. The differences are not consistent with different ploidy states within the same species, but can most easily be interpreted as indicating different species.