Genetic evidence for a protozoan (phylum Apicomplexa) associated with corals of the Muntastraea annularis species complex

Scleractinian corals associate with diverse microbial communities (e.g., Rowan 1998; Rohwer et al. 2001). Some eukaryotic microbes are common, well-known associates of corals; notably dinoflagellates of the genus Symbiodinium (e.g., Trench 1987), endolithic algae (e.g., Lukas 1974), and fungi (e.g., Bentis et al. 2000). Other eukaryotic associates have not received detailed study. Descriptions of these normal associations are a necessary first step towards identifying abnormal microbial associations (Le., pathogens) which lead to coral disease (Richardson 1998). Methods for molecular genetic analysis have revolutionized the study of marine microbes (e.g., Brinkmeyer et al. 2000) and have proven useful in the study of coral microbial communities (e.g., Rowan 1998; Rohwer et al. 2001). Here we give a brief account of a coral-associated eukaryote which was identified by molecular methods during a bleaching experiment with the Caribbean coral Montastruea annuluris (Toller et al. 2001a). This symbiont, provisionally named genotype N, was identified during routine screening of Symbiodinium samples by restriction fragment length polymorphism (RFLP) analysis of small subunit ribosomal RNA genes (srDNA). Our data indicate that genotype N represents