Diatom symbionts in larger foraminifera from Caribbean hosts

Larger foraminifera, as a group, are the hosts for many different types of algae. The majority of modern families host small (< 10 μm) pennate endosymbiotic diatoms. In these, the host/symbiont relationship is not finical. Studies from hosts harvested from Indo-Pacific habitats have shown some symbiont species are found with greater frequency than others, but any one of twenty different diatom species may be found in the same host. This study examined the endosymbionts from two diatom-bearing hosts from the Caribbean, Amphistigina gibbosa and Heterostegina antillarum. A high number of hosts harbored more than one symbiont species. A new variety of Nitzschia frustulum was involved in many (33%) of the symbioses. Many of the isolates of this taxon, if it is to be considered only one, are extremely aberrant forms for the genus. Another common (18%) isolate was an unidentified species of Navicula. A highly variable Amphora sp. was also isolated. These taxa will require more detailed examination in the future. Many of the isolates from the Caribbean hosts also were known as endosymbionts from previous studies: Nitzschia laevis N. frustulum var. symbiotica N. valdestriata, Amphora tenerrima, Navicula muscatini, Cocconeis andersoni and Fragillaria shiloi. A number of endosymbiotic species, common in Indo-Pacific hosts, were not found in the Caribbean hosts studied. The results of the present study are in consonance with those of previous studies.