The cyst-theca relationship of oblea rotunda (Diplopsalidaceae, dinophyceae)

Oblea rotunda is a small, heterotrophic dinoflagellate regularly found during the summer in coastal waters. Working with sediment from Scottish sea lochs, Creran, Melfort and Striven, the cyst theca relationship was investigated using single cyst germination techniques and light and scanning electron microscopy. O. rotunda has a small, round, brown cyst with a large theropylic archeopyle. Observations were also made on the cysts of two other diplopsalid species, Diplopsalis lenticula and Zygabikodinium lenticulatum. In comparison with these and other published diplopsalid cyst types the cyst of O. rotunda is most similar to that of D. lenticula. The archeopyles of O. rotunda and D. lenticula are considered in relation to the plate overlap patterns of the motile thecate stages.