DESCRIPTION OFTHECADINIUM MUCOSUMSP. NOV. (DINOPHYCEAE), A NEW SAND-DWELLING MARINE DINOFLAGELLATE, AND AN EMENDED DESCRIPTION OFTHECADINIUM INCLINATUMBALECH.

A new thecate, phototrophic, marine, sand-dwelling dinoflagellate,Thecadinium mucosumHoppenrath et Taylor sp. nov., is described from a culture isolated from Boundary Bay, British Columbia, Canada. It was illustrated with LM as well as SEM and TEM, and its position in the phylogenetic tree of dinoflagellates was investigated using molecular methods. Cells are asymmetrical, oval, laterally flattened, and strongly pigmented, with the plate formula P 3′ 1a 6′′ 7/8c 5 s 6′′′ 2′′′′. Thecal plates are smooth with scattered pores, and there is a distinctive anterior intercalary plate that could be involved in mucus secretion.Thecadinium inclinatumBalech (= Sabulodinium inclinatum(Balech) Saunders et Dodge), a thecate, marine, sand-dwelling species that has been previously confused with what we now callT. mucosum, was also examined and illustrated through LM and SEM. New information onT. inclinatumis provided, including its plate formula P 3′ 6′′ 7c ?s 5′′′ 1p 1′′′′; we considerT. inclinatumto be related to most otherThecadiniumspecies and not toSabulodinium. Molecular phylogenetic analyses based on the small subunit ribosomal gene ofT. mucosum,T. kofoidii(the type species of the genus), andT. dragescoiweakly support earlier suspicions based on morphology thatT. dragescoiis not a member ofThecadinium. Tabulational patterns of the species suggest a relationship to the genusAmphidiniopsis. [ABSTRACT FROM AUTHOR]