A Reinvestigation of the Marine Ciliate Trachelocerca ditis (Wright, 1982) Foissner and Dragesco, 1996 (Ciliophora, Karyorelictea) from the Yellow Sea and an Assessment of Its Phylogenetic Position Inferred from the Small Subunit rRNA Gene Sequence

The karyorelictean ciliate Trachelocerca ditis (Wright, 1982) Foissner and Dragesco, 1996 isolated from the Yellow Sea coast at Qingdao, China is reinvestigated based on examination of specimens in vivo and following protargol impregnation. The infraciliature and the general morphology of living cells closely resemble those of a population from the French Atlantic coast at Roscoff (Foissner and Dragesco 1996b). However, some differences were noted including the size of the macronuclei, the appearance of the nucleoli and the presence of vacuoles that contained peculiar figure-of-eight inclusions. The small subunit ribosomal RNA (SSU rRNA) gene was sequenced for the China-population and phylogenetic trees based on SSU rRNA gene sequence data were constructed. These revealed that Trachelocerca ditis clusters with another trachelocercid, Tracheloraphis sp. (sensu Hirt et al. 1995), with high support.