Phylogenetic Position of Licnophora, Lechriopyla, and Schizocaryum, Three Unusual Ciliates (Phylum Ciliophora) Endosymbiotic in Echinoderms (Phylum Echinodermata)

. Various echinoderms are colonized by species from several classes of the Phylum Ciliophora, indicating that the eachinoderm “habitat” has been invaded independently on numerous occasions throughout evolutionary history. Two “echinoderm” cliates whose phylogenetic positions have been problematic are Licnophora macfarlandi Stevens, 1901 and Schizocaryum dogieli poljansky and Golikova, 1957. Licnophora macfarlandi is an endosymboint of the repirato;ry trees of holothuroids, and S. dogieli is found in the esophahus of echinoids. A third species, Lechriopyla mystax Lynch, 1930, is plagiopylid ciliate found in the intestine of echino‐ids. Host echinoderms were collected near the Friday Harbor Laboratories, San Juan Island, WA. Specimens of S. dogieli and L. mystax were obtained from the eso[phgue and tintestine, repectively, of the sea urchin Strongylocentrothus pallidus . Specimens of L. Macfarlandi were collected from the fluid obtained from the respiratory trees of Parastichopus califormicus . Using small subunit ribosomal RNA (SSrRNA) sequences of these three ciliates and a global alignement of SSrRNA sequnes of other ciliates, we estabilished the following. 1) Licnophora is a spirotrich ciliate, clearly related to the hypotrichs and stichotrichs; this is corrovorated by its possession of macronuclear replication bands. 2) Lechriopyla is the sister genus to Plagiopyla and is a number of the Class Plagiopylea, which was predicted based on its cytology. 3) Schizocaryum clusters in the Class Oligohymenophorea and is most closely related to the scuticociliates; there are currently no morphologica features known to relate Schizocaryum to the scuticociliates.