Morphology and Phylogenetic Placement of Three New Zoothamnium species (Ciliophora: Peritrichia) from Coastal Waters of Southern China

The morphology, infraciliature, and silverline system of three peritrichous ciliates, Zoothamnium bucciniiformum sp. n., Zoothamnium florens sp. n., and Zoothamnium zhanjiangense sp. n., were investigated based on both living and silver‐stained specimens. Zoothamnium bucciniiformum sp. n., collected from coastal waters (salinity 30‰) off Zhanjiang, southern China, can be distinguished by the following characters: dichotomously branched stalk, peristomial lip with medial circumferential infolding, contractile vacuole apically positioned, 32–49 silverlines between the anterior end and the aboral trochal band, 15–26 between the aboral trochal band and the scopula; two kineties in peniculus 3, not parallel to each other. Zoothamnium florens sp. n., collected from a mangrove wetland (salinity 13‰) off Zhanjiang, is characterized by its large conical zooid, tuberculate peristomial lip, asymmetrical dichotomously branched colony, 59–81 silverlines between the anterior end and the aboral trochal band and 29–36 between the aboral trochal band and the scopula. Zoothamnium zhanjiangense, collected from a mangrove wetland (salinity about 9.5‰) off Zhanjiang, differs from its congeners by the alternately branched stalk, peristomial lip with medial circumferential infolding, 40–63 silverlines from the peristomial area to the aboral trochal band and 13–24 from the aboral trochal band to the scopula. The comparison and analysis of SSU rDNA sequences also support present identifications.