Morphology and Molecular Phylogeny of Two New Ciliates,Holostichides heterotypicus n. sp. and Holosticha muuiensis n. sp. (Ciliophora: Urostylida)

Two new urostylid species, Holostichides heterotypicus n. sp. and Holosticha muuiensis n. sp., were discovered in South Korea. Morphological and phylogenetic analyses were carried out to confirm that these species are new to science. Holostichides heterotypicus is mainly characterized by the following combination of features: 110–205 μm long in vivo; 5–10 frontoterminal cirri; 6–8 midventral pairs with 2–3 midventral cirral rows; cortical granules present; four bipolar dorsal kineties; and 6–9 caudal cirri. Ontogenetic features of H. heterotypicus are similar to those of H. typicus. Phylogenetic analyses revealed that H. heterotypicus was distantly separated from bakuellid genera Apobakuella, Bakuella, Metaurostylopsis, and Neobakuella. This result is supported by the following features: transverse cirri (present in the other four bakuellids vs. absent in Holostichides) and caudal cirri (absent in the other four bakuellids vs. present in Holostichides). Holosticha muuiensis n. sp. is mainly distinguished from its congeners by the following combination of features: 100–185 long in vivo; shortened undulating membrane; cortical granules lacking; contractile vacuole absent; 51–66 adoral zone of membranelles; 42–60 macronuclear nodules; and five bipolar dorsal kineties. In the phylogenetic tree, Holosticha muuiensis n. sp. clustered with a Holosticha group (containing Holosticha diademata, Holosticha foissneri, and Holosticha heterofoissneri).