Epistylis, Ehrenberg, 1830

Zhou, Tong, Wang, Zhe, Yang, Hao & Gu, Zemao, 2019, Morphological and molecular identification of epibiontic sessilid Epistylis semiciculus n. sp. (ciliophora, Peritrichia) from Procambarus clarkia (Crustacea, Decapoda) in China, International Journal for Parasitology: Parasites and Wildlife 10, pp. 289-298 : 296

4.3. Comparison with other Epistylis

The present species shows the typical morphological characteristics of the genus Epistylis and can be distinguished from other sessilid genera by the following typical morphological characteristics: noncontractile stalk, well-defined peristomial lip, and oral ciliary rows circling for less than two turns around peristomial disk ( Lynn, 2008).

The present Epistylis can be distinguished from other Epistylis species by the following morphological characteristics: (1) body shape of several species is not vase shape, such as E. aselli Stiller, 1941 , E. gammari Precht, 1935 , E. helicostylum Vavra, (1962) and E. hentscheli Kahl, (1935) (vs. body shape of the present Epistylis is vase shape ( Vavra, 1962; Foissner et al., 1992; Shen and Gu, 2016); (2) peristomial lips of several species are double layer, such as E. chrysemydis Bishop and Jahn, 1941 and E. clampi Hongwei and Overstreet, 2006 (vs. peristomial lip of the present Epistylis is single layer) ( Hongwei and Overstreet, 2006; Jiang et al., 2016); (3) contractile vacuoles of several species are on the ventral wall of infundibulum, such as E. acuminata Song, 1986 , E. chlorelligerum Shen, 1980 and E. nympharum Engelmann, 1862 (vs. contractile vacuole of the present Epistylis is on the dorsal wall of infundibulum) ( Song, 1986; Foissner et al., 1992; Jiang et al., 2016); (4) peristomial disks of several Epistylis species are gradient, such as E. chlorelligerum and E. vaginula Stokes, 1884 (vs. peristomial disk of present Epistylis is semicircular) ( Jiang et al., 2016; Shen and Gu, 2016) (5) contractile vacuole of several species are above peristomial lip, such as E. acuminata , E. aselli , E. clampi , E. harpaticola Kahl, 1933 , E. plicatilis Ehrenberg, 1838 and E. vaginula (vs. contractile vacuole of the present Epistylis is below peristomial lip) ( Song, 1991; Hong and Overstreet, 2006; Shi et al., 2014; Shen and Gu, 2016; (6) macronuclei of several species are J-shaped or band-shaped, such as E. elongata Stokes, 1889 and E. nympharum (vs. macronucleus of the present Epistylis is Cshaped) ( Kahl, 1935; Foissner et al., 1992). Detailed comparisons are presented in Table 5.

The BLAST results show that the present Epistylis is most similar to E. chlorelligerum (KM096375, SSU rDNA sequences) and E. chrysemydis (GU586187, ITS1-5.8S-ITS2 sequences), which can be morphologically distinguished from the present Epistylis (see above). Phylogenetic analyses based on SSU rDNA sequences and ITS1-5.8S-ITS2 sequences both revealed that the present Epistylis obviously separates from other Epistylis species. Therefore, we identified the present Epstylis as a new species based on both morphological and molecular comparisons. We assigned it the name Epistylis semiciculus n. sp. with respect to the shape of its peristomial disk.