taxonID	type	description	language	source
039487821807FF8FFEF90C83FA3DF9B4.taxon	description	(FIGS 1 – 6; TABLES 3, 4) urn: lsid: zoobank. org: act: F 5 BDD 236 - 92 B 3 - 42 A 3 - A 220 - E 6 D 7 CB 1 BD 95 F Diagnosis: Body about (arithmetic mean ± SD, Х ± SD) 74.1 ± 6.1 × 38.3 ± 6.9 μm after silver staining; cells yellowish to beige colour in vivo; 41 – 51 rows of somatic monokinetids; striated band long 42.5 ± 4.4 µm on average; single macronucleus, 1 – 5 vesicular-type micronuclei; single contractile vacuole with 2 – 5 pores; cytoproct forming a suture (long 21.8 ± 2.4 µm on average) with two dense cytoproct-related ciliary rows on its left; curved extrusomes (long 1.9 μm on average); habitat freshwater in the hypoxic / anoxic part of the water column, nearby the sediment. Type locality: Kolleru Lake, in the proximity of the back of Sri Peddintlamma Thalli temple, Kolletikota, Andhra Pradesh, Southern India (N 16 ° 36 ’ 48.0 ” E 81 ° 18 ’ 32.0 ”). This species inhabits freshwater sites with oxygen-depleted water, in presence of decomposed sediments (sapropel) and is mainly a consumer of sapropel-dependent bacteria and diatoms. Type material: The slide with the silver-stained holotype specimen (indicated with a black circle of ink on the coverslip) and some paratype specimens has been deposited in the collection of the ‘ Museo di Storia Naturale dell’Università di Pisa’ (Calci, Pisa, Italy) with registration number ‘ 2017 - 1 ’. Etymology: We dedicate this new species to Professor Emeritus Akkur V. Raman from Andhra University (India), for his contribution to the development of protistological study in India. Gene sequence: The 18 S rRNA sequence of P. ramani has been deposited in NCBI GenBank database with the following accession number: KY 563720. Description: Cells small, non-contractile and dorso-ventrally convex, with ovoid-reniform shape (Figs 1 – 4). Cells in vivo about (Х ± SD) 84.0 ± 2.5 × 58.5 ± 6.4 μm, after silver staining 74.1 ± 6.1 × 38.3 ± 6.9 μm (body size reduction about 10 – 15 %) (Table 3). Length / width ratio approximately 1.4 for live cells and 1.9 for stained specimens. Live cells yellowish or beige in colour. Negative phototaxis behaviour, swimming in anticlockwise direction with respect to the longitudinal body axis when viewed from the posterior end. Anterior and posterior end rounded (Figs 1 – 4). Somatic cilia equally distributed around body surface (Figs 2 A – C, 3 A, B), arranged in about 41 – 51 rows of somatic monokinetids (22 – 25 dorsal rows and 19 – 26 ventral rows) (Fig. 1 A, B). Not all somatic cilia reach posterior end of cell dorsal side: 3 rows terminating near opening of cytoproct, remaining ciliary rows terminating at posterior end, meeting each other and forming a suture (Figs 1 A, 3 A). On antero-ventral side characteristic oral apparatus opens with slit-like aperture, inclined toward inner part of body as a transverse groove (Figs 1 B, 2 B, D, 3 B, 4 C – E). Oral region folding inward, forming a deep buccal-pharyngeal cavity, curving towards left with respect to longitudinal body axis (Figs 1 A, 3 C). Buccal region formed by two lip-like structures (upper lip and lower lip), composed of oral polykinetids (Figs 1 B, 4 D). Oral cilia not in continuity with somatic ones, which terminate before, leaving a small gap in between (Figs 1 B, 4 D, E). Oral lips bearing longer and densely arranged cilia than somatic kinetids (Fig. 4 D, E). Striated band running along right margin of dorsal side and terminating close to cytoproct region (Figs 1 A, 2 C, 3 A, 4 A, F). Striated band length 42.5 ± 4.4 µm on average after silver staining, composed of thick, transverse ridges (Fig. 4 G). Transverse ridges perpendicular to vertical axis of the body. Cell length / striated band ratio 1.7. Cytoproct located on dorsal side of body, in sub-equatorial position, forming a longitudinal suture, about 21.8 µm long (Figs 1 A, 3 A, D, 4 H). On the left side of cytoproct, two short rows of narrowly spaced cilia (Figs 1 A, 3 A, D, 4 H, J). Cytoproct terminating slightly before contractile vacuole opening region. Contractile vacuole in posterior body portion (Fig. 2 B, E). It opened dorsally with 2 – 5 distinct pores, aligned in series following cell longitudinal axis (Figs 1 A, 2 C, 3 D, 4 H, I) A single ovoid macronucleus (on average 15.1 × 12.4 µm after Feulgen staining) with uniformly arranged chromatin, situated in the equatorial region of the cell beneath the buccal region (Figs 1 A, 2 B), and 1 – 5 small micronuclei (diameter of 1.8 µm on average after Feulgen staining) of vesicular-type (Fokin, 1997, 2010 / 2011), close to the macronucleus (Fig. 2 H). In cortical region, presence of uniformly distributed, slightly curved extrusomes (Figs 2 F, G, 5 A), measuring around 1.9 μm in length, and roundish, electron-dense cortical granules (diameter around 0.3 μm) (Figs 2 E, 5 B). In TEM preparations ectosymbionts detected, lying on the cell surface in ciliate cortex invaginations (Fig. 5 B), appearing as rods of about 0.80 × 0.20 μm. Ectosymbionts not observed in SEM preparations (Fig. 4). Two different forms of endosymbiotic organisms detected inside the cytoplasm. First form: short rods with tapered ends, surrounded by a lighter layer of cytoplasm, a sort of ‘ halo’ (Fig. 5 C – E), about 1.20 × 0.31 μm in size. Their cytoplasm, more electron-dense in the periphery, contains a long loop of DNA (Fig. 5 C, E). Second type of endosymbionts: rod-shaped, about 1.28 × 0.32 μm in size; surrounded by a halo, encircled by a double membrane (Fig. 5 F). All endosymbionts flanked by hydrogenosome-like structures (Fig. 5 C, D), scattered in the cytoplasm throughout the host cell. No bacterial flagella retrieved. Hydrogenosomes showing an electron-dense matrix and an irregular body shape when associated to endosymbionts (Fig. 5 C). Some roundish and lighter structures could be interpreted as an early stage of hydrogenosome formation (Fig. 5 G), showing a clear matrix with several membranous foldings without cristae (Fig. 5 H). Fluorescence in situ hybridization (FISH) analysis confirmed the presence of Archaea inside P. ramani: host cells were positive to Archaeal universal probe ARCH 915 and, later, to the species-specific probe, Methanoc 512 (Fig. 5 I). The positivity to the probe Methanoc 512 ascribed at least one type of these symbionts to the methanogenic Archaea genus Methanocorpusculum (Methanomicrobiales, Euryarchaeota). No signals detected with EUB 338 probe (data not shown). Molecular characterization and phylogeny: From molecular analysis on 18 S rRNA encoding gene of P. ramani, a sequence of 1715 bp was obtained. Identity values to database published Plagiopylidae sequences are reported in Table 4 and range between 97.4 % (Plagiopyla narasimhamurtii, see later) and 96.1 % (P. nasuta). The phylogenetic position of P. ramani was within the clade of the Plagiopylidae family, more precisely in one of the two subclades including also Lechriopyla mystax, P. narasimhamurtii (see later), and some sequences of unidentified Plagiopyla species (Fig. 6). A more detailed description of the phylogeny will be presented in the last paragraph of the ‘ Results’ section.	en	Nitla, Venkatamahesh, Serra, Valentina, Fokin, Sergei I., Modeo, Letizia, Verni, Franco, Sandeep, Bhagavatula Venkata, Kalavati, Chaganti, Petroni, Giulio (2019): Critical revision of the family Plagiopylidae (Ciliophora: Plagiopylea), including the description of two novel species, Plagiopyla ramani and Plagiopyla narasimhamurtii, and redescription of Plagiopyla nasuta Stein, 1860 from India. Zoological Journal of the Linnean Society 186: 1-45
039487821805FF80FC870FADFB07FAE0.taxon	description	(FIGS 6 – 11; TABLES 4, 5) urn: lsid: zoobank. org: act: 8 C 939483 - A 855 - 4 FAE-AD 72 - CA 23 E 67 A 71 A 7 Diagnosis: Body about 81.8 ± 6.7 × 41.3 ± 4.8 µm after silver staining; cells yellowish to beige colour in vivo; 51 – 69 rows of somatic monokinetids; striated band present (44.5 ± 1.4 µm long on average); single macronucleus, one compact-type micronucleus; single contractile vacuole with 2 or 3 pores; cytoproct forming a suture (long 24.0 ± 2.3 µm on average) with 3 dense cytoproct-related ciliary rows on its left; two types of extrusive organelles: straight, multi-layered extrusomes (3.7 µm in length on average), and curved homogeneous extrusomes (1.6 µm in length on average); habitat freshwater in the hypoxic / anoxic part of the water column, nearby the sediment. Type locality: Kolleru Lake in the proximity of Malki Mohammed Puram, a small village in Bhimadole Mandal, in West Godavari District of Andhra Pradesh, Southern India (N 16 ° 43 ’ 42.0 ” E 81 ° 24 ’ 30.0 ”). This species inhabits freshwater sites with oxygen-depleted water, in presence of decomposed sediments (sapropel) and is mainly a consumer of sapropel-dependent bacteria and diatoms. Type material: The slide with the silver-stained holotype specimen (indicated with a black circle of ink on the coverslip) and some paratype specimens has been deposited in the collection of the ‘ Museo di Storia Naturale dell’Università di Pisa’ (Calci, Pisa, Italy) with registration number ‘ 2017 - 2 ’. Etymology: We dedicated this new species to Professor Chatti C. Narasimhamurti (1931 – 93), from Andhra University (India), for his contribution to the development of protistological study in India. G e n e s e q u e n c e: T h e 1 8 S r R N A s e q u e n c e o f P. narasimhamurtii has been deposited in NCBI GenBank database with the following accession number: KY 563721. Description: Cells dorso-ventrally flattened, with an elongated oval shape (Figs 7, 8, 9, 10). Live specimens about (Х ± SD) 91.9 ± 9.8 × 70.4 ± 11.5 µm. After silver staining about 81.8 ± 6.7 × 41.3 ± 4.8 µm (Table 5). Length / width ratio approximately 1.3 in vivo and 1.9 in stained specimens. Negative phototaxis behaviour, swimming in anticlockwise direction with respect to longitudinal body axis when viewed from the posterior end. Silver-stained specimens showing about 51 – 69 rows of somatic monokinetids (27 – 36 dorsal rows, 24 – 33 ventral rows) (Fig. 9 A, B). All somatic kineties reach posterior end of body, except for 3 or 4 rows on dorsal side, terminating near cytoproct (Figs 7 A, 9 A, D). Somatic ciliature not in continuity with oral one, leaving a small gap around upper and lower oral lips (Figs 7 B, 9 B). Buccal region bearing longer and denser cilia than somatic ciliature (Figs 8 B, D, 10 D). Oral region folding inward, forming a deep buccal-pharyngeal cavity, curving to left with respect to longitudinal body axis, with oral cilia reaching the end of pharyngeal tube (Figs 7 B, 9 C, 11 C). Striated band arising from right margin of body and running along dorsal side (Figs 7 A, 8 C, 9 A, 10 A, E). Striated band measuring about 44.5 ± 1.4 µm in length after silver staining and terminating in correspondence to cytoproct, separated from it by four parallel kineties (Fig. 9 A). Cell length / striated band ratio 1.8. During cell division, early stage of duplication of striated band detected (Fig. 10 C). Cytoproct about 24.0 ± 2.3 µm, forming a longitudinal suture beneath equatorial region of the cell (Figs 7 A, 9 A, D). On left side of cytoproct, 3 dense short rows of narrowly spaced cilia (Figs 7 A, 9 A, D). Contractile vacuole in posterior body portion, opening on dorsal surface with 2 – 3 pores (Figs 7 A, 8 B, C, 9 A, 10 G). After SEM analysis, presence of a putative mucous layer secreted by the cell, all over the body (Fig. 10 D), probably with defensive function, MIN: minimum value; MAX: maximum value; X: arithmetic mean; SD: standard deviation; CV: coefficient of variation (%); N: number; n: number of specimens analysed; SI: silver impregnation; SEM: scanning electron microscopy; FE: Feulgen staining. as already reported by Fenchel and colleagues in P. frontata and Sonderia vorax (Fenchel et al., 1977). Macronucleus ovoid (15.1 × 14.3 µm on average after Feulgen staining), one micronucleus (diameter of 1.5 µm on average after Feulgen staining) of compact-type (Fokin 1997, 2010 / 2011) (Figs 7 A, 8 G). Numerous, roundish cytoplasmic inclusions of unknown function present all over the body, especially abundant at the margins of the cortex underneath the cell membrane (Fig. 8 E, F). Two types of extrusive organelles (Fig. 8 E) uniformly distributed along the cortex: straight, multi-layered extrusomes (E 1, 3.7 µm in length on average), and curved homogeneous extrusomes (E 2, 1.6 µm in length on average), (Fig. 11 A, B). TEM analysis provided information on two different morphotypes of endosymbiotic organisms associated with hydrogenosomes: the first corresponds to a short rod with electron-dense, homogeneous cytoplasm and a central long loop of DNA (average size: 1.7 × 0.4 μm) (Fig. 11 D, E); the second is rod-shaped, with one blunt end and a clearer cytoplasm (average size: 2.3 × 0.4 μm) (Fig. 11 F). Bacterial locomotory structures, such as flagella, not retrieved; cytoplasmatic roundish structures, possibly vesicles containing mineral crystals useful for redox reactions (Pflugfelder et al., 2005), sometimes observed (Fig. 11 F). Endosymbionts associated with hydrogenosomes in the classical ‘ sandwich-like’ fashion, sometimes even completely surrounded by these organelles (Fig. 11 F, G). Roundish, light structures additionally detected interpreted as a putative early stage during hydrogenosome development (Fig. 11 G). FISH analysis on this species showed positivity to universal Archaea probe ARCH 915 (Fig. 11 H), suggesting the presence of methanogens. No signals detected with EUB 338 probe (data not shown). Molecular characterization and phylogeny: From molecular analysis of the 18 S rRNA encoding gene of P. narasimhamurtii we obtained a sequence of 1722 bp. Identity values as compared with a database published Plagiopylidae sequences are reported in Table 4 and range between 97.9 % (L. mystax) and 95.9 % (P. nasuta). The identity value with P. ramani sequence was 97.4 %. In the phylogenetic analysis P. narasimhamurtii was positioned within the Plagiopyla clade, clustering together with P. ramani (Fig. 6).	en	Nitla, Venkatamahesh, Serra, Valentina, Fokin, Sergei I., Modeo, Letizia, Verni, Franco, Sandeep, Bhagavatula Venkata, Kalavati, Chaganti, Petroni, Giulio (2019): Critical revision of the family Plagiopylidae (Ciliophora: Plagiopylea), including the description of two novel species, Plagiopyla ramani and Plagiopyla narasimhamurtii, and redescription of Plagiopyla nasuta Stein, 1860 from India. Zoological Journal of the Linnean Society 186: 1-45
03948782180AFF80FC5D0C1BFA85F89D.taxon	description	(FIGS 6, 12 – 16; TABLES 4, 6) Neotype material: The slide with the silver-stained neotype specimen (indicated with a black circle of ink on the coverslip) has been deposited in the collection of the ‘ Museo di Storia Naturale dell’Università di Pisa’ (Calci, Pisa, Italy), with registration number ‘ 2017 - 3 ’. Neotype locality: Kolleru Lake in the proximity of Tokalapalli Village in West Godavari District of Andhra Pradesh, Southern India (N 16 ° 44 ’ 16.0 ”, E 81 ° 24 ’ 18.0 ”). This species inhabits freshwater sites with oxygen-depleted water, in presence of decomposed sediments (sapropel). Gene sequence: The 18 S rRNA sequence of P. nasuta has been deposited in NCBI GenBank database with the following accession number: KY 563719.	en	Nitla, Venkatamahesh, Serra, Valentina, Fokin, Sergei I., Modeo, Letizia, Verni, Franco, Sandeep, Bhagavatula Venkata, Kalavati, Chaganti, Petroni, Giulio (2019): Critical revision of the family Plagiopylidae (Ciliophora: Plagiopylea), including the description of two novel species, Plagiopyla ramani and Plagiopyla narasimhamurtii, and redescription of Plagiopyla nasuta Stein, 1860 from India. Zoological Journal of the Linnean Society 186: 1-45
03948782180EFF95FF410F9EFA98F95F.taxon	description	The two newly described species clearly belong to the genus Plagiopyla, owing to the presence of typical morphological traits and due to the molecular results. Indeed, the 18 S rRNA based phylogeny showed that the two new Plagiopyla species fall within the riboclass Plagiopylea in the clade of the family Plagiopylidae, clustering with the Plagiopyla spp. already present in the database (i. e. P. frontata and P. nasuta). Identification at species level was somewhat more challenging. Indeed, available morphological data regarding the species included in the genus are scarce. Descriptions of other species, especially in former literature, generally lack some morphological information that would have been important for species discrimination (i. e. presence and number of vacuole pore / s, presence and morphology of extrusive organelles, cytoproct-related ciliary rows, etc.). Also, morphometric data are generally fragmentary or missing. In the present paper, we report an overview of past species descriptions, which are summarized in Table 7, where the scarcity of available details is evident. Nevertheless, we succeeded in discriminating P. ramani and P. narasimhamurtii, as true novel freshwater species, describing them according to the most recent criteria of integrative taxonomy. If compared with other Plagiopyla species from the freshwater environment, i. e. P. nasuta, P. simplex and P. megastoma, the two newly described species have reduced body sizes and a lower number of somatic kineties. In detail, P. ramani is the only species of the genus so far described with multiple vesicular micronuclei. Additionally, it shows 2 – 5 pores of contractile vacuoles and a curved type of extrusomes: this combination of features has never been reported before for any other freshwater Plagiopyla species (for further comparison see Table 7). As for Plagiopyla narasimhamurtii, it has some traits in common with other congeners, such as the overall body shape and the nuclear composition, with one ovoid macronucleus and one compact-type micronucleus (except for P. ramani and P. stenostoma, which have several micronuclei). However, P. narasimhamurtii has a peculiar trait that allowed us to propose this species as novel, e. g. the presence of two types of extrusomes, differing in appearance and structure; this feature has never been reported for any other Plagiopyla species, except for P. nasuta according to de Puytorac et al. (1985) (see discussion of P. nasuta and for further comparison see Table 7). Straight extrusomes of P. narasimhamurtii closely resemble ‘ extrusome type I’ of Sonderia vorax at ultrastructural level; interestingly, the latter plagiopylid carries two types of such structures as well (Modeo et al., 2013). CONSIDERATIONS ON PLAGIOPYLA NASUTA STEIN, 1860	en	Nitla, Venkatamahesh, Serra, Valentina, Fokin, Sergei I., Modeo, Letizia, Verni, Franco, Sandeep, Bhagavatula Venkata, Kalavati, Chaganti, Petroni, Giulio (2019): Critical revision of the family Plagiopylidae (Ciliophora: Plagiopylea), including the description of two novel species, Plagiopyla ramani and Plagiopyla narasimhamurtii, and redescription of Plagiopyla nasuta Stein, 1860 from India. Zoological Journal of the Linnean Society 186: 1-45
03948782180EFF95FF410F9EFA98F95F.taxon	description	Despite all these contributions, P. nasuta has never been redescribed up to now according to requirements of integrative taxonomy (morphology, ultrastructure and molecular characterization of a marker gene). Concerning molecular analysis, only a single 18 S rRNA sequence of P. nasuta was available in on-line databases (accession number Z 29442) before our study; this sequence was provided by Embley and colleagues (Embley et al., 1995), allowing in the mid- 1990 s the first phylogenies of plagiopylids together with P. frontata and Trimyema sequences. Due to the sequencing technology available at the time, it is possible that their sequence could have included nucleotide errors; indeed, four nucleotides were not properly resolved. Remaining differences between that and our sequence are represented by five mismatches, four of which are present in highly conserved columns when aligned with other sequences from Plagiopylea. Therefore, it is feasible that only the remaining mismatch located in a variable site represents a real difference between the two populations, which are then extremely similar. In the morphological analysis, we focused our attention on the same traits proposed by previous authors, as well as on new, in our view significant, morphological details. Thus, we produced a detailed formal redescription based on a more complete set of morphological and morphometric data, also enriched by the results of the first SEM investigation of this species. Our morphometric analyses agree with some of the previous studies while deviating from other MIN: minimum value; MAX: maximum value; X: arithmetic mean; SD: standard deviation; CV: coefficient of variation (%); N: number; n: number of specimens analyzed; SI: silver impregnation; SEM: scanning electron microscopy; FE: Feulgen staining. descriptions (Table 8). Indeed, in past reports the size of P. nasuta varied conspicuously in length, ranging from 50 – 70 µm (Wetzel, 1928) to 100 – 240 µm (Kent, 1880 – 82). The original description by Stein (1860) did not report any precise measurements for the species, but he mentioned that its size was almost identical to that of Pleuronema chrysalis (i. e. about 70 – 120 µm in length); Kahl (1931) described a P. nasuta about 80 – 180 µm long, presumably measured in live conditions. Plagiopyla nasuta redescribed in the present work does not vary so greatly either in live or in stained specimens (Table 6), and is much more similar in size (i. e. 86 – 100 µm in length) to those reported by Levander (1894) and Sola et al. (1988) (Table 8). COMPARISON WITH PREVIOUS DESCRIPTIONS OF PLAGIOPYLA NASUTA In our study, the use of silver staining and SEM analysis allowed the detection of some features never reported before, which should be considered, in our opinion, for diagnostic purposes. In detail: (1) in our P. nasuta from Kolleru, the striated band terminates beneath the equatorial line of the body, in proximity to the anterior region of the cytoproct, at a distance of four parallel somatic kineties from the latter. Our observation agrees with the schematic drawings by de Puytorac et al. (1985), but disagrees with the study of Sola et al. (1988), in which the striated band terminates in contact with the cytoproct. Foissner et al. (1995) focused on the presence of the striated band, which they considered a sensory structure, although not mentioning where it terminates. In our study, this structure gains importance as an additional diagnostic trait, since we have also introduced its length as an additional feature in morphometric analysis. (2) Several authors described the composition of oral and somatic ciliature (Jankowski, 1964; Bick, 1972; de Puytorac et al., 1985; Dragesco & Dragesco-Kerneis, 1986; Sola et al., 1988; Foissner et al., 1995), although none of them gave an exhaustive description of their junction. Indeed, all interpreted the somatic cilia in continuity with the oral kineties. The present morphological analysis clarifies this issue by revealing the presence of a small gap between the somatic cilia and the oral lips. (3) The micronucleus had always been recorded by past authors, although none of them gave a precise definition regarding its composition. After our comparative analysis among different Plagiopyla species we have decided to define the micronucleus of P. nasuta as ‘ compact-type micronucleus’, because it is formed by a compact mass of chromatin. This definition was used by Fokin (Fokin, 1997; 2010 / 2011) for the description of Paramecium species, but also seems appropriate for the genus Plagiopyla. (4) As for previous Plagiopyla descriptions, we also detected the presence of a very dense ciliature in P. nasuta, aligned along the left side of cytoproct. Two cytoproct dense rows were depicted by de Puytorac et al. (1985), but they did not highlight this feature, nor even indicate the position of the cytoproct. In our opinion, the composition of this dense ciliature should be considered another useful trait for species identification. (5) Our analysis detected the presence of a single type of extrusomes (straight) as already reported by Foissner et al. (1995), while the study by de Puytorac et al. (1985) proposed two types of extrusomes, i. e. curved-long and curved-short. As TEM pictures published by de Puytorac and colleagues (1985) are unfortunately scarcely explanatory, and a detailed description of extrusomes has not been provided, in our view the presence of a single type of straight extrusomes has to be considered a diagnostic characteristic for P. nasuta. Dragesco and Dragesco-Kernéis raised the importance of extrusomes, although they doubted they would be considered a diagnostic feature (Dragesco & Dragesco-Kernéis, 1986). In our opinion, these structures are useful for species identification, because they constitute a stable characteristic among organisms of the same species. Therefore, they should be taken into account as additional information in cell description, together with other morphological features; in keeping with this view, we also reported the presence of cortical granules in our P. nasuta.	en	Nitla, Venkatamahesh, Serra, Valentina, Fokin, Sergei I., Modeo, Letizia, Verni, Franco, Sandeep, Bhagavatula Venkata, Kalavati, Chaganti, Petroni, Giulio (2019): Critical revision of the family Plagiopylidae (Ciliophora: Plagiopylea), including the description of two novel species, Plagiopyla ramani and Plagiopyla narasimhamurtii, and redescription of Plagiopyla nasuta Stein, 1860 from India. Zoological Journal of the Linnean Society 186: 1-45
03948782180EFF95FF410F9EFA98F95F.taxon	description	NEOTYPIFICATION OF PLAGIOPYLA NASUTA STEIN, 1860 No type or voucher slides are available from the P. nasuta populations described by Stein (1860) and other authors (see above). Moreover, past descriptions of this species present some details that are not in agreement with each other: body size, presence / absence and shape of extrusomes, type of habitats, etc. Thus, it seems wise to define P. nasuta objectively by the designation of a neotype (ICZN, 1999; Foissner, 2002), associated with an 18 S rRNA sequence deposited in online database. According to Article 75.3 of the ICZN (1999), our designation is accompanied by the publication of the following statements: 1. The taxonomic status of the present species is somewhat unclear because the original description does not report morphometrics and subsequent redescriptions do not agree in some important features, such as body size, extrusomes, habitats, etc. (see above for details). 2. For a differentiation of P. nasuta from related taxa, see above and further in the text. 3. The neotype specimen (Figs 12 – 16; Table 6), from Kolleru Lake is described in detail (see above); thus, recognition of the neotype designated is ensured and associated with an 18 S rRNA sequence deposited in GenBank (KY 563719). 4. It is generally known that no type material is available from species described by Stein (1860). Further, there is no indication that other authors made permanent preparations of the present species. 5. There is strong evidence that the neotype is consistent with P. nasuta as originally described by Stein (1860) and subsequentely by other authors. For a detailed comparison, see above and below. Moreover, the 18 S DNA sequencing confirms the identity of the species at a molecular level (see above). 6. Unfortunately, the neotype population does not come from very near the original type locality (freshwater bodies in Czech Republic and Germany vs. freshwater Kolleru Lake, in India; distance about 6000 km). However, both sites are freshwater habitats and P. nasuta is a cosmopolitan ciliate (see further), so this point should not be over-interpreted as suggested by Foissner (2002): ‘ neotypes of protists, especially ciliates, should be freed from the type locality regulation of Article 75.3.6 of the Code, provided that neotypification is based on a through redescription of the organism and usable neotype material has been deposited in an acknowledged repository’. Other authors have already performed ciliate neotypification despite the same issue: as examples, see Foissner et al. (2002), Berger (2004), Li et al. (2007, 2010) and Modeo et al. (2013). A detailed description of the neotype locality is provided in the ‘ Material and Methods’ and ‘ Results’ sections. 7. The slide containing the neotype specimen is deposited in the collection of the ‘ Museo di Storia Naturale dell’Università di Pisa’ (Calci, Pisa, Italy), with the code ‘ 2017 - 3 ’. CONSIDERATIONS ON THE PHYLOGENY OF THE FAMILY PLAGIOPYLIDAE The ingroup topology obtained in our phylogenetic analysis agrees with previous topologies (Modeo et al., 2013; Xu et al., 2013; Liu et al., 2015), showing four distinctive clades corresponding to the four families of the class Plagiopylea. In particular, the family Plagiopylidae consists of two sister clades including sequences of characterized and uncharacterized Plagiopyla species, plus Lechriopyla mystax. Unfortunately, sequences of Paraplagiopyla kiboko and Pseudoplagiopyla sinistra are still not available in on-line databases, so it was not possible to obtain an exhaustive phylogeny of the family, following the current systematic definition of the group (Lynn, 2008). The monophyly of Plagiopylidae is supported by the present analysis, although the clade of Plagiopyla also includes the sequence belonging to L. mystax. The latter clusters with some uncharacterized plagiopylids and our two novel species, which can undoubtedly be assigned to the genus Plagiopyla based on their morphology (see discussion above). The phylogenetic tree made by Lynn & Strüder-Kypke (2002) did not show this discrepancy because only the sequences of P. nasuta and P. frontata were available at the time. The availability of more sequences of Plagiopyla and related environmental sequences would have helped to understand that L. mystax is not the sister genus of Plagiopyla but, more likely, a congener.	en	Nitla, Venkatamahesh, Serra, Valentina, Fokin, Sergei I., Modeo, Letizia, Verni, Franco, Sandeep, Bhagavatula Venkata, Kalavati, Chaganti, Petroni, Giulio (2019): Critical revision of the family Plagiopylidae (Ciliophora: Plagiopylea), including the description of two novel species, Plagiopyla ramani and Plagiopyla narasimhamurtii, and redescription of Plagiopyla nasuta Stein, 1860 from India. Zoological Journal of the Linnean Society 186: 1-45
03948782180EFF95FF410F9EFA98F95F.taxon	description	MIN: minimum value; MAX: maximum value; X: arithmetic mean; SD: standard deviation; CV: coefficient of variation (%); N: number; n: number of specimens analyzed; SI: silver impregnation; SEM: scanning electron microscopy; FE: Feulgen staining. furcula. Thus, we propose that the genus Lechriopyla represents a junior synonym of Plagiopyla and that L. mystax should be renamed as Plagiopyla mystax comb. nov. As an alternative, it could be hypothesized that when the authors collected L. mystax specimens from sea urchin gut for their study (Lynn & Strüder-Kypke, 2002), a few Plagiopyla specimens had been erroneously selected (e. g. both Plagiopyla minuta and P. nyctotherus occur in the gut of sea urchins according to: Beers, 1954; Poljansky & Golikova, 1959; Berger & Lynn, 1984) and their DNA preferentially amplified with respect to L. mystax ’ s DNA. In this case, the sequence published as L. mystax (AF 527757) could be attributed to an uncharacterized Plagiopyla, and Lechriopyla would remain a valid genus needing a molecular characterization. Considering that there is no evidence of the occurrence of such a technical error, and that these authors are extremely skilled in comparative morphology and species identification, we consider the first hypothesis to be more reliable, and consequently propose to synonymize the two genera. Our conservative interpretation leads us to maintain the monophyly of the genus Plagiopyla. Indeed, we chose a ‘ lumper’ approach (Corliss, 1976) given the high morphological and molecular affinities between the genera Lechriopyla and Plagiopyla CRITICAL REVISION OF THE FAMILY PLAGIOPYLIDAE The present critical revision is based on several, selected publications concerning members of the family, i. e. what we consider to be milestone works regarding morphological description, molecular characterization, ecology, and distribution. As some other papers have not been included, the present section is meant as a non-comprehensive overview of plagiopylid literature. To date, family Plagiopylidae comprises four genera: Plagiopyla, Lechriopyla, Paraplagiopyla and Pseudoplagiopyla. Some of them share common features, such as the holotrichously ciliated body, the peculiar oral apparatus and the striated band. However, it is not the case for Paraplagiopyla, whose morphology raises some doubts on its systematic account. Paraplagiopyla kiboko, surveyed by Thurston & Grain (1971) in the stomach contents of Hippopotamus amphibius from Queen Elisabeth Park (Uganda), has been described as 48 – 110 µm long and 25 – 62 µm wide, after staining. The surface of its body is not uniformly ciliated: only a peripheral ciliated furrow departs from the oral groove, although protargol staining reveals lines of non-ciliated kinetosomes on the remaining cell surface. The striated band is lacking. One elongated macronucleus, a single micronucleus and two contractile vacuoles are present; no extrusomes detected. The attribution of Paraplagiopyla to the family Plagiopylidae has already been questioned by Lynn (2008) who remarked that, ‘ Paraplagiopyla, if truly a plagiopylean, is an exception as its somatic kineties are restricted to a narrow furrow that extends around the For Plagiopyla spp. described in the present work (in bold) we reported measurements from fixed specimens (silver and Feulgen stainings); N: number; ND: no data; (l): measurements from live specimens; (f): measurements from fixed specimens; (ns): not specified if measurements were from live or fixed specimens; AV: average value, calculated on minimum and maximum measurements reported in cited literature; * trait observed or measured from the representative illustration; ° / °° indicates the source of the information within the column if more than one reference is indicated. For Plagiopyla nasuta described in the present work (in bold) we reported measurements from fixed specimens (silver and Feulgen stainings); MA: macronucleus; MI: micronucleus; SB: striated band; CVP: contractile vacuole pore; ND: no data; (l): measurements from live specimens; (f): measurements from fixed specimens; (ns): not specified if measurements were from live or fixed specimens; Ellips.: Ellipsoidal; Irreg.: Irregular; Spher.: Spheroidal; Renif.: Reniform; * trait observed or measured from the representative illustration; # Misinterpreted by authors as trichocysts. edges of the flattened cell’. Moreover, it lacks the striated band which, in our opinion, is an apomorphic feature of the family. For all these reasons, we propose the exclusion of this genus from the family Plagiopylidae. As for Pseudoplagiopyla sinistra, its description is poor. Authors (Small & Lynn, 1985) did not mention either the place / habitat of retrievement or some important morphological features (i. e. body size, striated band, contractile vacuole, extrusomes, etc.). Given the limited available data, any change in its systematic position is not advisable, and we do recommend a redescription of the species, possibly using a multidisciplinary integrated approach also comprising the analysis of molecular markers. Regarding Lechriopyla, as previously discussed, the only species belonging to that genus has been moved and included as a new combination in the genus Plagiopyla. Moreover, two novel species of Plagiopyla have been described. Therefore, the genus Plagiopyla now comprises three additional species: P. ramani sp. nov., P. narasimhamurtii sp. nov. and P. mystax comb. nov., reaching a total of 14 included species (Fig. 18). We analysed all the considered descriptions of Plagiopyla spp. in order to pinpoint possible synonyms and uncertain / wrong species attributions. The majority of described Plagiopyla spp. (Table 7) have distinctive features, except for P. cucullio, the description of which is poor. Actually, this marine species could be easily misidentified either as P. frontata, P. ovata or P. marina. Indeed, Wallengren (1918) himself proposed to synonymize Plagiopyla nasuta var. marina (former description of P. marina) found by Gourret & Roeser (1886) with P. cucullio. Since Kahl (1931) and Jankowski (2007) kept P. cucullio separate from P. marina, we still prefer to treat P. cucullio as a distinct species, although we do notice a marked resemblance with P. frontata. The type of habitat, in most cases, could help discriminate Plagiopyla species: P. simplex, P. megastoma, P. ramani and P. narasimhamurtii are typically found in freshwater; Plagiopyla cucullio, P. frontata, P. ovata and P. marina in marine environment; while P. mystax, P. minuta and P. nyctotherus are endocommensals of sea urchins. The only exception is P. nasuta that, apparently, was described both from freshwater and marine environments (see discussion above). Further details on species discrimination are treated in the following compendium of the family Plagiopylidae, providing a diagnosis and a key for species identification. Nevertheless, due to the scarcity of morphological details, it was not possible to insert P. cucullio in the present taxonomic key. Further investigation and, perhaps, a redescription of P. cucullio are necessary to give a detailed account of the species features.	en	Nitla, Venkatamahesh, Serra, Valentina, Fokin, Sergei I., Modeo, Letizia, Verni, Franco, Sandeep, Bhagavatula Venkata, Kalavati, Chaganti, Petroni, Giulio (2019): Critical revision of the family Plagiopylidae (Ciliophora: Plagiopylea), including the description of two novel species, Plagiopyla ramani and Plagiopyla narasimhamurtii, and redescription of Plagiopyla nasuta Stein, 1860 from India. Zoological Journal of the Linnean Society 186: 1-45
03948782181DFF97FC4E0A29FAADF95F.taxon	diagnosis	Improved diagnosis: Ovoid body shape, dorso-ventrally compressed; slit-like buccal aperture; deep oral cavity, with tubular part usually extending to left (Fig. 17 A), or curving anteriorly, then posteriorly (P. mystax) (Fig. 17 B); uniform, dense somatic ciliature; striated band on dorsal surface, arising near right margin of oral cavity; cytoproct suture opening on dorsal side; usually single contractile vacuole with pores (usually two) opening on dorsal surface; one macronucleus (or two in the case of P. binucleata); one compact-type micronucleus in most species (more than one in P. ramani and P. stenostoma); extrusomes (straight and / or curved) inserted in body cortex. Type species: Plagiopyla nasuta Stein, 1860, by monotypy. Stein (1860) describes P. nasuta as a ciliate with the body size almost equal to that of Pleuronema chrysalis (namely about 70 – 120 µm in length), found in the swamp waters near Prague and Niemegk. It has a dense cortical layer, crossed by tactile corpuscles (presumably the striated band). The oral slit is located in the centre of the body, extending from the right side to the longitudinal axis. At the end of oral slit, Stein describes ‘ a very small pharynx that leads to the oral opening’. The author points out that the cilia in the dorsal part of the body are missing (!). The ovoid nucleus is located on the right side of the body behind the peristome. The contractile vacuole is located at the body end.	en	Nitla, Venkatamahesh, Serra, Valentina, Fokin, Sergei I., Modeo, Letizia, Verni, Franco, Sandeep, Bhagavatula Venkata, Kalavati, Chaganti, Petroni, Giulio (2019): Critical revision of the family Plagiopylidae (Ciliophora: Plagiopylea), including the description of two novel species, Plagiopyla ramani and Plagiopyla narasimhamurtii, and redescription of Plagiopyla nasuta Stein, 1860 from India. Zoological Journal of the Linnean Society 186: 1-45
03948782181DFF97FCB008ACFC57FD30.taxon	diagnosis	Diagnosis: Ovoid body shape, dorso-ventrally compressed; deep oral cavity, opening on ventral side with a more internal tubular part, preceding the cytostome (Fig. 17); dense somatic ciliature; striated band on dorsal surface, arising near right margin of oral cavity; usually one macronucleus (except for Plagiopyla binucleata); extrusomes inserted in body cortex. G e n e r a a s s i g n e d: P l a g i o p y l a (t y p e g e n u s); Pseudoplagiopyla.	en	Nitla, Venkatamahesh, Serra, Valentina, Fokin, Sergei I., Modeo, Letizia, Verni, Franco, Sandeep, Bhagavatula Venkata, Kalavati, Chaganti, Petroni, Giulio (2019): Critical revision of the family Plagiopylidae (Ciliophora: Plagiopylea), including the description of two novel species, Plagiopyla ramani and Plagiopyla narasimhamurtii, and redescription of Plagiopyla nasuta Stein, 1860 from India. Zoological Journal of the Linnean Society 186: 1-45
03948782181DFFA9FC730FC1FB98FADB.taxon	description	1881 – 82: Plagiopyla nasuta Stein, 1860 – Kent, A Manual of the Infusoria, D Bogue ed., London, vol. II: p. 538, vol. III: pl. XXVII; figs 50, 51 (illustrated record). 1886: Plagiopyla varians – Maskell, Trans. N. Z. Inst., 19: 55; pl. 4; figs 6, 7 (p. 52) (illustrated record). 1894: Plagiopyla nasuta Stein, 1860 – Levander, Soc. F. & Fl. Fenn., 62 – 71 pp.; pl. III; figs 28 – 30 (illustrated record, revision). 1898: Tillina distincta – Smith, Trans. Am. Microsc. Soc., 20: 52; pl. IV; fig. 3 (illustrated record). 1899: Plagiopyla nasuta Stein, 1860 – Roux, Rev. Suisse Zool., 6: 601 – 602; pl. 13; fig. 20 (illustrated record). 1922: Plagiopyla nasuta Stein, 1860 – Penard, Études sur les infusoires d’eau douce. Georg & Cie eds, Genève, 186 – 188 pp.; figs 186, 187 (illustrated record). 1928: Plagiopyla nasuta Stein, 1860 – Wetzel, Zoomorphology, 13: 198 – 201; figs 7, 8 (illustrated record). 1931: Plagiopyla nasuta Stein, 1860 – Kahl, Tierwelt Dtl., 21: 264 – 265; figs 45.1, 45.2 (guide; revision). 1935: Plagiopyla nasuta Stein, 1860 – Wang & Nie, Sinensia, 6: 433 – 435; fig. 26 (illustrated record). 1946: Plagiopyla nasuta Stein, 1860 – Kudo, Protozoology, 3 rd edn, CC Thomas ed., Springfield, 596 – 597 pp.; fig. 262 a (revision). 1964: Plagiopyla nasuta Stein, 1860 – Jankowski, Arch. Protistenkd., 107: 286, 288; fig. 58 a, b (illustrated record). 1971: Plagiopyla nasuta Stein, 1860 – Mahajan & Nair, Rec. Zool. Surv. India, 63: 12; fig. 2 (illustrated record). 1972: Plagiopyla nasuta Stein, 1860 – Bick, Ciliated protozoa. An illustrated guide to the species used as biological indicators in freshwater biology. World Health Organisation, Geneva, p. 66; fig. 38 (guide, illustrated record). 1972: Plagiopyla nasuta Stein, 1860 – Borror, Acta Protozool., 10: 46 – 47; figs 25, 26 (illustrated record). 1978: Plagiopyla nasuta Stein, 1860 – Agamaliev, Acta Protozool., 17: 129 – 130; fig. 9 (illustrated record). 1985: Plagiopyla nasuta Stein, 1860 – De Puytorac et al., Annls. Sci. Nat., 7: 189 – 198; figs 1 – 12 (redescription after silver impregnation, morphogenesis, electron microscopy analysis). 1986: Plagiopyla nasuta Stein, 1860 – Dragesco & Dragesco-Kernéis, Faune tropicale, 26: 217; pl. 43; figs A, B (illustrated record, short taxonomic and ecological monograph). 1988: Plagiopyla nasuta Stein, 1860 – Sola et al., Acta Protozool., 27: 279 – 285; figs 1, 2 (redescription and revision). 1995: Plagiopyla nasuta Stein, 1860 – Foissner et al., Inf. ber. Bayer. Landesamtes Wasserwirtsch., 266 – 268 pp.; figs 1 – 24 (taxonomic and ecological revision, redescription after silver impregnation). 2001: Plagiopyla nasuta Stein, 1860 – Al-Rasheid, Trop. Zool., 14: 151; figs 52, 53 (redescription after silver impregnation). 2004: Plagiopyla nasuta Stein, 1860 – Şenler & Yildiz, Tuk. J. Zool., 28: 261 – 262; fig. 17 (redescription after silver impregnation). 2005: Plagiopyla nasuta Stein, 1860 – Alekperov, Borchali Publishing House, p. 74; figs 20.2, 20.3 (illustrated record). 2007: Plagiopyla nasuta Stein, 1860 – Jankowski, Russian Acad. Sci., p. 792; fig. 355 (revision). 2007: Plagiopyla wetzeli Kahl, 1931 – Jankowski, Russian Acad. Sci., p. 793 (revision). 2008: Plagiopyla nasuta Stein, 1860 – Kalavati & Raman, Rec. Zool. Surv. India Occ. Paper N ° 282, p. 107; fig. 130 (illustrated record). Improved diagnosis (Fig. 18 A): Body length 80 – 130 µm on average (total range: 50 – 240 µm), body width 45 – 80 µm on average (total range: 25 – 190 µm). Somatic kineties: 42 – 90. Striated band 60 – 68 µm long. One ovoid macronucleus (22 – 38 × 7 – 24 µm) and a single, compact-type micronucleus (diameter, Ø 2.1 – 3.1 µm). One contractile vacuole with two pores opening on the dorsal part of the cell. Cytoproct 25.4 µm long, located on the dorsal part of the cell, with two cytoproct-related ciliary rows on its left. Straight, multi-layered extrusomes (length: 4 – 8 µm). Type locality: Freshwater ponds in Prague (Czech Republic) and Niemegk (Germany) (Stein, 1860). Neotype locality: Freshwater in the hypoxic / anoxic part of the water column. Found in Kolleru Lake, Andhra Pradesh, India (present study). Ecology and distribution: Freshwater, brackish and marine species. Cosmopolitan. Found in: AFRICA – Freshwater: UGANDA, Lake George (Dragesco, 1972; Dragesco & Dragesco-Kerneis, 1986). Marine water: Red Sea, Suez Canal (El-Serehy, 1993). AMERICA – Freshwater: ARGENTINA, pond in Tierra del Fuego province (Küppers & Claps, 2016); BRAZIL, freshwater bodies nearby Manguinhos (Da Cunha, 1916), and in phytotelmata of tank bromeliads in the Upper Paraná River floodplain (Buosi et al., 2014); USA, river of Florida (Beaver & Crisman, 1989), Illinois River (Kofoid, 1908), Lake Borgne, Louisiana (Smith, 1898), Mississippi delta (Bamforth, 1969). Marine water: USA, New Hampshire (Borror, 1972); South Atlantic (Petz, 1999).	en	Nitla, Venkatamahesh, Serra, Valentina, Fokin, Sergei I., Modeo, Letizia, Verni, Franco, Sandeep, Bhagavatula Venkata, Kalavati, Chaganti, Petroni, Giulio (2019): Critical revision of the family Plagiopylidae (Ciliophora: Plagiopylea), including the description of two novel species, Plagiopyla ramani and Plagiopyla narasimhamurtii, and redescription of Plagiopyla nasuta Stein, 1860 from India. Zoological Journal of the Linnean Society 186: 1-45
03948782181DFFA9FC730FC1FB98FADB.taxon	materials_examined	ANTARCTICA – Freshwater: Sombre Lake, Signy Island (Hawthorn & Ellis-Evans, 1984). ASIA – Freshwater: AZERBAIJAN (Alekperov, 2005, 2012); CHINA, freshwater bodies nearby Nanking (Wang & Nie, 1935), and Tibetan Plateau (Wang, 1977); INDIA, Kolkata (Mahajan & Nair, 1971), and Kolleru Lake (present study); ISRAEL, Lake Kinneret (Madoni, 1990); TURKEY, Van Castle (Şenler & Yildiz, 2004). Brackish water: INDIA, Chilka Lake (Das, 1995). Marine water: INDIA, Visakhapatnam coast (Kalavati & Raman, 2008); Red Sea, Saudi Coast (Al-Rasheid, 1999, 2001), AUSTRALIA – Freshwater: NEW ZEALAND, from Wellington district (Maskell, 1886). EUROPE – Freshwater: AUSTRIA (Schneider, 1930), River Traun (Foissner, 1974); CZECHOSLOVAKIA, river Danube (Tirjaková, 1992); FINLAND, Helsinki (Levander, 1894); FRANCE, Lorraine (Florentin, 1899); GERMANY (Engelmann, 1862; Levander, 1894; Wetzel, 1928; Schneider, 1930; Kahl, 1931; Liebmann, 1938; Kaufmann, 1958; Grabacka, 1971, 1973, 1977; Alekperov, 1983; Foissner et al., 1995), Bonn (Wilbert, 1969), forest ponds near river Elbe (ProkeŠová, 1959), Hamburg city canal (Caspers & Schulz, 1962; Bartsch & Hartwig, 1984), North Württemberg and Bavaria (Buck, 1961); HUNGARY, river Danube (Bereczky, 1977); ITALY, river in the Northern part (Madoni, 1979), and alpine lake (Wagener, 1989); LATVIA, rivers (Veylande & Liyepa, 1985); POLAND, river Drwinka (Wiackowski, 1981), river Lyna (Hul, 1987); ROMANIA, Lake Floreasca, Bucharest (Vuxanovici, 1963); RUSSIA, rivers (Neiswestnowa-Shadina, 1935), and St. Petersburg (Jankowski, 1964); SPAIN, river Henare, Guadalajara (Sola et al., 1988), and Lake Arcas- 2 (Finlay et al., 1991); SWITZERLAND, Geneva (Roux, 1899; Penard, 1922), Sainte-Croix – Jura vaudois (Mermod, 1914); UKRAINE, Odessa (Butschinsky, 1897); UNITED KINGDOM, river Medlock (Frost et al., 1976). Marine water: Barents Sea (Azovsky, 1996); Black Sea (Detcheva, 1992); Caspian Sea (Agamaliev, 1978), French Atlantic (Dragesco, 1960), Mediterranean Sea (Dini et al., 1995). Note: not all the references regarding Plagiopyla nasuta distribution have been herein cited, so this is only a partial review of species distribution. Gene sequences: 18 S rRNA gene, accession numbers: Z 29442 (Embley et al., 1995 – authors did not provide morphological description and sampling place of the organism), KY 563719 (present study). Remarks: According to Kahl (1931), and in our opinion, it is plausible that marine P. nasuta could represent a different species, possibly P. marina. One variety exists: P. nasuta var. bivacuolata (Vuxanovici, 1963).	en	Nitla, Venkatamahesh, Serra, Valentina, Fokin, Sergei I., Modeo, Letizia, Verni, Franco, Sandeep, Bhagavatula Venkata, Kalavati, Chaganti, Petroni, Giulio (2019): Critical revision of the family Plagiopylidae (Ciliophora: Plagiopylea), including the description of two novel species, Plagiopyla ramani and Plagiopyla narasimhamurtii, and redescription of Plagiopyla nasuta Stein, 1860 from India. Zoological Journal of the Linnean Society 186: 1-45
03948782181DFFA9FC730FC1FB98FADB.taxon	description	1918: Plagiopyla cucullio Quenn – Wallengren, Lunds Univ. Årsskr., 30: 19 – 24; figs J – L (redescription, combining author). 1931: Plagiopyla (Paramecium) cucullio (Quennerstedt, 1867), Wallengren, 1915 – Kahl, Tierwelt Dtl., 21: 267; fig. 45.5 (guide; revision). 1933: Plagiopyla cucullio Wallengren, 1918 – Kahl, Tierwelt N., p. 74; fig. 9.6 (guide, revision). 2007: Plagiopyla cucullio (Quennerstedt, 1867), Wallengren, 1918 – Jankowski, Russian Acad. Sci., p. 792 (revision). Improved diagnosis (Fig. 18 I): Body length 73 – 79 µm, body width 31 – 37 µm. Number of somatic kineties estimated around 50. Striated band present. One ovoid macronucleus and a single compact-type micronucleus. One contractile vacuole in terminal position. Cytoproct and extrusomes not discussed. Ty p e l o c a l i t y: S e a w a t e r i n Va r b e r g, S w e d e n (Quennerstedt, 1867). Ecology and distribution: Marine. Found in Sweden, Varberg (Quennerstedt, 1867), and in Öresund, Baltic Sea (Wallengren, 1918).	en	Nitla, Venkatamahesh, Serra, Valentina, Fokin, Sergei I., Modeo, Letizia, Verni, Franco, Sandeep, Bhagavatula Venkata, Kalavati, Chaganti, Petroni, Giulio (2019): Critical revision of the family Plagiopylidae (Ciliophora: Plagiopylea), including the description of two novel species, Plagiopyla ramani and Plagiopyla narasimhamurtii, and redescription of Plagiopyla nasuta Stein, 1860 from India. Zoological Journal of the Linnean Society 186: 1-45
039487821822FFA8FCB30B83FB7FF9AC.taxon	description	1930: Plagiopyla nasuta Stein 1860 – Lynch, Univ. Calif. Publ. Zool., 33: 337 – 339; fig. B 4 – 6 (illustrated report). 1931: Plagiopyla marina Gourret & Roeser, 1886 – Kahl, Tierwelt Dtl., 21: 265, 267; fig. 45.11 (the author elevates the variety to the rank of species; guide; revision). 1933: Plagiopyla marina Gourret & Roeser, 1886 – Kahl, Tierwelt N., p. 74; fig. 9.4 (guide, revision). 2007: Plagiopyla marina Gourret & Roeser, 1886 – Jankowski, Russian Acad. Sci., p. 792 (revision). Improved diagnosis (Fig. 18 G): Body length 70 – 114 µm, body width 31 – 56 µm after staining. Somatic kineties not described. Striated band present. One ovoid macronucleus (size 28 × 23 µm) and a single micronucleus (Ø 5 µm). One contractile vacuole. Cytoproct 10 µm long, located on the dorsal part of the cell. Straight extrusomes (length: 7 – 8 µm), sometimes absent. Type locality: S eawater in the Gulf of Marseille, France (Gourret & Roeser, 1886). Ecology and distribution: Marine species. Found in France, Gulf of Marseille (Gourret & Roeser, 1886) and California, Monterey (Lynch, 1930).	en	Nitla, Venkatamahesh, Serra, Valentina, Fokin, Sergei I., Modeo, Letizia, Verni, Franco, Sandeep, Bhagavatula Venkata, Kalavati, Chaganti, Petroni, Giulio (2019): Critical revision of the family Plagiopylidae (Ciliophora: Plagiopylea), including the description of two novel species, Plagiopyla ramani and Plagiopyla narasimhamurtii, and redescription of Plagiopyla nasuta Stein, 1860 from India. Zoological Journal of the Linnean Society 186: 1-45
039487821822FFA8FF5D0C4BFB25FE79.taxon	description	1931: Plagiopyla (Tillina) megastoma (Smith, 1899) – Kahl Tierwelt Dtl., 21: 265; fig. 45.9 (guide; revision). 2007: Plagiopyla megastoma (Smith, 1899) – Jankowski, Russian Acad. Sci., p. 792 (revision). Improved diagnosis (Fig. 18 J): Body length 100 – 150 µm, body width estimated around 73 µm in live specimens. The number of somatic kineties is not reported. Striated band present (estimated length: around 68 µm). One ovoid macronucleus (estimated size: 24 × 14 µm) and a single, compact-type micronucleus. One contractile vacuole with two pores opening on the dorsal part of the cell. Curved extrusomes. Type locality: Freshwater, in Lake Borgne, Louisiana (Smith, 1898). Ecology and distribution: Freshwater and brackish water species. Found in Louisiana, Lake Borgne (Smith, 1898), in Germany (Kahl, 1931) and in the Gulf of Mexico (Borror, 1962).	en	Nitla, Venkatamahesh, Serra, Valentina, Fokin, Sergei I., Modeo, Letizia, Verni, Franco, Sandeep, Bhagavatula Venkata, Kalavati, Chaganti, Petroni, Giulio (2019): Critical revision of the family Plagiopylidae (Ciliophora: Plagiopylea), including the description of two novel species, Plagiopyla ramani and Plagiopyla narasimhamurtii, and redescription of Plagiopyla nasuta Stein, 1860 from India. Zoological Journal of the Linnean Society 186: 1-45
039487821822FFA8FEE608B5FED0FC31.taxon	description	1931: Plagiopyla simplex Wetzel, 1928 – Kahl Tierwelt Dtl., 21: 265; fig 45.4 (guide; revision). 2007: Plagiopyla simplex Wetzel, 1928 – Jankowski, Russian Acad. Sci., p. 793 (revision). Improved diagnosis (Fig. 18 D): Body length 135 – 150 µm, body width 60 – 70 µm. Final part of the body pointed. Somatic kineties: 80. Striated band absent. One ellipsoidal macronucleus (35 – 40 × 15 – 16 µm) and a single compact-type micronucleus (Ø about 7.5 µm). One contractile vacuole. Extrusomes present (about 6 – 7 µm in length). Type locality / ecology and distribution: Freshwater, in Leipzig (Germany).	en	Nitla, Venkatamahesh, Serra, Valentina, Fokin, Sergei I., Modeo, Letizia, Verni, Franco, Sandeep, Bhagavatula Venkata, Kalavati, Chaganti, Petroni, Giulio (2019): Critical revision of the family Plagiopylidae (Ciliophora: Plagiopylea), including the description of two novel species, Plagiopyla ramani and Plagiopyla narasimhamurtii, and redescription of Plagiopyla nasuta Stein, 1860 from India. Zoological Journal of the Linnean Society 186: 1-45
039487821821FFABFF1609E3FECFF9EF.taxon	description	1933: Plagiopyla frontata Kahl, 1931 – Kahl, Tierwelt N., p. 74; fig. 9.3 (guide, revision). 2000: Plagiopyla frontata Kahl, 1932 – Esteban et al., J. Nat. Hist., 34: 177 – 179; figs 34 – 37 (redescription after silver impregnation). 2007: Plagiopyla frontata Kahl, 1931 – Jankowski, Russian Acad. Sci., p. 792 (revision). Improved diagnosis (Fig. 18 H): Body length 78 – 115 µm on average (total range: 75 – 120 µm), body width 37 – 67 µm. Somatic kineties: 40 – 68. Striated band present although not described. One ovoid macronucleus (estimated size: about 22 × 16 µm) and a single, compact-type micronucleus. One contractile vacuole with two pores opening on the dorsal part of the cell. Cytoproct located on the dorsal part of the cell. Curved extrusomes. Type locality: Salt water nearby Bad Oldesloe village, and sapropel of Sylt, Germany (Kahl, 1931). Ecology and distribution: Marine, brackish in hypoxic / anoxic environment. Found in: Germany (Kahl, 1931, 1933); Denmark, Nivå Bay, the Helsingør Beach and the Isefjord (Fenchel, 1968) and Danish fjord (Fenchel et al., 1995); Australia, in Hopkins estuary near Warrnambool (Esteban et al., 2000). Gene sequences: 18 S rRNA accession number: Z 29440 (Embley et al., 1995 – authors did not provide morphological description and sampling place of the organism). Remarks: In Kahl’s description (1931) it is 80 – 120 µm long, according to Esteban et al. (2000) it is 75 – 110 µm long. Esteban and colleagues (2000) indicate P. frontata as ‘ Kahl, 1932 ’, although the description of the species was made in 1931 (Kahl, 1931 – page 267).	en	Nitla, Venkatamahesh, Serra, Valentina, Fokin, Sergei I., Modeo, Letizia, Verni, Franco, Sandeep, Bhagavatula Venkata, Kalavati, Chaganti, Petroni, Giulio (2019): Critical revision of the family Plagiopylidae (Ciliophora: Plagiopylea), including the description of two novel species, Plagiopyla ramani and Plagiopyla narasimhamurtii, and redescription of Plagiopyla nasuta Stein, 1860 from India. Zoological Journal of the Linnean Society 186: 1-45
039487821821FFABFEFF0F63FAD2FAF3.taxon	description	1933: Plagiopyla ovata Kahl, 1931 – Kahl, Tierwelt N., p. 74; figs 9.1, 9.2 (guide, revision). 1941: Plagiopyla ovata Kahl, 1931 – Ozaki & Yagiu, J. Sci. Hiroshima Univ., 8: 178 – 179; pl. II; figs 5, 6 (illustrated record). 1986: Plagiopyla ovata Kahl, 1930 – Dragesco & Dragesco-Kernéis, Faune tropicale, 26: 219; pl. 43; figs C, D, E (illustrated record, short taxonomic and ecological monograph). 1996: Plagiopyla ovata Kahl, 1930 – Alekperov & Asadullayeva, Zool. Zh., 75: 768; fig. 2 b (illustrated record). 2005: Plagiopyla ovata Kahl, 1930 – Alekperov, Borchali Publishing House, 74, 76 pp.; fig. 20.4 (illustrated record). 2007: Plagiopyla ovata Kahl, 1931 – Jankowski, Russian Acad. Sci., p. 792; fig 355 (revision). Improved diagnosis (Fig. 18 L): Body length 60 – 80 µm on average (total range: 35 – 99 µm), body width 35 – 40 µm on average (total range: 26 – 46 µm). Somatic kineties: 48 – 66. Striated band present (estimated length: about 31 µm). One reniform / ovoid macronucleus (about 23 × 17 µm) and a single, compact-type micronucleus (Ø 3.5 – 4.2 µm). One contractile vacuole with 1 pore opening on the dorsal part of the cell. Cytoproct not described. Elongated extrusomes. Type locality: Seawater in Sylt, Germany (Kahl, 1931). Ecology and distribution: Marine, brackish. Found in: Germany, Sylt (Kahl, 1931, 1933), Helgoland, Kiel, Oldesloe (Kahl, 1933) and Bottsand Kieler Fiord (Ax & Ax, 1960); Gulf of Mexico (Borror, 1962); White Sea in Kandalaksha Gulf (Burkovsky, 1970) and Chernaya River estuary (Mazei & Burkovsky, 2005); Benin, Cotonou (Dragesco & Dragesco-Kernéis, 1986); Azerbaijan in the Caspian Sea, South Apsheron, Shikov (Alekperov & Asadullayeva, 1996) and Shuvelyan (Alekperov, 2005); India, Chilka Lake (Das & Nair, 1987; Das, 1995); Black Sea (Azovsky & Mazei, 2003); Japan, Onomiti (or Onomichi) (Ozaki & Yagiu, 1941).	en	Nitla, Venkatamahesh, Serra, Valentina, Fokin, Sergei I., Modeo, Letizia, Verni, Franco, Sandeep, Bhagavatula Venkata, Kalavati, Chaganti, Petroni, Giulio (2019): Critical revision of the family Plagiopylidae (Ciliophora: Plagiopylea), including the description of two novel species, Plagiopyla ramani and Plagiopyla narasimhamurtii, and redescription of Plagiopyla nasuta Stein, 1860 from India. Zoological Journal of the Linnean Society 186: 1-45
039487821820FFAAFC9A0A97FC6AF93F.taxon	description	2007: Plagiopyla binucleata Agamaliev, 1978 - Jankowski, Russian Acad. Sci., p. 792 (revision). Improved diagnosis (Fig. 18 M): Body length 80 – 100 µm, body width 60 – 70 µm. Somatic kineties: 60 – 70. Striated band present (estimated length: 62 µm), reaching the rear end. Two rounded, ovoid macronuclei (estimated size: 11 × 10 µm each) and a single intermediate, spherical micronucleus (estimated Ø: 3.5 µm, presumably of vesicular-type). One contractile vacuole with a single pore opening on the dorsal part of the cell, above the cytoproct suture (while the typical opening position is underneath). Cytoproct located on the dorsal part of the cell (estimated length: 17 µm), with one cytoproct-related ciliary row on its left. Extrusomes not discussed in the description. Type locality / ecology and distribution: Periphyton on stones, in seawater of the Caspian Sea (Agamaliev, 1978, 1983).	en	Nitla, Venkatamahesh, Serra, Valentina, Fokin, Sergei I., Modeo, Letizia, Verni, Franco, Sandeep, Bhagavatula Venkata, Kalavati, Chaganti, Petroni, Giulio (2019): Critical revision of the family Plagiopylidae (Ciliophora: Plagiopylea), including the description of two novel species, Plagiopyla ramani and Plagiopyla narasimhamurtii, and redescription of Plagiopyla nasuta Stein, 1860 from India. Zoological Journal of the Linnean Society 186: 1-45
039487821820FFAAFEE10873FD57FAD3.taxon	description	1946: Plagiopyla minuta Powers, 1933 Kudo, Protozoology, 3 rd edn, CC Thomas ed., Springfield, 596 – 597 pp.; fig. 282 b (revision). 1954: Plagiopyla minuta Powers, 1933 – Beers, J. Protozool., 1: 86 – 89; figs 1 – 4 (illustrated record). 1984: Plagiopyla minuta Powers, 1933 – Berger & Lynn, J. Protozool., 31: 436, 441 – 442; figs 1 A, 5 – 7, 29 – 30 (ultrastructural study). 2007: Plagiopyla minuta Powers, 1933 – Jankowski, Russian Acad. Sci., p. 792 (revision). Improved diagnosis (Fig. 18 F): Body length 50 – 75 µm, body width 36 – 46 µm. Number of somatic kineties estimated around 50. Striated band present (estimated length: 48 µm; width: 3 µm). One dumb-bell-shaped to ovoid macronucleus (estimated size: 30 × 15 µm) and a single, compact-type micronucleus. One contractile vacuole. Cytoproct, located on the dorsal part of the cell (estimated length: 12 µm). Spindle-shaped extrusomes. Ty p e l o c a l i t y: I n t e s t i n e o f t h e s e a u r c h i n Strongylocentrotus droebachiensis. Found in the Bay of Fundy, USA (Powers, 1933). E c o l o g y a n d d i s t r i b u t i o n: E n d o c o m m e n s a l o f Strongylocentrotus droebachiensis. Found in USA in the Bay of Fundy (Powers, 1933) and Mt. Desert Island, Maine (Beers, 1954), Canada, Logy Bay (Berger & Lynn, 1984).	en	Nitla, Venkatamahesh, Serra, Valentina, Fokin, Sergei I., Modeo, Letizia, Verni, Franco, Sandeep, Bhagavatula Venkata, Kalavati, Chaganti, Petroni, Giulio (2019): Critical revision of the family Plagiopylidae (Ciliophora: Plagiopylea), including the description of two novel species, Plagiopyla ramani and Plagiopyla narasimhamurtii, and redescription of Plagiopyla nasuta Stein, 1860 from India. Zoological Journal of the Linnean Society 186: 1-45
039487821827FFADFF470C5EFC33FADD.taxon	description	1931: Lechriopyla mystax Lynch, 1930 – Kahl, Tierwelt Dtl., 21: 267; fig. 45.22 (guide; revision). 1946: Lechriopyla mystax Lynch, 1930 – Kudo, Protozoology, 3 rd edn, CC Thomas ed., Springfield, p. 597; fig. 282 c (revision). 1984: Lechriopyla mystax Lynch, 1930 – Berger & Lynn, J. Protozool., 31: 436, 441 – 442; figs 1 B, 1 – 4, 8 – 28 (ultrastructural study). 2007: Lechriopyla mystax Lynch, 1930 – Jankowski, Russian Acad. Sci., p. 793 (revision). Improved diagnosis (Fig. 18 E): Body length 113 – 174 µm, body width 86 – 133 µm after staining. Tubular part of the oral cavity curving anteriorly, then posteriorly. A fork-like structure, called the furcula (25 – 30 µm long) apparently supports part of the oral cavity. Number of somatic kineties estimated around 128. Striated band present (estimated length: 76 µm; width: 2.5 – 4.5 µm). One spherical to ovoid macronucleus (33 × 28 µm after staining) and a single micronucleus (11 × 7.5 µm in live specimens; 9 × 6.75 µm after staining; presumably of the endosomal-type). One contractile vacuole plus two accessory vacuoles. Cytoproct long 18 – 28 µm, located on the dorsal part of the cell. Spindle-shaped extrusomes (size: 8.5 – 10 × 0.5 µm). Ty p e l o c a l i t y: I n t e s t i n e o f t h e s e a u r c h i n s Strongylocentrotus franciscanus and S. purpuratus, from Pacific Grove, California – USA (Lynch, 1930). Ecology and distribution: Endocommensal of Strongylocentrotus franciscanus, S. purpuratus (Lynch, 1930) and S. pallidus (Lynn & Strüder-Kypke, 2002). Found in USA, California, Pacific Grove (Lynch, 1930) and Venice (Berger & Lynn, 1984), Washington in San Juan Island (Lynn & Strüder-Kypke, 2002). Gene sequences: 18 S rRNA accession number: AF 527757 (Lynn & Strüder-Kypke, 2002; authors provide a picture of the living organism and the sample location: Washington in San Juan Island, in S. pallidus) submitted as Lechriopyla mystax. Remarks: Plagiopyla mystax was initially considered as belonging to a different genus (Lechriopyla) based on the orientation of the tubular part of the oral cavity and the presence of the furcula. For detailed discussion see above.	en	Nitla, Venkatamahesh, Serra, Valentina, Fokin, Sergei I., Modeo, Letizia, Verni, Franco, Sandeep, Bhagavatula Venkata, Kalavati, Chaganti, Petroni, Giulio (2019): Critical revision of the family Plagiopylidae (Ciliophora: Plagiopylea), including the description of two novel species, Plagiopyla ramani and Plagiopyla narasimhamurtii, and redescription of Plagiopyla nasuta Stein, 1860 from India. Zoological Journal of the Linnean Society 186: 1-45
039487821827FFADFC410CA3FA25F8BE.taxon	diagnosis	Diagnosis (Fig. 18 B): Body length 66 – 88 µm, body width 30 – 53 µm after silver staining. Somatic kineties: 41 – 51. Striated band 42.5 µm long. One ovoid macronucleus (size: 15.1 × 12.4 µm after Feulgen staining) and 1 – 5 vesicular-type micronuclei (Ø 1.2 – 2.4 µm). One contractile vacuole with 2 – 5 pores opening on the dorsal part of the cell. Cytoproct 21.8 µm long, located on the dorsal part of the cell, with 2 cytoproct-related ciliary rows on its left. Curved extrusomes (length: 1.9 µm). Type locality / ecology and distribution: Freshwater in the hypoxic / anoxic part of the water column. Found in Kolleru Lake, Andhra Pradesh, India (present study).	en	Nitla, Venkatamahesh, Serra, Valentina, Fokin, Sergei I., Modeo, Letizia, Verni, Franco, Sandeep, Bhagavatula Venkata, Kalavati, Chaganti, Petroni, Giulio (2019): Critical revision of the family Plagiopylidae (Ciliophora: Plagiopylea), including the description of two novel species, Plagiopyla ramani and Plagiopyla narasimhamurtii, and redescription of Plagiopyla nasuta Stein, 1860 from India. Zoological Journal of the Linnean Society 186: 1-45
039487821826FFACFF09089BFBC3FE1C.taxon	diagnosis	Diagnosis (Fig. 18 C): Body length 72 – 88 µm, body width 34 – 49 µm after silver staining. Somatic kineties: 51 – 69. Striated band 44.5 µm long. One ovoid macronucleus (15.1 × 14.3 µm after Feulgen staining) and one compact-type micronucleus (Ø 1.2 – 2.2 µm). One contractile vacuole with 2 – 3 pores opening on the dorsal part of the cell. Cytoproct 24 µm long, located on the dorsal part of the cell, with 3 cytoproct-related ciliary rows on its left. Straight, multi-layered extrusomes (lenght: 3.7 µm), and curved, homogeneous extrusomes (length: 1.6 µm). Type locality / ecology and distribution: Freshwater in the hypoxic / anoxic part of the water column. Found in Kolleru Lake, Andhra Pradesh, India (present study). Gene sequences: 18 S rRNA gene, accession number: KY 563721 (present study).	en	Nitla, Venkatamahesh, Serra, Valentina, Fokin, Sergei I., Modeo, Letizia, Verni, Franco, Sandeep, Bhagavatula Venkata, Kalavati, Chaganti, Petroni, Giulio (2019): Critical revision of the family Plagiopylidae (Ciliophora: Plagiopylea), including the description of two novel species, Plagiopyla ramani and Plagiopyla narasimhamurtii, and redescription of Plagiopyla nasuta Stein, 1860 from India. Zoological Journal of the Linnean Society 186: 1-45
039487821826FFAFFCBF0B1EFD5EFE89.taxon	diagnosis	Diagnosis: Ovoid body shape, dorso-ventrally compressed; oral cavity deep, opening on ventral side with a more internal tubular part extending directly backwards (Fig. 17 C); dense somatic ciliature; one dumb-bell-shaped macronucleus and one roundish micronucleus; one species. Type species: Pseudoplagiopyla sinistra, by monotypy.	en	Nitla, Venkatamahesh, Serra, Valentina, Fokin, Sergei I., Modeo, Letizia, Verni, Franco, Sandeep, Bhagavatula Venkata, Kalavati, Chaganti, Petroni, Giulio (2019): Critical revision of the family Plagiopylidae (Ciliophora: Plagiopylea), including the description of two novel species, Plagiopyla ramani and Plagiopyla narasimhamurtii, and redescription of Plagiopyla nasuta Stein, 1860 from India. Zoological Journal of the Linnean Society 186: 1-45
039487821825FFAEFEC50E30FD12FBDB.taxon	description	Some groups of ciliates are known to host methanogenic Archaea in their cytoplasm (for review see: Hackstein, 2010); this association appears common, even obligate, for those living in oxygen-depleted environments, such as wet sediments poor in oxygen or animal digestive systems (gut, rumens, etc.). Mutual benefits, in this kind of symbiosis, are mostly related to physiological processes in the anaerobic lifestyle. Indeed, methanogenic Archaea are able to use H 2 and CO 2 to produce CH 4, thus reducing H 2 concentration and partial pressure inside the host cell, optimizing the chemo-physical condition for anaerobic respiration mediated by ciliate hydrogenosomes (van Brugen et al., 1984; Embley et al., 1995). However, other authors suggested that the main role of methanogens in symbiosis with ciliates is the production of organic material, quickly available for the host cell, rather than the control of H 2 partial pressure (Fenchel & Finlay, 1991). Several different methanogenic endosymbionts have been identified so far from anaerobic, free-living ciliates (Fenchel et al., 1977; van Brugen et al., 1983, 1984, 1986; Wagener et al., 1990; Embley et al., 1992 a, b; Finlay et al., 1993; Embley & Finlay, 1994; Narayanan et al., 2009; Filker et al., 2014). In plagiopylids, for example, P. nasuta has been infected by Methanobacterium formicicum (Goosen et al., 1988) and Methanocorpusculum sp. (Embley & Finlay, 1994), P. frontata hosted a species of Methanolobus (Embley & Finlay, 1994), whereas in Trimyema compressum, Methanobacterium formicicum and Methanobrevibacter arboriphilicus have been detected (Wagener et al., 1990; Shinzato et al. 2007). Our Plagiopyla populations were not an exception, showing the presence of at least one Archaea endosymbiont (putative for P. nasuta TP 2, since unfortunately the strain became extinct before FISH experiments with Archaea probe) showing one or two morphotypes in close association with their hydrogenosomes. Alternatively, the second endosymbiotic organism could be another Archaea or, perhaps, a bacterium not detected by EUB 338 probe at applied experimental conditions. In most of the cases, hydrogenosomes seemed to adapt their shape to maximize the surface in contact with these microorganisms, as already reported by other studies (Fenchel et al., 1977; Embley & Finlay, 1994; Modeo et al., 2013). This indicates a close, mutualistic association among Plagiopyla hosts and their endosymbionts. The rod-shaped morphology of these endosymbionts closely resembled those described by previous authors, with comparable size and without flagella (Fenchel et al., 1977; Goosen et al., 1988). In P. ramani, P. narasimhamurtii and P. nasuta we observed two forms of endosymbionts, either indicating the presence of multiple symbionts, as already described for other ciliate species (Görtz, 1987; Boscaro et al., 2012; Senra et al., 2016), or a single species of symbiont with different polymorphic life cycle, as supposed by previous studies on anaerobic ciliates (Fenchel & Finlay, 1991; Finlay et al., 1993) and observed in some bacterial endosymbiont such as Caedibacter (Anderson et al., 1964; Schrallhammer, 2010), Holospora (reviewed in: Fokin & Görtz, 2009) and Gortzia (Boscaro et al., 2013; Serra et al., 2016), or ectosymbionts such as epixenosomes (Petroni et al., 2000). In line with this, we could suppose that the more electron-dense type of endosymbiont detected in both P. ramani and P. narasimhamurtii (Figs 5 C – E, 11 D, E, G), and P. nasuta (Fig. 16 A, C) could represent a sort of reproductive form, since it was the only one observed during binary fission. However, further analyses are required to solve this interesting issue. In addition, sulphate-reducing ectosymbiotic Archaea have been previously described from anaerobic ciliates such as Metopus contortus, Caenomorpha lavanderi, Parablepharisma sp. and Sonderia sp. (Fenchel et al., 1977; Fenchel & Ramsing, 1992). We detected ectosymbionts as well on P. ramani’ s and P. nasuta’ s surface with a shape and a size comparable to those of the above mentioned sulphate-reducing organisms (Fenchel & Ramsing, 1992); they could be potentially assigned to this group of microorganisms able to gain energy from secondary metabolites excreted by the host such as acetate, lactate, ethanol, hydrogen or methane (the latter if endosymbiotic methanogens are present) (Fenchel & Ramsing, 1992). A detailed molecular characterization of these ecto- and endosymbionts from Plagiopyla is ongoing.	en	Nitla, Venkatamahesh, Serra, Valentina, Fokin, Sergei I., Modeo, Letizia, Verni, Franco, Sandeep, Bhagavatula Venkata, Kalavati, Chaganti, Petroni, Giulio (2019): Critical revision of the family Plagiopylidae (Ciliophora: Plagiopylea), including the description of two novel species, Plagiopyla ramani and Plagiopyla narasimhamurtii, and redescription of Plagiopyla nasuta Stein, 1860 from India. Zoological Journal of the Linnean Society 186: 1-45
