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Phylogenetically distinct lineages may be hidden behind identical or highly similar morphologies. The phenomenon of morphological crypticity has been recently detected in symbiotic ciliates of the family Clevelandellidae, as multivariate and Fourier shape analyses failed to distinguish genetically distinct taxa. To address the question of species boundaries, the phylogenetic information contained in the rDNA cistron of clevelandellid ciliates, which had been isolated from the digestive tract of blaberid cockroaches, was studied using a multifaceted statistical approach. Multigene phylogenies revealed that the genus Clevelandella is paraphyletic containing members of the genus Paraclevelandia. To resolve the paraphyly of Clevelandella, two new genera, Anteclevelandella gen. nov. and Rhynchoclevelandella gen. nov., are proposed based on morphological synapomorphies and shared molecular characters. Multigene analyses and Bayesian species delimitation supported the existence of 13 distinct species within the family Clevelandellidae, eight of which represent new taxa. Moreover, two new Nyctotherus species were recognized within the clade that is sister to the Clevelandellidae. According to the present distance and network analyses, the first two domains of the 28S rRNA gene showed much higher power for species discrimination than the 18S rRNA gene and ITS region. Therefore, the former molecular marker was proposed to be a suitable group-specific barcode for the family Clevelandellidae.

A compilation of the ciliate epibiont species (Ciliophora) found on marine and fresh water cnidarians has been carried out based on published records. The checklist includes the taxonomic position of each species of epibiontic ciliate, the species of basibiont cnidarians, the geographic zones and the bibliographic references where they were recorded. Cnidarians, especially colonial sessile forms, represent suitable substrates for numerous sessile and vagile ciliates. Altogether 79 ciliate species belong to five classes viz. Spirotrichea, Heterotrichea, Phyllopharingea, Suctorea and Oligohymenophorea were listed. The most diverce as epibions on cnidarians are representatives of Suctorea with 41 species and Peritrichia (under the class Oligohymenophorea) with 25 species. Three species belong to class Spirotrichea, four Heterotrichea and one Phyllopharingea. Among the other representatives (except Peritrichia) of class Oligohymenophorea, four species belong to subclass Scutucociliatia, one species each in subclass Hymenostomatia and Apostomatia. One suctorian species Ophryodendron abietinum and two species of peritrichs, Cothurnia cordylophora and Rhabdostyla sertularium one Heterotrichea Halofolliculina corallasia and one Scutucociliatia Philaster guamensis are likely specific to cnidarian hosts only.

A compilation of the ciliate (Ciliophora) species found on marine and fresh water bryozoans as epibionts has been carried out based on published records. The checklist includes the taxonomic position of each species of epibiontic ciliate, the species of basibiont bryozoans, localities and the bibliographic references. Altogether 40 ciliate species from classes Spirotrichea (two species); Suctorea (sixteen species); Oligohymenophorea, subclass Peritrichia (sixteen species) and Heterotrichea, family Folliculinidae (six species) were listed. Among registered species, six were reported on bryozoans only. Only one species of peritrich ciliate Ellobiophrya conviva adapted to inhabit on tentacles of bryozoans with special adhesive organelle (cinctum or adhesive ring) indicate a possible specific to bryozoan host.

Species from almost all classes of ciliates are prone to be found inhabiting bromeliads in the Neotropics, from Mexico to Brazil, and the Antilles. Studies of ciliates recorded from bromeliads have been carried out from few bromeliad species, mainly in tropical forest. We compiled all available data of free living and sessile ciliates from bromeliads, including their geographic distribution and bromeliad identity. We provide a list of 170 ciliate species that have been recorded in 52 epiphytic and terrestrial bromeliad species, distributed in ten Neotropical countries . Most of the species belong to the Classes Oligohymenophorea, Colpodea and Spirotrichea. The largest number of ciliate species has been recorded in Brazil and Mexico. Bromeliothrix metopoides and Glaucomides bromelicola were the two species with the widest geographical distribution, 19 species have been recorded only in Mexico, 11 in the Antillean islands, and 89 only in Southamerica. Free living species prevailed over sessile species, and both represent 2% of the total ciliate species number. Sixteen ciliate species have been recorded only inhabiting in bromeliads. Although bromeliads show a high endemicity, their specificity is low in relation to ciliates.

The endozoic ciliates of the family Clevelandellidae Kidder, 1938 typically inhabit the hindgut of wood-feeding panesthiine cockroaches. To assess the consistency of species delimitation in clevelandellids, we tested the utility of three sources of taxonomic data: morphometric measurements, cell geometrical information, and 18S rRNA gene sequences. The morphometric and geometrical data delimited the clevelandellid morphospecies consistently and unambiguously. However, only Paraclevelandia brevis Kidder, 1937 represented a homogenous taxon in both morphological and molecular analyses; the morphospecies Clevelandella constricta (Kidder, 1937) and C. hastula (Kidder, 1937) contained two or three distinct, more or less closely related genotypes each; and the genetic homogeneity of the morphospecies C. panesthiae (Kidder, 1937) and C. parapanesthiae (Kidder, 1937) was not corroborated by the 18S rRNA gene sequences at all. Moreover, the 18S rRNA gene phylogenies suggested the C. panesthiae-like morphotype to be the ancestral phenotype from which all other clevelandellid morphotypes arose. The only exception was the C. constricta-like morphotype, which very likely branched off before the diversification of the C. panesthiae-like progenitor. The present molecular analyses also suggested that a huge proportion of the clevelandellid diversity still waits to be discovered, since examination of only four panesthiine populations revealed 10 distinct clevelandellid genotypes/molecular species.

The morphologies of the three freshwater stentorid ciliates in Korea, Stentor coeruleus (Pallas, 1766); Stentor muelleri Ehrenberg, 1831, and Stentor tartari Murthy & Bai, 1974, were investigated based on live observations and protargol impregnation. The Korean population of S. tartari exhibits the following characteristics: body size 200–355 × 85–135 µm in vivo, 62–106 somatic kineties, 8–13 peristomial kineties, 110–180 adoral membranelles, mostly two macronuclear nodules and 5–18 micronuclei, reddish and colorless cortical granules and the presence of symbiotic algae. We identified S. tartari based on unique characteristics compared to close congeners. Korean populations of S. coeruleus and S. muelleri are congruent with previously described populations in most aspects of their morphologies. Here, for the first time, we report molecular gene sequence information for S. tartari. Small subunit (SSU) rRNA gene sequence-based phylogeny indicates that S. tartari, which has multiple macronuclei, forms a monophyletic group with other Stentor species having a single macronucleus. Our findings based on morphology and SSU rRNA gene sequence information corroborate the hypothesis that the elongated macronucleus evolved from the compact single or multi macronucleus state.

It is known that the freshwater heterotrich ciliate Blepharisma japonicum uses five pigments called blepharismins, stored in its extrusive pigment granules, for both light perception and chemical defense against predators. In this work we focused our attention on the defensive strategies of two additional pigmented species of Blepharisma, B. stoltei and B. undulans. In particular: (1) we observed the predator–prey interactions of B. stoltei or B. undulans against one multicellular and two unicellular predators; (2) we clarified the nature of B. stoltei and B. undulans pigments by means of High Performance Liquid Chromatography (HPLC) and Liquid Chromatography Mass Spectrometry (LC-MS); and (3) we demonstrated and compared the toxicity of the purified pigments on a panel of ciliated protists, and against one metazoan predator. The results indicate that the chemical defense mechanism present in B. stoltei and B. undulans is mediated by the same five blepharismins previously characterized for B. japonicum, although produced in different proportions.

Two Spirostomum species were collected from freshwater in Jindo Island, Korea and identified as Spirostomum ambiguum (Muller, 1786) Ehrenberg, 1835 and Spirostomum minus Roux, 1901. This study is the first known morphological record of these two species being found in Korea. The description is based on the observation of living specimens and protargol impregnated specimens. Diagnostics of Spirostomum ambiguum: body size 340- 930×45-80 μm in vivo; long and slender body with truncated posterior part; macronucleus moniliform with 7-22 nodules; cortical granules irregularly arranged 4-5 rows in between somatic kineties; 24-58 somatic kineties arranged longitudinally; adoral zone of membranelles (AZM) covered about 60-80% of body length. Diagnostics of Spirostomum minus: body size 500-730×35-45 μm in vivo; long and slender body with truncated posterior part; macronucleus moniliform with 11-16 nodules; micronucleus 20-37 oval shape; cortical granules regularly arranged 3-4 rows in between somatic kineties; 20-30 somatic kineties arranged longitudinally; AZM covered about 40-50% of body length with 120-150 adoral membranelles.

The study of ciliate diversity in tropical environments remains scarce. In Neotropical forests, bromeliads are a common component of the vascular flora; bromeliads with tank morphology intercept rain water and detritus, resulting in the formation of a phytotelm, where heterotrophic protist communities like ciliates can establish. However, it is not known if ciliates inhabit tank-less bromeliads. For this reason, the goal of the present study was to investigate if ciliates can establish between the leaf axils of five terrestrial and epiphytic tank-less bromeliad species in a dry tropical forest in west Mexico. We collected samples of rain water and detritus from the leaf axils during the humid season of years 2015 and 2016. For ciliate taxonomical identification, we used optical microscopy, in vivo observation, and silver impregnation techniques. To summarize information about geographical distribution of ciliates identified at species level in the Neotropics, we provided their records from previous works, at country level with locality and georeferenciation. We recorded 27 taxa of ciliates, where the class Oligohymenophorea contained the largest richness of taxa. Drepanomonas revoluta, Leptopharynx bromeliophilus, and Tetrahymena sp. were recorded from all the species of bromeliads. Bromelia karatas was the species that hosted the largest number of ciliate taxa (22). Our results indicated that Glaucomides bromelicola, Gonostomum bromelicola, Leptopharynx bromelicola and L. bromeliophilus, species which are considered endemic to tank bromeliads, can also inhabit tank-less bromeliads. We provided previous records of 19 ciliate species from eleven countries within the Neotropical region, and Bromeliothrix metopoides was the species most frequently recorded in Neotropical countries (9). Therefore, tank-less bromeliads can constitute a temporal habitat for ciliates, and function as cysts reservoirs in environments with a pronounced seasonality like dry tropical forests.

Two heterotrichid ciliates, Climacostomum virens (Ehrenberg, 1838) Stein, 1859 from brackish water and freshwater, and Fabrea salina Henneguy, 1890 from a solar saltern, were collected in Korea. They are novelly investigated in Korea by means of live observation, protargol staining and nuclear small subunit (SSU) rRNA gene sequencing. Climacostomum virens is characterized by pouch-like body shape, body length of $200-370{\mu}m$ 수식 이미지 in vivo, conspicuous cytopharyngeal tube, macronuclei ribbon-like shape, and one to four in number, with or without symbiont algae in cytoplasm, 34-66 somatic kineties, 67-113 adoral zone of membranelles, 8-42 peristomial kineties, 24-37 apical membranelles. SSU rDNA sequence size is 1,591 bp and GC contents 48.52%. Fabrea salina is also characterized by scoop-like body shape with proboscis, body length of $190-240{\mu}m$ 수식 이미지 in vivo, one to two rod-shaped macronuclei, oval micronuclei, grayish green cortical granules, 104-186 somatic kineties, 4-8 preoral kineties, 7-19 peristomial kineties and fragmented paroral membrane. SSU rDNA sequence size is 1,598 bp and GC contents 47.50%.

Heterotrichous ciliates were isolated from marine and brackish habitats in Korea, and their morphology, infraciliature and morphometrical characters were investigated using silver impregnated methods. These three Condylostoma species were identified as Condylostoma curva Burkovsky, 1970, C. minutum Bullington, 1940 and C. spatiosum Ozaki and Yagiu in Yagiu, 1944. The species of Condylostoma based on morphology are highly variable in most of characters and distinguished as following. Condylostoma curva is oval to elongate ellipsoidal, size about 245×100 μm in vivo, and conspicuously dark greenish brown with cortical granules on their surface, buccal cavity relatively large about 40% of body length, 5-11 macronuclear nodules, 4-8 frontal cirri serially arranged and 22-38 somatic kineties. Condylostoma minutum is elongate ellipsoidal and the size about 310×55 μm in vivo, buccal field about 35% of body length, 12-20 macronuclear nodules, adoral zone consisted of 82-107 membranelles, large and long one frontal cirrus and 38-44 somatic kineties. Condylostoma spatiosum is large elongate ellipsoidal, size about 670×105 μm in vivo, buccal cavity about 25% of body length, 11-25 macronuclear nodules, 111-144 adoral membranelles, membrane-like 2 frontal cirri, 49-74 somatic kineties. These three Condylostoma species are described here for the first time in Korea.

Two well-known and one new species of folliculinids, obligate symbionts of the gribble (Limnoria Leach, 1814) are illustrated, and the new species is described in detail. Its placement in Eufolliculina Hadzi, 1951 is temporary because of the doubtful taxonomic status of this genus.

Two ciliate species of Blepharisma were collected from the riverine wetland and mountain peak soil in Korea, Blepharisma undulans Stein, 1867 and B. steini Kahl, 1932, which are reported for the first time from Korea. The description was based on the observations of live and protargol impregnation specimens. Diagnostics of these species (Blepharisma undulans vs. B. steini) are as follows. Body length/width ratio in vivo about 6/1 vs. 2/1, shaped in spindle vs. pyriform to ellipsoid and colored in pinkish vs. reddish. Macronuclei 2 vs. 1, with 4-9 vs. 4-7 spherical micronuclei. Adoral zone of membranelles extends from anterior end to 1/3 vs. 1/2-2/3 of body length, with 47-56 vs. 33-45 adoral membranelles. The numbers of somatic kineties are 22-27 vs. 18-22.

A 1 mm-long Spirostomum with symbiotic chlorellae has been found in the oxygen-depleted sediment of a shallow fen pond in the South of England (UK). The ciliate lives amongst sediment debris, where it builds a lorica that covers about half the length of the ciliate. It is common to find several of the green Spirostomum cells sharing the same patch of sediment particles.

Summary The morphology and infraciliature of five heterotrichous and hypotrichous marine ciliates were investigated using live observation and protargol impregnation: Peritromus faurei Kahl, 1932, Kiitricha marina, Nozawa, 1941, Holosticha warreni nov. spec., Tachysoma ovata nov. spec. and T. dragescoi nov. spec. According to our observations and comparison, Peritromus minor Ozaki & Yagiu, 1941, P. californiens Kirby, 1934, P. kahli Villeneuve-Brachon, 1940 and P. tortugensis Bullington, 1940 are synonymous with Peritromus faurei. Our investigations do not support the hypothesis suggested by some authors that Kiitricha marina has a close relationship with euplotids. Holosticha warreni: 80–120×40–55 μm sized marine Holosticha with 1 buccal, 2 frontoterminal, 10–12 transverse cirri and about 28 membranelies; midventral row with 7–9 cirral pairs extending to 2/3 of cell length; cortical granules conspicuous, flattened-ovoid with central depression, arranged in 3 irregular rows; 3 dorsal kineties; about 50 macronuclear segments in ring-like band. Tachysoma ovata: marine, body delicate and slightly twisted, in vivo about 35–50×20–30 μm with 14–15 left and 13–17 right marginal cirri and about 14–17 membranelies; cortical granules sparse, on both dorsal and ventral side, 2 macro- and 1 micronucleus; 3 dorsal kineties. Tachysoma dragescoi: small marine Tachysoma, 40–50×20–25 μm, 7–9 left and 5–8 right marginal cirri; about 12–15 membranelies; cortical granules in groups of 2–4 arranged in irregular rows; 3 dorsal kineties; 2 macround 2 micronuclei.

The marine, loricate ciliate Eufolliculina uhligi (Heterotrichida) has a complex life-cycle which includes a motile swarmer. The swarmer settles on the substrate, secretes a lorica and transforms into the trophic stage. This is metamorphosis. Swarmers have been induced to settle by treatment with EGTA to synchronize metamorphosis. Stomatogenesis was observed in protargol-stained cells. It can be characterized as follows: Stomatogenesis of E. uhligi (suborder Coliphorina) is compared with that of members of the suborder Heterotrichina. It is concluded that folliculinids are closely related to the Stentoridae. The separation of the Folliculinidae from the other Heterotrichida should be reconsidered.

Summary The new oral infraciliature comes from the posterior longitudinal proliferation of numerous somatic kineties of the parental perizonal zone during the bipartition of Caenomorpha medusula . The new perizonal zone of the opisthe originates from proliferation of the anterior extremes of all the somatic kineties that make up the parental perizonal zone. The proter retains both, the oral infraciliature and the perizonal zone of the parental cell. Conjugation in C. medusula presents three maturation divisions and three postzygotic divisions. During conjugation the oral infraciliature of each conjugant degenerates to be replaced by a new one.

Summary The infraciliature of two sapropelic heterotrich ciliates, Cirronter mobilis and Saprodinium dentatum , is described. The somatic infraciliature of C. mobilis is constituted by a pcrizonal zone and one kinety of the bell. The perizonal zone is formed by numerous short longitudinal kinelies with 4 kinetids each (dikinetids). Complex longitudinal fibrillar systems connect the kinetosomes of each kinety. The kinety of the bell is composed of two rows of kinetosomes with long fibrillar derivates. In the oral zone, the paroral membrane is formed by one row of kinetosomes, and the adoral zone of membranelles is constituted by numerous membranelles each one with two rows of kinetosomes. Ihese membranelles are connected one another through transversal microfibrillar tracts. Our observations concerning the somatic infraciliature of S. dentatum indicate that the perizonal zone (PZ), the longitudinal somatic kineties (LK) and the kineties of the spines (SK) are closely related between them. The right extremes of each kinetosomal row of the PZ continuate with somatic longitudinal kinetics, which lack of fibrillar derivates. Moreover, the SK constitute the modified posterior extremes of some of LK. At the ventral margin of ciliate, the most posterior row of kinetosomes of the PZ is connected through fibrillar bundles with two short rows of kinetosomes (additional kineties) with a complex cytoskeletal array. Groups of 2–4 kinetosomes without fibrillar associates constitute the infraciliature of the bell kinety. The oral infraciliature ol this species is composed by 9–10 membranelles each one with 2–3 kinetosomal rows of different length and 2–3 argentophilic rows, which as in C. mobilis , have not been described until now.

Twenty‐eight littoral ciliates including one new genus and seven new species were collected from King George Island, Antarctica. Among them, 21 species are morphologically and taxonomically described in this paper: Bickella antarctica nov. gen., nov. spec., Chlamydonella apoprostomata nov. spec., Condylostoma spatiosum Ozaki and Yagiu in Yagiu, 1944, Diophrys scutum Dujardin, 1842, Diophrys aff. oligothrix Borror, 1965, Diophrys appendiculata (Ehrenberg, 1838), Euplotes balteatus (Dujardin, 1841), Euplotes dragescoi nov. spec., Euplotes petzi nov. spec., Euplotes rariseta Curds et al., 1974, Euplotes vannus (Mueller, 1786), Hartmannula angustipilosa Deroux and Dragesco, 1968, Hemigastrostyla szaboi Wilbert and Song, 2005, Holosticha antarctica nov. spec., Holosticha apodiademata nov. spec., Holosticha diademata (Rees, 1884), Litonotus sp., Metaurostylopsis marina (Kahl, 1932), Pleuronema coronatum Kent, 1881, Pseudocohnilembus persalinus Evans and Thompson, 1964, Urotricha antarctica nov. spec. The new ge...

Twenty‐six marine benthic ciliates including seven new species were isolated from King George Island, Antarctic. The morphology and taxonomy of 19 of them are described in the present paper: Aegyriana paroliva, Amphileptus sp., Amphisiella antarctica nov. spec., Condylostoma cf. magnum, Dysteria parovalis nov. spec., Folliculina ? sp., Hartmannula cf. angustipilosa, Hemigastrostyla szaboi nov. spec., Heterostentor coeruleus, Holosticha sp., Intranstylum antarcticum nov. spec., Metaurostylopsis rubra, Orthodonella shenae, Philasterides cf. armatalis, Pithites pelagicus nov. spec., Pleuronema coronatum, Strombidium apolatum nov. spec., Telotrochidium sp., and Thigmokeronopsis magna nov. spec. Based on the new observations, an improved diagnosis for the genus Aegyriana is suggested: dorsoventrally flattened Dysteriidae with tail‐shaped podite, which is positioned subcaudally in a glabrous region within somatic kineties; oral structure in two parts: ca three close‐set fragments on right and one preoral kinety...

Summary The cortical surface of Stentor has two types of main structures: a) One infraciliary structure which consists of the oral infraciliature and somatic infraciliature, both formed by kinetosomes. On the frontal field and somatic surface, the kinetosomes have derivates which are bundles of postciliary microtubules. b) One myonemic system, deeper than the ciliary part, formed by an oral and somatic network which is linked to the kinetosomes. At present, our interpretation of the oral myonemic fibrilar system is quite different from those previously given ( Fernandez-G-aliano and Fernandez-Leborans 1979). According to the figure 13, the perimembranellar fibre (PMF) is a myonemic fibre which the primary somatic myonemes converge in; we have not considered that this fibre is homologous to the subadoral fibres group (Fa) by Tuffrau (1967). From the perimembranellar fibre there come out fibres, parallel to the membranellar kineties. They are the submembranellar fibres (SMF); the subadoral fibres by Tuffrau make bundles which arrive as far as the SMF, the bundle from each kinety reaches its corresponding SMF. The technique of Protargol ( Tuffrau 1967) allows to observe in detail, the postciliary microtubules and the subadoral fibres, however, it does not allow to observe the myonemic system which is placed on the middle and anterior part of ciliate, including the oral zone. Thus one cannot observe a continuity by means at any kind of structure, between the somatic kineties and the membranelies of the AZM. This way the subadoral fibres described by Tuffrau can be seen on the preparation obtained by the Protargol technique as isolated structures in the ectoplasmic compound, without any structure that would relate them neither with the rest of oral zone nor with somatic surface. By the means of method by Fernandez-Galiano (1976) are obtained us preparations in which the silver impregnation is deeper; this allows to describe the cortical morphology of S. coeruleus as a whole, where the kinetosomes are connected with the myonemes which, at the same time, build an oral and somatic network.

RESUME L'ampoule rectale de quelques Batraciens Anoures d'Afrique et d'Asie heberge 4 especes de Nyctotheres caracterisees par la presence d'une ventouse sur toute la face inferieure et une topographie ciliaire presque identique. L'observation des formations squelettiques polysaccharidiques montre que ces elements constituent un critere taxonomique complementaire ayant une signification phylogenetique, Chez Sicuophora macropharyngea (Bezzenberger 1904) comb. n. et S. xenopi de Puytorac & Grain, 1968, les plaques de la ventouse forment un pavage. Les plaques marginales sont acuminees. Metasicuophora petteri gen. n., sp. n. est une espece de grande taille, tres aplatie. Les plaques marginales de la ventouse sont elargies a leur extremite et l'armature squelettique de la face superieure est tres developpee. Chez Parasicuophora xavierae sp. n., les elements squelettiques de la ventouse sont constitues par des filaments identiques a ceux observes chez P. mantellae Albaret, 1968. SYNOPSIS The rectum of several African and Asian anuran amphibians harbors 4 species of nyctotherid ciliates characterized by the presence of a sucker on the entire lower surface, and a nearly identical ciliary distribution. Observations of the skeletal structures made up of polysaccharides indicate that these elements constitute a complementary taxonomic criterion with a phylogenetic significance. In Sicuophora macropharyngea (Bezzenberger 1904) comb. n. and S. xenopi de Puytorac & Grain, 1968, the plaques of the sucker have a pavement-like arrangement and the marginal plaques are pointed. Metasicuophora petteri gen. n., sp. n. is a large, very flattened species. The marginal plaques of the sucker have terminal enlargements and the skeleton of the upper surface is well developed. In Parasicuophora xavierae sp. n., the skeletal elements of the sucker consist of filaments identical to those observed in P. mantellae Albaret, 1968.

SYNOPSIS. A large heterotrich ciliate (Family: Bursariidae) found in a papyrus swamp in Uganda was used for oxygen tension experiments by Beadle & Nilsson, 1959, under the name of Bursaria sp. This organism has now been identified as Neobursaridium gigas Balech. The morphology of the organism was studied in living and stained specimens, especially with the silver impregnation technique, and the present findings are compared to those of Balech.

SYNOPSIS. N. gigas Balech, 1941, has been found again in Uganda and cultured in the laboratory. Some features of its morphology and behavior were studied. The buccal cavity has a small pit. Trichocysts are found in the endoplasm as well as the cortex. The ciliate appears to be highly sensitive to light. Cyclops was an important predator. The size of N. gigas is very variable.

In cells of the ciliated protozoa Stentor polymorphus and S. roeseli, infections by microsporidia were observed. In both stentors, the microsporidia were maintained in the laboratory and new cells could be infected when transferred to a culture of parasitized cells. The parasites were more pathogenic on S. roeseli than on S. polymorphus, which harbors green algal endocytobionts.