New contributions to the marine benthic ciliates from the Antarctic area, including description of seven new species (Protozoa, Ciliophora)

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 on left; left postoral kineties shortened posteriorly and continuous with right ones, leaving no median gap or suture; cytopharyngeal rods dominant. According to the new understanding and information obtained, a refined diagnosis of the genus Hemigastrostyla is also suggested: hypotrich with Oxytricha‐like cirral pattern; eight to ten frontal (including one buccal) and five to seven ventral cirri; five transverse and three caudal cirri; no right‐lateral anlagen of dorsal kineties occurring and the old adoral zone will be partly replaced by newly formed structure during morphogenesis; dorsal cilia located in small pits, fibre system highly developed; marine habitat.


Introduction
In 2000-2001, the present authors investigated and reported 22 benthic ciliated protozoans collected from the Antarctic area, including six new species and two new genera (Song and Wilbert 2002). The current work is based on a new research project undertaken early 2002 and has confirmed the estimation that in this area there are still many taxa that remain unknown or should be studied further by modern methods, as has been noticed by many previous researchers (Fenchel and Lee 1972;Thompson 1972; Thompson and Croom 1978;Corliss and Snyder 1986;Agatha et al. 1990Agatha et al. , 1993Luporini 1990a, 1990b;Wilbert et al. 1993;Petz 1994Petz , 1995Petz et al. 1995;Foissner 1984Foissner , 1986Wiencke et al. 1998;Song andWilbert 2000, 2002).
In February to April 2002, a new taxonomic survey on the periphytic ciliates in the same area as that surveyed 2 years ago was carried out. As a result, at least 26 species have been isolated and observed (Table I), of which 19 species are morphologically or morphometrically described here.

Organisms and preparation
Specimens were collected (February to April 2002) from the periphyton on rocks and tidal pools in the littoral zone of Potter Cove, King George Island (62u149S, 58u409W), as in the previous investigation (Song and Wilbert 2002).
Specimens were either observed immediately with a pre-cooled microscope and photographed by a video camera or maintained for days in the laboratory. Wheat grains were added to the medium to provide bacterial food. Protargol and nitrate silver impregnations according to Wilbert (1975) and Song and Wilbert, respectively, were applied to reveal the infraciliature and the silverline system.  number of the contractile vacuoles as well as other diagnostic characters remain unclear, this organism has to be hence treated as an unknown form here.

Description
Cells after protargol impregnation generally form-constant ( Figure 1A), ca 200 mm in length, which seems not to have evident (?) tail. Two ellipsoid macronuclear nodules, large and in mid-body position, arranged closely together. No micronucleus detected. Extrusomes (in protargol-impregnated specimens) rod-shaped, slightly curved, about 8-10 mm long; densely distributed in oral region and scattered in other parts of body ( Figures 1A, 15A). Infraciliature typical of genus. On right side, ca 50 densely ciliated somatic kineties forming a conspicuous suture in mid-body (arrows in Figure 1A) whereas on left side probably over 12 (? not clearly detected) loosely ciliated kineties (including perioral kinety), all of which seem to extend along whole length of cell. Dorsal brosse composed of ''numerous'' basal body pairs and extending posteriorly to about half of cell length.

Remarks
Most studies using modern methods on this genus have been carried out on freshwater forms (Fryd-Versavel et al. 1975;Foissner 1984Foissner , 1986Dragesco and Dragesco-Kernéis 1986;. Considering the cell size, general appearance after impregnation and the habitat, the present organism is similar to the large marine form, Amphileptus marinus (Kahl 1931) which was recently redescribed by Song et al. (2003). The latter has, however, conspicuously lower number of right somatic kineties (ca 50 versus 20-27). It possibly represents an undescribed form, but further information is required.
Order NASSULIDA Jankowski, 1967 Genus Orthodonella Bhatia, 1936 Orthodonella shenae Song and Wilbert, 2002 (Figure 2E-G; Table II) This species was newly established by the present authors (Song and Wilbert 2002), but unfortunately, was assigned incorrectly to the order Cyrtophorida (Corliss 1979). The current population resembles that previously described by Song and Wilbert (2002) very well except that it exhibits more variability in size and shape of cells: from 52 to 126 mm in length after impregnation (Table II). In addition, two pores for each of two contractile vacuoles are found on the dorsal side in at least two specimens ( Figure 2F, arrows). As an additional contribution, we also supply here the statistical data that was previously lacking (Table II).
Order CYRTOPHORIDA Fauré-Fremiet in Corliss, 1956 Genus Dysteria Huxley, 1857 Dysteria parovalis nov. spec. (Figures 2A-D; Table III) Diagnosis Marine oval Dysteria, in vivo 50-80640-60 mm; constantly with nine ventral kineties in right field, of which three extend to anterior cell end; ca six to eight short fragments of kineties in left equatorial field; oral ciliature consisting of three double-rowed fragments; macronucleus oval; three contractile vacuoles.

Etymology
Composite of par (similar to) and the species name ovalis, indicating that this species is similar to the well-known form Dysteria ovalis.

Description
Mostly about 70650 mm in vivo. Body bilaterally flattened by about 1:2-3. From side view, cell broadly oval and quadrilateral with posterior portion often slightly wider than anterior; apical end considerably truncated while posterior end obliquely truncated ( Figure 2A). No furrows or ridges detected. Podite about 15 mm long, posteriorly positioned on narrow ventral side ( Figure 2B). Cytoplasm colourless, containing numerous tiny granules but no food vacuoles recognizable. Cytostome ventrally positioned at anterior end, diagonally oriented, with inconspicuous nematodesmata (cytopharyngeal rods) extending dorsocaudally ( Figure 2D). Three contractile vacuoles detected (to be confirmed as pulsation was not observed) two near dorsal margin, the third one near base of podite ( Figure 2A). Macronucleus oval, about in mid-body, ca 25615 mm in vivo in size, characteristically dimorphic ( Figure 2D). Movement genus-typical, slowly crawling over substratum and slightly thigmotactic. Infraciliature as shown in Figure 2D: when viewed from lateral aspect, ''right'' field of ciliature composed of nine densely spaced, slightly fragmented kineties of variable length,  of which three extend to dorsal anterior end, while other six are shortened anteriorly ( Figure 2C). To left of distal end of these kineties, one fragment of kineties is always present as a double-rowed structure. In mid-body, about six to eight short rows of densely packed basal bodies forming left equatorial field ( Figure 2C, arrow). Equatorial fragment consisting of about 10 basal bodies. One large argentophilic patch-like ''gland'' positioned subcaudally, about 10 mm in length, always present near the base of podite (Figures 2C,15J,arrows). Oral ciliature composed of three fragment-like kineties ( Figure 2D, arrow).
Dysteria monostyla and D. antarctica can be identified by only five ventral kineties (versus nine in D. parovalis Petz et al. 1995;Gong et al. 2002). Dysteria brasiliensis can be recognized by the presence of the long caudal spine and also fewer ventral kineties (consistently five; Song and Packroff 1997).
Dysteria derouxi is large (75-110 mm long in vivo), has constantly eight ventral kineties (versus nine in D. parovalis) and has two ventrally located contractile vacuoles (Gong and Song 2003b), hence easily separated from D. parovalis.
Compared with the new species described here: Dysteria procera can be identified by having only three ventral kineties (versus nine in D. parovalis) (Gong and Song 2003a); D. magna is an extremely large form (1506100 mm versus 50-80640-60 mm for D. parovalis) with broadly rectangular body shape and constantly eight ventral kineties (versus nine in D. parovalis) (Gong and Song 2003a).
Genus Aegyriana Deroux in Song and Wilbert, 2002 In original description, the oral structure was insufficiently and incorrectly interpreted as it is difficult to detect because of its extremely anterior position (Deroux 1970;Song and Wilbert 2002). With the current population we had the opportunity to make further observations, so that an improved definition can be given here.

Improved diagnosis
Dorsoventrally flattened Dysteriidae with tail-shaped podite, which is positioned subcaudally in a glabrous region within the somatic kineties; oral ciliature in two parts: ca three close-set fragments on right and one kinety on left; left postoral kineties shortened posteriorly and continuous with right ones, leaving no median gap or suture; cytopharyngeal rods prominent.

Redescription
Body generally less variable (less flexible) than in original population, generally oval in shape with conspicuous snout-like projection on anterior left ( Figure 3A, B). Cells in median area distinctly thickened ( Figure 3B). Cytoplasm dark grey due to numerous globules and food vacuoles ( Figure 3C). Food vacuoles often large (about 5-10 mm across), full of green or reddish algae or flagellates, but not many diatoms ( Figure 3C). No contractile vacuoles observed. Ciliation basically matching original description well, preorally about six to seven kineties arched to left margin of cell with some anterior-most kineties consistently shifted dorsally ( Figure 3D). Perioral kineties (oral apparatus) clearly in two groups: right one three-rowed and fragment-like, separated from the single left kinety; all structures consisting of densely arranged dikinetids. On ventral side, general arrangement of kineties similar to that described previously (Song and Wilbert 2002) with all postoral kineties terminating anteriorly at buccal region and forming dominant buccal area ( Figure 3D). However, 18-20 kineties on left posteriorly shortened gradually leftwards ( Figures 3D, 15E, arrowheads and arrows). About nine kineties at posterior end ''interrupted'' by podite and hence forming large glabrous area, on the right of which there are about eight kineties, and ca four on the left ( Figure 3D).

Genus Hartmannula Poche, 1913
Hartmannula cf. angustipilosa Deroux and Dragesco, 1968 (Figures 3F-I, 12G; Table IV) We failed to observe some critical features in vivo such as contractile vacuoles and other living characters for this Antarctic form. Although many well-impregnated specimens have been obtained. Its identification remains uncertain and we can here only tentatively describe it as a population of Hartmannula angustipilosa Deroux and Dragesco, 1968.

Description
Body size about 60-90630-50 mm in vivo, mostly long oval with inconspicuous snoutshaped projection on anterior left ( Figure 3H). Dorsoventrally distinctly flattened, ventral side flat, dorsal vaulted. Podite about 15 mm long. Cytostome prominent, sub-apically located in a longitudinal to oblique orientation; pharyngeal basket consisting of about 15 cytopharyngeal rods, extending slightly leftwards and posteriorly ( Figure 3G). Dimorphic macronucleus large and oval, positioned in mid-body and containing several large nucleoli ( Figure 3G, H). Micronucleus not detected. About nine rightmost kineties extending preorally, with anterior portion curved to left margin; one terminal fragment positioned on anterior-left margin of cell. All other kineties (ca 18-26 in number) terminating around cytostome, leaving narrow glabrous buccal area. In addition to these normal kineties, there is one fragment-like equatorial right kinety with about 15 basal bodies in mid-body ( Figure 3H, I). Oral ciliature consisting of (constantly) three short rows of dikinetids, which are obliquely (and preorally as well) positioned: one is anteriorly located and two posteriorly ( Figures 3I, 12G, arrows).

Remarks
Deroux and Dragesco (1968) described three populations under the name Hartmannula angustipilosa, these are remarkably different in size and numbers of somatic kineties. The Antarctic form resembles the largest population in both body shape, size and the number of kineties. We speculate that the three populations in the original description might represent different species. Further information is required.

Diagnosis
Large-sized marine Pithites with slightly dorsoventrally flattened body shape, about 50-80635-50 mm in vivo; oral ciliature consisting of ca seven fragments; seven to eight somatic kineties on right side, of which four rightmost ones extend dorsally around the cytostome; eight left kineties; equatorial and terminal fragments present; one contractile vacuole subcaudally positioned left of median; one ellipsoid dimorphic macronucleus; about 15 cytopharyngeal rods.

Etymology
The Latin word pelagic (planktonic, free swimming), indicating that this organism is a planktonic form.

Description
In vivo mostly 50-60640 mm in size. Body shape rather stable, oval to cordiform when viewed from ventral side, with posterior end more or less narrowed. Dorsoventrally flattened by about 2:3, conspicuously asymmetrical: ventral side flat, dorsal vaulted ( Figure  4B). Pellicle thin and conspicuously notched in apical area on dorsal side, where the somatic kineties are arranged. When viewed from ventral side, one conspicuous shallow subcaudal cavity located near meridian of cell, which renders the associated area transparent and bright ( Figure 4A). Cytoplasm colourless to slightly greyish, often containing numerous tiny granules. Cytostome prominent, apically located. Cytopharynx typical of genus, long and extending posteriorly; pharyngeal basket consisting of about 9-12 cytopharyngeal rods ( Figure 4H). One large contractile vacuole subcaudally positioned ( Figure 4A, arrowhead). Food vacuoles not detectable. One macronucleus irregularly ellipsoid and positioned in midbody, containing large nucleoli ( Figure 4E). Micronuclei not detected. Cilia about 7 mm long, densely arranged. Movement fast and jerky when swimming and attempting to attach to substratum by the apical area. Another form of locomotion is a circular movement on the bottom of Petri dish as shown in Figure 4C.
Infraciliature as shown in Figure 4E-G: four densely ciliated rightmost kineties extending preorally, curved on to dorsal side and terminating at left margin, parallel to which one terminal fragment is positioned at anterior left end ( Figure 4F, arrow). About 12 postoral kineties arranged longitudinally around cytostome. Of these, almost always eight kineties on right of subcaudal cavity, with the posterior ends considerably more densely ciliated than the remainder ( Figure 4G, arrowheads), and ca eight kineties on left, which are gradually shortened posteriorly. Contractile vacuole pore always located between third and fourth kineties ( Figure 4G, arrow).
Oral ciliature consisting of ca seven short fragment-like dikinetids, mostly anterior to cytostome ( Figure F). Telokinetal stomatogenesis; overview of very early stages as in Figure 4I, J.

Remarks
Only one known species in this genus has been reported, namely the type species, Pithites vorax Deroux and Dragesco, 1968. The new species can be distinguished from the former by its larger size (30-35616-20 versus 50-80635-50 mm in P. pelagicus), higher number of somatic kineties (six left and five to seven right versus eight and seven to eight, respectively) and lack of the thread-like structure present in the caudal region of Pithites vorax (Deroux and Dragesco 1968).

Order SCUTICOCILIATIDA Small, 1967
Genus Philasterides Kahl, 1931 Philasterides cf. armatalis Song, 2000 ( Figure 1C) Only a few cells found in two protargol-impregnated slides, so that it can be described only at infraciliature level. According to the oral structure and general somatic infraciliature, it seems to be an undescribed member of the genus Philasterides. However, it has to be treated as an unknown species until further information is obtained.

Description
Cells about 40620 mm long after protargol impregnation; body shape long oval to slender, circular in cross-section; apical end widely pointed with small apical plate surrounded by somatic kineties ( Figure 1C, arrowhead); posterior end generally rounded. Ventral surface slightly indented around buccal area, dorsally convex. Buccal field about 50% of cell length. One large oval macronucleus centrally located, 12616 mm in size; position of micronucleus uncertain, possibly adjacent to macronucleus. About 22 somatic kineties longitudinally arranged, extending over entire length of body and mainly composed of dikinetids throughout. Each row with about 28 (paired or single) basal bodies.
Buccal apparatus consisting of three well-developed membranelles (M1-3) and one short paroral membrane which extends anteriorly to about the middle of membranelle 2. Membranelle 1 (M1) long and consisting of about 11 transverse rows of kinetosomes; membranelle 2 (M2) about half as long as M1 with ca five rows; membranelle 3 (M3) smaller, close to M2 with only three transverse rows. Paroral membrane likely not bipartite (? impossible to detect since cells lying on side). Scutica (Sc) with several pairs of basal bodies, sparsely arranged, posterior to cytostome ( Figure 1C, double-arrowheads).

Remarks
This organism differs from the marine form P. armatalis Song, 2000 in structure of scutica, buccal apparatus, smaller body size and lower in having fewer ciliary rows (see Song 2000).
This species was also identified from protargol-impregnated specimens (with numerous individuals). All morphometrical data correspond to the previous descriptions perfectly (Dragesco 1968;Song and Wilbert 2002). Hence only some extra data will be supplied here.
Micronuclei almost always several in number and closely adjacent to the rounded, large macronucleus. The Antarctic population has on average 40 somatic kineties, of which about five are shortened posteriorly on the left of the buccal field ( Figure 1B).
The genus Intranstylum is a relatively rarely reported taxon, most of its members having been only superficially described using classical methods (Kahl 1935;Stiller 1971). As accepted by previous researchers, it is recognized by: (1) the colonial form of all congeners and (2) the extremely reduced or degenerated spasmoneme, which may connect all zooids but has no contractile function, thus the stalk is non-contractile.
In our recent publication (Song and Wilbert 2002), one Zoothamnium sp. with abnormal spasmoneme was described from the same biotope as in the current investigation. However, after rechecking the slides, we believe it was a misidentification and should be conspecific with the population found this time. With reference to the large size, body shape, appearance of colony, the habitat and the poorly developed myoneme system, this form should represent an undescribed Intranstylum.

Diagnosis
Large-sized marine Intranstylum ca 100660 mm in vivo with ellipsoidal body shape, smooth pellicle and thick, single-layered peristomial border; one contractile vacuole located apically; macronucleus C-shaped, transversely positioned. Colony large, with about 20 or more zooids; stalk smooth, with regular, dichotomous branching; myoneme long with branches of different thickness.

Description
Zooids in similar size, in vivo about 100 mm long with thick, single-layered peristomial border; body form-constant, slender and elongated vase-shaped, only slightly constricted below peristomial collar; peristomial disc large and flattened ( Figure 5A). Cells not very sensitive to mechanical stimuli. When contracted, zooids usually globular in shape with distinctly truncated or folded plate at both cell ends. Pellicle smooth when observed at low magnification, fine transverse striations recognizable only under high magnification, with no visible granules or any other pellicular structure. Cytoplasm colourless or slightly greenish, usually containing many food vacuoles, which are oval or irregularly shaped and measure about 3-6 mm in length ( Figure 5A). Contractile vacuole large, apically located. Macronucleus C-shaped, thick and transversely positioned. Colony large (probably over 500 mm in length), having about 20 (probably more ?) zooids and a regular dichotomously branching stalk. Stalk with smooth surface, about 10 mm thick. Myoneme system consisting of long spasmoneme within stalk, which is about as long as the body length, relatively poorly developed as described in previous report (Song and Wilbert 2002 under the name of Zoothamnium sp.). In the present population, spasmoneme also varied in length (20-100 mm) and in different parts of the stalk thickness ( Figure 5B). No differentiation of macro-and microzooids.

Remarks
Though numerous cells/colonies were found, no information about the infraciliature is available due to over-staining of the impregnation. Hence the comparison to known congeners can be carried out only on the basis of observations in vivo.
This new species can be recognized by the combination of the following characters: large cell size and dichotomous by branched stalk, long and poorly developed spasmoneme, generally oval to ellipsoidal body shape of zooids and the marine habitat (Kahl 1935;Stiller 1971;Song et al. 2003).
( Figure 5D-F) Only several cells were found on protargol-stained slides, thus no further identification can be carried out. Here only a brief description is given based on the impregnated specimens.
Aboral ciliary wreath consisting of broad band of kineties, which are obliquely and densely arranged and each of which consists of more than 10 basal bodies ( Figure 5D). No scopula recognizable. Buccal ciliature as shown in Figure 5F, epistomial membrane near distal end of polykinety (double-arrowheads in 5F), while haplokinety (arrowhead in 5F) considerably shifted anteriad; peniculus 3 distinctly short (arrow in 5F).

Remarks
As noticed by other researchers, sometimes it is difficult to separate the swarmers of other stalked peritrichs and the genus Telotrochidium, hence it is not completely ensured that there is no misidentification of the present organism concerned. We await further observations.
Order Heterotrichida Stein, 1859 Genus Folliculina Lamark, 1816 Folliculina ? sp. (Figure 6) Several individuals were observed and impregnated, but no cells with lorica have been found (really not present ?). Since the genus identification depends largely on the shape or structure of the lorica, the definition of the genus is, therefore, questionable.

Description
Body shape in vivo as shown in Figure 6A. Total length of cell about 250 mm long in vivo, shape relatively constant (not very sensitive to disturbance); two ear-shaped wings wide and relatively long (about 120 mm in length), generally transparent except the border area where membranelles arranged ( Figure 6A, B). Cytoplasm colourless, but mostly dark grey to black due to numerous food vacuoles (with algae or diatoms) and lipid granules, especially under lower magnification. Macronucleus globular, about 30 mm across with many large nucleoli ( Figure 6C). This organism seems to be a typical benthic form: always using its caudal area to attach to surfaces such as debris.
About 110 somatic kineties, which are typical of folliculinids, consisting of densely arranged dikinetids, each with ca 7 mm long cilia. Membranelles along margin of two wings, extending into deep buccal cavity ( Figure 6C, arrowheads). Paroral membrane mostly multi-rowed with irregularly arranged basal bodies, parallel to adoral zone ( Figure 6C, arrow).
Genus Condylostoma Bory, 1824 Condylostoma cf. magnum Spiegel, 1926 ( Figure 7A-C) This organism was only found from protargol-impregnated slides and no in vivo data (e.g. concerning the body shape and size) are available. With reference to the infraciliature, it is extremely similar to the well-known species, Condylostoma magnum Spiegel, 1926, but differs from the latter, however, in having fewer somatic kineties (ca 30 versus 47-56) (Dragesco 1996;Song and Wilbert 1997), which indicates that these two forms might not be conspecific. As a document contribution to studies in the future, a brief description is supplied here.

Description
Cells about 250 mm long after impregnation, no tail present although caudal end might be conspicuously pointed ( Figure 7A). Buccal field probably relatively small (about one-sixth of body length after fixation) ( Figure 7C). Macronucleus moniliform with ca 10 ellipsoid nodules, lying slightly to right of main body axis ( Figure 7B). Somatic kineties composed of paired basal bodies as in other congeners, both ciliated with relatively short cilia. About 30 somatic kineties, some of which terminate subcaudally.
Adoral zone of membranelles conspicuous, consisting of more than 120 membranelles with proximal portion extending spirally into dominant buccal cavity. Paroral membrane developed, on right of dominant buccal cavity, terminating posteriorly near cytopharynx ( Figure 7C). The number of cirri-like membranelles at distal end of adoral zone (at least Genus Heterostentor Song and Wilbert, 2002 Heterostentor coeruleus Song and Wilbert, 2002 ( Figures 7D-H, 14J-N) The present population resembles the form described previously (Song and Wilbert 2002), so a complete redescription is unnecessary. Only the main features found to vary from the 2002 population are included here. Body often more slender oval than elongated cylindrical, dorsoventrally only slightly flattened, length to width about 1:2-3 when moving freely, but 1:3-5 when attached to substratum by posterior end of cell and contracting from time to time ( Figure 7F). Dark blue pigments beneath pellicle arranged in at least two patterns: sparsely distributed between ciliary rows with larger granules or conspicuously densely distributed ( Figure 7G, H). In anterior cell end (around adoral zone of membranelles), these pigments/granules render the cell dark blue. Numerous membranelles in adoral zone which, in vivo, appear to be clustered into about 20 groups of membranelles ca 25 mm long and extend forwards ( Figure 7E).
Order STROMBIDIIDA Jankowski, 1980 Genus Strombidium Claparède and Lachmann, 1859 This well-known, species-rich genus has typical family characters: adoral zone of membranelles generally consisting of collar and buccal parts and two somatic kineties: circularly arranged girdle/equatorial kinety and the short, subcaudally positioned ventral kinety, although the former may have a small gap, i.e. not be completely continuous. Unlike Strombidium, the related genus Spirostrombidium established by Jankowski (1978) is characterized by the differently arranged somatic kineties, i.e. the girdle (equatorial) kinety does not encircle the equatorial area, but is opened and extends spirally to the caudal region, often very close and parallel to the short ventral kinety. Thus, some members of this genus seem to possess only one somatic kinety when observed superficially Song and Packroff 1997;.
Based on the pattern of the girdle kinety, the most critical feature to separate the two genera is the posterior end of the equatorial kinety which extends to the caudal area and is parallel to the ventral one versus terminates anterior to the proximal end of ventral kinety.
According to this definition, the new form we obtained should be classified within the genus Strombidium.

Diagnosis
Cordiform Strombidium in vivo about 50640 mm; ca 13 collar and seven buccal membranelles not continuous; girdle and ventral kinety with ca 45 and 60 basal body pairs, respectively; single elongate to sausage-like macronucleus; extrusomes evenly distributed along the somatic kineties; marine habitat.

Etymology
Composite of apo (derived from) and the species name latum, indicating that this species is different from the congener S. latum.

Description
Size about 40-60630-45 mm in vivo, after fixation ca 35-50 mm in length; cell ratios about 3:2 for length/width and ca 4:3 for dorsoventral flattening. Body shape consistently cordiform, often slightly asymmetrical when viewed ventrally; anteriorly broadly rounded, posteriorly slightly pointed ( Figure 8A). Buccal cavity shallow, about one-quarter of cell length. Transparent subpellicular platelet layer in posterior three-quarters of cell ( Figure  8G, arrow), although the polygonal platelets often found in other congeners were not detected here. Equatorial girdle in anterior two-thirds length, ca 2 mm wide, immediately ahead of subpellicular platelet layer ( Figure 8H, arrow); extrusomes densely and uniformly distributed, inserting along girdle ( Figure 8D, arrows). Cytoplasm tightly packed with dark globules (especially directly below the cell surface) and lipid droplets, rendering cells dark to almost black at low magnification. Macronucleus elongated to sausage-like (but sometimes irregularly shaped after fixation), about 25-3067-10 mm in size, with many large nucleoli ( Figures 8H, 14D, H). Micronucleus not detected.
Movement fast and almost without pause, hectically to and fro on the debris ( Figure 8C). Adoral zone spirally around peristomial field, cilia of most membranelles about 25-30 mm long, always extending anteriorly ( Figure 8A). Twelve to fourteen collar membranelles (CM), bases ca 7 mm in length and conspicuously longer than those in buccal zone. The buccal zone (BM) consists of six to eight membranelles and is positioned in the shallow buccal cavity, hence conspicuously separated from the CM ( Figure 8F). Pharyngeal fibres highly developed, ca 20 mm long and extending obliquely to right side ( Figure 8F, G).
Girdle kinety (equatorial kinety) composed of about 45 dikinetids (n55), running along the edge of subpellicular platelet layer, begins at right margin, turns to dorsal side and then curves slightly towards the posterior (but clearly separated from the ventral kinety; Figure 8H, arrowhead). Ventral kinety more densely ciliated than girdle one, containing ca 60 basal body pairs, extending from right body margin subcaudally to the left and terminating laterally at posterior end of girdle kinety at level of about anterior third of cell length ( Figure 8H). Cilia in girdle kinety about 2 mm long, while in ventral one ca 5 mm in length ( Figure 8G, H).

Remarks
The genus Strombidium is a species-rich taxon containing more than 30 nominal species (Kahl 1932;Maeda and Carey 1985;Lynn et al. 1988;Montagnes et al. 1988Montagnes et al. , 1990Montagnes and Taylor 1994;Montagnes and Lynn 1991;Lynn and Gilron 1993;Petz et al. 1995). With respect to the subpellicular platelet layer which covers almost two-thirds of cell length, the flattened body shape, the shallow buccal cavity, densely arranged cilia in ventral All data are based on protargol-impregnated specimens.
kinety, the laterally positioned ventral kinety and the sausage-like macronucleus, this species clearly differs from all other known members of this genus Montagnes et al. 1988Montagnes et al. , 1990Montagnes and Lynn 1991;Petz et al. 1995;Song and Packroff 1997;.

Description
Size mostly about 200660 mm, body very flexible and variable in shape but generally slender and elongate, with anterior part distinctly narrower than posterior; anteriorly narrowly rounded, posteriorly tapered; buccal field wide, about 30% of cell length ( Figure 9A). Pellicle thin, no cortical granules observed although cytoplasm usually brownish to dark brown in colour (due to food?) as observed under low magnifications. Cytoplasm with many tiny lipid droplets and food vacuoles containing mainly small and large pennate diatoms or small protozoans. Contractile vacuole on left of body and near equatorial level ( Figure 9A, H). More than 150 macronuclear nodules scattered throughout the cell ( Figure 9F), spherical to ellipsoid, usually with one to several large nucleoli ( Figure 9G). Movement slow, usually three different modes observed: (1) crawling on bottom of Petri dish or debris, making small circular movement ( Figure 9I); (2) attached by thigmotactic field to the bottom while the raised anterior part of body makes (slow) left-right movements ( Figure 9J); or (3) when disturbed, relatively faster, crawling around irregularly. When swimming in water, moves slowly with no special features ( Figure 9B).
Buccal field large and deep. Adoral zone of membranelles extending far on to right side. Paroral and endoral membranes about equal in length, slightly bent in posterior portion, optically appearing to intersect ( Figure 9K). One buccal cirrus at about mid-level of undulating membranes.
About 15 frontal cirri forming bicorona, which are not clearly distinguished from the midventral cirri posteriorly although the anterior-most (usually three) cirri are conspicuously enlarged ( Figure 9K). Two midventral rows distinctly separated (so that the cirri are not arranged in typical zig-zag pattern), terminating near posterior rightmost transverse cirri ( Figure 9E, K). Left postoral cirral field (5thigmotactic field) consisting of about 13 (in maximum width) densely packed longitudinal rows, in each of which the cirri are basically loosely arranged ( Figure 15K). Bases of cirri in this thigmotactic field mostly smaller than other ''normal'' ones and more or less ovoid in shape (Figures 9K, 15K). Transverse cirri slightly enlarged and arranged in J-shape, joining thigmotactic field ( Figures 9D, E, 15L). Marginal rows not confluent posteriorly. Dorsal kineties constantly three in number, densely ciliated (ca 3 mm long, Figure 15J); without caudal cirri.
( Figure 10A-C) In view of its body size, the extremely shortened midventral rows with only a few pairs of cirri and the presence of large ''extrusomes'' (cortical granules ?), this small Holosticha possibly represents an unknown form. Unfortunately, only a small number of protargolimpregnated individuals were observed on a permanent slide and no other necessary information, e.g. features observable in life or biometrical data, is available. Further studies are required in order to determine the identity of this taxon.

Description
Body shape in vivo unknown; after impregnation, broadly oval, about 65640 mm in size; buccal field about two-fifths of cell length ( Figure 10A). Distal end of adoral zone evenly bent towards right side with ca 17 membranelles, the longest bases of adoral membranelles about 8-10 mm long. Paroral and endoral membranes short and straight, pharyngeal fibres over 20 mm long ( Figure 10A). About 30 macronuclear nodules distributed throughout the cell, each oval in shape and ca 4 mm long; four globular micronuclei recognizable, which are relatively large (3 mm across). On dorsal side, always several argentophilic extrusome-like structures (cortical granules ?), which are about 3 mm in length, vase-shaped with rounded posterior end and positioned along dorsal kineties ( Figure 10B, C). Three frontal cirri, only slightly enlarged and difficult to separate from the midventral cirri; one buccal cirrus near anterior end of undulating membranes; two fronto-terminal cirri between distal end of adoral zone of membranelles and anterior end of right marginal row. Midventral rows atypical and very short, consisting of only three to four pairs of cirri, posterior to which there is a single row with three to five cirri extending to about midway along the cell ( Figure 10A). Six to seven enlarged transverse cirri forming J-shape, immediately anterior to which two small cirri are often observed. Right marginal row consisting of ca 17 cirri, left row with about 14; the two rows are widely separated at posterior cell end.

Genus Metaurostylopsis Song, Petz and Warren, 2001
Metaurostylopsis rubra Song and Wilbert, 2002 (Figures 10D-G, 15A-I, N) The current population matches the original description very well. We thus supply here only some information derived from recent observation of its morphological features and the morphogenetic process.

Description
Body often more oval than originally reported, size in vivo about 150650 mm. Eight left and six right marginal rows on average; adoral zone about one-third of body length with 45 membranelles; about 12 pairs of cirri in midventral rows, single ventral row extending to about posterior third of cell length with ca 13 cirri; ca 10 fronto-terminal, one buccal, four frontal and five transverse cirri ( Figures 10D, 15E, F, I). Constantly three dorsal kineties, no caudal cirri. On the basis of the morphogenetic stages obtained from the present population, formation of the ciliature in Metaurostylopsis rubra can be summarized as follows: (1) The parental oral apparatus is entirely renewed by the proter's oral primordium. (2) Two sets of fronto-ventral-transverse cirral anlagen give rise to the buccal, fronto-terminal, transverse and anterior most frontal cirri, as well as to the ventral and the midventral rows in both divisional parts. (3) The leftmost frontal cirrus develops from the undulating membrane primordium in both proter and opisthe. (4) Streak II-III generates the other frontal and the buccal cirri. (5) Streaks IV to n-1 give rise to the midventral rows. (6) The short ventral row posterior to the midventral rows originates also from the anlage n-1 (the last but one). (7) The fronto-terminal cirri are formed by the last streak of the fronto-ventral-transverse anlagen. (8) Two anlagen develop within each marginal cirral row, each of which forms a separate marginal row. (9) One anlage develops within each of the three parental dorsal kineties in both dividers. (10) No caudal cirri are differentiated.     Thus the morphogenetic process is very similar to its congener, Metaurostylopsis marina (Kahl, 1932) Song et al., 2001(Song et al. 2001, though some details of this new species remain unknown because certain divisional stages have not yet been observed. Genus Hemigastrostyla Song and Wilbert, 1997 This genus was established by Song and Wilbert (1997), which was defined originally by (1) generally having an Oxytricha-like cirral pattern; (2) usually possessing slightly cephalized body shape; and (3) presence of two ''extra'' ventral cirri.
On the basis of the new understanding subsequently obtained (Song and Hu 1999), however, the diagnosis of this genus should be slightly amended and some new points need to be added: (1) no right-lateral anlagen of dorsal kineties occurrs during morphogenesis; (2) the proximal portion of the old adoral zone (AZM) will be replaced by newly formed structure; (3) 8-10 frontal (including one buccal), five to seven ventral cirri; (4) highly developed fibre system which is associated with cirri; (5) inflexible body shape; (6) dorsal cilia located in small pits.
According to this new definition, the organism found in the present investigation should be assigned as a new species of the genus Hemigastrostyla.

Dedication
We dedicate this species to the Hungarian protozoologist, Dr Andras Szabo, in recognition of his contributions to the study of ciliates.

Description
Cells generally inflexible; body shape distinctly slender with both ends only slightly narrowed, ratio of cell length to width about 3:1 ( Figure 11A); buccal field narrow, about one-third to two-fifths of body length; dorsoventrally flattened 1:2. Cell margins generally parallel but in anterior portion often slightly swelling outward. Ventral side conspicuously grooved because of the presence of marginal rows ( Figure 11A, arrow).
Pellicle thin; no cortical granules recognizable (not carefully observed). Cytoplasm often containing numerous light-reflecting globules (3 mm across), which render the cell completely dark, especially in posterior portion of body. Food vacuoles basically not detectable. No contractile vacuole detected. Two macronuclei, elongate and often conspicuously separated from each other ( Figures 11D, 16K); two to five oval micronuclei near macronuclei ( Figure 16G, arrows). Movement relatively slow, crawling without pause on debris. Buccal field narrow, adoral zone of membranelles (AZM) extending to about one-third of body length, bases of membranelles up to 8 mm long, cilia ca 15 mm long in vivo. Distal end of adoral zone of membranelles bending considerably posteriad at right margin. Paroral and endoral membranes about equally long, parallel to each other. Pharyngeal fibres short and conspicuous after protargol impregnation ( Figure 11C).
Frontal area constantly eight cirri, anterior two to three of which are distinctly enlarged, while others are smaller ( Figure 11C). Single buccal cirrus (counted among frontal cirri in Table VIII), situated beside mid-point of undulating membranes. Three postoral ventral cirri anteriorly located, immediately beneath the cytostome level ( Figure 11C), while two pretransverse ventral cirri close to five terminally positioned thick transverse cirri. Right marginal row terminating subcaudally anterior to rightmost transverse cirrus, which often gives an appearance of confluence of right marginal cirri and TC ( Figure 16L, arrow). Cirri All data are based on protargol-impregnated specimens. Measurements in mm. a Including one buccal cirrus; b only the complete rows counted.
in both marginal rows rather large and densely spaced; anterior portions of right marginal row often extending on to dorsal side. At posterior end, the two marginal rows widely separated. All cirri associated with strongly impregnated fibre system ( Figures 11B, 16I, L). Dorsal kineties constantly three, cilia about 3 mm long, positioned in small pit as recognized after impregnation. Three caudal cirri located caudally on cell margin ( Figure 11D, arrowheads).

Remarks
The genus Hemigastrostyla previously contained only two species (Borror 1963;. This new organism can be separated from the closely related H. enigmatica (Dragesco and Dragesco-Kernéis 1986) Song and Wilbert by having fewer frontal and buccal cirri (eight versus consistently more than eight in the latter), no ''extra'' ventral cirri (versus present), fewer dorsal kineties (three versus five) and the body shape (non-cephalized versus cephalized) (Dragesco and Dragesco-Kernéis 1986;Song and Wilbert 1997). Differences from H. stenocephala (Borror 1963) Song and Wilbert 1997, are that the new species has conspicuously shorter dorsal cilia (ca 3 versus 16 mm in length in H. stenocephala), fewer frontal and ventral cirri (13 versus 17), less slender body shape and no extra ventral cirri (versus two in H. stenocephala) (Borror 1963

Diagnosis
Slender marine Amphisiella 120-200630-50 mm in vivo with narrowed caudal portion. Eight to twelve frontal and five transverse cirri; single ventral row extending to posterior third of cell length with about 29 cirri on average; two small ventral cirri close to transverse cirri; 25-32 adoral membranelles; 39-56 left and 42-55 right marginal cirri; four dorsal kineties and four caudal cirri; two macro-and two micronuclei. Cortical granules large and sparsely distributed on dorsal side.

Description
In vivo mostly about 160640 mm in size. Cells flexible, slightly contractile and often more or less distorted in middle portion (even twisted while gliding on debris, Figure 11H); dorsoventrally flattened by about two-thirds. Body shape distinctly slender with posterior portion distinctly narrowed; ratio of cell length to width about four to one ( Figure 11E), buccal field narrow and inconspicuous, about one-quarter of body length; cell margins generally parallel but often curved outward in middle portion. Dorsal side slightly uneven, irregularly bulging ( Figure 11G). Pellicle soft and thin; ''cortical granules'' colourless and large (about 1 mm), not grouped and sparsely distributed on dorsal side ( Figure 11F). Cytoplasm greyish or colourless, often containing numerous light-reflecting globules (2-5 mm across), which render the cell dark under low magnification. Contractile vacuole not observed. Food vacuoles several to many, always containing small diatoms or flagellates ( Figure 11E). Two elongate macronuclei, ca 20615 mm in size in vivo, slightly separated from one another near left side of body; constantly two large (4-5 mm across), globular micronuclei, adjacent to macronuclei ( Figures 11K, 16B).
Movement relatively slow, crawling without pause on debris. When swimming, spirally rotating about the longitudinal axis.
Four enlarged frontal cirri followed by usually five smaller ones posteriorly; single ventral row consisting of 21-36 cirri extends to about posterior third of cell length. Always two small cirri anterior to five enlarged transverse cirri, which are positioned almost completely at posterior end of cell ( Figure 11J) and are connected by five fibres about 40 mm long. The two marginal rows are widely separated posteriorly and terminate near transverse cirri ( Figure 11J).
Four dorsal kineties loosely ciliated, cilia about 5 mm long, comprising ca 10 pairs of basal bodies each. Four caudal cirri at margin of cell ( Figure 11K).

Remarks
Considering the body shape, size, habitat and general appearance, at least two marine morphotypes should be compared with the new species described here: Amphisiella thiophaga (Kahl, 1928) Kahl, 1932 andA. annulata (Kahl, 1928) Kahl, 1932. The new species differs from the former in having a narrowed caudal portion (versus broadly rounded in A. thiophaga) and a relatively shorter ventral row of cirri that terminates far away from the transverse cirri (versus extends completely to the transverse cirri) (Kahl 1932).
Compared with A. annulata, the new species can be distinguished by body shape (with narrowed posterior end versus broadly rounded), lack of ring-like granules (''Ringkugeln'') in cytoplasm (versus present in the former species) and probably the presence of conspicuous cortical granules (versus absence ?; none were mentioned in original description).