The Kinetid Structures of the Choreotrichous Ciliate Strobilidium velox and an Assessment of Its Evolutionary Lineage1

The ciliary (kinetid) structures of the ciliate Strobilidium velox have been examined with scanning and transmission electron microscopes. Somatic kineties consist of a linear row of kinetosomes (monokinetids) and short cilia lying partially beneath a thin fold of cytoplasm. The only fibrillar kinetid structure extending from the kinetosomes is a transverse ribbon of microtubules. The paroral membrane is a single-file polykinetid possessing a possible transverse ribbon of microtubules and a nematodesma. The oral polykinetids or membranelles are complex, with microtubules extending from both anterior and posterior rows of cilia. While the kinetid structures do not satisfy the criteria for the order Choreotrichida, they are similar to the tintinnids in several other relevant ways. Strobilidium velox is proposed to be an unusual ciliate that is an exception to the concept that somatic kinetids are conservative and reliable phylogenetic indicator structures.     

Ultrastructural aspects of the somatic and buccal infraciliature ofColeps amphacanthus Ehrenberg 1833

Summary Somatic and buccal infraciliature ofColeps amphacanthus Ehrenberg 1833 were studied by light and electron microscopy. The somatic kineties are composed of monokinetids and 2 dikinetids at the anterior end of each kinety. The monokinetids are associated with postciliary microtubules at triplet 9, a kinetodesmal fiber at triplet 5 and 7 and nearly radially arranged transverse microtubules at triplet 4. The associated fibrillar systems of the posterior kinetosome of the dikinetids are like those of the monokinetids. The anterior kinetosome is associated with transverse microtubules at triplet 4 and one or few postciliary microtubules at triplet 9. The anterior kinetosome bears only a short cilium.The oral ciliature is composed of a kinety of nearly circumorally arranged paroral dikinetids and 3 adoral organelles at the ventral left side of the oral opening. Nematodesmata arising from the oral ciliature form the major component of the cytopharyngeal apparatus which is lined by microtubular ribbons of postciliary origin. The buccal cavity is surrounded by oral papillae which often contain toxicysts.     

Cortical ultrastructure of Coleps bicuspis Noland, 1925 and the phylogeny of the class Prostomatea (Ciliophora)

The ultrastructure of Coleps bicuspis Noland, 1925 is described. The ciliate is a typical prostomate: the somatic kinetid is a monokinetid with a postciliary ribbon at triple 9, a kinetodesmal fibril originating near triplets 5, 6, 7 and an apparently radial transverse ribbon at triplet 4. The oral area is circular and has three brosse kineties associated with it. The brosse kineties are composed of dikinetids whose anterior kinetosome bears a tangential transverse ribbon and whose posterior kinetosome bears the fibrillar associates typical of a somatic monokinetid. The oral dikinetids are oriented parallel to the circumference of the oral cavity, which is surrounded by oral papillae and oral ridges. Pairs of nematodesmata, originating from oral dikinetid kinetosomes, are typically triangular in transection. A phylogeny of rhabdophoran ciliates is presented using the mixed parsimony algorithm and is discussed with reference to the systematic revisions of the phylum Ciliophora.     

The Ultrastructure of Chaenea teres and an Analysis of the Phylogeny of the Haptorid Ciliates

Chaenea teres has typical haptorid ultrastructure. The somatic monokinetid has two transverse microtubular ribbons, an overlapping postciliary microtubular ribbon, and a laterally directed kinetodesmal fiber. The evered cytopharynx forms a dome at the apical end of the cell. The base of the dome is surrounded by oral dikinetids. The left, anterior kinetosome of the oral pair is not ciliated and has a transverse microtubular ribbon, a nematodesmata and a single postciliary microtubule. The right, posterior kinetosome is ciliated and has only postciliary microtubules. The kinetosomes at the anterior ends of the somatic kinetics are close together and their transverse microtubules and nematodesmata contribute to the support of the cytopharynx. The transverse microtubules of these oralized somatic kinetosomes, together with those from the oral dikinetids, line the cytopharynx. Accessory or bulge microtubules arise perpendicular to the transverse microtubules. A dorsal brush of three kineties of clavate cilia is found on the cell surface just posterior to the oral region. Mucocysts and a single type of toxicyst are present. The toxicysts are confined to the oral region. There are multiple ovoid macronuclei that stain weakly. Micronuclei were not observed. Cladistic analysis indicates the Chaenea may be most closely related to Fuscheria and Acropisthium. The cladistic analysis also suggests that existing taxonomies of the subclass Haptoria need to be revised. We propose some modifications to Foissner & Foissner's classification that include transferring Helicoprorodon, Actinobolina, the buetschiliids, and the balantidiids to the order Haptorida and recognizing the close relationship between pleurostomes and spathidiids.     

Studies on the gill ciliation of the American oyster Crassostrea virginica (Gmelin)

Latero-frontal, para-latero-frontal, and frontal ciliary tracts on the gill filaments of Crassostrea virginica (Gmelin) were studied with light microscopy and scanning electron microscopy. Latero-frontal cirri are complex structures composed of varying numbers of paired cilia. The multiple pairs of cilia which constitute a single cirrus are closely appressed for a portion of their length; they then branch laterally from the central axis in a plume-like fashion. Latero-frontal cirri of adjacent gill filaments create a filtration sieve which should be capable of retaining particles smaller than 1 μm in diameter. Para-latero-frontal cilia are short, closely spaced cilia arranged as a staggered row along the frontal side of each tract of latero-frontal cirri. Latero-frontal cirri and para-latero-frontal cilia occur on ordinary, principal, and transitional gill filaments. Frontal ciliary tracts of ordinary filaments are divided into a central, ventrally directed coarse tract, flanked on either side by a dorsally directed fine ciliary tract. The coarse tract is covered by cirri which are comprised of five to eight cilia, while the fine frontal tracts are made up of individually functioning cilia. The frontal ciliary tracts of principal and transitional filaments bear only dorsally directed fine cilia. The unique direction of effective beat of the coarse frontal cirri of ordinary filaments, in combination with the action of fine frontal cilia and the strategic location of mucus producing cells, is used to describe a possible mechanism for the sorting of filtered particles.     

Apotrachelocerca arenicola (Kahl, 1933) n. g., comb. n. (Protozoa, Ciliophora, Trachelocercidae): morphology and phylogeny

During faunistic study on psammophilic ciliates along the coast of Qingdao, China, a population of Trachelocerca arenicola Kahl, 1933 was found and then investigated using silver staining and gene sequencing methods. The results indicated that it represented a new genus Apotrachelocerca characterized by uninterrupted circumoral kineties composed of two rows of dikinetids and no brosse or ciliary tuft in the oral cavity. This new genus should be assigned to the family Prototrachelocercidae Foissner, 1996. Based on the small subunit rRNA gene sequence, phylogenetic trees revealed that Apotrachelocerca arenicola occupied a basal position to other trachelocercids.     

The Ultrastructure of Zosterodasys agamalievi (Ciliophora: Synhymeniida)

ABSTRACT. The cell surface of the synhymeniid ciliate, Zosterodasys agamalievi , consists of shallow kinetal grooves separated by low cortical ridges. Numerous electron-opaque bodies are located in the cortical ridges, inside the kinetal grooves, and are distributed in parallel rows between adjacent kineties. Well-developed alveoli are present beneath the cell surface membrane. Zosterodasys agamalievi has a single micronucleus and a homomerous macronucleus. The infraciliature of the somatic monokinetid consists of an anteriorly-directed kinetodesmal fiber, a well-developed divergent postciliary microtubular ribbon, radially-oriented transverse microtubules, and a short striated rootlet, which extends anteriorly from the base of the kinetosome into the cell. Zosterodasys agamalievi has a perioral band of paired cilia, the synhymenium, that winds obliquely across the ventral surface of the body, just posterior to the cytostome. The infraciliature of the anterior kinetosome of the synhymenium consists of two postciliary microtubules; a well-developed, divergent post-ciliary ribbon of microtubules and a short kinetodesmal fiber are associated with the posterior kinetosome. The cytopharynx is supported by 14-16 nematodesmata which are capped distally by a capitulum. The cytopharynx is bound proximally by a fibrous sheath and is lined by radially-arranged microtubular ribbons. No obvious oral ciliature is present.     

Somatic kinetics or paroral membrane: which came first in ciliate evolution?

The ciliate species which lack a distinctive oral ciliature are considered to represent an ancestral state in ciliate evolution. Consequently, the somatic kineties composed of kinetids (kinetosomes plus cilia and associated fibrillar systems) are thought to be the ancestral ciliature. Results on stomatogenesis in 'gymnostomial ciliates' have shown that these ciliates probably have evolved from ancestors already equipped with an oral ciliature. Thus instead of the somatic, the oral ciliature may be regarded an ancestral. Based on these ideas a hypothesis on the evolution of the ciliate kinetome (assembly of all kinetids covering the body of a given ciliate) is presented. The first step in the evolution of the kinetome was the formation of a paroral membrane, a compound ciliary organelle lying along the right side of the oral area which historically but falsely is termed membrane. It was composed of kinetosomal dyads (dikinetids), derived from the kinetid of a dinoflagellate-like ancestor. From the beginning the paroral membrane was responsible for locomotion, ingestion and for the formation of a cytopharyngeal tube which the first ciliate probably had inherited from its flagellate ancestor. In the second step a first somatic kinety was formed from the right row of kinetosomes of the paroral membrane as a result of a longitudinal splitting of the paroral membrane and a subsequent migration of the forming kinety to the right into the somatic cortex. To increase the number of somatic kineties this process was repeated until the kinety produced first reached the left border of the oral area. By this step the locomotive and the nutritional functions were differentiated between somatic and oral structures. In a third step the adoral organelles were formed from somatic kinetids left of the oral area. The primitive type of stomatogenesis was a buccokinetal one derived from the mode the flagellate ancestor used to distribute its replicated kinetosomes to the offspring cells (buccokinetal means that at least parts of the oral anlage for the posterior offspring cell has its origin in the parental oral apparatus). This hypothesis, based on comparative studies on ciliate morphogenesis, is corroborated by molecular data from other laboratories.     

Oral Monokinetids in the Free-Living Haptorid Ciliate Enchelydium polynucleatum (Ciliophora,Enchelyidae): Ultrastructural Evidence and Phylogenetic Implications1

Special ultrastructural characteristics of the haptorid soil ciliate Enchelydium polynucleatum Foissner, 1984 are the restriction of the parasomal sacs to the area of the “brush” and finger-like projections of the food vacuole membrane into the lumen of the vacuole. The general organization of the infraciliature is similar to that of Spathidium and some buetschliids because the anterior ends of the somatic kineties are condensed and obliquely bent. Enchelydium is similar to haptorids and buetschliids in possessing monokinetid somatic fibrillar structures with the classical fibrillar associates: 1) a short kinetodesmal fiber; 2) two transverse microtubular ribbons; 3) a long postciliary microtubular ribbon; and 4) a system of overlapping subkinetal microtubules, which seems to be absent in the buetschliids. Unlike Spathidium and all other haptorids so far investigated ultrastructurally, serial sections show that there are no oral dikinetids, as in the endocommensal buetschliids and balantidiids. Instead, three to six anterior kinetids in each ciliary row have nematodesmal bundles extending into the cytoplasm and surrounding the cytopharynx. These kinetids lack cilia and all fibrillar associates except enlarged transverse ribbons, which extend anteriorly and inwards to support the cytopharynx. Other similarities between the buetschliids and Enchelydium are the conspicuous rough endoplasmic reticulum and abundant sausage-like vesicles in the oral region. As in other haptorids, Enchelydium has two types of toxicysts and one type of mucocyst. These observations strongly suggest that Enchelydium belongs to the ancestral stock of both the Haptorida and the Archistomatida. The similarities in the somatic and oral infraciliature and ultrastructure of the Haptorida and the Archistomatida suggest that they belong to the same subclass, Haptoria Corliss, 1974.     

Updating the Trachelocercids (Ciliophora, Karyorelictea). I. A Detailed Description of the Infraciliature of Trachelolophos gigas N. G., N. Sp. and T. filum (Dragesco & Dragesco-Kernéis, 1986) N. Comb

ABSTRACT. Trachelolophos gigas n. g., n. sp. and T. filum (Dragesco & Dragesco-Kernéis, 1986) n. comb. (basionym: Tracheloraphis filum) were discovered in the mesopsammon of the French Atlantic coast at Roscoff. Their morphology and infraciliature were studied in live and protargol impregnated specimens. The new genus, Trachelolophos, belongs to the family Trachelocercidae and is unique in having a conspicuous ciliary tuft, which is very likely a highly modified brosse, in the oral cavity. The two species investigated have a very similar infraciliature, differing only in morphometric characteristics and in the nuclear configuration. The entire somatic and oral infraciliature consists of dikinetids which have both basal bodies ciliated or only the anterior or posterior ones, depending on the region of the cell. The right side is densely and uniformly ciliated. Its kineties extend onto the left side to the glabrous stripe, where an anterior and posterior secant system are formed, reducing the number of kineties in the narrowed neck and tail region. The left side bears a narrow glabrous stripe bordered by slightly irregularly arranged dikinetids having rather stiff cilia (bristles), possibly forming an uninterrupted, prolate ellipsoidal (bristle) kinety as indicated by their ciliation. The bristle kinety commences subapically at the right margin of the glabrous stripe, extends posteriorly, then anteriorly at the left, to end up at the right margin again. The dikinetids of the right posterior portion of the bristle kinety have the posterior basal bodies ciliated, whereas the anterior basal bodies are ciliated in its left and right anterior portion. The ends of the bristle kinety meet distinctly subapically at the right margin of the glabrous stripe, as indicated by the diametrically opposed ciliation of the dikinetids. The anterior region (head) of the cell bears a distinct circumoral kinety composed of very regularly arranged dikinetids, associated with nematodesmata forming an oral basket together with the nematodesmal bundles originating from the oralized somatic dikinetids at the anterior end of the somatic kineties. The systematics of trachelocercid ciliates are briefly reviewed and discussed.     

Description of the Infraciliature and Morphogenesis in the Ciliate Urotricha ondina N. Sp. (Prorodontida, Urotrichidae)

Recent works on prostomatid ciliates show that some genera of this group have a differentiated oral infraciliature and that their stomatogenesis during division involves the proliferation of only a few somatic kineties. These findings have significant implications regarding the iaxonomic status of these genera and also on the terminology used for the oral structures. In Urotricha ondina , the oral infraciliature consists of (1) a paroral kinety formed of paired kinetosomes that encircle the cytostome at the anterior pole of the cell and (2) 3 adoral organelles, each formed of 2 rows of kinetosomes, ventral in position and obliquely disposed, lying above 3 short somatic kineties that do not reach the anterior pole of the cell. This oral ciliature —formerly known as the corona and brosse, respectively—originate during stomatogenesis from the proliferation of 4 somatic kineties that lie posterior to the adoral organelles of the parental cell.     

Morphology and infraciliature of two new marine ciliates, Paracyrtophoron tropicum nov. gen., nov. spec. and Aegyria rostellum nov. spec. (Ciliophora, Cyrtophorida), isolated from tropical waters in southern China

The morphology and infraciliature of two new marine cyrtophorid ciliates, Paracyrtophoron tropicum nov. gen., nov. spec. and Aegyria rostellum nov. spec., isolated from tropical waters in southern China, were investigated using live observation and protargol impregnation methods. Paracyrtophoron nov. gen. differs from the closely related Cyrtophoron by lack of fragment kinety at anterior ends of right somatic kineties and thigmotactic cilia in posterior portion of ventral surface, while from the well-defined Chlamydodon by lack of the cross-striped band around the periphery of the somatic field. Paracyrtophoron tropicum nov. spec., the type of the new genus, can be recognized by the combination of the following characters: cell size about 150-175×70-90μm in vivo; elliptical to kidney-shaped in outline, dorsoventrally flattened about 2.5:1; conspicuous cortical granules; one canal-like depression extending from postoral area to subcaudal region of cell; ca. 90 somatic kineties; 12-16 nematodesmal rods; one or two terminal fragments on dorsal side. Aegyria rostellum is characterized by the following features: size about 90-150×40-70μm in vivo, triangular or ear-shaped body with broad anterior end, having a rostriform structure and pigment spots, 56-63 somatic kineties, one preoral kinety, three or four circumoral kineties, and 32-42 nematodesmal rods. Based on previous and current studies, the definition for the genus Aegyria is updated: body dorsoventrally flattened; oral ciliature consisting of one preoral and several circumoral kineties; podite located in posterior ventral region and surrounded by somatic kineties; no obvious gap between right and left somatic kineties; postoral and left somatic kineties progressively shortened posteriorly from right to left. Additionally, two new combinations were proposed.     

Light and Electron Microscopical Observations on the Stomatogenesis of the Ciliate Coleps amphacanthus Ehrenberg, 1833

Light and electron microscopical observations on the stomatogenesis of Coleps amphacanthus Ehrenberg, 1833, show that this "gymno"-stome ciliate has a well developed oral ciliature made of 19–23 "paroral dikinetids" and three "adoral organelles." These structures were previously known as "circumoral ciliature" and "dorsal brosse," and it was thought that they originated from the distal ends of all the 22–26 somatic kineties. Contrary to this view, only four stomatogenic kineties (K1, Kn, Kn-1, and Kn-2) are involved in stomatogenesis of the opisthe. All paroral dikinetids arise from one single kinetofragment (KF1) to the right of the oral anlage while the adoral organelles originate from the three left kinetofragments (KFn, KFn-1, and KFn-2). In particular, the future paroral dikinetids perform a complex morphogenetic movement that leads to a situation where the postciliary microtubules of the once posterior kinetosome of each oral dikinetid give rise to the cytopharyngeal microtubular ribbons. The postciliary origin of the cytopharyngeal ribbons which could only be detected by an EM study of stomatogenesis shows that the basket of Coleps belongs to the cyrtos-type and not to the rhabdos-type basket, where transverse microtubules accompany the basket-forming nematodesmata. The taxonomic implications of these observations, which may lead to a revision of the systematic position of the genus Coleps , are discussed.     

Kyaroikeus cetarius N. G., N. Sp.: A Parasitic Ciliate from the Respiratory Tract of Odonticete Cetacea

ABSTRACT. Examination of mucus discharged from the blowholes of live odonticete Cetacea and material collected from nasal orifices of dead hosts routinely revealed infestations of a large spindle-shaped ciliate. Kyaroikeus cetarius n. g., n. sp. These ciliates had a prominent posterior podite and were holotrichously ciliated except for a conspicuous bipolar stripe extending along the left margin of the cell. Most specimens were free-swimming and moved slowly through freshly collected mucus, but some individuals were attached to host cells or cellular debris by a transparent thread secreted from the podite. The oral architecture of protargol-impregnated K. cetarius consisted of one preoral and two circumoral kinetics set within a deep oral cavity continuous with an extensive, posteriorly directed cytopharynx. Somatic kineties were composed entirely of monokinetids and formed an expansive right ciliary field covering most of the cell surface, a reduced left ciliary field adjacent to the oral cavity, and a group of four kinetal fragments located mid-ventrally within a shallow pocket. Subkinetal microtubules were associated with the kineties of the right and left fields, and the non-ciliated stripe was underlain by a series of longitudinal fibers. The ciliate's large, heteromeric macronucleus was centrally positioned and clearly evident in living or stained specimens, while the ellipsoid micronucleus was located adjacent to the cytopharynx and often inconspicuous. K. cetarius has several morphological attributes typical of phyllopharyngian ciliates (e.g., adhesive organelle, heteromeric macronucleus, somatic kineties of monokinetids, subkinetal microtubules), and, except for its nearly holotrichous ciliation, most closely resembles dysteriine ciliates.     

The fine structure of the paralabial organelle in the rumen ciliate Ophryoscolex purkinjei Stein, 1858

The paralabial organelle of the rumen ciliate Ophryoscolex purkinjei, located on the ventral side of the ciliophor, is a highly specialized part of the somatic cortex. It consists of alternating rows of short modified cilia and thin pellicular folds which form a ridge-like structure. The central "top kinety" is composed of monokinetids which bear cilia with 9 + 2 axonemes and 2 microns in length. The top kinety is accompanied by a comb-shaped fold on its distal side and by a broad wedge-shaped fold on its proximal side. To both sides there follow two or three lateral kineties made of dikinetids. The anterior kinetosome of each pair bears a clavate cilium, only 0.5-0.7 micron in length and with a 9 + 0 axoneme while the cilium of the posterior kinetosome is even shorter. Lateral folds with numerous microtubules cover these lateral kineties and rows of barren basal bodies. The fine structure of this supposed sensory organelle show a basic pattern in four other ophryoscolecids, and its increasing complexity parallels the suggested phylogenetic line of evolution of these ciliates.     

Ultrastructure of the cytoplasm of the lower holotrichous infusorian Tracheloraphis prenanti]

The ciliature of T. prenanti Dragesco 1960 (forma oligocineta Raikov et Kovaleva, 1968) consists of 14-18 ventral and lateral longitudinal kineties with paired kinetosomes, carrying either two cilia or one cilium per kinetosome pair (in the latter case, the nonciliated kinetosome is always the posterior one). The ectoplasmic fibrillar system belongs to the postciliary type. A pair of kinetosomes shares a common basal plate. The anterior kinetosome gives rise to a short ribbon of transverse microtubules, the posterior one, to a poorly developed kinetodesmal filament and to a strong ribbon of postciliary microtubules. The latter proceeds backwards along 8 to 12 kinetosome pairs, being incorporated into a laminated postciliodesma which accompanies each kinety on its right side. Rows of Golgi elements, sending secretory vesicles and channels towards the body surface, exist beneath the kinetosome bases. Each kinety is accompanied on its left by a microfibrillar myoneme, surrounded by perimyary vesicles and underlain by a row of mitochondria. The median part of the dorsal surface is nonciliated; the cytoplasm here is rich of membrane systems, contains peripheral, electron-dense, extrusible inclusions and sometimes also bacteria. The electron-dense inclusions develop in the endoplasm, in close contact with mitochondria. The endoplasm contains also large microfibrillar spheres of unknown nature.     

CILIARY MEMBRANE DIFFERENTIATIONS IN TETRAHYMENA PYRIFORMIS : Tetrahymena Has Four Types of Cilia

We have examined thin sections and replicas of freeze-fractured cilia of Tetrahymena pyriformis. The ciliary necklace located at the base of all freeze-fractured oral and somatic cilia has been studied in thin sections. Since electron-dense linkers have been found to connect both microtubule doublets and triplets to the ciliary membrane at the level of the necklace, the linkers and the associated necklace seem to be related to the transition region between the doublets and triplets of a cilium. Plaque structures, consisting of small rectangular patches of particles located distal to the ciliary necklace, are found in strain GL, but are absent in other strains examined in this study. In freeze-cleaved material, additional structural differentiations are observed in the distal region of the ciliary membranes of somatic and oral cilia. Somatic cilia contain many randomly distributed particles within their membrane. Oral cilia can be divided into three categories on the basis of the morphology of their freeze-fractured membranes: (a) undifferentiated cilia with very few randomly distributed particles: (b) cilia with particles arranged in parallel longitudinal rows spaced at intervals of 810–1080 Å that are located on one side of the cilium; and (c) cilia with patches of particles arranged in short rows oriented obliquely to the main axis of the cilium. The latter particles, found on one side of the cilium, seem to serve as attachment sites for bristles 375–750 Å long and 100 Å wide which extend into the surrounding medium. The particles with bristles are located at the tips of cilia in the outermost membranelle and may be used to detect food particles and/or to modify currents in the oral region so that food particles are propelled more efficiently into the buccal cavity. Examination of thin-sectioned material indicates that the particles in oral cilia which form the longitudinal rows could be linked to microtubule doublets. Linkage between microtubule doublets and adjacent membrane areas on one side of the cilium could modify the form of ciliary beat by restricting the sliding of the microtubules. It is suggested that membrane-microtubule interactions may form the basis for the various forms of ciliary beat observed in different organisms.     

Ciliary sieving and active ciliary response in capture of particles by suspension-feeding brachiopod larvae

Larvae of a brachiopod, Glottidia pyramidata, used at least two ciliary mechanisms to capture algal cells upstream from the lateral band of cilia that produces a feeding/swimming current. (1) Filtration: the larvae retained algal cells on the upstream (frontal) side of a sieve composed of a row of stationary laterofrontal cilia. Movement of the laterofrontal cilia could not be observed during capture or rejection of particles, but the laterofrontal cilia can bend toward the beating lateral cilia, a possible mechanism for releasing rejected particles from the ciliary sieve. (2) Localized changes of ciliary beat: the larvae may also concentrate particles by a local change in beat of lateral cilia in response to particles. The evidence is that the beat of lateral cilia changed coincident with captures of algal cells and that captured particles moved on paths consistent with a current redirected toward the frontal side of the tentacle by an induced local reversal of the lateral cilia. The change of beat of lateral cilia could have been an arrest rather than a reversal of ciliary beat, however. The similar ciliary bands in adult and larval lophophorates (brachiopods, phoronids, and bryozoans) suggest that these animals share a range of ciliary behaviours. The divergent accounts of ciliary feeding of lophophorates could be mostly the result of different authors observing different aspects of ciliary feeding.     

The role of cortical orientation in the control of the direction of ciliary beat in Paramecium

The swimming behavior of many ciliate protozoans depends on graded changes in the direction of the ciliary effective stroke in response to depolarizing stimuli (i.e., the avoiding reaction of Paramecium). We investigated the problem of whether the directional response of cilia with a variable plane of beat is related to the polarity of the cell as a whole or to the orientation of the cortical structures themselves. To do this, we used a stock of Paramecium aurelia with part of the cortex reversed 180 degrees. We determined the relation of the orientation of the kineties (ciliary rows) to the direction of beat in these mosaic paramecia by cinemicrography of particle movements near living cells and by scanning electron microscopy of instantaneously fixed material. We found that the cilia of the inverted rows always beat in the direction opposite to that of normally oriented cilia during both forward and backward swimming. In addition, metachronal waves of ciliary coordination were present on the inverted patch, travelling in the direction opposite to those on the normal cortex. The reference point for the directional response of Paramecium cilia to stimuli thus resides within the cilia or their immediate cortical surroundings.     

The Fine Structure of the Paralabial Organelle in the Rumen Ciliate Ophryoscolex purkinjei Stein, 1858

The paralabial organelle of the rumen ciliate Ophryoscolex purkinjei , located on the ventral side of the ciliophor, is a highly specialized part of the somatic cortex. It consists of alternating rows of short modified cilia and thin pellicular folds which form a ridge-like structure. The central "top kinety" is composed of monokinetids which bear cilia with 9 + 2 axonemes and 2 μm in length. The top kinety is accompanied by a comb-shaped fold on its distal side and by a broad wedge-shaped fold on its proximal side. To both sides there follow two or three lateral kineties made of dikinetids. The anterior kinetosome of each pair bears a clavate cilium, only 0.5–0.7 μm in length and with a 9 + 0 axoneme while the cilium of the posterior kinetosome is even shorter. Lateral folds with numerous microtubules cover these lateral kineties and rows of barren basal bodies. The fine structure of this supposed sensory organelle show a basic pattern in four other ophryoscolecids, and its increasing complexity parallels the suggested phylogenetic line of evolution of these ciliates.