Species Structure in Euplotes crassus (Ciliophora, Hypotrichida)

ABSTRACT. We observed different low salinity tolerances between two groups of populations of Euplotes crassus. After mating analysis, the less tolerant populations could be assigned to three mating groups. Two of them were separated by preconjugative barriers but both conjugated with a third one. A breeding test showed evidence of (potential) introgression mediated by this "bridging" group. On the other hand, the more tolerant populations formed a fourth mating group unable to conjugate with the others and characterized by distinct zymogram patterns. We conclude that natural introgression among the studied populations is not complete and that the species structure of E. crassus comprises intrafertile sets of populations among which gene flow may be difficult or virtually absent.     

Nuclear Behavior During Reconjugation in Euplotes patella (Ciliophora,Hypotrichida)1

Nuclear behavior during reconjugation and the ultimate fate of the ex-reconjugants were followed after induction of reconjugation in Euplotes patella. An exconjugant could reconjugate with a vegetative cell or with another exconjugant. Exconjugants at an early stage of macronuclear development (oval macronuclear anlagen) did not reconjugate frequently whereas exconjugants at a late stage of macronuclear development (rod-like macronuclear anlagen) reconjugated frequently. In all cases, the micronucleus underwent normal meiosis and other nuclear changes. After reconjugation, a new macronuclear anlage and a new micronucleus were formed normally, so that there were two kinds of macronuclear anlagen in the exconjugants, an old and a new. The old rod-shaped anlage did not disappear after the differentiation of a new one, but it was broken up into several fragments. While the survival rate after normal conjugation was 78%, it was 0–20% after reconjugation. These results suggest that the micronuclei of exconjugants can act as germ nuclei even at a very early stage and that reconjugation, unlike conjugation, is harmful to the cell.     

Mating Types and Mating Type Inheritance in Euplotes minuta Yocom (Ciliata, Hypotrichida)

SYNOPSIS. Thirty-one stocks of a marine ciliate, Euplotes minuta Yocom, collected from different localities, can be grouped in seven mating types. True pairs are formed only in mixtures of stocks belonging to different mating types. No selfing pairs or intraclonal conjugation have ever been observed. Synclonal inheritance of mating types is the rule, although about 10% of pairs show clonal inheritance. The latter can be explained by assuming syncaryon formation through cytogamy or through caryogamy of pronuclei derived from different products of meiosis. Mating type determination is due to 7 alleles at the single locus mt . There is complete dominance among the 7 alleles which can be orderly seriated, as shown in Table 3, according to their dominance relationship. The 5 stocks, and only these 5, of mating type VII have the autogamy trait. The mortality rate in F₁ and F₂ is very low–a maximum of 10%; however, the F₂'S obtained by autogamy from F₁ progenies in which mating type VII is involved have a very high mortality rate. The two facts (high mortality rate in F₂ and strict association of autogamy trait with mating type VII in natural populations) have been considered as evidences of a probable isolation mechanism existing between mating type VII and the other 6 mating types. Thus, the 7 mating types have been assigned to the same syngen only tentatively.     

A Marine Euplotes (Ciliophora, Hypotrichida) with Reduced Number of Prezygotic Micronuclear Divisions

In contradistinction to the pattern of 3 prezygotic micronuclear divisions found in 10 species of Euplotes, a marine species resembling Euplotes crassus in structure, has only 2 divisions. This atypical division pattern was observed in all matings involving the 4 available mating types. The critical stages of the nuclear events are demonstrated by using special strains having the micronuclear DNA content and chromosome number only 1/2 the normal values. The employment of such strains facilitates differentiation between the stationary and migratory pronuclei in a given conjugant and determination of the times of conclusion of prezygotic divisions and of the pronuclear exchange.     

Euplotes raikovi Agamaliev, 1966 (Ciliophora, Hypotrichida) From New Hampshire: Description and Morphogenesis

Euplotes raikovi, an interstitial hypotrich ciliate described once from the Caspian Sea, was isolated from intertidal sand at Rye Harbor, New Hampshire. Specimens were observed in life, and also stained by Corliss’ modification of the Chatton-Lwoff wet-silver technic and by 2 nigrosin methods. Living individuals and those fixed with Parducz's fluid are 43 × 30 (37-50 × 25–35) μm. The AZM has an average length of 27 μm and contains 24–32 membranelles. The anterior part of AZM lies on the ventral face of an apical channel, much as in E. bisulcatus. There are 7 fronto-ventral, 4 transverse, 1 left marginal, and 2 right caudal cirri. An additional small, rounded argentophilic area resembling a cirrus base is evident in silver-stained preparations, but it is barren in virtually 100% of the population. There are 7–8 (usually 7) dorsal ciliary rows with E. patella-type argyrome. The modal number of cilia in rows I-VII are 3-7-9-9-9-10-10. The unique fronto-ventral cirrus pattern is stable and predictable at the time of streak phase. Morphogenetic development indicates that the barren cirrus base is 2/V (Wallengren system), and that it apparently buds from 1/V. The left marginal cirrus and right caudal cirri have different origins.     

Local and Temporal Pattern of Con A-Binding Site Aggregation During Conjugation in Euplotes vannus (Ciliophora,Hypotrichida)1

ABSTRACT. Conjugating cells of Euplotes vannus (syngens Naples and Barcarès) were investigated for Con A-binding sites by means of fluorescence microscopy. Cells fixed with 0.4% paraformaldehyde and incubated with 15 μg/ml FITC-Con A showed a distinct region of strong fluorescence, the size, shape and localization of which characteristically changed during the course of conjugation, first appearing at courtship stage (cells contact without forming pairs) and vanishing soon after the migration pronuclei have been exchanged, but before cells have separated. Con A binding and conjugation were blocked by cyclohexamide and α-galactosidase. Con A-binding was also inhibited by α-mannosidase, α-glucosidase and β-galactosidase without affecting conjugation except a delay of pair formation. The results suggest an involvement of newly formed or translocated glycoconjugates in cell pairing during conjugation.     

Fine Structure of Pseudokeronopsis carnea (Ciliophora,Hypotrichida)1

ABSTRACT Two kinds of pigment structures, pigment vacuoles and pigmentocysts, cause the orange-red color of Pseudokeronopsis carnea (Cohn, 1866). The pigment vacuoles are undischargeable and two to five layers of them form a characteristic ectoplasmic zone. The pigmentocysts mainly surround the infraciliature and show a unique channel which is probably used for extrusion. Previous data on the fine structure of subpellicular granules and extrusomes of hypotrich ciliates are summarized. Their obviously diverse organization argues for a great value of these structures in species identification. The basic structural features of the infraciliature and the cytoplasmic organelles of P. carnea are similar to those found in other hypotrichs; however, a special kind of linear microtubular array borders the longer sides of the cirral bases and the margins of the adoral membranelles and those of the membranes in the right buccal area. To the left of the endoral membrane, these microtubular arrays result in a highly ordered structure reminiscent of oral ribs. This peculiar arrangement of microtubules in cirri and paramembranelles has also been found in the related form, Thigmokeronopsis jahodai, probably indicating a homogeneity of the fine structure of urostylid hypotrichs. In P. carnea, the basal bodies of the paroral membrane are proximally connected like a polykinetid. Its cilia are unlinked, whereas those of the endoral membrane are fused by microfibrillar material. The terms diplostichomonad and polystichomonad only refer to quantitative aspects and omit the evident, high diversity of microtubular and microfibrillar associates occurring in the membranes in the right buccal area. These terms need to be redefined on the basis of more material that is better described.     

Systematics of Euplotes (Ciliophora, Hypotrichida); Toward Union of the Old and the New

SYNOPSIS. Prior to the general use of methods revealing the silverline system, members of the genus Euplotes were separated on the basis of body shape, sculpturing and arrangement of cirri. Since 1954, species have been separated on the basis of number of dorsolateral cilium rows, dorsal silverline system, number of fronto-ventral cirri, and form of the macronucleus. This paper describes E. charon Müller, 1773, E. quinquecarinatus Gelei, 1950, E. alatus Kahl, 1932, and E. bisulcatus Kahl, 1932, 4 species that are difficult to separate solely on the basis of the latter set of characters. By discussion of characters elucidated by a nigrosin-HgCl₂-formalin method, it is suggested that the following can form a basis for identification of members of this genus: 1) cortical sculpturing, 2) arrangement of all ciliary organelles, including dorsal and endoral cilia, and 3) details of the silverline system. Existing methods are indicated, some far more simple than silver methods, with which these characters can be elucidated.     

Methods for the Large-Scale Cultivation of an Oxytricha (Ciliophora: Hypotrichida)1

ABSTRACT. Oxytricha strains used in biochemical studies have traditionally been grown in unaerated, unagitated culture tubes or Fernbach flasks. These cultures are limited in volume to about one liter and have a very nonuniform distribution of cells, with the majority of the cells at the very top or bottom of the medium. We have found conditions in which Oxytricha can be grown in 50-liter fermentation vats. The cultures grow to a uniform density of about 6000 cells/ml.     

The Behavior and Fine Structure of the Dorsal Bristles of Euplotes minuta,E. aediculatus,and Stylonychia mytilus (Ciliata,Hypotrichida)1

ABSTRACT. Studies of the bristle (dorsal) cilia of Euplotes minuta. E. aediculatus, and Stylonychia mytilus by light and electron microscopy indicate that these cilia do not beat metachronously in any of the species. The bristle cilia in Stylonychia may beat actively, but those in Euplotes stand erect or are bent in different directions with the flow of water. The duration and degree of bending appear correlated with the duration and velocity of the water current. The fine structure of the bristle complex is similar in both Euplotes species and like other reports of Euplotes in the literature. The complex consists of paired kinetosomes, the anterior bearing a short cilium containing four to six rows of fibrous balls (lasiosomes) oriented along the anterior surface of the axoneme, the posterior lacking a cilium but with a small cap. Microtubular ribbons are associated with the paired kinetosomes, and a collar with a pronounced alveolar ring underneath the pellicular membrane tightly surrounds the cilium at the opening of the bristle pit. The bristle complex in S. mytilus differs from that of Euplotes and other hypotrichs in that it has a single kinetosome in interphase cells and, attached to the kinetosome, a prominent fibrous structure (parakinetosomal body). Microtubules are attached to the parakinetosomal body. As in Euplotes, the bristle unit is surrounded by mucocyst-like organelles (ampules). Observations of behavior and fine structure suggest that the dorsal bristles may be sensory, perhaps responding to stimuli from water currents, although other functions are possible, too.     

纤毛虫念珠异列虫射出胞器的超微结构观察

应用扫描电镜术和透射电镜术显示,纤毛虫念珠异列虫(Anteholosticha monilata)的射出胞器早期发生在细胞质深处,附近有不同类型的囊泡结构。成熟后射出胞器向表膜迁移,结构由不同电子密度片层的体部、结晶状的中心轴杆部和多层膜的帽部组成。受外界刺激时胞器冲破皮层射出,形态呈"蘑菇"状。据上述观察结果推测:该射出胞器具有防御作用,它可能起源于高尔基体活动产生的小泡;在亲缘关系较近的纤毛虫中,其射出胞器可能具有相似的分化特征。     

Cytochemical investigations of the alveolar plates of theEuplotidae (Ciliophora,Hypotrichida)

Summary The ultrastructural appearance of organic plates lying in the alveoli of a freshwater species ofEuplotes is described and seen to be similar to those previously reported from the marine speciesE. vannus. Enzymatic digestion using pepsin and trypsin indicates that the plates in both species are mainly composed of protein with a fine coating of polysaccharides, as revealed using the Thiéry-technique for polysaccharide staining.     

Redescription of Phacodinium metchnikoffi (Ciliophora, Hypotrichida): General Morphology and Taxonomic Position

ABSTRACT Living and stained specimens of Phacodinium metchnikoffi , collected near Madrid, Spain, were studied under light microscopy. Infraciliature was stained using a silver-impregnation procedure. The somatic infraciliature is composed of a relatively small number of discontinuous kineties, formed by groups of few kinetosomes (pallets). The buccal ciliature is composed of an adoral zone of membranelles and a paroral formation otherwise unknown in ciliates, with many short kineties, which lie on a rigid stem. We propose that P. metchnikoffi is a primitive hypotrich and, consequently, we present a new classification system for hypotrichs.