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.     

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.     

Mating-Type Polymorphic Variation in Euplotes minuta (Ciliophora: Hypotrichida)1

An investigation was carried out to probe into the mating-type structure of a local population of the marine ciliate, Euplotes minuta. From this population, nine different mating types belonging to a unique set were isolated. The nine type-representative wild stocks analyzed were found to be heterozygous at the mating-type (mat) locus and provided, together with their sexual progeny, a total of 15 pure mating types. In E. minuta, the high-multiple nature of the basic mating system controlled by a series of peck-order alleles at a single locus should be considered a virtual certainty. The relationships among the genetic economies of the similar bottom-dwelling marine ciliates of the genus Euplotes, the E. vannus-crassus-minuta group, are discussed.     

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.     

An investigation of the tolerance to ammonia of the marine ciliate Euplotes vannus (Protozoa,Ciliophora)

Hydrobiologia - The toxicity of ammonia and its effects on growth inhibition for the marine ciliate, Euplotes vannus, were measured in a conventional open system. Linear regression analysis showed...     

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.     

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.     

Time-course analysis of nuclear events during conjugation in the marine ciliate Euplotes vannus and comparison with other ciliates (Protozoa,Ciliophora)

Ciliates represent a morphologically and genetically distinct group of single-celled eukaryotes that segregate germline and somatic functions into two types of nuclei and exhibit complex cytogenetic events during the sexual process of conjugation, which is under the control of the so-called “mating type systems”. Studying conjugation in ciliates may provide insight into our understanding of the origins and evolution of sex and fertilization. In the present work, we studied in detail the sexual process of conjugation using the model species Euplotes vannus, and compared these nuclear events with those occurring in other ciliates. Our results indicate that in E. vannus: 1) conjugation requires about 75 hours to complete: the longest step is the development of the new macronucleus (ca. 64h), followed by the nuclear division of meiosis I (5h); the mitotic divisions usually take only 2h; 2) there are three prezygotic divisions (mitosis and meiosis I and II), and two of the eight resulting nuclei become pronuclei; 3) after the exchange and fusion of the pronuclei, two postzygotic divisions occur; two of the four products differentiate into the new micronucleus and macronucleus, respectively, and the parental macronucleus degenerates completely; 4) comparison of the nuclear events during conjugation in different ciliates reveals that there are generally three prezygotic divisions while the number of postzygotic divisions is highly variable. These results can serve as reference to investigate the mating type system operating in this species and to analyze genes involved in the different steps of the sexual process.     

Morphogenetic characters of the model ciliate Euplotes vannus (Ciliophora,Spirotrichea): Notes on cortical pattern formation during conjugational and postconjugational reorganization

Ciliated protists represent a morphologically and genetically distinct group of single-celled eukaryotes which can reproduce asexually and sexually. Morphogenesis occurs in both asexual and sexual modes of reproduction which is of interest for researchers investigating cell differentiation, regeneration, systematics and evolution. However, studies of morphogenesis have concentrated almost entirely on the asexual mode. Here we use protargol staining to investigate the morphogenetic processes during sexual reproduction in the model species Euplotes vannus (Müller). The major events include: (1) two rounds of morphogenesis occur during sexual reproduction, i.e., conjugational and postconjugational reorganization; (2) in both processes the oral primordium is generated de novo in a pouch beneath the cortex; (3) the frontoventral-transverse cirri anlagen are formed de novo and fragment in a 3:3:3:3:2 pattern; (4) the leftmost cirrus and the paroral membrane do not change during conjugational morphogenesis, but reorganize de novo during postconjugational morphogenesis; (5) marginal cirral anlagen are formed de novo in both morphogenetic processes; (6) two or three caudal cirri are formed at the ends of the rightmost two or three old dorsal kineties; (7) the dorsal kineties are retained entirely. These results can serve as reference to investigate the morphogenetic events in the different stages of sexual reproduction.     

Morphogenetic Pattern in Laurentiella acuminata (Ciliophora,Hypotrichida): Its Significance for the Comprehension of Ontogeny and Phylogeny of Hypotrichous Ciliates1

Morphogenetic events during division, physiological reorganization, and postraumatical regeneration, the last being induced both chemically and microsurgically, were studied by light microscopy on protargol-impregnated specimens of the hypotrichous ciliate, Laurentiella acuminata. Parakinetal stomatogenesis, from transverse cirrus-1 during division and reorganization, changes during regeneration to a parakinetal one which characterizes more primitive members of Hypotrichida in the S. O. Stichotrichina, but solely when the AZM is damaged. These morphogenetic events a) confirm the previous inclusion of L. acuminata among the Oxytrichidae on the basis of its morphological characters and indicate that it is a primitive species of this family related with the Stichotrichina through genera Pleurotricha and Paraurostyla; b) suggest a synthetic model that explains both the positioning and timing of cortical morphogenesis in the cell cycle. The key point of this model is the attribution to the AZM of a repressive capacity on the stomatogenic area, the last one being positioned according to the system of gradients of morphogenetic activity proposed by Jerka-Dziadosz to explain location of primordia in urostylids. This repression is manifested not as a gradient, as indicated by De Terra, but as a long-term repression limited to a certain distance. Simultaneous repression and stimulation occurring in a growing cortex with the AZM remaining constant in size could explain the critical ratio, buccal cortex/somatic cortex, at which stomatogenesis is triggered as indicated by De Terra.     

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.     

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.     

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.     

拟翁口虫形态学及形态发生学现象的初步研究

应用荧光紫杉醇直接荧光标记方法显示了一种腹毛类纤毛虫拟翁口虫(Onychodromopsis sp.)腹皮层纤毛器微管胞器及形态发生,根据该纤毛虫的皮层纤毛模式和纤毛器基部微管的形态,将其归为侧毛虫科(Pleurotrichidae)拟翁口虫属(Onychodromopsis);并据后仔虫口原基的发生、左右缘棘毛原基的...     

Cladotricha and Phylogeny in the Suborder Stichotrichina (Ciliophora,Hypotrichida)*

Synopsis. The cortical anatomy and morphogenesis of Cladotricha koltzowii Gajewskaja and Cladotricha variabilis Rumen from the Great Salt Lake, Utah, are described. When compared with 2 marine hypotrichs, Uroleptoides kihni Wenzel and Stichotricha secunda Kahl, from the east coast of the United States, their structure and development suggest that Cladotricha may have descended from an intermediate species within the line of evolution of the Spirofilidae from primitive Kahliella-like hypotrichs. It is suggested that the Kahliella-Cladotricha-Uroleptoides series is separated at the familial level from both the tubicolous and planktonic spirofilids. Further, the structural and morphogenetic differences between Cladotricha and the holostichid Uroleptus appear to be at a subordinal level. These findings are significant in revising definitions of the Hypotrichida, its suborders, and the Urostylidae.