Quantitative Analyses of Interbreeding in Populations of vannus-Morphotype Euplotes, with Special Attention to the Nominal Species E. vannus and E. crassus

ABSTRACT. Classical genetic techniques were applied to clonal cultures of the Euplotes vannus-crassus-minuta sibling species complex in an effort to provide some resolution to the species problem among these hypotrichs. Complex mating interactions were observed among clonal stock cultures derived from samples collected from sympatric and allopatric populations in a wide geographic survey. These results suggested that the classical model for the mating type inheritance and determination in these Euplotes is necessary but not sufficient to describe the mating mating interactions among populations of these ciliates. Successful conjugation between the nominal species E. crassus and E. vannus was observed routinely, and crosses between these two nominal species did not differ significantly from those among the other clonal stock cultures with respect to mating intensity and exconjugant survival. Data from backcrosses suggests that E. vannus and E. crassus can and do exchange genes. Based upon these data, we conclude that E. vannus and E. crassus comprise a single, highly polymorphic species with countless small populations, among which incomplete genetic exchange takes place.     

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.     

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.     

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.     

Mating Types in Aspidisca sp. (Ciliophora, Hypotrichida): a Cluster of Cryptic Species

A mating-type analysis was performed on 78 stocks of the marine hypotrich ciliate, Aspidisca sp., from a sufficient number of diverse geographic locations, some widely separated. Evidence is provided for the existence of a binary mating system in this "morphospecies." The collected stocks have been challenged by the most rigorous criterion, namely breeding affinity in the laboratory, and have yielded at least four reproductively, not necessarily geographically, isolated groups that are in fact "biological species," here referred to as "syngens." Different syngens contain different pairs of mating types. Syngens are morphologically indistinguishable; hence Aspidisca sp. can be considered a conservative taxon comprising a number of "cryptic" or "sibling species." Information is also presented about the mating behavior and the pattern of nuclear events at conjugation in Aspidisca sp. Search for soluble pheromones of the mating types gave only negative results. Hence, direct contact with potential partners is postulated to play a critical role in preparing individuals to mate. Mating reaction and mating which actually involves cross-fertilization (conjugation, sensu stricto) are completely inhibited by 10 μg/ml cycloheximide, suggesting the necessity of protein synthesis for recognition and union in conjugation of potential partners.     

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.     

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.     

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.     

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.     

世界今生砂壳纤毛虫名录

砂壳纤毛虫隶属于纤毛门、旋毛纲、环毛亚纲、砂壳目.本文总结了自Kofoid和Campbell(1929)以来的分类学资料,参照Lynn(2008)的分类系统,整理成世界砂壳纤毛虫新名录.厘清砂壳纤毛虫共有15科69属954种,其中海洋种为15科69属925种,淡水种为3科5属29种.在所有属中,以拟铃虫属(Tintinnopsis包含物种最多,为137种,其中海洋种为118种.我国水体共记录有13科36属164种,海洋种13科36属144种,淡水种2科3属20种.除杯形铃壳虫(Codonella cratera)、湖泊领细壳虫(Stenosemella lacustris)、蜉蝣筒壳虫(Tintinnidium ephemeridum)、蝌蚪筒壳虫(Tintinnidium ranunculi)、半缘筒壳虫(Tintinnidium semiciliatum)、纺锤拟铃虫(Tintinnopsis fusiformis)、伊利诺拟铃虫(Tintinnopsis illinoisensis)、卵圆拟铃虫(Tintinnopsis ovalis)、圆柱拟铃虫(Tintinnopsis cylindrata)、这9个种外,其他淡水种在我国都有记录.该名录中,除了已有中文名的159种外,其余的种我们给出了中文译名,并将部分译为似铃虫属(Tintinnopsis)的中文名统一为拟铃虫属,部分译为麻铃虫属(Leprotintinnus)的中文名统一为薄铃虫属,将截短角口虫(Salpingella decurtata)改为截短号角虫,将冰生拟铃壳虫(Codonellopsis glacialis)改为冰生类铃虫.     

A Comparative Analysis of the Morphology and Morphogenesis of Gonostomum strenua (Engelmann, 1862) (Ciliophora, Hypotrichida) and Related Species

The morphology and morphogenesis of the hypotrichous ciliate, Gonostomum strenua, found in the soil of a hill in Qingdao (Tsingtao, 36°08’N, 120°43’E), People's Republic of China is described. Some characteristics (organization of the frontoventral cirral rows, origin of the primary primordium and arrangement of the marginal as well as transverse cirri) are sufficiently different from a closely related species Gonostomum affine to suggest that it is a separate species, though its body shape, nucleus and buccal apparatus are very similar to that of G. affine. A comparison of the infraciliatures of the two species is necessary since morphological characteristics alone are sometimes insufficient for species separation.     

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.     

Morphology and morphogenesis of Holosticha heterofoissneri nov. spec. from the Yellow Sea,China (Ciliophora,Hypotrichida)

The morphology and morphogenesis of the marine hypotrichous ciliate Holosticha heterofoissneri nov. spec. from mollusc culture in Qingdao, China are described based on living and protargol-impregnated specimens. The new species is characterized by: adoral zone slightly bipartite, consisting of on average 43 membranelles; constantly 5 dorsal kineties, and 12 pairs of cirri in midventral rows, and 14–16 macronuclear segments, which differs from the closely related species, H. foissneri. Its morphogenetic process shows the following features: (1) the parental AZM is retained unchanged and will be inherited by the proter, only the old UM reorganized; (2) FVT-cirral anlagen in both division parts derive from the breaking of primary primordia; (3) during the formation of FVT-cirral anlagen, most midventral cirri remain intact; and there appears an 'extra' anlage (EA) between the UMA and other FVT-cirral primordia; (4) the generation type of the dorsal kineties is of 'one group mode', the leftmost one of the 4 primordia fragmentates to form a new kinety; (5) at the early stage of morphogenesis, replication bands of macronuclear segments are apparently present.     

The Species Problem in a Ciliate with a High Multiple Mating Type System, Euplotes crassus

ABSTRACT. One hundred twenty non-autogamous wild-type strains of Euplotes crassus , collected over seven years, mainly from the Mediterranean coasts, were investigated for their mating interactions. The strains were mixed pair-wise and data from mating reactions were evaluated and organized by means of a specially constructed computer program. The program identified 38 strains with distinctive mating patterns which could be clustered in nine clumps, all of which were connected either directly or indirectly. Thus, all these strains appeared to be components of the same gene pool, even though direct genetic exchange between strains was not possible in every combination. Subsequently, the 38 strains were subjected to cytometric analysis and scored for zymic variations resulting from electrophoretic patterns of five enzyme systems (acid phosphatases, amylases, malic dehydrogenase, malic enzyme, and tetrazolium oxidases) of proved diagnostic value in the identification of Euplotes species. No significant discontinuities correlated with mating patterns was apparent from these analyses. It was concluded that the E. crassus strains analyzed are not properly divided in sibling species and it was consistently suggested to avoid a genetic partitioning of ciliate species endowed with high multiple mating type systems, in which the sets of wild strains brought under investigation with difficulty represent the natural dimensions of the species.     

A Comparative Analysis of the Morphology of Holosticha corlissi N. Sp. (Ciliophora,Hypotrichida) and Related Species1

ABSTRACT The morphology of the hypotrichous ciliate, Holosticha corlissi n. sp., found in the moss Calliergonella cuspidata taken from the beech wood of Montejo de la Sierra (Madrid, Spain) is described. Some characteristics (organization of the mid-ventral, frontal and fronto-terminal cirri, presence of a buccal cirrus and the number of transverse cirri) are sufficiently different from the closely related species H. intermedia, H. sigmoidea and H. xanthichroma to suggest that it is a separate species, although its body shape, nucleus and buccal apparatus are very similar.     

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。