Transmission and Scanning Electron Microscopy of the Evaginative Budding Process in Heliophrya sp. (Ciliata,Suctoria)1

ABSTRACT. A sessile, tentacle-bearing protozoon, Heliophrya sp. (Suctoria, Ciliata), reproduces asexually by evaginative budding to form a ciliated swarmer, which begins metamorphosis to the adult form within 30 min of its release from the parent cell. Morphological features of embryogenesis were investigated using transmission and scanning electron microscopy and found to correspond, with certain exceptions, to the few previous reports concerning evaginative budding in suctorians. Following invagination of a portion of the pellicle to form an embryonic cavity within the parent cell, numerous kinetosomes, apparently formed de novo, organize into rows which surround the embryonic cavity and eventually develop cilia that project into the cavity. When the cavity is complete, its walls are extruded through an opening in the parent cell surface. Parent cell cytoplasm streams into the incipient swarmer, thus supplying it with at least the minimum requirement of all cytoplasmic organelles. The ciliated swarmer remains attached to its parent cell for several minutes before it detaches. A complete pellicle is formed in both parent and swarmer prior to detachment. The numerous mitochondria underlying the parent cell pellicle in the vicinity of the attachment area suggest that cross wall formation is an energy-dependent process.     

The family Xystonellidae (Ciliophora, Tintinnina) in the Adriatic Sea

This paper reports quantitative, horizontal and vertical distributiondata of the 11 species of the family Xystonellidae found inthe Adriatic Sea and in the Strait of Otranto. The samples werecollected in coastal and open waters, with a plankton net equippedwith a closing system, in the period from 1973 to 1986. At thedeeper stations of the South Adriatic Pit, hauls were takenin eight vertical layers, while at other stations sampling dependedon the respective depth of each station. Xystonellidae are oceanictintinnines, mainly present in the South Adriatic and the Straitof Otranto throughout the year. They are characteristic of SouthAdriatic and Eastern Mediterranean water masses. Horizontaldistribution of lower mesopelagic species is limited by the200 m isobath. Only sparse individuals of the upper mesopelagicand epipelagic species were found in the Jabuka Pit, probablydue to the late autumn and winter current. These species werenot registered to the north of this region. They were registeredbelow the 200 m depth as dominant tintinnines, while in summerthey represented an average of 81% of the total tintinnine population.     

Mexican Ciliated Protozoa III. Hypophrya fasciculata gen. nov., sp. nov. (Ciliata: Suctorida)

SYNOPSIS. Hypophrya fasciculata gen. nov., sp. nov., a mesosaprobic epibiotic suctorian ciliate, was collected from stagnant water in Chapultepec Park, Mexico, D.F., on Epistylis plicatilis , in turn epibiotic on the molluscans Limnaea attenuata and Physa osculans. The zooids (average size, 118 × 78 μ) have fasciculate tentacles distributed on the apical and proximal regions, and the stalks are ca. 248 μ in length. Feeding and internal budding were observed.     

Field and laboratory studies of Ophryoglena sp. (Ciliata: Ophryoglenidae) infection in zebra mussels,Dreissena polymorpha (Bivalvia: Dreissenidae)

This study, conducted in the Dnieper-Bug Canal in Belarus, is the first to monitor the seasonal (June-November) dynamics of infection with the parasitic ciliate Ophryoglena sp. in a zebra mussel (Dreissena polymorpha) population. Mean population prevalence and intensity of infection varied, respectively, from 11 to 62% and from 0.9 to 24.1 ciliates/mussel. Mean prevalence was highly correlated with mussel length in mussels <20 mm (R(2)=0.97) and was lower in larger mussels. Mean infection intensity in mussels 1-25 mm long was similarly correlated with their size (R=0.98), reached a maximum in the 20-25 mm size-class, and then sharply decreased, thus providing evidence, albeit limited, that high intensity of infection might be lethal. Transinfection of zebra mussels by Ophryoglena sp. was achieved in the laboratory-a first for a protozoan parasite of D. polymorpha; from an initial complete lack of infection, mean prevalence and intensity rose, respectively, to 86.7% and 8.3 ciliates/mussel.     

Reproduction of Ichthyophthirius multifiliis (Ciliata, Ophryoglenidae)

A case of reproduction of Ichthyophthirius multifiliis in the superficial tissues of larvae and fry of Amur wild carp is described. At a temperature of water from 28 to 29 degrees trophonts of Ichthyophthirius encysted on fishes. Inside cysts repeated cell division occurred but this process did not result in swarm spores formation. Later on with the increase of temperature to 29.5--31.5 degrees cysts degenerated.     

Peculiar Epibionts in Euplotidium itoi (Ciliata, Hypotrichida)

ABSTRACT. Euplotidium itoi share with some other species of the same genus a peculiar feature: the presence of a band of particles running along the right and left borders of the cell body and forming a sort of "scarf" at the dorsal anterior end. The ultrastructural analysis, here performed, revealed that these particles (reported in the literature as extrusomes) are always external to the cell and are inserted in matching depressions on the euplotidium cortex. They are present in two different forms: type I, whose ultrastructure recalls that of bacteria, are able to reproduce by binary fission; type II are not able to divide and contain peculiar structures (a granular dome-shaped zone, a complex extrusive apparatus and a network of regularly arranged fibrils) which render them more complicated with respect to the majority of prokaryotic organisms. These observations, together with the finding that these particles contain DNA, indicate that we are dealing with epibionts, that will be referred to as "epixenosomes" (ecto-organisms), rather than extrusomes. Some ideas about the nature of "epixenosomes" and their relationship with the host cell are proposed and discussed.     

Observations on Neobursaridium gigas Balech, 1941 (Ciliata Heterotrichida)

SYNOPSIS. A large heterotrich ciliate (Family: Bursariidae) found in a papyrus swamp in Uganda was used for oxygen tension experiments by Beadle & Nilsson, 1959, under the name of Bursaria sp. This organism has now been identified as Neobursaridium gigas Balech. The morphology of the organism was studied in living and stained specimens, especially with the silver impregnation technique, and the present findings are compared to those of Balech.     

DNA damage and repair in Stylonychia lemnae (Ciliata, Protozoa)

Irradiation with X rays, UV irradiation after incorporation of bromodeoxyuridine (BU) into the DNA, and cis-platinum (cis-Pt) treatment each cause the loss of micronuclei of Stylonychia lemnae while the macronuclei are not severely affected. The abilities of both nuclei to repair DNA were investigated. Unscheduled DNA synthesis could not be demonstrated after X-ray irradiation, but it was found after treatment with BU/UV and cis-Pt in macro- and micronuclei. The extent of the repair process in the micro- and macronuclei was alike, as indicated by grain counts of [6-3H]thymidine-treated cells. One reason for the different sensitivity of both nuclei to DNA-damaging treatment may be the different number of gene copies in the macro- and micronuclei.     

DNA Damage and Repair in Stylonychia lemnae (Ciliata,Protozoa)1

ABSTRACT Irradiation with X rays, UV irradiation after incorporation of bromodeoxyuridine (BU) into the DNA, and cis-platinum (cis-Pt) treatment each cause the loss of micronuclei of Stylonychia lemnae while the macronuclei are not severely affected. The abilities of both nuclei to repair DNA were investigated. Unscheduled DNA synthesis could not be demonstrated after X-ray irradiation, but it was found after treatment with BU/UV and cis-Pt in macro- and micronuclei. The extent of the repair process in the micro- and macronuclei was alike, as indicated by grain counts of [6-³H]thymidine-treated cells. One reason for the different sensitivity of both nuclei to DNA-damaging treatment may be the different number of gene copies in the macro- and micronuclei.