R. D. Butler

Ciliate populations and metals in an activated-sludge plant

Abstract Twenty-nine species of ciliate protozoa were recorded in samples of activated sludge collected monthly from tanks at Davyhulme Sewage Works, Manchester, U.K., over a two-year period (1991–1992). The most frequent species present included Aspidisca cicada, Chilodonella uncinata, Vorticella convallaria and Vorticella microstoma . The total ciliate population showed clear seasonal variation, with highest counts between February and August. Only two species showed significant correlation with ambient temperature. Species diversity had little variation, with 8–13 ciliate species being identified in most samples. Significant positive interspecies correlations were noted for ten species, but were not consistent for both years. Mean concentrations of the metals Fe, Ni, Zn, Cu and Cr in the liquid phase of activated sludge varied considerably over the two annual sampling periods, with no seasonal pattern. Major ciliates present were able to tolerate high concentrations of contaminant metals, including Fe (> 2000 ppb), Zn (> 500 ppb), Cu (> 60 ppb) and Cr (100 ppb). Specific positive and negative ciliate species—metal correlations were observed in each annual sampling period, but were not consistent for both years. The lack of consistent correlations over the two-year sampling period between populations of individual protozoan species and single biological (other species) or physicochemical (temperature, metal concentrations) factors is in accordance with a complex (multifactorial) determination of protozoan populations in activated sludge.

Ultrastructural studies of the commensal suctorian, Choanophrya infundibulifera hartog

SummaryTentacle structure, movement and feeding of the commensal suctorian Choanophrya infundibulifera have been examined by light, scanning and transmission electron microscopy. The tentacles possess a flattened tip and rounded shaft externally, with a neck and root region internally. There is a microtubule canal consisting of 150 ring microtubules within which are 20–35 curved lamellae each containing about 20 microtubules. Novel structural features include pairs of short oblique arranged microtubules at the tip, and a collar of epiplasm in the neck region. No haptocysts are found in Choanophrya but the tentacle cytoplasm contains two types of inclusions named solenocysts and spherical vesicles. These features are discussed in relation to the processes of tentacle movement and feeding. The rapid longitudinal movements of the tentacles are described and compared to those of other suctorians and possible mechanisms are suggested. Ingestion in Choanophrya is described and several theories involving tentacle microtubules in the feeding process are examined.

Spermatozoon ultrastructure of Platichthys flesus

The ultrastructure of the spermatozoon of Platichthys flesus (flounder) has been determined. The cell is of the primitive type and lacks an acrosome. The bullet-shaped, homogeneously electron-dense nucleus has a deep, caudal articular fossa containing proximal and distal centrioles. Both centrioles are embedded in pericentriolar material which is intimately associated with the nuclear envelope. Around the proximal centriole the material is organised into a dense ring which bears nine fibres associated with the triplets, and a large fibrous body, all connected to the nuclear envelope. Connections exist also between the pericentriolar material of the proximal and distal centrioles. The material around the distal centriole is organised into a complex collar. The anterior surfaces of eight spherical mitochondria lie within shallow depressions of the nuclear caudal surface. They form a ring surrounding the posterior opening of the articular fossa and the proximal region of the 9 + 2 flagellar axoneme.

An in vitro model to evaluate cell adhesion to metals used in implantation shows significant differences between palladium and gold or platinum

Adhesion of tissue cells to metallic implants is a major factor that is important for proper tissue integration. Adhesion of Swiss mouse 3T3 fibroblasts to gold, platinum and palladium surfaces was investigated. Immunofluorescence staining for the integrin subunits αv and β1 and the focal contact protein vinculin revealed that cells growing on gold and platinum expressed many focal contacts. In contrast, cells on palladium surfaces had reduced numbers of focal contacts shown by vinculin staining and failed to demonstrate expression of αv and β1 in focal contacts. Spread cell area was also significantly reduced on palladium than on other surfaces suggesting that cells on palladium were more weakly attached. This may be due to either a different molecular composition of focal contacts in cells grown on palladium surfaces or unusual microstructural properties of the palladium surface. This model is useful to evaluate adhesion of cells to different metal surfaces.

Ultrastructure of the rumen ciliate Dasytricha ruminantium

The ciliate Dasytricha ruminantium possesses cilia over the entire surface. Both the oral and somatic kineties are composed of monokinetids comprising a kinetosome, a tangential ribbon of 5 transverse microtubules, a weakly convergent bundle of 5 postciliary microtubules, a short kinetodesmal fibre, and a single microtubule homologous to T(2) of other litostomate ciliates [15]. The reversed orientation of the kineties within and around the vestibulum may be a consequence of the evolutionary migration of the vestibulum from the anterior to the posterior of the cell. The vestibulum leads to the cytostome and a cytopharynx of the rhabdos type [3]. Microtubules lining the exit canals of the posterior contractile vacuole and cytoproct are believed to originate from somatic kinetids. The ecto-endoplasmic boundary layer (eeb) is composed of two microfibrillar layers. A large extension of the eeb connects the vestibulum to the cell cortex but does not form a karyophore as seen in the closely related genus Isotricha [12].

Morphogenesis of infraciliature in the entodiniomorphid ciliate Eudiplodinium maggii

Abstract The morphogenesis of ciliary zones has been studied in the ciliate Eudiplodinium maggi which has a vestigial somatic infraciliature consisting of subcortical barren kinetosomes. These replicate and migrate into the subequatorial ciliary anlagen of the dividing cells. The kinetid pattern of the barren kinetosomes changes sequentially to that of the ciliary zones. Postciliary and transverse microtubules are derived from basal and cortically directed microtubules while a dense spur coincides with the origin of the kinetodesma. All kinetics produce potential cytopharyngeal components. Nematodesmata originate in granular subkinetosomal dense plates, while two of the three types of cytopharyngeal ribbon are formed from tansverse microtubules. A spatial selectivity ensures that these components extend only from specific kinetids. It is concluded that 91) morphogenesis of the intricate cytoskeletal network of infraciliature involves a “pattern generator” in the vestigial somatic kinetids; and 92) entodiniomorph stomatogenesis in not truly apokinetal but is more like the telokinetal process of related ciliates.

Selected lines of Aedes aegypti with persistently distorted sex ratios.

A breeding scheme to isolate X chromosomes sensitive to drive by the T8 (Trinidad) Y chromosome of Aedes aegypti (the MD haplotype) is reported. Crosses with an Australian strain Th.I (Thursday Island) revealed not only sensitive and resistant X chromosomes but also some with the capacity to drive against the T8 Y chromosome. Four strains were created in which sex ratio was male-distorted (28–36 per cent ♀) for 10 generations, with no regression towards sexual parity. The proportion of females varied significantly between generations in each of the four strains. Further selection produced strains with normal sex ratios, capable of generating fewer than 15 per cent ♀ on outcrossing to T8 males.

Distribution of calcium in the suctorian Discophrya collini: An X-ray microanalytical study

Discophrya collini is a free-living suctorian with tentacles which can be induced to contract by means of a range of experimental stimuli, including the application of CaCl2 and MgCl2 but not BaCl2. X-ray microanalysis of glutaraldehyde-only fixed cells shows Ca to be present in the cytoplasmic ground substance and elongate dense bodies (EDB). In 10(-1) M CaCl2-treated cells, calcium levels remain unchanged except for a three-fold increase in the EDB. Treatment of cells with 10(-1) M MgCl2 and 10(-1) M BaCl2 does not result in their detection in the cell. It is suggested that EDB may act as reservoirs controlling levels of calcium.

Spermiogenesis in Platichthys flesus

Early spermatids of Platichthys flesus (flounder) have a central spherical nucleus and cytoplasm with numerous dispersed mitochondria and a pair of peripheral centrioles. One of the centrioles acts as a kinetosome for axoneme formation. After the start of chromatin condensation the centrioles and developing axoneme migrate to adopt a tangential orientation adjacent to a flattened, lateral margin of the nucleus. During migration, pericentriolar material becomes reorganised. The proximal centriole becomes surrounded by nine fibres, and the distal centriole by a complex collar. As the nucleus condenses it undergoes a rotation which shifts it to the anterior of the centrioles and deepens the articular fossa which houses, and is connected to, the two centrioles and their associated structures. This rotation also results in the mitochondria becoming relocated to form a ring around the proximal region of the axoneme to give the cell its mature ultrastructure.

Bacteria-like endobionts of the suctorian,Discophrya sp.

SummaryIndividuals ofDiscophrya sp. contain approximately 11,000 endobionts, interpreted as gram-positive bacteria. Treatment with the antibiotic rifampin resulted in destruction of the bacteria, but with an accompanying gigantism, loss of reproductive capacity and a restricted lifespan of the suctorian. Treatment with penicillin G resulted in a reduction of the bacterial population and gigantism. A subsequent increase in the number of bacteria coincided with a reduction in cell size of the suctorian. Copper ions were also found to destroy the bacteria. The possible existence of a symbiotic relationship between the two organisms is discussed.