Warwick L. Nicholas

Effect of Bacteria On Dispersal of Caenorhabditis Elegans (Rhabditidae)

The dispersal and behaviour of Caenorhabditis elegans in the presence of various species of bacteria were studied on agar plates. Several species proved attractive to the nematode, the proximity of colonies of living bacteria increasing the rate of dispersal of the nematodes, which on contact tended to remain within the colonies feeding on the bacteria. Other species showed little attraction, or proved repellent. Escherichia coli, Pseudomonas fluorescens and P. aeruginosa were attractive as well as supporting the growth and reproduction of the nematode. Dead bacteria were unattractive. Bacillus megatherium repelled C. elegans.

AXENIC CULTIVATION OF CAENORHABDITIS BRIGGSAE (NEMATODA: RHABDITIDAE) WITH UNSUPPLEMENTED AND SUPPLEMENTED CHEMICALLY DEFINED MEDIA*

In 1944 Margaret Briggs Gochnauer (Gochnauer and McCoy, 1954) isolated the free-living, self-fertilizing, hermaphroditic soil nematode Caenorhabditis briggsae.1 Since that time it has been maintained and intensively studied in the laboratory, first by Gochnauer (Briggs, 1946) and then by Dougherty and his co-workers (for example, Dougherty and Hansen, 1956~) in the United States, by Nigon and Dougherty (1949; 1950) in France, and by Nicholas (in press) in England. A major objective of this work has been, and continues to be, development of a chemically defined medium8 capable of supporting the indefinite axenic culture of C. briggsae and related rhabditid nematodes. Such a medium would open unexplored vistas on the physiology-especially the biochemistry of nutrition and metabolism-of nematodes. From the studies that would then become possible, new generalizations on metazoan physiology could be confidently anticipated. Despite much work on this problem, a defined medium capable of supporting the indefinite axenic culture of C. briggsae has yet to be devised. The best result realized has been the slow rearing of isolated larvae to reproductive adults in certain media, with slight development of the F1 progeny in one of them (Dougherty and Hansen, 1956~). Yet one has only to add relatively small amounts of suitable tissue extracts to such media to obtain an excellent response: rapid growth and repeated subculture, with no diminution of vigor, insofar a

The nematode fauna of a temperate Australian mangrove mudflat; its population density, diversity and distribution

tested. Four successive transfers, with at least eight generations, were made on a defined medium (GS-25)1/ plus a low level (1 per cent) of a liver preparation, Liver Protein Fraction C (LPF-C).

The free-living nematodes of a temperate, high energy, sandy beach: faunal composition and variation over space and time

The nematode fauna of an estuarine mangrove Avicennia marina mudflat in Southeastern Australia has been intensively studied. About 85% of the nematodes occur in the top cm of soft mud, but 5–7 species inhabit the deeper anoxic mud down to 10 cm, both at low and high tide. One square metre was intensively sampled from four zones with different nematode faunas. At the low tide zone 58% of the nematodes were epistrate feeders, including many diatom-feeders, but in the mangrove zone selective microbial feeders made up over 60% of the population, while between high water neap and high water spring, above the mangrove zone, omnivore/predators and plant root feeding nematodes increased in relative importance. Random replicate cores reliably sampled species occurrence, but gave a high variance in density estimates. Replicate aliquots from homogenised mud gave lower density variance. Nematode densities (maximum 5 × 106 m-2) were not as high as have been reported from non-mangrove estuaries in other countries, but were within the range found in mangroves elsewhere in Australia. Margalef Species Richness values ranged from 1.7 to 3.89, which is similar to values found in other mangroves mudflats in Australia. Nematode biomass ranged from 888 mg dry weight m2 (383 mg C m-2) at the low tide zone to 19 mg dry weight m-2 (8 mg C m-2) at the upper tide level.

T-cell dependent collagenous encapsulating response in the mouse liver to Mesocestoides corti (Cestoda).

Free-living marine nematodes were sampled extensively over a 2-year period on a long sandy beach exposed to high-energy ocean swells in southeastern Australia. Samples were taken in summer and winter at different tide levels on the beach, and at different positions along the beach. A total of 58 species from 48 genera were found, many as yet known only from Australia. Predators and particle feeders were always the most abundant feeding guilds, but species composition varied markedly between samples. The variation in abundance and composition of the fauna was analysed statistically. There were considerable differences between high-, mid- and low-tide faunas along a single transect of the beach which persisted for 24 h with calm seas, but not over several months. There were also considerable differences between locations along the beach. It appears that hydrodynamic forces constantly redistribute the fauna, introducing a large probabilistic element into patterns of total nematode abundance and faunal composition.

The reaction of the cockroach Periplaneta americana to the injection of foreign particulate material

Abstract Pollacco S ., Nicholas W.L ., Mitchell G.F. and Chaicharn Stewart A . 1978. T-cell dependent collagenous encapsulating response in the mouse liver to Mesocestoides corti (Cestoda). International Journal for Parasitology 8 : 457–462. Experiments with genetically hypothymic mice show that the tetrathyridial larvae of Mesocestoides corti (Cestoda) multiply much more rapidly in the liver than in normal mice. In the hypothymic mouse, collagen fibres are not laid down and the parasite is not encapsulated as it is in the normal mouse. Encapsulation probably restricts the parasites multiplication, and it is suggested that the failure to encapsulate the parasite accounts for its more rapid multiplication in the hypothymic mouse. Fibrogenesis and encapsulation is restored to hypothymic mice by transferring syngeneic thymus cells, spleen cells or peritoneal exudate cells. It is concluded that the encapsulation of M. corti is a T-cell dependent process.

The Efficiency With Which Caenorhabditis Briggsae (Rhabditidae) Feeds On the Bacterium, Escherichia Coli

Abstract The cockroach Periplaneta americana rapidly clears the hemocoel of injected suspensions of foreign particles. Hemocytes phagocytose the particles and either digest them, as with unfixed sheep red cells, or deposit them in cellular aggregates scattered through tissues, as with fixed red cells, yeasts, polyhedral bodies, carmine, carbon, and Sudan stain particles. With the exception of the viral polyhedra (which were not infective) the aggregate becomes transformed into a melanized nodule. Three species of bacteria were not effectively cleared from the hemocoel, though the hemolymph showed lytic activity against one, Bacillus thuringiensis. In the 24 hr following injection, the hemocoel volume increased, the number of circulating hemocytes increased, especially plasmatocytes, the cells most active in phagocytosis. No evidence was found of enhanced mitosis in the circulating hemocytes following injection. These reactions resemble those previously reported from the wax moth Galleria mellomella but differ in some respects.

Seasonal variations in nematode assemblages on an Australian temperate ocean beach: the effect of heavy seas and unusually high tides

The rate of removal of the bacterium E. coli from aqueous suspensions by C. briggsae in feeding has been studied. The decrease in bacteria with time follows a negative exponential equation when bacterial multiplication was restricted and nematode growth was minimal. It was inferred that the feeding activity of the nematodes is maintained at a constant level over a wide range of bacterial concentrations. Other experiments supported the contention that C. briggsae requires dense suspensions of bacteria for the maintenance of cultures and gave estimates of the efficiency of conversion of bacterial protoplasm to worm protoplasm.

The Mineral Composition of Intracellular Inclusions in Nematodes From Thiobiotic Mangrove Mud-Flats

Free-living nematodes inhabiting a sandy beach exposed to strong ocean waves were sampled at bimonthly intervals for two years. Six 1.3-litre core samples were taken on each occasion down to a depth of 60 cm. The numbers of each species and their status as juveniles, males and females (with or without eggs) was recorded. In the common species all these stages occur throughout the year, but the population increases in the warmer months of the year and falls to a much lower level in winter. Most species are dispersed throughout the sand to a depth of at least 60 cm, but several species where almost always found below the water table at about 60 cm. The faunal composition of the nematode assemblages changed significantly from month to month. Additional samples were taken to monitor the effects of very strong waves coupled with a very high tide which remodelled the beach. The nematode fauna was partially reconstituted by this event. It is concluded that the intertidal beach fauna is a dynamic extension of the near shore sub-littoral nematode fauna.

Caenorhabditis Briggsae (Rhabditidae) Under Anaerobic Conditions

Some marine nematodes from anoxic mangrove mud-flats contain densely packed intracellular inclusions within their tissues which are visible by light microscopy. Transmission electron microscopy of sections of Sabatieria wieseri, Terschellingia longicaudata and Sphaerolaimus papillatus shows these inclusions within the intestinal and other cells. Energy dispersive analysis of secondary X-rays by scanning electron microscopy of thick epoxy sections shows concentrations of Si, P, S, K, Ca and Fe in their tissues. EDS of secondary X-ray emissions from thin epoxy unstained sections by transmission electron microscopy shows these elements together with Na, Zn and Al concentrated in the intracellular inclusions. The physiological implications of these observations are discussed.