Biodegradation of litter in Eucalyptus pauciflora communities—II. Fungal succession in fungicide- and insecticide-treated leaves

Fungal succession on untreated and fungicide- and insecticide-treated leaves of Eucalyptus pauciflora was compared. Natural succession on untreated leaves fits the general scheme for succession on deciduous tree leaves. Initial colonizers are species of Coelomycetes and Moniliales. When the numbers of Coelomycetes decrease in the late stages of decomposition, the frequency of Penicillium species and species of Zygomycetes increases. The succession is affected only marginally by DDT and dieldrin treatment while benomyl severely restricts the occurrence of most fungal species. The effect of benomyl persists even after exposure for 48 weeks in the field.     

Some problems in assessing the fluorescein diacetate-active fungal biomass in the soil

A technique for assessing the metabolically-active fungal biomass by means of fluorescein diacetate (FDA) staining was recently described (Söderström, 1977). In this note some practical details in the application of this technique to studies of FDA-active fungal biomass in the soil are discussed.     

Interactions between bacteria and ectomycorrhizal fungi

Interactions between eight ectomycorrhizal fungi and eight bacteria were tested on five laboratory media and in the rhizoplane of Pinus radiata. Depression of growth of the fungi by the bacteria in laboratory media was dependent on the medium and bore little relation to effects in the rhizoplane. In the rhizoplane, different bacteria could depress, have no effect or even stimulate growth of mycorrhizal fungi. Competition and antagonism are suggested as mechanisms for depression of the fungi. Some bacteria gave protection against the depressive effects of other bacteria. Considerable differences occurred between ectomycorrhizal fungi in their colonization of the rhizoplane in the absence of bacteria and also in their presence. The common mycorrhizal fungi Rhizopogon luteolus and Thelephora terrestris generally colonized roots well but the strain of Pisolithus tinctorius studied colonized poorly. Direct microscopy showed the percentage cover of the root by microorganisms was usually only 10–20%.It is proposed that interactions of ectomycorrhizal fungi with soil organisms are important in determining the successful introduction and persistence of inoculated ectomycorrhizal fungi. Fungi should be selected for compatibility with a wide range of soil microflora as well as efficiency in plant stimulation.     

Distribution and partial characterisation of acid hydrolysable organic nitrogen in six New Zealand soils

Six New Zealand topsoils of widely different origins and properties were subjected to 6m HC1 hydrolysis and the distribution of N fractions and amino acids were determined qualitatively and quantitatively.Of the total-N in the soils studied 83–91%, was hydrolysable with 6m HCl. The largest proportion of the hydrolysable N was α-amino acid N (38– 42%). followed by hydrolysable-unknown N (HUN) (14–24%), and NH₄⁺-N (14–22%). A significant proportion (25–50%) of the HUN fraction was accounted for by the non α-amino acid-N. Oxidative (3% H₂O₂) hydrolysis released N-phenoxy amino acid-N and possibly N-compounds which were complexed with phenols and sugars. All soils had a similar amino-acid composition with a predominance of acidic amino-acids.     

Colonization by Rhizobia of the seed and roots of legumes in relation to exudation of phenolics

A study of the colonization pattern of Rhizobium inoculated either in the soil or on to the seeds of green gram (Phaseolus aureus Roxb.), black gram (P. mungo L.) and sun hemp (Crotalaria juncea L.) revealed a significant reduction of Rhizobium in the spermosphere of sun hemp which was attributed to excretion of phenolic compounds by the seed. As the plants aged, the quantity of phenolics exuded by the roots was reduced and there was a parallel increase in the Rhizobium population in the rhizospheres of the three plant species.     

Remarks on the anatomy and ontogeny of scales of teleosts. I

Densitometer records were made from the scales of a number of fish species, mainly from pikeperch. Analysis of the records showed that the pattern of hollows, representing the circuli in the curves, was very regular. No arrangement into groups of narrowly interspaced circuli could be demonstrated. It was therefore concluded that the circuli of the surface layer do not produce the “growth-checks”. Ringlike structures were also present in the fibrous basal plate. These were about 3–5 μm closer together than the circuli. These two circular gratings of slightly different inter-ring spacing will create an interference pattern, in this case a circular moiré pattern, having no direct relation to the structures present in the two layers forming the scale.     

Comparison of yeast and algal diets for bivalve molluscs

Four species of bivalve molluscs were fed diets consisting of varying proportions of the yeast Candida utilis and the diatom Thalassiosira pseudonana. Juvenile Argopecten irradians, Mercenaria mercenaria, and Mytilus edulis grew as fast or faster than controls when fed diets containing as much as 50% yeast. Growth of soft tissue in Crassostrea virginica, however, decreased with the amount of yeast in the diet. The relative food values of the different diets were not closely correlated with gross chemical composition or amino acid composition.     

Glugea heraldi n. sp. (Microsporida, Glugeidae) from the seahorse Hippocampus erectus Perry

Abstract. A new species of Microsporida, Glugea heraldi , is described from the seahorse Hippocampus erectus . Measurements of fixed spores and notes on the histopathology of parasitized tissue are given.     

The evaluation of piromidic acid as an antibiotic in fish: an in vitro and in vivo study

Abstract. The activity of piromidic acid (PA, 8-ethyl-5, 8-dihydro-5-oxo-2-prior lidinopyrido [2,3–d] pyrimidine-6-carboxylic acid) against bacteria in fish was evaluated in vitro and in vivo .
In vitro , PA was effective against a wide range of pathogenic bacteria stocked in this laboratory and freshly isolated from fish. PA was active against organisms showing multiple drug-resistance and showed no cross-resistance to chloramphenicol, tetracycline and sulfamonomethoxine.
In vivo , orally administered PA was effective against experimental infections with Aeromonas hydrophila and Vibrio spp. in goldfish and eels. The efficacy of PA against these infections was equal to or higher than that of chloramphenicol, and higher than that of tetracycline. Distribution of PA in the Ash was investigated by bioassay and autoradiography. In the bioassay, orally administered PA was easily absorbed and distributed in the blood and tissues of major organs within 1 h after the administration. Peak levels were attained 2 to 4 h post dosing, and no residue was detected in the blood and tissues 48 h post dosing. The results obtained from the autoradiographic investigation in goldfish were similar to those from the bioassay. Therapeutic levels of PA were well tolerated by fish when administered with feed.     

Cellular immune response in rainbow trout Salmo gairdneri Richardson to Yersinia ruckeri O-antigen monitored by the passive haemolytic plaque assay test

Abstract. The specificity and kinetics of the immune response of rainbow trout ( Salmo gairdneri ) to single injections of an O-antigen extracted from the bacterial pathogen Yersinia ruckeri , which causes enteric redmouth in fish, were investigated by the passive haemolytic plaque assay and serum antibody quantitation. Doses ranging from 5 ng to 500 mg in 10-fold increments were injected intraperitoneally into groups of trout held at 17 × 1°5°C. The occurrence of plaque forming cells (PFC) and humoral antibody was followed for 35 days after injection. Trout gave an immune response to doses of 500 ng and above. Seven days after injection no humoral antibody was detected, but PFC were found in the spleen. The maximum PFC numbers occurred 11 days after injection. On day 21, few PFC were found, whereas serum antibody titres were highest. The antibody from immunized trout showed little or no cross-reactions with sheep red blood cells passively labelled With antigens from other fish pathogens.