The thesis compares the effects of temperature and substrate on the growth of fish pathogen Saprolegnia diclina and the saprophyte Saprolegnia ferax. Studies revealed optimal growth of both species occurs at 20-25'C depending upon the substrates used. Growth is restricted at higher and lower temperatures. For both species optimum growth was recorded on medium containing 1% casein and 1% glucose, but high levels of lipid and glucose inhibited growth. However, S. _diclina exhibits a higher growth rate than S. ferax at high lipid concentrations. S. diclina produces more proteolytic activity per unit weight at 100C than S. ferax, regardless of substrate. S. diclina also demonstrated greatest lipase activity at 10°C, particularly in the presence of casein or lipid. These factors may facilitate colonisation of fish tissues by S. diclina at low temperatures. Carp maintained at 10° C showed greater infection by S. diclina, than carp kept at 20°C. Evidence is presented for a lack of antibody production in infected carp maintained at 10°C. Fish kept at 20°C only produced antibody to Saprolegnia antigens when they were coupled to erythrocyte carriers. During infection phagocytic, macrophages and neutrophils increased; there was a decrease in the numbers of mucous secreting goblet cells in the skin, and lymphoid organs showed increased pigment deposition. Infected fish showed evidence of physiological stress including decreased levels of erythrocytes, haemoglobin, liver glycogen and protein, and an increase in liver lipid. Ascorbic acid levels decreased in interrenal tissue. Histological and scanning E. M. studies of skin lesions provide new information about changes in the surface during UDN disease. Key words: Saprolggnia infection and UDN Temperature, substrates
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:378528 |
| Date | January 1987 |
| Creators | El-Feki, Mostafa A. E. |
| Publisher | Aston University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://publications.aston.ac.uk/14524/ |
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