Taxonomic differences exist between Thyasira gould! and T. flexuosa both in conchological features and in the soft parts, perhaps the best of these differences are those concerning the sperm which are easily seen even in badly curated specimens. The occurrence of a population of T. gouldi within Loch Etive on the west coast of Scotland extends the known distribution of this arctic bivalve considerably further south. The development is nonpelagic and this, associated with the non-synchronized reproductive activity , means that independence is gained from plankton blooms and other external triggers allowing the characteristic dense but patchy populations to be built up. Salinity and sediment particle size both limit the distribution of T. souidi within L. Etive, the VI naturally occurring sediment is altered by the inhabi tants of the area into a sediment vlhich is better suited to the needs of T. gouldi. Asynchronized breeding, slow growth rate, longevi ty of life and 10\'1 adul t mortality all combine to give a characteristic bimodal population, the modes of which do not appear to shift with time. A method is described whereby an indication of both the mean state of the population and the state of the individual can be obtained for any period of the year. The biochemical composition varies with size and time of the year as well as with gonad state. Dry weight fluctuations are, however, not entirely explained by variations in the stage of gonad development as seasonal variations in the amount of somatic tissue do exist. Thyasira gouldi is one of the Lucinaceans infected by the much modified copepod parasite Axinophilus thyasirae. The life cycle and infective stage of this parasite are described as is the external morphology of the nauplius copopedite and adult. The reproductive system of both the male and the female are also described. The first infected parasite is always female and only rarely does more than one female reach maturity within anyone host even though up to five parasites may be present. The parasite has been shown to affect the biochemical composition of the host, reducing the amount of each of the components present, but tending to reduce the amount of nitrogenous material in preference to the amount of carbohydrate. VII The parasite affects the gonad of the host resulting in castration probably as an indirect effect of 'food robbing'. The interference to the host's food supply by the parasite is thought to be so great as to reduce the host to starvation levels of food,

This research study is divided into 4 major sections. Section A deals with the world-wide distribution of the haematoprotozoan parasites of marine fishes. These are tentatively divided into 3 major groups: the Haemogregarines, the Trypanosomes and the Trypanoplasms and one group of ill defined and controversal organisms including Haemohormidium sp. and Dactylosoma sp. The results of extensive surveys of the coastal waters of France, Scotland and Wales with added examples from the Mediterranean Sea substantiate the zoogeographical distribution of these parasites. Two species of haematoprotozoan parasites Haemogregarina simondi and Trypanosoma soleae are re-described, earlier accounts dating from the beginning of the century being considered incomplete. A new species of haemogregarine is described from the farmed turbot (Scophthalmus maximus) as Haemogregarina sachai n. sp. and an unidentified species of Haemohormidium found occasionally in turbot and Dover sole (Solea soles) is also described. In addition Haemogregarina sp. were encountered in certain wild marine fish from the Atlantic coast of France e. g. Zeus faber, Sebastes sp., Trisopterus luscus, Pagellus bogaraveo and Raja sp. and from the coastal waters of Malta e. g. Peristedion cataphractum and Oblade melanura. However, they were not found in sufficient numbers to allow a definite description. The value of surveys of wild fish populations is discussed in the light of zoogeographical distribution, the apparent periodicity of these parasites and a seasonal variation of parasitism. Section B attempts to summarize the knowledge of the mode of transmission of marine haematoprotozoan parasites by piscicolid leeches as intermediate hosts and vectors. The developmental stages of a trypanosome, probably Trypanosoma murmanensis from the Atlantic cod Gadus morhua are described in the marine leech Calliobdella nodulifera. Stages of a haemogregaririe were observed in the same leech. The development of the turbot haemogregarine Haemogregarina sachai n. sp. in artificially infected leeches is also described up to the 20th day post infection. Transmission of this haemogregarine to apparently uninfected turbot via this leech was not successful. Various stages of development of Haemogregarina simondi are described in its apparently natural vector, the marine leech Hemibdella soleae, and transmission with infected leeches to apparently healthy hatchery reared soles was achieved. Thus it was shown for the first time that marine leeches can serve also as vectors for haemogregarines. Stages of this haemogregarine are also described in the blood-sucking ectoparasitic copepod Lernaeocera sp. parasitizing the haemogregarine infected soles. These results are discussed in relation to the feeding behaviour and migration patterns of the fish hosts, the periodicity of the parasites and possible other vectors or other ways of acquiring an infection with these haematoprotozoan parasites. In Section C the pathogenicity of the haematoprotozoan parasites of marine fishes is summarized from previous accounts among wild fish populations and compared with the situation in aquaculture. The pathogenicity of the two haemogregarines, Haemogregarina simondi and Haemogregarina sachai n. sp., accidentally introduced into several fish farming establishments connected with the effluent cooling waters of a nuclear power station is described with special reference to the possible source of the infection. The results of therapy trials and control programs are discussed in the light of the periodic reappearance of the parasites, the possibility of carrier fish existing, the immune status of the host and the possible role of an intermediate host or vector in maintaining the infection. Possible means of controlling the pathogenicity of marine haemogregarines and perhaps other haematoprotozoan parasites when they occur in farmed marine fishes are also discussed. In Section D are described for the first time, the ultrastructural characteristics of various stages of the haematoprotozoan parasites of marine fishes in fish hosts and vectors. The electronmicroscopical studies are limited to Haemogregarina sachai n. sp. and Haemogregarina simondi, for which the ultrastructure of schizonts from the spleen and blood, intracellular merozoites and free gametocytes were contrasted. In addition stages of H. simondi were demonstrated in Hemibdella soleae and Lernaeocera sp. The fine structure of the various organelles encountered was compared with that of related organisms from other cold-and warm-blooded vertebrates. In conclusion attention is drawn to the need for more investigations in this field of host-parasite relationship of marine haematoprotozoan parasites and their vectors and their pathogenic-action as seen in a confined and artificial environment such as the marine aquaculture.

Larval Anisakis simplex, Pseudoterranova decipiens, Contracaecum osculatum and larvae and adults of Hysterothylacium aduncum were recovered from specimens of cod, haddock, blue whiting and bull rout; however, only A.simplex were retrieved from long rough dab. The epidemiology of infection by these four nematode species was examined both in whole fish, and in individual host tissues and organs. Frequency distributions of nematodes were found to be generally overdispersed in fish. Preliminary investigations revealed no strong evidence to suggest that competi tive interactions occurred between ascaridoid nematodes wi thin fish. Stomach lesions in gadoids were associated with single (partially penetrated) and mul tiple (throughout stomach wall) worm infections of larval A.simplex; such lesions were discrete and raised in appearance. Lesions associated with 1-3 larval P.decipiens in an open cavity within the stomach of angler fish were diffuse and not significantly raised. Histological examination of each form of ulcer revealed general similarities in pathology, with infil tration of inflamatory cells being the initial response to the nematode\s. Changes in the cephalic morphology of A.simplex, P.decip1ens, C.osculatum and H.aduncu were examined at different life cycle stages under scanning electron microscopy. Due to their small size, newly hatched third stage larvae of P .decip1ens were cultured in a bacterial mat prior to fixation for S.E.M., and the external ultrastructure of these larvae is described. The most prominent external feature at this stage is the cephalic boring tooth. Aspects of the internal ultrastructure of A. simplex, P.decipiens, C.osculatum and H.aduncu were examined using transmission electron microscopy. Newly hatched third stage larvae of P.decipiens show little differentiation of internal organs. The ultrastructure of sensory amphids in H.aduncum and A. simplex is cons i stent wi th that of a chemoreceptor, that of the single papilla in P.decipiens a mechanoreceptor. The ultrastructure of the digestive tract, excretory gland and body wall of marine ascaridoids were also examined.

The objectives of this study were to isolate and characterize the fungi associated with saprolegniasis of Pacific salmon and to determine the conditions which allow the infections to become initiated. The fungi isolated from the salmon were either sterile Saprolegnia species, or Saprolegnia species with affinities to the S. diclina-S. parasitica complex. Two morphologically and physiologically distinct strains were recognized in this latter group. Difficulties associated with the identification of these and other Saprolegnia isolates focussed attention on the inadequacy of existing species concepts and also showed that more attention should be directed toward the effect of nutritional and environmental factors on the morphology and growth of these fungi. A study of the DNA base compositions of eleven isolates belonging to the genus Saprolegnia sensu stricto showed that, contrary to expectations based on the literature, this character could not be used to distinguish groups at the infrageneric level, but the results did suggest that isolates included in the genus may have relatively homogeneous genomes. The existence of a satellite DNA was confirmed and was found in all isolates examined. This satellite DNA separates Saprolegnia species from all other Oomycetes which have been similarly examined. An argument is present favouring the rejection of the name Saprolegnia parasitica Coker as a nomen ambiguum and it is shown that all existing oogonium producing isolates included in this species can be legitimately considered to be Saprolegnia diclina Humphrey. Infection experiments, and observations on the histo- and gross pathology of saprolegniasis, when considered in the light of modern concepts concerning the nature of infectious diseases and existing knowledge of the physiology of Pacific salmon, suggest that there is a direct link between increased plasma corticosteroid levels in the fish and their susceptibility to saprolegniasis and other infections caused by normally non-pathogenic organisms. It is hypothesized that natural increases in the plasma corticosteroid levels of the salmon, either alone, or in conjunction with further stress-induced increases, create a situation where natural immunity and the ability to repair tissue damage are greatly impaired. This combination of factors allows an infection to be initiated and, once established, it becomes progressively worse, and ultimately terminal, at a rate which can be directly correlated with increasing temperature. / Science, Faculty of / Botany, Department of / Graduate

Call number: LD2668 .T4 1979 L48 / Master of Science

The efficacy of a range of anti-parasitic chemotherapeutic agents against the salmon louse Lepeophtheirus salmonis following topical application was studied in vitro and in vivo. In general, adult and preadult lice were susceptible to a wide range of compounds with dose rates, following 1 hour exposures, ranging several orders of magnitude (10.0 - 0.001 mg/L). Overall the pyrethroid compounds which were tested were found to have the widest therapeutic ratios, indicating the potential of this group of chemotherapeutants for sea lice control. Resistance to the organophosphorus (OP) compounds dichlorvos and azamethiphos was detected in isolated populations of lice. Field trials with azamethiphos indicated that the compound was highly efficacious against sensitive lice (@ 0.1 mg/L; however, where resistance was present, efficacy (@ 0.2 mg/L) was highly variable. When used at the above dose rates, azamethiphos was found to be well tolerated by fish as indicated by a lack of significant brain acetylcholinesterase inhibition. Results on cross resistance (between pyrethroids and OPs) were inconclusive which was believed to be, primarily, due to the overall high toxicity of the group; but also to the variable responses from exposed lice. In a series of preliminary trials, one of the pyrethroid compounds, PHRDL-D, was found to effectively remove lice when administered orally to infected salmon, indicating the potential of pyrethroids as oral chemotherapeutants. A comparison of the relative toxicity of azamethiphos (OP), resmethrin (pyrethroid), ivermectin (avermectin) and the structurally similar compound SKB7 (milbemycin), indicated that chalimus stages were only susceptible to ivermectin and SKB7 following topical and intra-peritoneal injection to lice infected fish. In contrast, azamethiphos and resmethrin were found to be non toxic to chalimus larvae at dose rates which were highly toxic to both adult lice and treated fish. Preliminary studies on the uptake of r4C]azamethiphos in adult lice indicated that uptake was both concentration and time dependant, reaching a plateau at the onset of toxicity. Uptake appeared to be primarily associated with frontal plates, 1st antennae and anus. The fmdings indicated that several compounds/compound classes are highly active against lice and, given the limited number of compounds available for sea lice control and the development of resistance to OPs, might be considered as alternatives. In light of these findings, the potential of chemotherapy for the future control of sea lice is discussed.

Aquaculture is being seriously considered as a promising sustainable industry in the Sultanate of Oman. Fish farming commenced in Oman in 1986, but it was only in 2011 that it became a more commercially driven sector. While worldwide aquaculture production is expected to rise to meet the shortage in capture fisheries, there is a parallel requirement to identify potential threats to the health and welfare of existing aquatic farmed stocks and to take appropriate steps to mitigate them. As aquaculture in Oman is in an early stage of development, it is important to acquire baseline data on the existence and prevalence of aquatic diseases and pathogens to help the Government make policy decisions to develop health management regimes applicable for Omani aquaculture. Therefore, this study was conducted to evaluate current farming practices of tilapia in Oman, to investigate the bacterial species composition and distribution from different sites in some of the economically important fish species, and to study the characteristics and pathogenicity of Aeromonas species. The current practices were studied for 9 Nile tilapia (Oreochromis niloticus) farms from four areas (Al Batinah, Ad Dhahirah, Ad Dakhiliyah and Ash Sharqiyah North) during the period of September to November 2012 by using questionnaires and interviews with the farm owners and staff. In total 417 fish representing 5 target species were chosen on the basis of the commercial importance and their potential for aquaculture in Oman, including red spot emperor (Lethrinus lentjan), king soldier bream (Argyrops spinifer), white spotted rabbit fish (Siganus canaliculatus), abalone (Haliotis mariae) and tilapia (Oreochromis niloticus). The fish were collected from 5 main sampling areas in Oman (Muscat, Mudhaibi, Manah, Sohar and Salalah) based on the Atlas of suitable sites for aquaculture in Oman to investigate the bacterial species composition and distribution. The animals were examined for clinical signs of disease prior to routine bacteriology. Bacterial isolates were recovered using traditional methods and identified to species level using phenotypic and molecular approaches using 16S rDNA, 16S rDNA RFLP and 16S rDNA sequencing. Experimental fish challenge studies were also conducted using both live bacterial cells and ECP protein to investigate the pathogenicity of Aeromonas isolates. In addition, the presence of some virulence factors was investigated using both phenotypic and genotypic methods. The results of this study showed that, the most farms in the Oman follow very similar farming practices. The major proportion of the tilapia is consumed within the local communities. A number of farmers have experienced mortalities, which were considered to be attributable to poor water quality, overcrowding or due to excessive feeding. Farmers facing fish mortalities tended not to record the problems due to a lack of understanding of the concept of fish farm management. There is a regulation about aquaculture and related quality control, but it has not yet been implemented in an appropriate manner in Oman. From the diverse group of bacteria recovered from wild and farmed fish, 83% of the total isolates comprised Gram negative, rod-shaped bacteria. The most frequently isolated groups from marine and cultured fish were Aeromonas spp., Vibrio spp., Sphingobacterium spp., Micrococcus spp. and Staphylococcus spp., with Aeromonas spp. being the predominant group representing 25% of the isolates recovered in this study. Identification of the Aeromonas spp. showed 57% agreement between the results of phenotypic and genotypic methodologies, and determined 6 species as the dominant organisms, i.e. A. veronii, A. jandaei, A. caviae, A. trota, A. encheleia and A. salmonicida. 65% of the iso-lates shared 99% 16S rDNA sequence similarity with the closest sequences in GenBank, and the dominant species was A. veronii. In conclusion, the Aeromonas isolates recovered from fish with clinical signs of disease showed heterogeneity in their identification profiles and their pathogenicity.

Sterile triploid Atlantic salmon represent a solution to the issues of pre-harvest sexual maturation and mature escapees from open aquaculture systems. Although the initial problems of reduced performance and increased deformities in triploids have been thoroughly researched, there is a continued lack of information on their susceptibility and response to disease and routine on-farm treatments compared to diploids. Thus, the main aim of this thesis was to enhance the current understanding of triploid health and immunity through experimental disease challenges and treatments, and aid in determining their robustness and, therefore, suitability for aquaculture. A commercial furunculosis vaccine equally protected diploids and triploids against challenge with Aeromonas salmonicida, and adhesion scores were similar between ploidy (Chapter 2). Interestingly, triploids had lower white blood cell counts but increased cellular activity, e.g. respiratory burst, compared to diploids. Following experimental cohabitation infection with Neoparamoeba perurans, causative agent of Amoebic Gill Disease (AGD), ploidy did not affect the manifestation or severity of AGD-associated gill pathology, or the serum innate immune response (Chapter 3). Hydrogen peroxide, used to treat against parasitic diseases, elicited similar primary and secondary stress responses in both ploidy, but led to differences in the expression of stress (cat, gpx1, gr, hsp70, sod1, sod2) and immune (saa5, crp/sap1a, crp/sap1b, il1β) genes (Chapter 4). Finally, vaccination with different vaccine treatments (4 commercial vaccines, 6 different vaccine combinations and a sham-vaccinated control) showed no ploidy differences in adhesion score or antibody response, although vertebral deformities remained higher in triploids (Chapter 5). Increasing severity of vaccine treatments negatively affected weight, length and thermal growth coefficient in both ploidy. Triploids were heavier than diploids at smolt (+ 14 %) and post smolt (+ 32 %). Overall, this research shows that triploid Atlantic salmon respond as well as diploids to disease and treatment challenges, and supports their application into full-scale commercial aquaculture.

Made available in DSpace on 2014-06-11T19:22:22Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-08-12Bitstream added on 2014-06-13T20:09:25Z : No. of bitstreams: 1 000739835.pdf: 1067732 bytes, checksum: 6267bee54889e5a1141ec452b2282ea4 (MD5) / Há inúmeras razões para a exploração da aquicultura mundial, principalmente no Brasil, país apontado pela FAO, como um dos poucos capazes de produzir alimentos suficientes para atender a demanda mundial nos próximos 30 anos. A piscicultura brasileira destaca-se pela produção de tilápias em tanques-rede, e este sistema foi alavancado graças ao desenvolvimento das técnicas de incubação artificial de ovos e masculinização de pós-larvas. Todavia, a masculinização pode sobrecarregar o metabolismo dos indivíduos, uma vez que, durante a fase de pós-larva, o sistema digestório destes animais ainda é imaturo. A utilização de hormônios esteroides aliado a níveis elevados de proteína, tem como consequência alterações fisiopatológicas, como o comprometimento hepático, que poderão perdurar por todo o ciclo de produção, com isso, os peixes podem tornar-se mais susceptíveis a patógenos oportunistas ou serem submetidos a tratamentos equivocados. Este trabalho propõe a utilização da homeopatia na ausência de produtos específicos e registrados para uso na aquicultura no Brasil. O medicamento foi avaliado em duas apresentações: complexo homeopático Fator Pró-digestão Inicial ® administrado na dieta de pós-larvas de tilápias-do-Nilo e o medicamento homeopático Isoterápico, gotejado na água dos peixes (2,5 gotas/minuto-1), ambos durante o ciclo inicial de produção (incluindo o período de masculinização) até 70 dias. O estudo foi realizado em uma piscicultura comercial do estado de São Paulo sendo avaliado: desempenho produtivo, sobrevivência, prevalência parasitária e realizados exames histopatológicos do fígado e brânquias das pós-larvas. A homeopatia, nas duas apresentações, melhorou a sobrevivência dos peixes, o complexo homeopático Fator Pró-digestão Inicial® e o seu veículo (sacarose) melhoraram o desempenho produtivo em relação aos grupos controle... / There are innumerous reasons to explore the worldwide aquaculture. Brazil has been pointed by FAO, as one of the few countries able to produce food to handle worldwide demand for the next 30 years., The aquaculture, as farming activity, is unique, and demands a vast knowledge in limnology, ictiology and ecology. Tilapia production in net-cages made a huge advance after the discovery of artificial incubation of eggs and masculinization of fingerlings. During this phase, the digestory system of fish is still immature and with the utilization of steroid hormones and high protein diets, it can overload the system, causing physiopathological alterations that will endure all the production cycle. With that, fish could be more susceptible to opportunistic agents. This way, it is desired to use products that can make fish with a higher ability to answer the challenges of farming. As a regulation therapy, homeopathy uses the natural force of the organism to reestablish the homeostasis. One of the unique application of population homeopathy is the easier to administrate, like in fish, wich is made by feed or dripping in the water. The knowledge of homeopathy is wide, and involves: physics concepts, like the ultradilution concept, drug action in non-existing molecular of the drug itself; biology concepts, approaching the dynamic of the function in organisms, as like as the interaction of life with physic-chemical environment; and medicine concept, applying the physical, mental, psychological and social welfare

Non-native parasites pose a significant threat to aquatic bio-diversity and fishery development. Many factors have facilitated the introduction of non-native parasites into England and Wales. Identifying the effects of these parasites and the importance of any changes to wild fish populations represents a considerable challenge. However, in order for the Environment Agency to identify future disease threats, effectively manage resources and implement practical and sustainable control measures, the risks posed by these parasites to fisheries must be better understood. A structured, risk-assessment process for non-native freshwater parasites is proposed. This approach includes procedures for hazard identification, impact assessment, risk management and communication. A quantitative approach to hazard identification provides an initial prediction of impact at the time of introduction to inform decisionmaking and guide preliminary control measures. This is followed by a more comprehensive framework for impact assessment that promotes understanding of changes at host, population and fishery levels. These are placed into context with the economic and ecological value of native resources. An independent 'non-native parasite review group' has been convened to ensure consistency of policy decisions and clear communication of disease risks to interested bodies. It is hoped that this wil assist the management of future invasions and provide a scientifically robust foundation on which to base proportionate control measures. The Category 2 parasites are defined as "species having a significant disease potential when introduced into waters where they do not already exist, or are non-indigenous species with unknown pathogenicity and distribution". Understanding of the dangers posed by these parasites varies considerably. Ergasilus sieboldi, Anguilicola crassus, Bothriocephalus acheilognathi and Lernaea cyprinacea, are well recognised non-native fish pathogens that pose a considerable threat to fisheries. Conversely, the effects of other introduced parasites remain poorly understood. In many cases, a paucity of published literature at the time of introduction has limited a reliable assessment of impact. Four non-native parasites were considered a priority for further study. These were Paraergasilus longidigitus (Copepoda: Poecilostomatoida), Ergasilus briani (Copepoda: Caryophylldae) Poecilostomatoida ), Atractolytocestus huronensis (Cestoda: and Philometroides sanguinea (Nematoda: Philometridae). Pathological, epidemiological and experimental investigations were undertaken to assess the effects of these parasites at host and population levels. P. longidigitus can cause pronounced pathological changes to the olfactory epithelium of infected fish. Although this damage provides the potential for disruption to spawning through reduced sensitivity to reproductive chemical cues, experimental observations combined with seasonality studies suggest that the parasite is unlikely to disrupt reproduction within infected cyprinid fisheries. Similarly, studies conducted on the caryophylidean cestode A. huronensis provide little evidence to suggest that the parasites poses a threat to car fisheries. Damage within the intesinal tract was characterised by relatively mild mechanical and inflammatory changes. Infections of up 213 parasites had no adverse affect upon the conditon of common carp. Based on these findings and the application of the aformentioned risk model, P. longidigitus and A. huronensis are considered to be of low disease risk to fisheries. The pathology of E. briani and P. sanguinea are described for the first time. Literature suggests that both parasites are pathogenic to juvenile fIsh. E. briani causes a number of pathological changes within the gils of juvenile cyprinids, although these remain localised due to the very strict site specificity of the parasite. Migrations of the nematode P. sanguinea causes damage to the fins and caudal musculature of juvenile crucian car. For both parasites, the extent and severity of pathological changes are inversely proprtional to host size. Further studies at the population level are needed before an assessment of impact to fisheries can be made. The difficulties associated with studying the effects of introduced parasites to juvenile fish populations in the wild are recognised. Recommendations for further study are given.